Ceramic veneers and continuous additive manufacturing for producing ceramic veneers

Abstract

The present disclosure provides a method for making a ceramic article. The method includes: (a) obtaining a photopolymerizable slurry or sol including a plurality of ceramic particles dispersed therein; and (b) selectively polymerizing the photopolymerizable slurry or sol to form a gelled article using actinic radiation and sequentially passing a build substrate through the photopolymerizable slurry or sol. The method also includes (c) extracting solvent from the gelled article to form an aerogel or xerogel article; (d) heat-treating the aerogel or xerogel article to form a porous ceramic article; and (e) sintering the porous ceramic article to form a sintered ceramic article. The sintered ceramic article exhibits a specific density. Additionally, additively manufactured ceramic articles are provided that exhibit a specific density, opacity, or both.

Description

[Technical Field]

[0001] The present disclosure relates generally to ceramic dental veneers having desirable properties and shapes. The disclosure also relates to additive manufacturing methods for producing such ceramic dental veneers. [Background technology]

[0002] A dental veneer is a thin layer of restorative material placed on a tooth surface or dental framework to improve the visible aesthetics of the tooth, for example, to improve color or hide stains. Veneers may be standardized or customized for one or more teeth of a particular patient. Dental veneers are preferably placed on portions of a dental restoration that are likely to be visible in the patient's mouth or that, in particular, functionally cooperate with, for example, the patient's adjacent or opposing teeth.

[0003] Dental veneers typically have three-dimensional inner and outer surfaces that include convex and concave features. The inner surface of the dental veneer typically corresponds substantially to the outer surface of the prepared tooth or tooth stump, while the outer surface of the dental veneer typically corresponds substantially to the final dental restoration (e.g., the desired final appearance of the patient's tooth).

[0004] Dental veneers can be temporary in that they can be easily removed from a patient's mouth by peeling away the underlying support structure. Because such veneers are formed with a thin cross-sectional thickness of the veneer body, they typically do not require tooth preparation or preforming, including cutting, drilling, grinding, and other forms of permanently removing material from the tooth. For example, U.S. Patent Application Publication No. 2005 / 0227204 describes temporary veneers that can be made from porcelain, plastic, or other semi-rigid composite materials, which can be removed by using a warm water rinse in the mouth to pull the veneer off the tooth. Other temporary veneers are formed from molded polymer or plastic materials.

[0005] While temporary veneers are a viable solution, they may lack aesthetic appeal or have insufficient material strength to withstand the forces encountered in a patient's mouth. Therefore, in some cases, it is necessary to provide a permanent veneer. Permanent veneers are often formed from glass or glass-ceramic materials and are created using at least one molding or milling process. U.S. Patent Application Publication No. 20120175799 features a method for producing personalized dental veneers with a personalized holder. The holder is complementary to the shape of the veneer, providing stability to an otherwise thin and fragile article. Veneers obtained by the method of U.S. Patent Application Publication No. 20120175799 are said to be capable of being produced with an average thickness of 200 microns or less. Summary of the Invention

[0006] Despite the myriad options for veneers, patients and practitioners still must make a series of compromises: temporary or permanent; brittle or robust; custom-fit or standard; aesthetics or function. There is a need for veneers that combine the strength, aesthetics, and wear resistance of ceramic veneers with the ease of manufacturing the thin profile of temporary veneers, while including surface features and elements that mimic the tooth surface and aid in the retention of the veneer on the tooth or other dental framework.

[0007] In a first aspect, the present disclosure provides a monolithic veneer comprising an incisal edge, a cervical edge, a body extending between the incisal edge and cervical edge regions, an opposing proximal edge, and a labial surface and an opposing tooth-facing surface. A cusp receptacle is provided adjacent to the incisal edge, the cusp receptacle having a central window area defined between the incisal edge and the cervical edge and offset from the proximal edge. The body of the veneer includes one or more structural features selected from the group consisting of an incisal tubercle at least partially within the cusp receptacle, a concave depression at least partially within the cusp receptacle, an engineered surface texture, and a relief feature. The thinnest portion of the body within the central window area is 400 microns or less.

[0008] In a second aspect, the present disclosure provides a method for making a dental veneer, comprising receiving a design for a dental veneer comprising an incisal edge, a cervical edge, an opposing proximal edge, and a body extending between the edges; a labial surface and an opposing tooth-facing surface, and a cusp receptacle at the incisal edge; and fabricating the dental veneer as a single piece from a ceramic sol using additive manufacturing, wherein the thinnest portion of the central window area of ​​the veneer is 400 microns or less, and the veneer exhibits a density of 94% or greater relative to the theoretical density of the ceramic material.

[0009] In a third aspect, an additive manufacturing method for making ceramic veneers is provided. The method includes: (a) obtaining a photopolymerizable slurry or sol including a plurality of ceramic particles dispersed therein; and (b) selectively polymerizing the photopolymerizable slurry or sol using actinic radiation and passing a build substrate through the photopolymerizable slurry or sol to form a gelled article. The method then includes: (c) extracting solvent from the gelled article to form an aerogel or xerogel article; (d) heat-treating the aerogel or xerogel article to form a porous ceramic article; and (e) sintering the porous ceramic article to form a sintered ceramic article. The sintered ceramic article exhibits a density of 94% or greater relative to the theoretical density of the ceramic material.

[0010] In a fourth aspect, there is provided an additively manufactured ceramic article, wherein the ceramic article exhibits a density of 94% or greater, an opacity of 80% or less, or both, relative to the theoretical density of the ceramic material.

[0011] The above summary of the present disclosure is not intended to describe each embodiment or every implementation disclosed in the present disclosure. For example, the methods of the present disclosure can be adapted to produce dental articles and orthodontic articles in addition to veneers. The following description more particularly exemplifies exemplary embodiments. In several places throughout the application, guidance is provided through lists of examples, which examples can be used in various combinations. In each instance, the recited list serves only as a representative group and should not be interpreted as an exclusive list. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view of a veneer according to an embodiment of the present disclosure, viewed from the direction of the tooth-facing surface. [Figure 2] 2 is a perspective view of the veneer of FIG. 1, viewed from the direction of the tooth-facing surface opposite the facial surface. [Figure 3] FIG. 1 is a perspective view of a veneer according to an embodiment of the present disclosure, viewed from the direction of the tooth-facing surface. [Figure 4] FIG. 4 is a cross-sectional view of the veneer of FIG. 3. [Figure 5] 1 is a photograph of a sintered veneer according to Example 3. [Figure 6A] FIG. 1 is a perspective view of a veneer according to an embodiment of the present disclosure, viewed from the direction of the tooth-facing surface. [Figure 6B] FIG. 1 is a perspective view of a veneer according to an embodiment of the present disclosure, viewed from the direction of the tooth-facing surface. [Figure 6C] FIG. 1 is a perspective view of a veneer according to an embodiment of the present disclosure, viewed from the direction of the tooth-facing surface. [Figure 7] FIG. 1 is a perspective view of a veneer according to an embodiment of the present disclosure, viewed from the direction of the facial surface. [Figure 8] FIG. 6 is a block diagram of a general system 600 for additive manufacturing of an article. [Figure 9] FIG. 1 is a block diagram of a generalized manufacturing process for an article. [Figure 10] 1 is a high-level flowchart of an exemplary article manufacturing process. [Figure 11] A flowchart of a process for constructing an article using the photopolymerizable composition disclosed herein. [Figure 12A] A perspective view of a digital file of an article having the shape of a dental veneer. [Figure 12B] Photographs of a gelled article in the shape of a central incisor veneer, an aerogel article in the shape of a veneer, a white body in the shape of a veneer, and a sintered veneer, prepared from a digital file of an article and in accordance with Example 2. [Figure 12C] A photograph of a sintered ceramic veneer for a lateral tooth prepared in accordance with Example 2. [Figure 12D] A photograph of a set of sintered ceramic veneers for central and lateral teeth prepared in accordance with Example 2. [Figure 13] A photograph of a series of veneers according to the prior art. [Figure 14] A photograph of a part of a sintered ceramic article of 12C with the support sprue removed. [Figure 15] Photographs of a series of gelled articles each in the shape of a veneer, prepared in accordance with Example 1. [Figure 16] A photograph of a sintered ceramic veneer made from the gelled article of FIG. 16.

[0013] The figures identified above describe some embodiments of the present disclosure, but as mentioned in the description, other embodiments are also contemplated. The drawings are not necessarily drawn to scale. In all cases, the present disclosure presents the invention by way of illustration and not limitation. Many other variations and embodiments are possible for those skilled in the art, and it should be understood that they are included within the scope and spirit of the principles of the present invention.

[0014] Term Explanation As used herein, "ceramic" or "ceramic article" refers to a non-metallic material formed by the application of heat, including amorphous materials, glasses, crystalline ceramics, glass-ceramics, and combinations thereof. Ceramics are typically classified as inorganic materials. The term "amorphous material" refers to a material lacking long-range crystalline structure as determined by X-ray diffraction and / or possessing an exothermic peak corresponding to the crystallization of the amorphous material as determined by DTA (differential thermal analysis). The term "glass" refers to an amorphous material that exhibits a glass transition temperature. The term "glass-ceramic" refers to a ceramic containing crystals formed by heat treating an amorphous material. The term "crystalline ceramic" refers to a ceramic material that exhibits a distinguishable X-ray powder diffraction pattern. "Crystalline" refers to a solid composed of atoms arranged in a three-dimensional periodic pattern (i.e., having a long-range crystalline structure that can be determined by techniques such as X-ray diffraction). "Crystalline" refers to a crystalline domain of a solid having a defined crystalline structure. Crystalline crystals can have only one crystalline phase.

[0015] As used herein, "ceramic particles" refers to non-metallic materials produced by the application of heat or made by chemical synthesis processes, including particles of amorphous materials, glasses, crystalline ceramics, glass-ceramics, and combinations thereof. Ceramic particles are typically classified as inorganic materials. The term "amorphous material," with respect to ceramic particles, refers to materials derived from the melt and / or vapor phase, as well as materials made from chemical synthesis, where these materials lack long-range crystalline structure as determined by X-ray diffraction and / or have an exothermic peak corresponding to the crystallization of the amorphous material as determined by DTA (differential thermal analysis). For example, amorphous silica nanoparticles can be produced by the condensation of silanes to form nanoparticles.

[0016] As used herein, "additive manufacturing" refers to a process used to create three-dimensional articles. An example of an additive manufacturing technique is stereolithography (SLA), in which successive layers of material are laid down under computer control. Articles can be of almost any shape or geometry and are generated from a three-dimensional model or other electronic data source.

[0017] As used herein, "sol" refers to a continuous liquid phase containing discrete particles having sizes ranging from 1 nanometer (nm) to 100 nm.

[0018] As used herein, "slurry" refers to a continuous liquid phase containing discrete particles having a size ranging from greater than 100 nm to 50 micrometers, or greater than 100 nm to 10 micrometers. The slurry may optionally further contain discrete particles having a size ranging from 1 nanometer (nm) to 100 nm.

[0019] As used herein, "machining" refers to milling, grinding, cutting, carving, or shaping a material with a machine. Milling is usually faster and more cost-effective than grinding. A "machinable article" is an article that has a three-dimensional shape and is strong enough to be machined.

[0020] As used herein, "powder" refers to a dry bulk substance composed of many particulates that can flow freely when shaken or tilted.

[0021] As used herein, "particle" refers to a solid substance having a geometrically determinable shape. The shape can be regular or irregular. Particles can typically be analyzed, for example, with respect to particle size and particle size distribution. Particles can include one or more crystallites. Thus, particles can include one or more crystalline phases.

[0022] As used herein, "associated" refers to a grouping of two or more primary particles that are aggregated and / or agglomerated. Similarly, the term "non-associated" refers to two or more primary particles that are free or substantially free of aggregation and / or agglomeration.

[0023] As used herein, "agglomeration" refers to a strong association of two or more primary particles. For example, the primary particles may be chemically bonded to each other. It is generally difficult to achieve the decomposition of the agglomerates into smaller particles (e.g., primary particles).

[0024] As used herein, "agglomerate" refers to a weak association of two or more primary particles. For example, the particles may be held together by charge or polarity. Breaking down agglomerates into smaller particles (e.g., primary particles) is less difficult than breaking down aggregates into smaller particles.

[0025] As used herein, "primary particle size" refers to the size of a non-associated single crystal or single amorphous ceramic particle, which is considered a primary particle. X-ray diffraction (XRD) for crystalline particles, and transmission electron microscopy (TEM) for amorphous particles, are typically used to measure primary particle size.

[0026] As used herein, "substantially spherical" means that the particle approximates a sphere in shape, and does not include sharp edges that may result from the milling process.

[0027] As used herein, "soluble" means that a component (e.g., a solid) can be completely dissolved in a solvent. That is, the substance can form individual molecules (like glucose) or ions (like sodium chloride) when dispersed in water at 23°C. However, the solubilization process may take some time, for example, requiring stirring of the components for several hours (e.g., 10-20 hours).

[0028] As used herein, "density" refers to the ratio of mass to volume of an object. Density is usually measured in grams per cubic centimeter (g / cm 3 ) The density of an object can be calculated, for example, by determining its volume (e.g., by calculation or by applying Archimedes' principle or method) and measuring its mass. The volume of a sample can be determined based on the overall outer dimensions of the sample. The density of the sample can be calculated from the measured sample volume and sample mass. The total volume of a material sample can be calculated from the mass of the sample and the density of the material used. The total volume of cells in the sample is assumed to be the remainder of the sample volume (100% - total volume of material).

[0029] As used herein, "theoretical density" refers to the maximum possible density that would be achieved in a sintered article if all pores were removed. The percentage of theoretical density of a sintered article can be determined, for example, from an electron micrograph of a cross-section of the sintered article. The percentage of the area of ​​the sintered article that is attributable to pores in the electron micrograph can be calculated. In other words, the percentage of theoretical density can be calculated by subtracting the porosity from 100%. That is, if 1% of the area of ​​an electron micrograph of a sintered article is attributable to pores, the sintered article is considered to have a density equal to 99% of the theoretical density. Density can also be determined by Archimedes' method.

[0030] As used herein, the term "porous material" refers to a material containing partial volumes formed by voids, pores, or cells in the ceramic technical field. Thus, an "open-cell" structure of a material may be referred to as an "open-porous" structure, and a "closed-cell" material structure may be referred to as a "closed-porous" structure. It should be noted that the term "pore" is sometimes used in this technical field instead of the term "cell." The material structure categories "open-cell" and "closed-cell" can be determined in accordance with DIN 66133 for different porosities measured on different material samples (e.g., using a mercury "Poremaster 60-GT" from Quantachrome Inc., USA). Materials with open-cell or open-porous structures, for example, allow gas to pass through.

[0031] As used herein, "heat treating," "sintering," "binder combustion," or "binder removal" refers to a process in which a solid material is heated to remove at least 90% by weight of chemically bound volatile components (e.g., organic components) (e.g., in contrast to drying, in which physically bound water is removed by heating). Heat treating is performed at a temperature lower than that required to carry out the sintering step.

[0032] As used herein, "sintering" and "firing" are used interchangeably. A porous (e.g., pre-sintered) ceramic article shrinks during the sintering process, i.e., when an appropriate temperature is applied. The sintering temperature applied depends on the ceramic material selected. Sintering typically involves densifying a porous material into a less porous material (or a material with fewer cells) with a higher density; in some cases, sintering may also involve a change in the composition of the material phases (e.g., partial conversion of an amorphous phase to a crystalline phase).

[0033] As used herein, "gel," "gelled article," and "gelled body" are used interchangeably and refer to a three-dimensional gel that results from the curing reaction of polymerizable components contained in a slurry or sol, including an organic binder and a solvent.

[0034] As used herein, "aerogel" refers to a three-dimensional low-density solid. Aerogels are porous materials derived from gels in which the liquid component of the gel has been replaced by a gas. Solvent removal is often performed under supercritical conditions. During this process, the network does not substantially shrink, resulting in a highly porous, low-density material.

[0035] As used herein, "xerogel" refers to a three-dimensional solid derived from a gel, where the liquid component of the gel has been removed by evaporation under ambient conditions or at elevated temperatures.

[0036] As used herein, "green body" means an unsintered ceramic article, typically having an organic binder present.

[0037] As used herein, "white body" and "porous ceramic article" are interchangeable and refer to a binder burned-out article or a pre-sintered ceramic article.

[0038] As used herein, a "pre-sintered" ceramic article is one from which solvents and binders have been removed and which exhibits a density of less than 93% of its theoretical density.

[0039] As used herein, "geometrically defined article" means an article whose shape can be described in geometric terms, including two-dimensional terms such as circle, square, rectangle, and three-dimensional terms such as layer, cube, cuboid, sphere.

[0040] As used herein, "isotropic linear sintering behavior" means that sintering of a porous body during a sintering process occurs essentially invariantly with respect to the directions x, y, and z. "Substantially invariant" means that the sintering behavior with respect to the directions x, y, and z varies by no more than about + / - 5%, or + / - 2%, or + / - 1%.

[0041] As used herein, the term "crack" refers to a material separation or division (i.e., defect) in any two dimensions in a ratio equal to at least 5:1, at least 6:1, at least 7:1, at least 8:1, at least 10:1, at least 12:1, or at least 15:1.

[0042] The term "mass inertia force" referred to herein may be specified as force per unit mass, and therefore has the units m / s 2 Furthermore, mass inertia force can be expressed in terms of G-force, which is a factor of the acceleration of gravity. For the purposes of this specification, the acceleration of gravity is 9.81 m / s 2 Therefore, for example, 9.81 m / s 2 The mass inertia force can be expressed as 1G.

[0043] As used herein, "dental article" means any article that can be or will be used in the dental or orthodontic field to produce or as, inter alia, dental restorations, tooth models and parts thereof.

[0044] Examples of dental articles include crowns (including monolithic crowns), bridges, inlays, onlays, veneers, facings, copings, crown and bridge frameworks, implants, abutments, orthodontic appliances (e.g., brackets, intraoral tubes, cleats, attachments, and buttons), and components thereof. Tooth surfaces are not considered dental articles.

[0045] If a material or composition does not contain a particular component as an essential feature, the material or composition is "essentially or substantially free" of this component within the meaning of the present invention. Therefore, the component is not intentionally added to the composition or material, either as is or in combination with other components or ingredients of other components. A composition or material that is substantially free of a particular component typically contains the component in an amount of less than about 1% by weight, or less than about 0.1% by weight, or less than about 0.01% by weight (or about 0.05 mol / l (solvent) or about 0.005 mol / l (solvent) or about 0.0005 mol / l (solvent)) based on the total weight of the composition or material. Ideally, the composition or substance is completely free of this component. However, sometimes, the presence of a small amount of the component is unavoidable, for example, due to impurities.

[0046] As used herein, "aliphatic group" means a saturated or unsaturated straight-chain, branched-chain, or cyclic hydrocarbon group. This term is used to encompass, for example, alkyl, alkenyl, and alkynyl groups.

[0047] As used herein, "alkyl" means a linear or branched, cyclic or acyclic saturated monovalent hydrocarbon radical having 1 to 32 carbon atoms, e.g., methyl, ethyl, 1-propyl, 2-propyl, pentyl, and the like.

[0048] As used herein, "alkylene" means a linear saturated divalent hydrocarbon radical having 1 to 12 carbon atoms or a branched saturated divalent hydrocarbon radical having 3 to 12 carbon atoms, e.g., methylene, ethylene, propylene, 2-methylpropylene, pentylene, hexylene, and the like.

[0049] As used herein, "alkenyl" refers to a monovalent linear or branched unsaturated aliphatic group having one or more carbon-carbon double bonds, such as vinyl. Unless otherwise specified, alkenyl groups typically contain 1 to 20 carbon atoms.

[0050] As used herein, "solidifiable" refers to a material or composition that can be hardened or solidified by, for example, heating to remove solvent, heating to cause polymerization, chemical crosslinking, radiation-induced polymerization or crosslinking, etc.

[0051] As used herein, "curing" means hardening or partially hardening of a composition by any mechanism, such as heat, light, radiation, electron beam, microwave, chemical reaction, or a combination thereof.

[0052] As used herein, "hardened" refers to a material or composition that has been hardened or partially hardened (eg, polymerized or crosslinked) by curing.

[0053] As used herein, "integral" refers to being made at the same time or not being able to be separated without damaging one or more of the (integral) parts, e.g., "one piece."

[0054] As used herein, "incisal" and "occlusal" are used interchangeably and refer to the cutting and / or chewing surfaces of the teeth located distal to the gums.

[0055] As used herein, the term "(meth)acrylate" is shorthand for acrylate, methacrylate, or a combination thereof; "(meth)acrylic" is shorthand for acrylic, methacrylic, or a combination thereof; and "(meth)acryl" is shorthand for acrylic and methacrylic groups. "Acrylic" refers to derivatives of acrylic acid, such as acrylates, methacrylates, acrylamides, and methacrylamides. "(Meth)acrylic" refers to a monomer or oligomer having at least one acrylic or methacrylic group, and if it contains more than one group, linked by an aliphatic segment. As used herein, a "(meth)acrylate-functional compound" is, inter alia, a compound containing a (meth)acrylate moiety.

[0056] As used herein, "non-crosslinkable" refers to a polymer that does not undergo crosslinking upon exposure to actinic radiation or high heat. Typically, a non-crosslinkable polymer is a non-functionalized polymer that lacks functional groups that would participate in crosslinking.

[0057] As used herein, "polymerizable slurry or sol" and "polymerizable composition" each refer to a curable composition that can undergo polymerization upon initiation (e.g., free-radical polymerization initiation). Typically, prior to polymerization (e.g., curing), the polymerizable slurry / sol or composition has a viscosity profile that matches the requirements and parameters of one or more additive manufacturing (e.g., 3D printing) systems. In some embodiments, for example, curing includes, for a "photopolymerizable slurry or sol," applying actinic radiation having sufficient energy to initiate a polymerization or crosslinking reaction. For example, in some embodiments, ultraviolet (UV) radiation, visible light radiation, electron beam radiation, or a combination can be used.

[0058] As used herein, "resin" includes all polymerizable components (monomers, oligomers, and / or polymers) present in a curable slurry / sol or composition. A resin may contain only one polymerizable component compound or a mixture of different polymerizable compounds.

[0059] As used herein, "sintered article" refers to a gelled article that has been dried, heated to remove the organic matrix, and then further heated to reduce porosity and densify. The density after sintering is at least 40% of the theoretical density. Articles with densities in the range of 40-93% of the theoretical density typically have open porosity (pores that are open to the surface). Above 93% or 95% of the theoretical density, closed porosity is typically present (no pores that are open to the surface).

[0060] As used herein, "thermoplastic" refers to a polymer that flows when heated sufficiently above its glass transition point and becomes solid when cooled.

[0061] As used herein, "thermoset" refers to a polymer that becomes permanently hardened upon curing and does not flow upon subsequent application of heat. Thermoset polymers are typically crosslinked polymers.

[0062] The words "preferred" and "preferably" refer to embodiments of the present disclosure that may offer certain benefits, under particular circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, or is intended to exclude other embodiments from the scope of the present disclosure.

[0063] In this application, terms such as "a," "an," and "the" are not intended to refer only to a singular entity, but include a general class for which a particular example may be used for illustration. The terms "a," "an," and "the" are used interchangeably with the term "at least one." The phrases "at least one of" and "including at least one of" following a list refer to any one of the items in the list, and any combination of two or more items in the list.

[0064] As used herein, the term "or" is generally used in its ordinary sense, including "and / or," unless the context clearly dictates otherwise. The term "and / or" refers to one or all of the listed elements or a combination of any two or more of the listed elements.

[0065] Also herein, all numbers are assumed to be modified by the term "about," and preferably by the term "exactly." When used herein in connection with a measured quantity, the term "about" refers to the variation in the measured quantity that would be expected by one of ordinary skill in the art making the measurement and exercising a level of care commensurate with the purpose of the measurement and the precision of the measuring device being used. Also herein, the recitation of numerical ranges by endpoints includes all numbers subsumed within that range, as well as the endpoints (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

[0066] The term "generally," when used herein as a modifier to a characteristic or attribute, means that the characteristic or attribute is readily recognizable by one of ordinary skill in the art, but does not require absolute precision or perfect agreement (e.g., within + / - 20% for quantifiable characteristics), unless otherwise specifically defined. The term "substantially," unless otherwise specifically defined, means a high degree of approximation (e.g., within + / - 10% for quantifiable characteristics), but again does not require absolute precision or perfect agreement. Terms such as same, equal, uniform, constant, exactly, etc., are understood to be within normal tolerances or measurement errors applicable to the particular situation, rather than requiring absolute precision or perfect agreement. DETAILED DESCRIPTION OF THE INVENTION

[0067] The present disclosure provides ceramic veneers with desirable optical and material properties. Veneers can be manufactured with relatively thin walls while maintaining adequate strength, if not desired. Such veneers may include structural features that, among other things, help secure the veneer to the tooth surface, help mimic the anatomical structure of the tooth, or better control the optical properties (e.g., opacity or translucency) of desired regions of the veneer body. The ceramic veneers of the present disclosure can be monolithically manufactured as a single piece from a particle-loaded slurry or sol. The ceramic dental veneers of the present disclosure exhibit unique physical characteristics and performance properties made possible by additive manufacturing.

[0068] The present disclosure also provides a method for producing ceramic articles (e.g., parts) using additive manufacturing from particle-filled slurries or sols. Articles can be fabricated according to conventional stereolithography, in which a digital object file is sliced ​​into cross sections and then used to irradiate each layer, with pauses for movement between each irradiation step. Ceramic composite parts constructed in this manner are often post-processed to obtain a solid ceramic. An alternative approach to layered stereolithography is to build the part serially. The same slicing of the digital object into two-dimensional cross sections is performed, but the layers are irradiated without significant pauses between them. By (essentially) continuously moving the part away from the light source, parts can be produced that are free of specific optical artifacts within their interiors. Other additive manufacturing methods, including inkjet printing and volumetric additive manufacturing (VAM) techniques, are also suitable.

[0069] The present disclosure provides additively manufactured ceramic veneers. The sintered ceramic veneers exhibit a density of 94% or greater, or even 98% or greater, relative to the theoretical density of the ceramic material, an opacity of 80% or less, or both. In some embodiments, the sintered ceramic veneers advantageously exhibit an opacity of 80% or less, 75% or less, or 70% or less, and an opacity of 1% or greater, 10% or greater, 20% or greater, 30% or greater, 40% or greater, 50% or greater, or 60% or greater. Opacity relates to the ability of a ceramic article to block the transmission of light. As used herein, the term "light" refers to electromagnetic radiation, whether or not visible to the unaided human eye. Ultraviolet light is light having a wavelength in the range of approximately 250 nanometers (nm) to 380 nm. Visible light is light having a wavelength in the range of 380 nanometers (nm) to 700 nm. Infrared light has a wavelength in the range of approximately 700 nm to 300 micrometers. In some embodiments, suitable actinic radiation provides wavelengths in the range of 220 nm to 550 nm. Opacity measurements can be performed in accordance with ASTM E-284 using a Lab Scan XE spectrophotometer (Hunterlab, Reston, Va.). Opacity is measured using the spectrophotometer, and the "L" values ​​are measured separately against a black background and a white background, respectively. Opacity is calculated as (L measured against a black background / L measured against a white background) × 100 and reported in units of %. The "L" value is one of three standard parameters in the CIELAB color space scale established by the International Commission on Illumination. "L" is a luminance value ranging from 0 (black) to 100 (maximum intensity).

[0070] In some embodiments, the opacity may vary across the surface of the veneer. For example, structural relief features may be printed on the surface of the veneer to vary the opacity of the surrounding ceramic. Varying opacity may be advantageous to mimic demineralization or fluorosis of the underlying teeth or to hide areas of underlying discoloration.

[0071] In some embodiments, the sintered ceramic veneer advantageously exhibits a flexural strength of 100 megapascals (MPa) or greater, 200 MPa, 300 MPa, 400 MPa, 500 MPa, 600 MPa, 700 MPa, 800 MPa, 900 MPa, 1000 MPa, 1100 MPa, or 1200 MPa or greater, and 2000 MPa or less, 1900 MPa, 1800 MPa, 1700 MPa, 1600 MPa, 1500 MPa, 1400 MPa, or 1300 MPa or less. Flexural strength can be determined using ISO 6872 (2008) after forming the sintered ceramic article into the shape of a test bar having dimensions of approximately 1 mm x 4 mm x 12 mm. Further details of the test method are provided in the Examples below.

[0072] In many embodiments, ceramic veneers comprise molded, one-piece articles in which two or more variations in size or texture are provided by a single, one-piece article. For example, the veneer may include one or more structural features selected from the group consisting of incisal knots, concave depressions, engineered surface textures, distinguishing features, channels, and relief features. Such features are typically not possible to provide in a one-piece article using conventional molding or milling methods. In particular, the size of available milling burrs is too large to create the structural features, or the surfaces of the veneer that would benefit from such features are generally inaccessible.

[0073] Veneers can be designed and produced to have a thickness after sintering of at least about 0.08 mm (80 microns) and less than 0.4 mm (400 microns), less than 0.3 mm, less than 0.2 mm, or less than 0.1 mm. The thickness of the veneer can be an average thickness. The veneer can be thinner or thicker in various areas. Typically, the veneers of the present disclosure are thinnest at the incisal, cervical, and proximal edges and thickest at the center of the veneer. As used herein, the center of the veneer refers to the region of the veneer located approximately 2 mm from the incisal and proximal edges, as further described below.

[0074] In certain embodiments, the veneer may be a non-framework dental product; for example, the veneer may be placed directly on the tooth surface without any intermediate framework to strengthen the veneer. Other embodiments may utilize other dental prostheses, such as a crown or bridge, and include a veneer layer on top of a framework, such as a coping or bridge framework. For certain embodiments, particularly those that match or adapt to the patient's anatomical features, it may not be necessary to remove material from the tooth before placing the veneer. In other embodiments, a small portion of the tooth may be prepared, for example, by grinding. This may be done, for example, to remove imperfections in the tooth surface or to achieve better mechanical retention.

[0075] 1 and 2 illustrate a dental veneer according to an embodiment of the present disclosure. FIG. 1 shows the facial surface of the veneer, while FIG. 2 illustrates the opposing tooth-facing (e.g., lingual) surface. The facial surface 11 is typically flat or convex to simulate the curvature of the patient's teeth, while the opposing surface 12 is generally flat or concave to conform to and accommodate the outer surface of the patient's teeth or dental framework. The tooth-facing surface 12 may also be designed to accommodate a bonding composition. Optionally, a non-ceramic staining and / or glazing layer may be added to at least one side of the veneer 10. The veneer 10 includes an incisal edge 20, a pair of proximal edges 21 and 22, and a cervical edge 23. The height and width of the veneer 10 are within known ranges for adult teeth, particularly within known dimensions for maxillary central incisors, lateral incisors, canines, and premolars. Heights ranging from 6 mm to 13 mm and widths from 6 mm to 11 mm are typical.

[0076] The central region 14 of the veneer is the major surface area located between the incisal edge 20 and the cervical edge 23 and offset from the proximal edges 21, 22. The central region 14 comprises a portion of the veneer body, which is typically, but not exclusively, thicker than the body at the edges 20, 21, 22, and 23. In some other embodiments, the thickness of the body in the central region 14 is substantially equal to the thickness at one or more of the edges 20, 21, 22, and 23. The thickness of any region of the veneer may be designed and dictated in the manufacturing process, or may be modified, for example, by grinding, when the veneer is secured in the patient's mouth or at another time prior to installation.

[0077] Veneer 10 includes a cusp receptacle 30 near the incisal edge 20. The cusp receptacle 30 includes an incisal overhang 31 dimensioned to receive the incisal surface of the patient's tooth and / or framework restoration. Although not shown in FIG. 2, the cusp receptacle 30 may include an area that extends above the lingual surface of the patient's tooth when the veneer is placed such that the incisal overhang 31 is partially enclosed (see FIGS. 3 and 4). The cusp receptacle 30 may be designed to include structural features that mimic the anatomical features of the patient's tooth, align with certain anatomical features to improve veneer seating, or a combination of both.

[0078] The cusp receptacle 30 of the veneer 10 includes two incisal tubercles 33, 34 that project from the incisal overhang 31 toward the cervical margin 23. The incisal tubercles 33, 34 can have a generally frustoconical shape with a maximum cross-sectional dimension of 2 mm or less and a height, measured from the overhang 31, of approximately 500 microns to 1.5 mm. In some embodiments, the incisal tubercles can include maximum cross-sectional dimensions of 1.75 mm or less, 1.5 mm or less, 1.25 mm or less, and 1 mm or less. For certain fine features used to mimic dental anatomy and aid in retention, the incisal tubercles can have a maximum cross-sectional dimension of 750 microns or less, 600 microns or less, 550 microns or less, and 500 microns or less. Height can also vary accordingly.

[0079] Other shapes and sizes for the incisal nodes are contemplated, including pyramidal, tetrahedral, cylindrical; elliptical cylindrical; cuboid (e.g., square cube or rectangular cuboid); conical; truncated conical, and any other regular or irregular shape that approximates an anatomical feature. In some embodiments in which the veneer 10 is suitably translucent, the incisal nodes 33, 34 may affect the shading of the facial surface near the incisal edge 20. Such incisal nodes are challenging, if not impossible, to create by conventional milling or casting, at least in part due to the larger size of conventional milling burrs and the difficulty of accessing the cusp receptacle surfaces.

[0080] 3 and 4 illustrate another embodiment of a ceramic dental veneer according to the present disclosure. Ceramic dental veneer 100 is similar to veneer 10 in that it includes an incisal edge 120, a cusp receptacle 130, and a cervical margin 123. Unlike dental veneer 10, dental veneer 100 of FIGS. 3 and 4 is a shell veneer having sidewalls 121 a and 122 b at proximal edges 121 and 122, respectively. Sidewalls 121 a and 122 b may extend partially into the interproximal space between adjacent teeth when veneer 100 is secured, although this is not strictly required. Sidewalls 121 a and 122 b may be relatively thin (e.g., about 200 microns or less) compared to central region 114 of veneer 100.

[0081] The cusp receptacle 130 may include a truncated wall 132 opposite the tooth-facing surface 112 to create a pocket for receiving the incisal tooth surface that is open primarily along the occlusal-gingival axis. The truncated wall 132 may be disposed adjacent to or in contact with the lingual tooth surface when the veneer 100 is secured to the patient's tooth. The cusp receptacle 130 includes a plurality of incisal tubercles 140 extending between the side walls 121 a, 122 a. The incisal tubercles 140 define a series of concave depressions 141 between the incisal tubercle peaks 142. Each depression 141 has a maximum cross-sectional dimension, measured in a plane substantially parallel to the overhang 131, of 200 microns or less, 175 microns or less, 150 microns or less, or in some embodiments, 100 microns or less. The presence of the truncated wall 132, along with the size and number of the incisal nodes, makes the creation of such a structural feature completely impractical by conventional milling and casting methods.

[0082] A further embodiment of a veneer according to the present disclosure is illustrated in the image of FIG. 5, created in accordance with Example 3 below. Veneer 200 can include any of the features of veneers 10 and 100. Veneer 200 includes a structural feature 250 in relief on the tooth-facing surface 212, in this example, the printed "3M" company name, in a central region 214 of the veneer body. The appearance of the facial surface 211 is altered by the presence of structural feature 250, which, in addition to the branding benefits provided, can be designed to conceal undesirable aesthetics or identify the part to the patient or practitioner. Structural feature 250 can be indented or protruding. Such identification or branding features are typically printed 100 microns high above the tooth-facing surface and can have dimensions of approximately 1 mm, although the dimensions may vary depending on the brand or message being conveyed. Bonded tooth identification, sub-brand, size, lot number, or custom case identification number, or any combination thereof, can be printed in a similar manner. Alternatively, the structural features 250 can penetrate the tooth-facing surface 212 in a similar dimension.

[0083] Structural features are not limited to identification and branding. For example, FIGS. 6A-6C illustrate an arrangement pattern of structural features 350 on the tooth-facing surface 312 of veneer 300. Veneer 300 can include any and all features of veneers 10, 100, and 200 in addition to the arrangement pattern of structural features. As with veneer 200, structural features 350 can be intrusive or protrusive. A "arrangement pattern" is a plurality of structural features (e.g., recesses, channels, ridges, etc.) arranged in predetermined locations or with some regularity or slack. Structural features arranged in this manner can impart surface texture to the tooth-facing surface, which can aid in the retention of the bonding agent between the veneer and the tooth / framework. The surface texture provided by the arranged structural features can also modify the light transmittance of the sintered veneer in desired locations.

[0084] For example, the structural feature arrangement pattern can include an arrangement row pattern, an arrangement grid pattern such as an arrangement square grid pattern, an arrangement zigzag pattern, or an arrangement radial pattern. The arrangement pattern need not be uniform across the entire surface of a given veneer, but may be formed on only a portion. The pattern of features may vary or remain the same across any portion of the article.

[0085] The structural features can take the form of any shape. Similarly, the three-dimensional shape of the features is not particularly limited, so long as the recesses do not extend through the thickness of the central veneer to the opposite major surface. Non-limiting examples of suitable cross-sectional shapes for the features include circles, triangles, squares, rectangles, and other polygons. The structural features within a pattern can be similarly shaped or can have different shapes. The structural features in Figures 6A-6C resemble channels in the tooth-facing surface. Such channels can follow any desired path and can be continuous or discontinuous across the surface of the core in any given direction.

[0086] As illustrated in FIGS. 6A-6C, the surface can include structural features of identifiable shapes arranged in repeating unit cells. The unit cells can be repeated in a unit cell arrangement pattern. A variety of shapes can be used to define the unit cells, including rectangles, circles, semicircles, ellipses, semi-ellipses, triangles, trapezoids, and other polygons (e.g., pentagons, hexagons, octagons), as well as combinations thereof. In such embodiments, the boundary of each unit cell is immediately adjacent to the boundary of an adjacent unit cell, such that the plurality of unit cells resembles, for example, a grid or tessellation. The unit cells (or individual structural features) can have similar dimensions across the entire printed surface (FIG. 6A or 6B) or can have larger dimensions near the central region 314 of the veneer, resulting in smaller dimensions of the features at the edges 320, 321, 322, and 323 (FIG. 6C). In certain embodiments, such gradients in feature shape and placement can be useful in modifying at least one of the translucency and opacity of particular regions of the veneer body (e.g., the central region), as well as improving retention of the tooth-facing surface against the patient's teeth and / or dental framework.

[0087] Structural features may also be created on the facial surface of the veneer body to mimic or align with dental anatomy. For example, the veneer 500 of FIG. 7 includes multiple classes of structural features on the facial surface 511. A first structural feature class includes a pair of grooves 550 extending occlusally-gingivally from the incisal edge 520. The grooves 550 are sized to correspond to the primary dental anatomy and do not extend across the entire facial surface 511 of the veneer to the cervical margin 523. In other embodiments, the grooves may extend across all or different portions of the facial surface 511.

[0088] The second feature class includes a series of channels 560 extending mesiodistally across the facial surface 511, substantially parallel to the grooves 550. The channels 560 are dimensioned to correspond to tertiary dental anatomical structures, such as ridges. Accordingly, the channels 560 include a smaller depth (i.e., distance into the facial surface 511) than the grooves 550, including less than about 100 microns. The channels are spaced from one another at a relatively close pitch (e.g., distance between channel valleys less than 90 microns) and are disposed across the entire area of ​​the facial surface 511, including the central region 514. In other embodiments, the veneer may feature only one of the first and second classes of structural features (e.g., only the channels 560) on the facial or tooth-facing surface. Other surface textures described above with respect to the veneer 300 may also be created on the facial surface 511.

[0089] The veneers of the present disclosure can be manufactured individually or as part of a set suitable for one or more patients. The veneers of the present disclosure may also be provided as part of a kit. The kit contents may include one or more of the following: a dental veneer for each of the various teeth (central, lateral, canine, and premolar); adhesive, applicators, and brushes; files and shaping tools for shaping the veneer; and a color-modifying agent. The veneers of the present disclosure can be bonded to the teeth using conventional techniques and dental compositions such as RELYX Cements and SCOTCHBOND Adhesives, available from 3M Oral Care (St. Paul, MN). Suitable bonding techniques are described in EP 2272458 (Karlsson et al.).

[0090] The systems and methods for producing veneers of the present disclosure are explored in more detail below. Generally, a method for producing dental veneers includes receiving a digital 3D model of intraoral structures or parameters for a preformed restoration that includes a veneer, generating a design for the veneer, generating instructions for a 3D printer (or other additive manufacturing device) to produce the veneer, outputting the instructions to the 3D printer to produce the veneer, producing the veneer, and possibly post-processing the 3D printed veneer.

[0091] Method and system for additive manufacturing of veneers In one embodiment, the functions or algorithms described herein may be implemented in software. Software may consist of computer-executable instructions stored on a computer-readable medium or computer-readable storage device, such as one or more non-transitory memories or other types of hardware-based storage devices, local or networked. Furthermore, such functions correspond to modules, which may be software, hardware, firmware, or any combination thereof. Multiple functions may be performed in one or more modules as desired, and the described embodiments are merely examples. Software may be executed on a digital signal processor, an ASIC, a microprocessor, or other type of processor operating on a computer system, such as a personal computer, server, or other computer system, to transform such a computer system into a specially programmed machine. The term “processor,” as used herein, may refer to any of the foregoing structures or any other structure suitable for implementing the techniques described herein. Furthermore, in some aspects, the functions described herein may be provided within dedicated software or hardware modules configured to perform the techniques of the present disclosure. Even when implemented in software, the techniques may use hardware, such as a processor for executing the software and memory for storing the software. In any such case, the computer described herein may define a particular machine capable of performing the particular functions described herein. Likewise, the techniques may be embodied entirely in one or more circuits or logic elements that may also be considered a processor.

[0092] In many cases, computer-readable media is provided as part of a computing device. A computing device may have one or more processors, volatile memory (RAM), a device for reading machine-readable media, and input / output devices such as a display, keyboard, and pointing device. Additionally, a computing device may include other software, firmware, or a combination thereof, such as an operating system and other application software. A computing device may be, for example, a workstation, laptop, tablet, smartphone, personal digital assistant (PDA), server, mainframe, or any other general-purpose or special-purpose computing device. A computing device may read executable software instructions from a computer-readable medium (such as a hard drive, CD-ROM, or computer memory) or may receive instructions from another source logically connected to the computer, such as another networked computer. Data may be communicated, for example, directly to an application on a mobile device and / or directly to a cloud platform system via a cellular connection, Wi-Fi router, or hub.

[0093] FIG. 8 is a schematic diagram of a system 600 for producing additively manufactured 3D dental veneers. The system 600 includes a processor 610 that receives a digital 3D model 612 of teeth from an intraoral 3D scan or a dental impression scan, or in other embodiments, the system receives manual user input. The system 600 can also include an electronic display device 616, such as a liquid crystal display (LCD) device, and an input device 618 for receiving user commands or other information, for example, for designing a dental veneer. The display device 616 can implement any electronic display, such as a cathode ray tube (CRT), a liquid crystal display (LCD), a light emitting diode (LED) display, or an organic light emitting diode (OLED) display. The input device 618 can implement any device for inputting information or commands, such as a keyboard, a microphone, a cursor control device, or a touchscreen.

[0094] These systems can use an intraoral scanner to acquire digital images from multiple views of teeth or other intraoral structures, which can then be processed to generate a digital 3D model representing the scanned teeth and gums. System 600 can be implemented, for example, on a desktop, notebook, or tablet computer. System 600 can receive the 3D scans locally or remotely over a network. System 600 also includes a 3D printer 614 or other additive manufacturing device for producing dental restorations.

[0095] Data representing the veneer may be generated using computer modeling, such as computer-aided design (CAD) data. Image data representing the veneer design can be exported to an additive manufacturing device in STL format or any other suitable computer-processable format. Scanning methods for scanning three-dimensional objects can also be used to create data representing the article. One exemplary technique for acquiring data is digital scanning. Digital scanning can capture information related to spatial color variations in the anatomical structure of interest (e.g., labial tooth surfaces) along with identification of anatomical features and margins for incorporation into the veneer design. A particularly suitable color scanner for capturing such information is the TRIOS scanner available from 3 Shape A / S (Copenhagen, DK). Any other suitable scanning technique can be used to scan the article, including radiography, laser scanning, computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound imaging. Other possible scanning methods are described, for example, in U.S. Patent Application Publication No. 2007 / 0031791 (Cinader, Jr. et al.). The initial digital data set, which may include both raw data from the scanning operation and data representative of the article derived from the raw data, may be processed to segment the article design from any surrounding structures (e.g., the article's support).

[0096] 9 is a flowchart illustrating a method for fabricating dental veneers using additive manufacturing. The method includes receiving a digital 3D model of an intraoral structure, such as model 612, or parameters for a preformed veneer (step 722), generating a design for the veneer (step 724), generating instructions for a 3D printer to fabricate the veneer (step 726), outputting the instructions to the 3D printer to fabricate the veneer (step 728), and possibly performing post-processing of the 3D printed veneer (step 732). Some steps of such a method, such as steps 722, 724, 726, and 728, may be implemented in software or firmware modules for execution by a processor, such as processor 720, and the method may potentially be implemented using cloud computing. The designed veneer may be displayed on a display device, such as display device 716, and a user may interact with the designed restoration via display device 716 and input device 718.

[0097] Step 724 of designing the veneers to be 3D printed can be performed with software applications, including those for computer-aided design (CAD) and finite element analysis (FEA). Examples of CAD applications for designing either standard or patient-specific veneers, or both, include software products from SOLIDWORKS Corp. (Waltham, Mass.), Dental Wings Inc. (Montreal, Canada), and Exocad GmbH (Darmstadt, Germany). Non-dental-specific CAD design software may also be used, including Unigraphics products from Siemens PLM Software (Plano, Tex.), products from SOLIDWORKS Corp., and Pro / ENGINEER products from PTC (Needham, Mass.), particularly when designing standard preformed crown shapes. Topology optimization software can be used to design structural features and specify parameters such as unit cell geometry, scale, location, and gradient parameters. nTopology, available from nTopology, Inc. (New York, NY), is suitable for this purpose. Stress analysis through FEA or modeling can be used to predict performance such as stress and deflection during design; an example of an FEA application is the software product from ANSYS, Inc. (Canonsburg, Pa.). Generative design software can be used to optimize the structure of the veneer for a desired response (e.g., flexibility, feature size, location, and volume) under simulated use conditions; an example of such a software application is the AUTODESK Within product from Autodesk Inc. (San Rafael, Calif.). Veneers may be designed based on a digital representation of the patient's teeth or based on a standardized shape.

[0098] Steps 726 and 728 can use a software application to convert the designed veneer into instructions, such as a stereolithography (STL) file, for a 3D printer or other additive manufacturing device. The instructions can include slicing the design into layers to additively build the restoration, possibly with support layers. An example of 3D printing is the vat polymerization method using a Pico 3D printer from Asiga (Sydney, Australia). Other types of additive manufacturing for forming gel or ceramic bodies include: inkjet printing; powder bed printing; selective laser sintering; fuse deposition modeling, and laminated object manufacturing. Examples of materials and processes for additive manufacturing, including 3D printable materials, are disclosed in U.S. Pat. No. 10,532,088, entitled "High Strength and Translucency Dental Zirconia, Ceramic Materials, Devices, and Methods," International Publication No. 2016 / 191162, entitled "Additive Manufacturing Process for Producing Ceramic Articles Using a Sol Containing Nano-Sized Particles," International Publication No. 2016 / 191534, entitled "Sol Containing Nano Zirconia Particles for Use in Additive Manufacturing Processes for the Production of 3-Dimensional Articles," International Publication No. 2017 / 011388, entitled "A Method of Making a Dental Article," International Publication No. 2016 / 140840, entitled "Gel Compositions, Shaped Gel Articles and a Method of Making a Sintered Article," and "Continuous Additive Manufacturing Method for Making Ceramic Articles, and International Publication No. 2021 / 024162 entitled "Ceramic Articles."

[0099] Post-processing in step 730 can include post-curing, support removal, extraction and / or firing of the 3D printed veneer, followed by sintering and finishing. Further details regarding the additive manufacturing process are detailed below.

[0100] In a currently preferred embodiment, additive manufacturing process 728 results in a gelled article obtained by selectively curing a photopolymerizable slurry or sol, which typically includes ceramic particles, at least one radiation-curable monomer, a solvent, a photoinitiator, and an inhibitor.

[0101] Referring to FIG. 10 , for example, but not by way of limitation, an additive manufacturing method in accordance with at least one embodiment of the present disclosure includes retrieving 810 data representing a 3D model of an article (e.g., a dental veneer) from a (e.g., non-transitory) machine-readable medium. The method further includes executing 820, by one or more processors, an additive manufacturing application that interfaces with a manufacturing device using the data, and producing 830, by the manufacturing device, a physical object of the article. The method may optionally include receiving a 3D digital object including data specifying the article, and producing the article based on the digital object by an additive manufacturing process using the manufacturing device. The additive manufacturing device can selectively harden a photopolymerizable slurry or sol to form a gelled article. The photopolymerizable slurry or sol typically includes ceramic particles, at least one radiation-curable monomer, a solvent, a photoinitiator, and an inhibitor. The components of the ceramic particles, radiation-curable monomer, solvent, photoinitiator, and inhibitor are discussed in detail below. One or more various optional post-processing steps 840 may be performed. Typically, the gelled article is dried, heat treated, and sintered to form a ceramic article.

[0102] In a currently preferred embodiment, the production process 830 generally includes the following steps: a) obtaining a photopolymerizable slurry or sol comprising a plurality of ceramic particles dispersed therein; b) selectively polymerizing the photopolymerizable slurry or sol using actinic radiation and sequentially passing a build substrate through the photopolymerizable slurry or sol to form a gelled article; c) extracting the solvent from the gelled article to form an aerogel or xerogel article; d) heat treating the aerogel or xerogel article to form a porous ceramic article; and e) sintering the porous ceramic article to form a sintered ceramic article; The sintered ceramic article exhibits a density of 94% or greater relative to the theoretical density of the ceramic material.

[0103] Stated differently, and with reference to Figure 11, a method for producing ceramic veneers includes step 1010 of obtaining a photopolymerizable slurry or sol, and step 1020 of selectively curing (e.g., polymerizing) the photopolymerizable slurry or sol using actinic radiation and passing a (e.g., build) substrate through the photopolymerizable slurry or sol to obtain a gelled article. The photopolymerizable slurry or sol is typically introduced into a reservoir, cartridge, or other suitable container for use by or with an additive manufacturing device. The additive manufacturing device selectively cures the photopolymerizable slurry or sol according to a set of computerized design instructions.

[0104] 11 , the method further includes either step 1040a of extracting the solvent from the gelled article (e.g., by drying) to form an aerogel article, or step 1040b of extracting the solvent from the gelled article to form a xerogel article. Optionally, the solvent extraction is carried out by applying a supercritical fluid drying process. The method further includes either step 1050a of heat-treating the aerogel article to form a porous ceramic article, or step 1050b of heat-treating the xerogel article to form a porous ceramic article, and step 1060 of sintering the porous ceramic article to obtain a sintered ceramic article. The photopolymerizable slurry or sol includes ceramic particles dispersed in the photopolymerizable slurry or sol, which often includes at least one radiation-curable monomer, a solvent, a photoinitiator, and an inhibitor.

[0105] It should be further understood that the methods for fabricating 3D articles described herein can include so-called "stereolithography / vat polymerization" 3D printing methods, and that the selective curing step may use stereolithography printing. Other techniques for three-dimensional fabrication may be suitable for use in the applications described herein. More generally, three-dimensional fabrication techniques continue to become available. All such techniques may be adapted for use with the photopolymerizable slurries and sols described herein, provided that they provide fabrication viscosities and resolutions compatible with the specific article characteristics. Fabrication may be performed using data representing the three-dimensional object, which may be reformatted or otherwise adapted as needed for specific printing or other fabrication techniques, using any of the fabrication techniques described herein, either alone or in various combinations.

[0106] Preferably, vat (co)polymerization with two-dimensional cross-sectional projection is used in the methods disclosed herein. This technique also involves a container of curable slurry or sol (e.g., photopolymerizable composition). However, the two-dimensional cross-section is projected onto the curable composition by computer-controlled digital light processing ("DLP"), liquid crystal display (LCD), laser scanning system, photomask, or the like, curing the desired section at a time across the entire plane transverse to the projected beam. Continuous printing with machines having these basic printer configurations is possible, for example, by projecting a succession of cross-sectional images onto the vat while continuously (e.g., essentially) advancing the build platform away from the surface of the polymerization liquid so that additional liquid photopolymerizable composition is drawn into the build zone during the polymerization process.

[0107] The two-dimensional pattern either blocks actinic radiation from passing through all areas of the exposure image that are not in the pattern (e.g., as in the combination of a light source and a photomask), or provides actinic radiation in the shape of the pattern (e.g., as in the case of a laser or an array of pixels). When the exposure image includes a photomask, the positioning of the exposure image is typically the physical positioning of the photomask adjacent to the vat. In contrast, when the exposure image includes actinic radiation in the shape of a pattern (e.g., by digital projection or laser scanning), the positioning of the exposure image is typically the positioning of the radiation source, which is directed toward the vat.

[0108] Successive cross sections of the 3D article can be joined or adhered to one another in the z-direction (or build direction corresponding to the above-mentioned ascending or descending directions) by the application of energy to solidify the photopolymerizable composition. Additionally, selectively applying energy to the photopolymerizable composition in the container can include applying actinic radiation, such as UV radiation, visible light, electron beam radiation, or any combination thereof, having sufficient energy to cure the photopolymerizable composition. One of ordinary skill in the art can select a suitable radiation source and wavelength range for a particular application without undue experimentation. In some embodiments, the actinic radiation provides a wavelength in the range of 220 nm to 550 nm. Optionally, the actinic radiation has a power of 1 to 50 milliwatts per square centimeter (mW / cm ). 2 ) strength.

[0109] It should be understood that one or more steps of the method described herein, such as selectively applying energy to a layer of photopolymerizable composition, can be performed according to an image of a 3D article in a computer-readable format. In certain embodiments, a device designed for use in continuous mode can be used, such as the ASIGA PICO PLUS 39 available from Asiga USA, Anaheim Hills, CA, or a device commercially available from Carbon (Redwood City, CA), as described in, for example, U.S. Patent Nos. 9,205,601 and 9,360,757 (both to DeSimone et al.). Suitable commercially available continuous printers include the M2 from Carbon, the ProMaker L8000 from Prodways Technologies (Les Mureaux, France), the Vida UHD cDLM from EnvisionTEC Inc. (Dearborn, MI), and the FIGURE4 from 3D Systems (Rock Hill, SC). Suitable devices can also be assembled from individual components, for example, as described in the following examples.

[0110] DLPs are well known in the art, and are described, for example, but not limited to, in U.S. Patent Nos. 5,658,063 (Nasserbakht), 5,905,545 (Poradish et al.), 6,587,159 (Dewald), 7,164,397 (Pettitt et al.), 7,360,905 (Davis et al.), 8,705,133 (Lieb et al.), and 8,820,944 (Vasquez). Suitable DLPs are commercially available, such as from Texas Instruments (Dallas, TX). As noted above, either LEDs or lamps can be used with DLPs. Suitable lamps include flash lamps, low-pressure mercury lamps, medium-pressure mercury lamps, and / or microwave-driven lamps. Those skilled in the art can select a suitable LED or lamp light source, such as the UV LED CBT-39-UV available from Luminus Inc. (Sunnyvale, CA), to provide the actinic radiation necessary to initiate polymerization of a particular polymerizable composition. Suitable photomasks are commercially available, such as the NanoSculpt Photomasks manufactured by Infinite Graphics (Minneapolis, MN). Similar to using a DLP, either an LED or a lamp can be used with a photomask. The advantage of using a digital photomask is that individual pixels can be easily adjusted (e.g., using computer control) to change the irradiation position and dose, thereby changing the shape of the resulting gel as needed without requiring major equipment modifications. Suitable LCDs are commercially available, such as the LCD LQ043T1DG28 available from Sharp Corporation (Osaka, Japan).

[0111] The methods described herein can also include planarizing the new layer of fluid photopolymerizable composition provided by raising or lowering the elevator platform. Planarization in continuous processes typically occurs between curing of the composition for separate sections only as different sections are formed. Such planarization can sometimes be accomplished by utilizing wipers or rollers or recoaters. Planarization corrects the thickness of one or more layers before curing the composition by removing excess material and flattening the dispensed material to create a uniformly smooth exposed or flat, upward-facing surface on the printer's support platform.

[0112] In other alternative embodiments, the methods for producing the 3D articles described herein can include so-called "volumetric additive manufacturing (volumetric AM)." Here, a gel body representing the core of the restoration may be printed with a composition that typically provides the properties of the inner tooth (i.e., dentin), such as color and translucency. The liquid printing medium can then be swapped out for a design that provides the properties of the outer tooth (i.e., enamel). Similarly, multiple series or sequential modifications to the composition of the printing bath can be made to create a gel that can later be post-processed into a fully dense restoration. Exemplary processes for volumetric AM useful in the present disclosure can be found in U.S. Pat. No. 10,647,061 (Kelly et al.) and Madrid-Wolff et al., "Controlling Light in Scattering Materials for Volumetric Additive Manufacturing." Adv. Sci. 2022, 9, 2105144 and U.S. Patent Application Publication No. 20220350127 (Huffman et al.).

[0113] As another alternative, the method for manufacturing a 3D article described herein can include inkjet printing. For example, the method can include inkjetting a sol through a nozzle to form a plurality of droplets of a printed sol, the sol including: i) metal oxide particles; ii) a solvent; iii) a surface modifier; and iv) optionally, a polymerizable component. The method can further include solidifying the printed sol to form a portion of the three-dimensional veneer. Exemplary details of inkjet printing a sol can be found in International Publication No. WO2022136969 (Korten et al.).

[0114] After the 3D article is formed, it is typically removed from the additive manufacturing apparatus, and at least a portion of the uncured photopolymerizable slurry or sol is removed from the surface of the gelled article. Referring again to Figure 11, the method optionally includes rinsing the gelled article (e.g., ultrasonically, or aerating, or spray rinsing) in a solvent that dissolves a portion of the uncured photopolymerizable slurry or sol but does not dissolve the cured solid-state article (e.g., gel). In some embodiments, step 1030 of the method (e.g., before step c)) includes step f) of moving the gelled article, thereby generating a mass inertial force on the uncured photopolymerizable composition disposed on the surface of the gelled article, thereby forming a coating layer of the uncured photopolymerizable composition on the surface of the gelled article, wherein the mass inertial force is generated using a centrifuge, shaker, or mixer that rotates along one or more axes. Suitable methods for generating mass inertia forces are described, for example, in International Publication No. 2020157598, entitled "Orthodontic Articles and Methods of Making and Postprocessing the Same." For example, the source of mass inertia forces may be generated using a centrifuge, shaker, or mixer that rotates along one or more axes. In some embodiments, the movement of the object is a rotation or spin of the object. This can generate mass inertia forces through centrifugal force. One suitable mixer that rotates along two or more axes is a double asymmetric centrifugal mixer, such as the DAC400FVZ available from Flacktek (Landrum, SC). The double asymmetric centrifugal mixer provides simultaneous biaxial rotation that automatically reorients the article during rotation, which tends to draw the uncured composition out of the recessed features of the article in a short period of time (e.g., 20, 15, or 10 seconds or less). Any other conventional method for cleaning an article and removing uncured material on the surface of the article may also be utilized.

[0115] At this stage, the three-dimensional article typically has sufficient green strength for handling in the remaining steps of the method. The photopolymerizable slurries or sols described herein in a cured (e.g., gelled) state can, in some embodiments, exhibit one or more desirable properties. The article surface and the bulk article itself typically still retain the photopolymerizable slurry or sol, indicating the need for further curing. Removal of residual uncured photopolymerizable composition is particularly useful because it minimizes undesired direct curing of the residual uncured photopolymerizable composition on the article when the article is subsequently post-cured. A photopolymerizable slurry or sol in a "cured" state can include a photopolymerizable composition including a polymerizable component that is at least partially polymerized and / or crosslinked. For example, in some instances, the gelled article is at least about 10% polymerized or crosslinked, or at least about 30% polymerized or crosslinked. In some cases, the gelled article is at least about 50%, at least about 70%, at least about 80%, or at least about 90% polymerized or crosslinked. The gelled article may also be from about 10% to about 99% polymerized or crosslinked.

[0116] Further curing can be achieved by further exposure to actinic radiation, heat, or both. Optionally, the gelled article can then be immersed in another solvent (e.g., diethylene glycol ethyl ether or ethanol). Exposure to actinic radiation can be carried out using any convenient radiation source, generally UV radiation, visible light, and / or electron beam radiation, for a time ranging from about 10 seconds to more than 60 minutes. Heating is generally carried out in an inert atmosphere at a temperature ranging from about 35°C to 80°C for a time ranging from about 10 minutes to more than 60 minutes. So-called post-cure ovens, which combine UV radiation and thermal energy, are particularly well suited for use in the post-cure process. Post-curing generally improves the mechanical properties and stability of the three-dimensional article compared to the same three-dimensional article that is not post-cured.

[0117] Referring to FIG. 12A , an image of a digital file for an article having the shape of a dental veneer is shown. FIG. 12B shows, from left to right, a gelled article 1100 prepared in accordance with an embodiment of the present disclosure using the digital file of FIG. 12A , an aerogel article 1101 prepared from the gelled article 1100, a white body or pre-sintered article 1103 prepared from the aerogel article 1101, and a sintered dental veneer 1105 prepared from the pre-sintered article 1103. The veneer article of FIG. 12B is molded for a central tooth made in accordance with Example 2 below. FIG. 12C shows another sintered dental veneer 1105 prepared in accordance with Example 2 below and designed for a lateral tooth. FIG. 12D illustrates a set of sintered veneers prepared in accordance with Example 2 and designed for a patient's central and lateral teeth.

[0118] The particular article of Figures 12B-12D includes a plurality of support structures 1170 positioned on the incisal edge 1120 of the veneer. The support structures 1170 can include a thickness of at least one of a base 1171 and a tip 1172 that is less than 200 microns, or in some embodiments, less than 150 microns. The series of fine support structures 1170 can provide adequate stability during printing and processing while being easily removed by conventional grinding or milling methods without leaving noticeable marks or burrs. This contrasts with the supports of the prior art veneer illustrated in Figure 13, which are significantly larger to allow for investment casting and other handling of significantly more fragile veneers. Removal of such structures risks disfiguring marks or damage to the veneer body, neither of which is possible with the veneer 1100 that includes the support structures 1170.

[0119] 14, a ceramic article having the shape of a dental veneer is shown that has been post-processed after additive manufacturing formation of the gelled article (e.g., including removal of the support structure from the gelled article).

[0120] The components of the photopolymerizable slurry or sol (eg, ceramic particles, solvent, radiation curable monomer, photoinitiator, and inhibitor) are each discussed in detail below.

[0121] ceramic particles The photopolymerizable compositions of the present disclosure include particles of at least one ceramic material. In many embodiments, the ceramic particles include metal oxide ceramic particles, non-oxide ceramic particles, or any combination thereof.

[0122] Preferably, the ceramic particles are selected from the group consisting of zirconia (ZrO2), silica (SiO2), alumina (Al2O3), yttria (Y2O3), cerium oxide (CeO2), magnesium-magnesium aluminate (MMA), magnesium oxide (MgO), hydroxyapatite (Ca5(PO4)3OH), calcium phosphate fluoride (Ca5(PO4)3F), calcium phosphate chloride (Ca5(PO4)3Cl), calcite (CaCO3), cordierite (Mg2Al4SiO5) 18 ), silicon carbide (SiC), silicon nitride (Si3N4), boron carbide (B4C), titanium diboride (TiB2), zirconium diboride (ZrB2), boron nitride (BN), titanium carbide (TiC), zirconium carbide (ZrC), aluminum nitride (AlN), calcium hexaboride (CaB6), MAX phase (M n+1 AX n ) and any combination thereof. In selected embodiments, high purity particles are used, preferably having a total metal impurity content of less than 100 ppm, and particularly preferably less than 50 ppm. In alternative embodiments, particles having a total metal impurity content of about 2,000 ppm are used.

[0123] Suitable zirconia particles include, for example and without limitation, nano-sized zirconia particles having at least one and up to all of the following parameters or characteristics: Primary particle size XRD (diameter): 2nm~100nm, 2nm~50nm, 2nm~20nm, 2nm~15nm or 4nm~15nm Substantially spherical, rectangular, or a mixture of spherical and rectangular shapes Not meeting It is crystalline Not coated with inorganic colorants.

[0124] Suitable nano-sized zirconia particles can have at least one and up to all of the following characteristics: ZrO2 content: 70mol%~100mol% or 80mol%~97mol%; HfO2 content: 0mol%~4.5mol%, 0mol%~3mol% or 0.1mol%~2.8mol%; a stabilizer selected from Y2O3, CeO2, MgO, CaO, La2O3, or combinations thereof in an amount of 0 mol% to 30 mol%, 1.5 mol% to 16 mol%, 2 mol% to 10 mol%, or 2 mol% to 5 mol%; Al2O3 content: 0 mol% to 1 mol%, or 0.005 mol% to 0.5 mol%, or 0.01 mol% to 0.2 mol%.

[0125] According to one embodiment, the nano-sized zirconia particles are characterized as follows: ZrO2 content: 70 mol% to 98.4 mol%; HfO2 content: 0.1 mol% to 2.8 mol%; Y2O3 content: 1.5 mol% to 28 mol%.

[0126] Nanosized zirconia particles can be obtained or are obtained by a process that includes a step of hydrothermal treatment of an aqueous metal salt solution or suspension (e.g., zirconium salt, yttrium salt). Such a process is described in WO 2013 / 055432 (Kolb et al.).

[0127] Suitable silica particles include, but are not limited to, spherical silica particles and non-spherical silica particles.Spherical silica particles (sols) in aqueous media are well known in the art and are commercially available, for example, under the trade name LUDOX from W.R. Grace & Co. (Columbia, MD), under the trade name NYACOL from Nyacol Nanotechnologies Inc. (Ashland, MA), or under the trade name NALCO from Nalco Company (Naperville, IL) as silica sols in water or alcohol solution.One useful silica sol with a volume average particle size of 5 nm, a pH of 10.5, and a nominal solids content of 15% by weight is available as NALCO2326 from Nalco Company.Other useful commercially available silica sols include those available as NALCO1115 and NALCO1130 from Nalco Company, as REMASOL SP30 from Remet Corp. (Utica, NY), and as LUDOX SM from W.R. Grace & Co. Other suitable silica particles include fumed silica. Agglomerated silica particles are commercially available, for example, from Degussa, Cabot Corp. or Wacker under the product names AEROSIL, CAB-O-SIL, and HDK. The specific surface area of ​​hydrophobic fumed silica is typically less than 100 m. 2 / g~300m 2 / g or 150m 2 / g~250m 2 / g. If desired, a mixture of different fumed silicas can be used. For example, a mixture of fumed silica whose surface has been treated with a hydrophobic surface treatment agent and fumed silica whose surface has been treated with a hydrophilic surface treatment agent can be used. Suitable nanosilicas comprising aggregated nano-sized particles can be produced, for example, according to the process described in U.S. Pat. No. 6,730,156 (Zhang et al., Preliminary Example A).

[0128] Suitable alumina particles include, for example, but are not limited to, aqueous alumina dispersions (e.g., alumina particles having an average particle size of 500 nm available from Sumitomo Chemical (New York, NY)) and alumina particles manufactured by Saint-Gobain Surface Conditioning Group (Anaheim, CA).

[0129] Suitable yttria particles include, for example, but are not limited to, yttrium oxide available from Treibacher Industrie AG (Althofen, Austria).

[0130] Suitable ceria oxide particles include, for example, but are not limited to, colloidal cerium oxide in the form of colloidal sol and nanostructured powder available from NYACOL Nano Technologies, Inc. (Ashland, Mass.). For example, NYACOL CDP has a particle size of 25 nm to 30 nm and is a dispersible ceria powder, while NYACOL Ce120 / 10 is a colloidal ceria with a particle size of 100 nm to 140 nm and water as the carrier.

[0131] In some embodiments, the photopolymerizable slurry or sol comprises 20 wt% or more, 21 wt% or more, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, 32 wt%, or 35 wt% or more ceramic particles based on the total weight of the photopolymerizable slurry or sol, and 60 wt% or less, 29.5 wt% or less, 28.5 wt% or less, 27.5 wt% or less, 26.5 wt% or less, 25.5 wt% or less, or 24.5 wt% or less ceramic particles based on the total weight of the photopolymerizable slurry or sol. In other words, the photopolymerizable slurry or sol can comprise between 20 wt% and 60 wt% ceramic particles based on the total weight of the photopolymerizable slurry or sol.

[0132] In some embodiments, the photopolymerizable slurry or sol contains 3 volume percent (vol.%) or more of ceramic particles, 4 vol.%, 5 vol.%, 6 vol.%, 7 vol.%, 8 vol.%, 9 vol.%, 10 vol.%, 11 vol.%, 12 vol.%, 13 vol.%, 14 vol.%, 15 vol.%, 17 vol.%, 19 vol.%, 21 vol.%, 23 vol.%, 25 vol.%, or 29 vol.% or more of ceramic particles, based on the total volume of the photopolymerizable slurry or sol, and 45 vol.%, 44 vol.%, 42 vol.%, 40 vol.%, 38 vol.%, 36 vol.%, 34 vol.%, 32 vol.%, or 30 vol.% or less of ceramic particles, based on the total volume of the photopolymerizable slurry or sol. In other words, the photopolymerizable slurry or sol may contain, for example, 3 vol.% to 45 vol.%, 5 vol.% to 45 vol.%, or 10 vol.% to 45 vol.% of ceramic particles, based on the total volume of the photopolymerizable slurry or sol.

[0133] The ceramic particles typically have an average (mean) particle size (i.e., D) of 1 nanometer (nm) or greater, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 12 nm, 15 nm, 17 nm, 20 nm, 25 nm, 30 nm, 40 nm, 50 nm, 60 nm, 75 nm, 90 nm, 100 nm, 125 nm, 150 nm, 175 nm, 200 nm, 225 nm, 250 nm, 350 nm, 500 nm, 750 nm, 1 micrometer, 1.25 micrometers, 1.5 micrometers, 1.75 micrometers, 2 micrometers, 2.5 micrometers, 3.0 micrometers, 3.5 micrometers, 4.0 micrometers, or 4.5 micrometers or greater. 50 ), and 10 micrometers or less, 9.5 micrometers, 9 micrometers, 8.5 micrometers, 8 micrometers, 7.5 micrometers, 7 micrometers, 6.5 micrometers, 6 micrometers, 5.5 micrometers, 5 micrometers, 4.5 micrometers, 3 micrometers, 2 micrometers, 1.5 micrometers, 1 micrometer, 900 nm, 800 nm, 700 nm, 600 nm, 500 nm, 400 nm, 300 nm or 250 nm or less D 50In other words, the ceramic particles have an average particle size (D) of 1 nm to 900 nm, 1 nm to 500 nm, 1 nm to 250 nm, 250 nm to 10 micrometers, 1 micrometer to 10 micrometers, 500 nanometers to 1.5 micrometers, or 250 nm to 1 micrometer. 50 ) can have a mean (average) particle size (D 50 ) refers to the particle diameter at which 50% by volume of the particles in a distribution of particles have a diameter at or below which they are measured by laser diffraction. Preferably, the average particle size is the primary particle.

[0134] sintering aids The photopolymerizable composition of the present disclosure optionally contains at least one sintering aid. Often, the sintering aid assists by removing oxygen during the sintering process. Similarly, the sintering aid may cause the phase to melt from solid to liquid at a lower temperature than the ceramic material, or may improve the transport of ceramic ions, thereby providing some alternative mechanism for increasing densification compared to compositions that do not contain a sintering aid.

[0135] Suitable sintering aids are not particularly limited and may include rare earth oxides, alkaline earth oxides, alkali oxides, and combinations thereof. Materials that form liquids at the sintering temperature of the ceramic particles may be useful.

[0136] Examples of rare earth oxides include cerium oxide (e.g., CeO2), dysprosium oxide (e.g., Dy2O3), erbium oxide (e.g., Er2O3), europium oxide (e.g., Eu2O3), gadolinium oxide (e.g., Gd2O3), holmium oxide (e.g., Ho2O3), lanthanum oxide (e.g., La2O3), lanthanum aluminum oxide (LaAlO3), lutetium oxide (e.g., Lu2O3), neodymium oxide (e.g., Nd2O3), and praseodymium oxide (e.g., Pr6O 11), samarium oxide (e.g., Sm2O3), terbium oxide (e.g., Tb2O3), thorium oxide (e.g., Th4O7), thulium oxide (e.g., Tm2O3), ytterbium oxide (e.g., Yb2O3), and yttrium oxide (e.g., YO3), and combinations thereof.

[0137] Alkaline earth oxides include barium oxide (BaO), calcium oxide (CaO), strontium oxide (SrO), magnesium oxide (MgO) and beryllium oxide (BeO) and combinations thereof.

[0138] Alkali oxides include lithium oxide (Li2O2), sodium oxide (Na2O2), potassium oxide (K2O), rubidium oxide (Rb2O) and cesium oxide (Cs2O) and combinations thereof.

[0139] In some embodiments, mixtures of alkaline earth oxides and rare earth oxides, such as a combination of aluminum oxide and yttrium oxide, are preferred.

[0140] Additional suitable sintering aids include, for example, but are not limited to, boron, carbon, magnesium, aluminum, silicon, titanium, vanadium, chromium, iron, nickel, copper, aluminum nitride, alumina, yttria, ethyl silicate, sodium silicate including Mg(NO3)2, other glasses, Fe2O3, MgF2, and combinations thereof.

[0141] In some embodiments, suitable sintering aids include aluminum oxide, yttrium oxide, zirconium oxide, silicon oxide, titanium oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, lithium oxide, sodium oxide, potassium oxide, carbon, boron, boron carbide, aluminum, aluminum nitride, or combinations thereof. For example, suitable commercially available sintering aids include sintered alumina from Almatis (Ludwigshafen, Germany) and yttrium oxide from Treibacher Industrie AG (Althofen, Austria).

[0142] coloring agent The photopolymerizable composition according to the present disclosure may further comprise one or more inorganic colorants. The nature and structure of the inorganic colorants are not particularly limited, provided that the desired results can be achieved. In a preferred embodiment, the metal ions are not free salts, but rather are incorporated into the ceramic particles. Up to 30 mol%, up to 25 mol%, up to 20 mol%, up to 10 mol%, up to 5 mol%, up to 2 mol%, or up to 1 mol% of the ceramic particles can be Y2O3, La2O3, Al2O3, CeO2, Pr2O3, Nd2O3, Pm2O3, Sm2O3, Eu2O3, Gd2O3, Tb2O3, Dy2O3, Ho2O3, Er2O3, Tm2O3, Yb2O3, Fe2O3, MnO2, Co2O3, Cr2O3, NiO, CuO, V2O3, Bi2O3, Ga2O3, Lu2O3, HfO2, or mixtures thereof. Inorganic oxides such as Fe2O3, MnO2, Co2O3, Cr2O3, NiO, CuO, Ga2O3, Er2O3, Pr2O3, Eu2O3, Dy2O3, Sm2O3, V2O3, or W2O3 may be added, for example, to change the color of the ceramic article produced.

[0143] When the slurry or sol is to be used to produce dental or orthodontic articles, the following inorganic colorants have been found to be useful: Mn, Fe, Cu, Pr, Nd, Sm, Eu, Tb, Dy, Er, Bi, and mixtures thereof, preferably Er, Tb, Mn, Bi, Nd, or salts of Fe, Pr, Co, Cr, or V, Cu, Eu, Sm, D, with Er, Tb, Mn, Bi, Nd sometimes being particularly preferred. The inclusion of a colorant may be particularly desirable when the ceramic particles comprise zirconia.

[0144] When present, the inorganic colorant is present in an amount of at least 0.001 mol %, at least 0.005 mol %, or at least 0.01 mol %, and at most 0.02 mol %, at most 0.05 mol %, or at most 0.5 mol %, based on the number of moles of coloring ions present in the colorant and relative to the total number of moles of inorganic oxides in the ceramic particles.

[0145] solvent In many embodiments, photopolymerizable slurries or sols according to the present disclosure further comprise at least one solvent (e.g., organic or aqueous). Suitable solvents are typically selected to be miscible with water. Furthermore, these solvents are often selected to be soluble in supercritical carbon dioxide or liquid carbon dioxide. The molecular weight of the solvent is typically at least 25 grams per mole (g / mol), 30 g / mol, 40 g / mol, 45 g / mol, 50 g / mol, 75 g / mol, or at least 100 g / mol. The molecular weight can be up to 300 g / mol, 250 g / mol, 225 g / mol, 200 g / mol, 175 g / mol, or up to 150 g / mol. The molecular weight is often in the range of 25-300 g / mol, 40-300 g / mol, 50-200 g / mol, or 75-175 g / mol. It is particularly preferred that the one or more solvents have a boiling point above the temperatures used during the additive manufacturing process to minimize solvent evaporation from the sol, slurry, or gelled article. For example, at least one solvent having a boiling point of 150° C. or higher, 160° C., 170° C., 180° C., or 190° C. or higher can be used.

[0146] In certain embodiments, the amount of one or more solvents in the photopolymerizable slurry or sol is 10 wt.% or more, 15 wt.%, 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, 40 wt.%, or 45 wt.% or more, based on the total weight of the photopolymerizable slurry or sol, and 70 wt.% or less, 65 wt.%, 60 wt.%, 55 wt.%, or 50 wt.% or less, based on the total weight of the photopolymerizable slurry or sol. In other words, the photopolymerizable slurry or sol can contain 10 to 70 wt.% solvent, or 20 to 50 wt.% solvent, based on the total weight of the photopolymerizable slurry or sol. Advantageously, in certain embodiments, the presence of a solvent can help maintain the pore structure in the article for removal of organic materials from the article.

[0147] Suitable solvents include, but are not limited to, diethylene glycol monomethyl ether, ethanol, 1-methoxy-2-propanol (i.e., methoxypropanol), isopropanol, ethylene glycol, N,N-dimethylacetamide, N-methylpyrrolidone, water, and combinations thereof. Suitable solvents are often glycols or polyglycols, mono-ether glycols or mono-ether polyglycols, di-ether glycols or di-ether polyglycols, ether ester glycols or ether ester polyglycols, carbonates, amides, or sulfoxides (e.g., dimethyl sulfoxide). Solvents typically have one or more polar groups. Organic solvents do not have polymerizable groups. That is, (e.g., organic) solvents do not contain groups capable of undergoing free radical polymerization. Furthermore, the components of the solvent medium do not have polymerizable groups capable of undergoing free radical polymerization.

[0148] In some embodiments, the solvent contains less than 15% water by weight, less than 10% water, less than 5% water, less than 3% water, less than 2% water, less than 1% by weight, or even less than 0.5% water by weight.

[0149] Suitable glycols or polyglycols, monoether glycols or monoether polyglycols, diether glycols or diether polyglycols, and ether ester glycols or ether ester polyglycols are often of formula (I).

[0150] [ka] In formula (I), R 1 are each independently hydrogen, alkyl, aryl, or acyl. Suitable alkyl groups often have 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms. Suitable aryl groups often have 6 to 10 carbon atoms and are often phenyl or phenyl substituted with an alkyl group having 1 to 4 carbon atoms. Suitable acyl groups often have the formula -(CO)R 3 (In the formula, R 3 is alkyl having 1 to 10 carbon atoms, 1 to 6 carbon atoms, 1 to 4 carbon atoms, 2 carbon atoms, or 1 carbon atom). Acyl is often an acetate group (—(CO)CH3). In formula (I), R 2 are typically ethylene or propylene, respectively. The variable n is at least 1 and can range from 1 to 10, 1 to 6, 1 to 4, or 1 to 3.

[0151] The glycol or polyglycol of formula (I) has two R groups equal to hydrogen. 1 Examples of glycols include, but are not limited to, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, and tripropylene glycol.

[0152] The monoether glycol or monoether polyglycol of formula (I) has a first R equal to hydrogen. 1 group, and a second R equal to alkyl or aryl. 1Examples of monoether glycols or monoether polyglycols include, but are not limited to, ethylene glycol monohexyl ether, ethylene glycol monophenyl ether, propylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tripropylene glycol monomethyl ether, and tripropylene glycol monobutyl ether.

[0153] The di-ether glycol or di-ether polyglycol of formula (I) comprises two R groups equal to alkyl or aryl. 1 Examples of di-ether glycols or di-ether polyglycols include, but are not limited to, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, dipropylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and pentaethylene glycol dimethyl ether.

[0154] The ether ester glycol or ether ester polyglycol of formula (I) comprises a first R equal to alkyl or aryl. 1 group, and a second R equal to acyl 1 Examples of ether ester glycols or ether ester polyglycols include, but are not limited to, ethylene glycol butyl ether acetate, diethylene glycol butyl ether acetate, and diethylene glycol ethyl ether acetate.

[0155] Other suitable solvents are carbonates of formula (II).

[0156] [ka] In formula (II), R 4 is hydrogen or alkyl, such as alkyl having 1 to 4 carbon atoms, 1 to 3 carbon atoms, or 1 carbon atom. Examples include ethylene carbonate and propylene carbonate.

[0157] Yet other suitable solvents are amides of formula (III).

[0158] [ka] In formula (III), the group R 5 is hydrogen, alkyl, or R 6 Together with R 5 Carbonyl and R bonded to 6 The group R forms a five-membered ring containing the nitrogen atom bonded to 6 is hydrogen, alkyl, or R 5 Together with R 5 Carbonyl and R bonded to 6 The group R forms a five-membered ring containing the nitrogen atom bonded to 7 is hydrogen or alkyl. 5 , R 6 and R 7 Suitable alkyl groups have 1 to 6 carbon atoms, 1 to 4 carbon atoms, 1 to 3 carbon atoms, or 1 carbon atom. Examples of amide organic solvents of formula (III) include, but are not limited to, formamide, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N-methyl-2-pyrrolidone, and N-ethyl-2-pyrrolidone.

[0159] Furthermore, in certain embodiments, the photopolymerizable slurry or sol further comprises a dispersing agent to aid in the dispersion of ceramic particles in the photopolymerizable slurry or sol. Typically, the one or more dispersing agents can be present in the photopolymerizable slurry or sol in an amount of at least 0.5 wt%, at least 0.55 wt%, at least 0.60 wt%, at least 0.65 wt%, or at least 0.70 wt%, based on the total weight of the photopolymerizable slurry or sol, and at most 5.0 wt%, at most 4.0 wt%, at most 3.0 wt%, at most 2.0 wt%, at most 1.0 wt%, at most 0.95 wt%, at most 0.90 wt%, at most 0.85 wt%, at most 0.80 wt%, or at most 0.75 wt%, based on the total weight of the photopolymerizable slurry or sol. In other words, the optional dispersing agent can be present in an amount of 0.5 wt% to 5.0 wt%, based on the total weight of the photopolymerizable slurry or sol. Suitable dispersants include, for example, but are not limited to, dispersants available under the trade name SOLPLUS or SOLSPERSE from Lubrizol (Wickliffe, Ohio), such as SOLPLUS D510, R700, R720, D540, D545 and D570, SOLSPERSE 20000, S71000, M387, M389, S41000 and S79000, and combinations thereof.

[0160] Radiation-curable monomers The photopolymerizable slurries or sols described herein include one or more radiation curable monomers that are part of or form an organic matrix.

[0161] The radiation-curable monomers present in the photopolymerizable slurry or sol can be described as first, second, third, etc. monomers. The nature and structure of the radiation-curable monomers are not particularly limited, provided that the desired results cannot be achieved. In some embodiments, at least one radiation-curable monomer comprises an acrylate. Preferably, at least one radiation-curable monomer comprises a (meth)acrylate, an epoxy, a silane, or a combination thereof.

[0162] In some embodiments, the radiation curable monomer, upon polymerization, forms a network with (preferably) uniformly dispersed ceramic particles.

[0163] According to one embodiment, the photopolymerizable slurry or sol contains a polymerizable surface modifier as the first monomer. Optionally, at least a portion of the ceramic particles in the photopolymerizable slurry or sol may include a surface modifier attached to the surface of the ceramic particles. The surface modifier may help improve the compatibility of the particles contained in the slurry or sol with the organic matrix material also present in the slurry or sol. The surface modifier may be represented by the formula AB, where the A group is capable of attaching to the surface of the ceramic particles and the B group is radiation-curable.

[0164] The A group can be bonded to the surface of the ceramic particle by adsorption, ionic bond formation, covalent bond formation, or a combination thereof. Examples of suitable A group moieties include acidic moieties (such as carboxylic acid groups, phosphate groups, sulfonic acid groups, and their anions) and silanes. The B group includes a radiation-curable moiety. Examples of suitable B group moieties include vinyl, especially acrylic or methacrylic moieties.

[0165] Suitable surface modifiers include polymerizable carboxylic acids and / or anions thereof, polymerizable sulfonic acids and / or anions thereof, polymerizable phosphoric acids and / or anions thereof, and polymerizable silanes. Suitable surface modifiers are further described, for example, in WO 2009 / 085926 (Kolb et al.), the disclosure of which is incorporated herein by reference.

[0166] Examples of radically polymerizable surface modifiers are those containing an acidic moiety or anion thereof, such as a carboxylic acid group. Exemplary acidic radically polymerizable surface modifiers include acrylic acid, methacrylic acid, beta-carboxyethyl acrylate, and mono-2-(methacryloxyethyl) succinate.

[0167] Exemplary radical polymerizable surface modifiers can be reaction products of polymerizable hydroxyl-containing monomers with cyclic anhydrides such as succinic anhydride, maleic anhydride, and phthalic anhydride. Exemplary polymerizable hydroxyl-containing monomers include hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate. Acryloxy- and methacryloxy-functional polyethylene oxides and polypropylene oxides may also be used as polymerizable hydroxyl-containing monomers.

[0168] An exemplary radically polymerizable surface modifier for imparting both polarity and reactivity to ceramic nanoparticles is mono(methacryloxypolyethylene glycol) succinate.

[0169] Another example of a radical polymerizable surface modifier is a polymerizable silane. Exemplary polymerizable silanes include methacryloxyalkyltrialkoxysilanes or acryloxyalkyltrialkoxysilanes (e.g., 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, and 3-(methacryloxy)propyltriethoxysilane); methacryloxyalkylalkyldialkoxysilanes or acryloxyalkylalkyldialkoxysilanes (e.g., 3-(methacryloxy)propylmethyldimethoxysilane and 3-(acryloxypropyl)methyldimethoxysilane); methacryloxyalkyl-dialkyl-alkoxysilanes or acryloxyalkyl-alkoxysilanes (e.g., 3-(methacryloxy)propylmethyldimethoxysilane and 3-(acryloxypropyl)methyldimethoxysilane); mercapto-alkyl-trialkoxysilanes (e.g., 3-mercaptopropyltrimethoxysilane); aryltrialkoxysilanes (e.g., styrylethyltrimethoxysilane); vinylsilanes (e.g., vinylmethyldiacetoxysilane, vinyldimethylethoxysilane, vinylmethyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, vinyltriisopropoxysilane, and vinyltris(2-methoxyethoxy)silane).

[0170] The surface modifier can be added to the ceramic particles using conventional techniques. The organic matrix can be added before, after, or simultaneously with the surface modification. Various methods of adding the surface modifier are further described, for example, in WO 2009 / 085926 (Kolb et al.), the disclosure of which is incorporated herein by reference.

[0171] The surface modification reaction can be carried out at room temperature (e.g., 20°C to 25°C) or at elevated temperatures (e.g., up to 95°C). When the surface modifier is an acid, such as a carboxylic acid, the ceramic particles can typically be surface modified at room temperature. When the surface modifier is a silane, the ceramic particles can typically be surface modified at elevated temperatures.

[0172] The optional first monomer can function as a polymerizable surface modifier. Multiple first monomers can be used. The first monomer can be the only type of surface modifier or can be combined with one or more other non-polymerizable surface modifiers. In some embodiments, the amount of the first monomer is at least 20% by weight, based on the total weight of the polymerizable material (radiation-curable monomer). For example, when present, the amount of the first monomer is often at least 25%, at least 30%, at least 35%, or at least 40% by weight. The amount of the first monomer can be up to 100%, up to 90%, up to 80%, up to 70%, up to 60%, or up to 50% by weight. Some photopolymerizable slurries or sols contain 20% to 100%, 20% to 80%, 20% to 60%, 20% to 50%, or 30% to 50% by weight of the first monomer, based on the total weight of the polymerizable material.

[0173] The optional first monomer (i.e., polymerizable surface modifier) ​​can be the only monomer in the polymerizable material or may be combined with one or more second monomers, as described in more detail below.

[0174] According to one embodiment, the photopolymerizable slurry or sol includes one or more second monomers containing at least one or two radiation-curable moieties. In particular, second monomers containing at least two radiation-curable moieties may act as crosslinkers during the gel-forming process. Any suitable second monomer without a surface-modifying group can be used. The second monomer does not have a group capable of bonding to the surface of the ceramic particles. That is, the optional second monomer does not have a carboxylic acid group or a silyl group. The second monomer is often a polar monomer (e.g., a non-acidic polar monomer), a monomer with multiple polymerizable groups, an alkyl (meth)acrylate, or a mixture thereof.

[0175] Successful builds typically require a specific level of gel strength and shape resolution, and adding a second monomer containing at least two radiation-curable moieties to the photopolymerizable slurries or sols described herein can help optimize both properties. Crosslinking techniques often allow for greater gel strength to be achieved at lower energy doses, as polymerization creates a stronger network. In some cases, higher energy doses are applied to increase layer adhesion in non-crosslinked systems. While articles are successfully built, higher energy often impacts the resolution of the final article, potentially causing overbuilding, especially in highly translucent materials where light and, with it, cure depth can penetrate further into the material. The presence of monomers with multiple polymerizable groups tends to increase the strength of the gel composition formed when the photopolymerizable slurry or sol is polymerized. The amount of monomers with multiple polymerizable groups can be used to adjust the flexibility and strength of the gelled body, indirectly optimizing the resolution of the gelled body and the resolution of the final article. Such gel compositions can be more easily processed without cracking, and the increased gel strength aids in the robustness of post-construction procedures when the gel is converted into a fully dense ceramic.

[0176] In many embodiments, the second monomer comprises a monomer having multiple polymerizable groups. The number of polymerizable groups can be in the range of 2 to 6, or even more. In many embodiments, the number of polymerizable groups is in the range of 2 to 5 or 2 to 4. The polymerizable groups are typically (meth)acryloyl groups.

[0177] Exemplary monomers having two (meth)acryloyl groups include 1,2-ethanediol diacrylate, 1,3-propanediol diacrylate, 1,9-nonanediol diacrylate, 1,12-dodecanediol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, butylene glycol diacrylate, bisphenol A diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, tripropylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, polyethylene / polypropylene copolymer diacrylate, polybutadiene di(meth)acrylate, propoxylated glycerin tri(meth)acrylate, and neopentyl glycol hydroxypivalate diacrylate modified caprolactone.

[0178] Exemplary monomers having three or four (meth)acryloyl groups include, but are not limited to, trimethylolpropane triacrylate (e.g., Cytec and from Sartomer (Exton, PA, USA) under the trade name SR-351), pentaerythritol triacrylate (e.g., commercially available from Sartomer under the trade name SR-444), ethoxylated (3) trimethylolpropane triacrylate (e.g., commercially available from Sartomer under the trade name SR-454), ethoxylated (4) pentaerythritol tetraacrylate (e.g., commercially available from Sartomer under the trade name SR-494), tris(2-hydroxyethyl isocyanurate) triacrylate (e.g., commercially available from Sartomer under the trade name SR-368), a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (e.g., commercially available from Cytec Examples of suitable acrylates include those commercially available from Epson Industries, Inc. under the trade name PETIA, which has a tetraacrylate to triacrylate ratio of approximately 1:1, and those commercially available from Epson Industries, Inc. under the trade name PETA-K, which has a tetraacrylate to triacrylate ratio of approximately 3:1; pentaerythritol tetraacrylate (e.g., commercially available from Sartomer under the trade name SR-295); and di-trimethylolpropane tetraacrylate (e.g., commercially available from Sartomer under the trade name SR-355).

[0179] Exemplary monomers having five or six (meth)acryloyl groups include, but are not limited to, dipentaerythritol pentaacrylate (e.g., commercially available from Sartomer under the trade name SR-399) and hexafunctional urethane acrylate (e.g., commercially available from Sartomer under the trade name CN975).

[0180] In some embodiments, the radiation-curable monomer comprises an epoxy. Suitable epoxy compounds for use as photopolymerizable slurries or sols include, but are not limited to, cycloaliphatic oxiranes, aliphatic oxiranes, aromatic oxiranes, or combinations thereof. These compounds, commonly known as epoxy compounds, can be monomers, polymers, or mixtures thereof. These materials generally have, on average, at least one polymerizable epoxy group (oxirane unit) per molecule, preferably at least about 1.5 polymerizable epoxy groups per molecule. Polymeric epoxides include linear polymers with terminal epoxy groups (e.g., diglycidyl ethers of polyoxyalkylene glycols), polymers with backbone oxirane units (e.g., polybutadiene polyepoxides), and polymers with pendant epoxy groups (e.g., glycidyl methacrylate polymers or copolymers). Epoxides can be pure compounds or mixtures containing one, two, or more epoxy groups per molecule. The "average" number of epoxy groups per molecule is determined by dividing the total number of epoxy groups in the epoxy-containing material by the total number of epoxy molecules present. The epoxy compounds can have a molecular weight of from about 58 to about 100,000 or more.

[0181] Suitable epoxy compounds include those containing cyclohexene oxide groups, such as epoxycyclohexanecarboxylates, for example, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-2-methylcyclohexylmethyl-3,4-epoxy-2-methylcyclohexanecarboxylate, and bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate. A more detailed list of useful epoxides of this nature is provided in U.S. Pat. No. 3,117,099 (Proops et al.).

[0182] Suitable epoxy compounds also include glycidyl ether compounds, such as glycidoxy alkyl and glycidoxy aryl compounds containing 1 to 6 glycidoxy groups. Examples include glycidyl ethers of polyhydric phenols, which can be obtained by reacting a polyhydric phenol with an excess of epichlorohydrin to obtain, for example, 2,2-bis(2,3-epoxypropoxyphenyl)propane. Additional epoxides of this type are described in U.S. Pat. No. 3,018,262 (Schroeder) and "Handbook of Epoxy Resins" by Lee and Neville, McGraw-Hill Book Co., New York (1967). Many suitable epoxy compounds are commercially available and are listed in U.S. Pat. No. 6,187,833 (Oxman et al.).

[0183] Some photopolymerizable slurry or sol compositions contain 0 to 80% by weight of a second monomer having multiple polymerizable groups, based on the total weight of the polymerizable material. For example, the amount can range from 10 to 80%, 20 to 80%, 30 to 80%, 40 to 80%, 10 to 70%, 10 to 50%, 10 to 40%, or 10 to 30% by weight.

[0184] The overall composition of the polymerizable material is often selected so that the polymerized material is soluble in the solvent medium. Uniformity of the organic phase is often preferred to avoid phase separation of the organic components in the gel composition. This tends to result in the formation of smaller and more uniform pores (pores with a narrower size distribution) in the subsequently formed aerogel or xerogel. Furthermore, the overall composition of the polymerizable material can be selected to adjust compatibility with the solvent medium and to adjust the strength, flexibility, and uniformity of the gel composition. Furthermore, the overall composition of the polymerizable material can be selected to adjust the burnout characteristics of the organic material prior to sintering.

[0185] In some embodiments, the optional second monomer is a polar monomer. As used herein, the term "polar monomer" refers to a monomer having a free-radically polymerizable group and a polar group. The polar group is typically non-acidic and often contains a hydroxyl group, a primary amide group, a secondary amide group, a tertiary amide group, an amino group, or an ether group (i.e., a group containing at least one alkylene-oxy-alkylene group of the formula -ROR, where each R is an alkylene having 1 to 4 carbon atoms).

[0186] Suitable optional polar monomers having a hydroxyl group include, but are not limited to, hydroxyalkyl (meth)acrylates (e.g., 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate), and hydroxyalkyl (meth)acrylamides (e.g., 2-hydroxyethyl (meth)acrylamide or 3-hydroxypropyl (meth)acrylamide), ethoxylated hydroxyethyl (meth)acrylates (e.g., monomers commercially available from Sartomer under the trade names CD570, CD571, and CD572), and aryloxy-substituted hydroxyalkyl (meth)acrylates (e.g., 2-hydroxy-2-phenoxypropyl (meth)acrylate).

[0187] Exemplary polar monomers having a primary amide group include (meth)acrylamide. Exemplary polar monomers having a secondary amide group include, but are not limited to, N-alkyl(meth)acrylamides such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-tert-octyl(meth)acrylamide, and N-octyl(meth)acrylamide. Exemplary polar monomers having a tertiary amide group include, but are not limited to, N-vinylcaprolactam, N-vinyl-2-pyrrolidone, (meth)acryloylmorpholine, and N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, and N,N-dibutyl(meth)acrylamide.

[0188] The polar monomer having an amino group includes various N,N-dialkylaminoalkyl(meth)acrylates and N,N-dialkylaminoalkyl(meth)acrylamides. Examples include, but are not limited to, N,N-dimethylaminoethyl(meth)acrylate, N,N-dimethylaminoethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylate, N,N-dimethylaminopropyl(meth)acrylamide, N,N-diethylaminoethyl(meth)acrylate, N,N-diethylaminoethyl(meth)acrylamide, N,N-diethylaminopropyl(meth)acrylate and N,N-diethylaminopropyl(meth)acrylamide.

[0189] Exemplary polar monomers having an ether group include, but are not limited to, alkoxylated alkyl (meth)acrylates such as ethoxyethoxyethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, and 2-ethoxyethyl (meth)acrylate, and poly(alkylene oxide) (meth)acrylates such as poly(ethylene oxide) (meth)acrylate and poly(propylene oxide) (meth)acrylate. Poly(alkylene oxide) acrylates are often referred to as poly(alkylene glycol) (meth)acrylates. These monomers can have any suitable terminal group, such as a hydroxyl group or an alkoxy group. For example, if the terminal group is a methoxy group, the monomer can be referred to as a methoxypoly(ethylene glycol) (meth)acrylate.

[0190] Suitable alkyl (meth)acrylates that can be used as the second monomer can have alkyl groups with linear, branched, or cyclic structures. Examples of suitable alkyl (meth)acrylates include, but are not limited to, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, 2-methylbutyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 4-methyl-2-pentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-methylhexyl (meth)acrylate, n-octyl (meth)acrylate, and isooctyl (meth)acrylate. (meth)acrylate, 2-octyl (meth)acrylate, isononyl (meth)acrylate, isoamyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, isobornyl (meth)acrylate, 2-propylheptyl (meth)acrylate, isotridecyl (meth)acrylate, isostearyl (meth)acrylate, octadecyl (meth)acrylate, 2-octyldecyl (meth)acrylate, dodecyl (meth)acrylate, lauryl (meth)acrylate and heptadecanyl (meth)acrylate. In some embodiments, the alkyl (meth)acrylate is a mixture of various isomers having the same number of carbon atoms, as described in PCT Patent Application Publication No. 2014 / 151179 (Colby et al.). For example, an isomeric mixture of octyl (meth)acrylate can be used.

[0191] The amount of the second monomer, which is a polar monomer and / or an alkyl (meth)acrylate monomer, is often in the range of 0% to 40%, 0% to 35%, 0% to 30%, 5% to 40%, or 10 to 40% by weight, based on the total weight of the polymerizable material.

[0192] The total amount of polymerizable material is often at least 10 wt%, at least 12 wt%, at least 15 wt%, or at least 18 wt%, based on the total weight of the photopolymerizable sol or slurry. The amount of polymerizable material can be up to 50 wt%, up to 40 wt%, up to 30 wt%, or up to 20 wt%, based on the total weight of the photopolymerizable sol or slurry. For example, the amount of polymerizable material can be in the range of 10 wt% to 50 wt%, 15 wt% to 40 wt%, 15 wt% to 30 wt%, or 10 wt% to 20 wt%, based on the total weight of the photopolymerizable sol or slurry.

[0193] In some embodiments, the polymerizable material contains 20% to 100% by weight of a first monomer and 0% to 80% by weight of a second monomer, based on the total weight of the polymerizable material. For example, the polymerizable material may contain 30% to 100% by weight of a first monomer and 0% to 70% by weight of a second monomer, 30% to 90% by weight of a first monomer and 10% to 70% by weight of a second monomer, 30% to 80% by weight of a first monomer and 20% to 70% by weight of a second monomer, 30% to 70% by weight of a first monomer and 30% to 70% by weight of a second monomer, 40% to 90% by weight of a first monomer and 10% to 60% by weight of a second monomer, 40% to 80% by weight of a first monomer and 20% to 60% by weight of a second monomer, 50% to 90% by weight of a first monomer and 10% to 50% by weight of a second monomer, or 60% to 90% by weight of a first monomer and 10% to 40% by weight of a second monomer.

[0194] In some embodiments, the polymerizable material contains 0% by weight of a first monomer and 100% by weight of a second monomer, based on the total weight of the polymerizable material.

[0195] Photoinitiator The photopolymerizable slurries or sols described herein typically further comprise one or more photoinitiators. In certain embodiments, the photoinitiator can be characterized as being soluble in the solvent contained in the slurry or sol and / or absorbing radiation in the range of 200 nm to 500 nm or 300 nm to 450 nm. The photoinitiator should be capable of starting or initiating the curing or hardening reaction of the radiation-curable components present in the photopolymerizable slurry or sol.

[0196] The following classes of photoinitiators can be used: a) two-component systems in which a radical is generated by abstraction of a hydrogen atom from a donor compound; b) one-component systems in which two radicals are generated by cleavage; and / or c) systems comprising an iodonium salt, a visible light sensitizer, and an electron donor compound.

[0197] Examples of photoinitiators according to type (a) typically contain a moiety selected from a benzophenone, a xanthone, or a quinone in combination with an aliphatic amine.

[0198] Examples of photoinitiators according to type (b) typically contain a moiety selected from benzoin ethers, acetophenones, benzoyl oximes, or acylphosphines. Suitable exemplary photoinitiators are available from IGM Resins (Waalwijk, The Netherlands) under the trade name OMNIRAD, including 1-hydroxycyclohexyl phenyl ketone (OMNIRAD 184), 2,2-dimethoxy-1,2-diphenylethan-1-one (OMNIRAD 651), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (OMNIRAD 819), 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propanol (OMNIRAD 820), 1-hydroxycyclohexylphenyl ketone (OMNIRAD 821), 2,2-dimethoxy-1,2-diphenylethan-1-one (OMNIRAD 822), 1-hydroxycyclohexylphenyl ketone (OMNIRAD 823), 2,2-dimethoxy-1,2-diphenylethan-1-one (OMNIRAD 824), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (OMNIRAD 825), 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propanol (OMNIRAD 826), 1-hydroxycyclohexylphenyl ketone (OMNIRAD 827), 1-hydroxycyclohexylphenyl ketone (OMNIRAD 828), 1-hydroxycyclohexylphenyl ketone (OMNIRAD 829 ... propan-1-one (OMNIRAD 2959), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone (OMNIRAD 369), 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (OMNIRAD 907), 2-hydroxy-2-methyl-1-phenylpropan-1-one (OMNIRAD 1173), 2,4,6-trimethylbenzoyldiphenylphosphine oxide (OMNIRAD TPO), and 2,4,6-trimethylbenzoylphenylphosphinate (OMNIRAD TPO-L). Further suitable photoinitiators include, for example but not limited to, oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone]ESACURE ONE (Lamberti SpA, Gallarate, Italy), 2-hydroxy-2-methylpropiophenone, benzil dimethyl ketal, 2-methyl-2-hydroxypropiophenone, benzoin methyl ether, benzoin isopropyl ether, anisoin methyl ether, aromatic sulfonyl chlorides, photoactive oximes, and combinations thereof.

[0199] Examples of photoinitiators according to type (c) typically contain the following moieties for each component: Suitable iodonium salts are described in U.S. Patent Nos. 3,729,313, 3,741,769, 3,808,006, 4,250,053, and 4,394,403, the disclosures of which are incorporated herein by reference. Iodonium salts include Cl - , Br - , I - or C4H5SO3 - Simple salts containing anions such as SbF5OH - or AsF6 -The iodonium salt may be a metal complex salt containing antimonate, arsenate, phosphate, or borate, such as . Mixtures of iodonium salts can be used if desired. For example, suitable iodonium salts include diphenyliodonium hexafluorophosphate and diphenyliodonium chloride, both of which are commercially available from Sigma-Aldrich (St. Louis, MO). The visible light sensitizer may be selected from ketones, coumarin dyes (e.g., ketocoumarins), xanthene dyes, acridine dyes, thiazole dyes, thiazine dyes, oxazine dyes, azine dyes, aminoketone dyes, porphyrins, aromatic polycyclic hydrocarbons, p-substituted aminostyryl ketone compounds, aminotriarylmethanes, merocyanines, squarylium dyes, and pyridinium dyes. Preferably, the visible light sensitizer is an alpha-diketone. Camphorquinone is particularly preferred and is commercially available from Sigma-Aldrich. The electron donor compound is typically an alkylaromatic polyether or an alkyl, arylamino compound, where the aryl group is substituted with one or more electron-withdrawing groups. Examples of suitable electron-withdrawing groups include carboxylic acids, carboxylic acid esters, ketones, aldehydes, sulfonic acids, sulfonates, and nitrile groups. The electron donor compound may be selected from polycyclic aromatic compounds (such as biphenylene, naphthalene, anthracene, benzanthracene, pyrene, azulene, pentacene, decacyclene, and derivatives (e.g., acenaphthene), as well as combinations thereof) and N-alkylcarbazole compounds (e.g., N-methylcarbazole). Preferred donor compounds include 4-dimethylaminobenzoic acid, ethyl 4-dimethylaminobenzoate, 3-dimethylaminobenzoic acid, 4-dimethylaminobenzoin, 4-dimethylaminobenzaldehyde, 4-dimethylaminobenzonitrile, and 1,2,4-trimethoxybenzene. Photoinitiators according to type (c) are described in detail, for example, in commonly owned US Pat. No. 6,187,833 (Oxman et al.).

[0200] The photoinitiator can be present in the photopolymerizable slurries or sols described herein in any amount, depending on the specific constraints of the additive manufacturing process. In some embodiments, the photoinitiator is present in the photopolymerizable slurry or sol in an amount of 0.005 wt.% or more, 0.01 wt.% or more, 0.05 wt.% or more, 0.1 wt.% or more, or 0.3 wt.% or more, and 5 wt.%, 4 wt.%, 3 wt.%, 2 wt.% or less, 1 wt.% or less, or 0.5 wt.% or less, based on the total weight of the photopolymerizable slurry or sol. In some cases, the photoinitiator is present in an amount of about 0.005 wt.% to 5 wt.% or 0.1 wt.% to 2 wt.% based on the total weight of the photopolymerizable slurry or sol.

[0201] Additionally, the photopolymerizable slurries or sols described herein can further include one or more sensitizers to improve the effectiveness of one or more photoinitiators that may also be present. In some embodiments, the sensitizer includes isopropylthioxanthone (ITX) or 2-chlorothioxanthone (CTX). Other sensitizers can also be used. When used in the photopolymerizable composition, the sensitizer can be present in an amount of about 0.001 wt. % or more, 0.01 wt. % or more, or about 1 wt. % or more, based on the total weight of the photopolymerizable slurry or sol.

[0202] inhibitors The photopolymerizable slurries or sols described herein also optionally contain one or more polymerization inhibitors (e.g., photoinhibitors). Polymerization inhibitors are often included in photopolymerizable slurries or sols to provide additional thermal or photostability to the composition. Inhibitors can extend the shelf life of the photopolymerizable slurries or sols, help prevent undesirable side reactions, and regulate the polymerization process of radiation-curable components present in the slurries or sols. Adding one or more inhibitors to the photopolymerizable slurries or sols can further help improve the surface precision or detail resolution of ceramic articles. Specific examples of inhibitors that can be used include p-methoxyphenol (MOP), hydroquinone monomethyl ether (MEHQ), 2,6-di-tert-butyl-4-methyl-phenol (BHT; Ionol), phenothiazine, 2,2,6,6-tetramethyl-piperidine-1-oxyl radical (TEMPO), and mixtures thereof.

[0203] In some embodiments, the polymerization inhibitor, if used, is present in an amount of about 0.001% to 5%, 0.001% to 1%, or 0.01 to 1% by weight, based on the total weight of the photopolymerizable slurry or sol.

[0204] The photopolymerizable slurries or sols described herein can also include one or more absorption modifiers (e.g., dyes, optical brighteners, pigments, etc.) to control the penetration depth of actinic radiation. One suitable optical brightener is Tinopal OB, benzoxazole, 2,2'-(2,5-thiophenediyl)bis[5-(1,1-dimethylethyl)], available from BASF Corporation (Florham Park, NJ). When used, the absorption modifier can be present in an amount of about 0.001% to 5%, about 0.01% to 1%, about 0.1% to 3%, or about 0.1% to 1% by weight, based on the total weight of the photopolymerizable slurry or sol.

[0205] Slurries and sols The preparation of the photopolymerizable slurry or sol is usually carried out under light-limiting conditions to avoid undesired premature polymerization. In some embodiments, the photopolymerizable slurry or sol is prepared by high-speed mixing of the components to preferably form a homogeneous slurry or sol. The slurry or sol is usually stored in a suitable device such as a vessel, bottle, cartridge, or container before use.

[0206] The photopolymerizable slurry or sol (e.g., uncured) has a viscosity profile consistent with the requirements and parameters of one or more additive manufacturing devices (e.g., 3D printing systems). In certain embodiments, the photopolymerizable slurry or sol exhibits a dynamic viscosity at 23 degrees Celsius of 500 millipascal-seconds (mPa·s) or less, 400 mPa·s, 300 mPa·s, 200 mPa·s, 100 mPa·s, 50 mPa·s, or 25 mPa·s or less. In some examples, the photopolymerizable slurry or sol described herein, before curing, exhibits a dynamic viscosity of 1 mPa·s to 500 mPa·s, 1 mPa·s to 100 mPa·s, or 1 mPa·s to 50 mPa·s using a Brookfield DV-E viscometer (Brookfield Engineering Laboratories, Middleboro, MA) using a disk and cylinder spindle at 23 degrees Celsius and a shear rate of 2 1 / s to 20 1 / s. In some cases, the photopolymerizable compositions described herein, before curing, exhibit a dynamic viscosity of less than about 50 mPa·s.

[0207] The photopolymerizable slurry or sol containing ceramic particles is solidified by curing (e.g., gelation). Preferably, the gelation process allows the gel to be formed into any shape without cracking, resulting in a gelled body that can be further processed without inducing cracks. For example, the gelation step preferably results in a gelled body with a structure that does not collapse when the solvent is removed; a so-called "free-standing gel." The gel preferably contains a minimal amount of organic material or polymer modifier. After processing the photopolymerizable slurry or sol to form a gel, the gelled article is typically removed from the device used to carry out the additive manufacturing process. If desired, the surface of the gelled article is cleaned, for example, by rinsing with a solvent, immersing in a solvent, and / or subjecting the gelled article to a mass inertial force. Suitable solvents preferably include mixtures thereof or the same solvents described hereinabove.

[0208] As noted above, aerogels are porous materials derived from gels in which the liquid component of the gel has been replaced by a gas. Solvent removal (e.g., extraction) is often performed under supercritical conditions. This type of drying eliminates capillary effects, and linear shrinkage is often in the range of 0%-25%, 0%-20%, 0%-15%, 5%-15%, or 0%-10%. Density is typically uniform throughout the structure. In contrast, xerogels are three-dimensional solids derived from gels in which the liquid component of the gel has been removed (e.g., extracted) by evaporation under ambient conditions or at elevated temperatures.

[0209] In some embodiments, the gel structure is compatible with and stable in the various solvents and conditions that may be required for supercritical extraction. Furthermore, the gel structure should be compatible with the supercritical extraction fluid (e.g., supercritical carbon dioxide). In other words, the gel should be sufficiently stable and robust to withstand drying to produce a stable aerogel and / or xerogel, resulting in a material that can be heated to burn out the organics, pre-sintered, and densified without inducing cracking. Preferably, the resulting aerogel and / or xerogel have relatively small and uniform pore sizes, which aids in their sintering to high densities at low sintering temperatures. However, the pores are preferably large enough to allow the product gases of organic burnout to escape without causing cracking of the aerogel or xerogel. It is believed that the rapid nature of the gelation process results in a substantially uniform distribution of ceramic particles throughout the gel, which may aid in subsequent processing steps such as supercritical extraction, organic burnout, and sintering.

[0210] When applied, the supercritical drying process may be characterized by at least one, more or all of the following features: a) Temperature: 20℃~100℃, 30℃~80℃ or 15℃~150℃; b) Pressure: 5MPa~200MPa, 10MPa~100MPa, 1MPa~20MPa or 5MPa~15MPa; c) time: 2 hours to 175 hours, 5 hours to 25 hours, or 1 hour to 5 hours; and d) Extraction or drying medium: carbon dioxide in the supercritical stage.

[0211] Combinations of features (a), (b), (c) and (d) are sometimes preferred.

[0212] Supercritical extraction can remove all or most of the (e.g., organic) solvent in the printed gel article. In some embodiments, the aerogel contains some residual solvent. The residual solvent can be up to 6 wt. % based on the total weight of the aerogel. For example, the aerogel can contain up to 5 wt. %, up to 4 wt. %, up to 3 wt. %, up to 2 wt. %, or up to 1 wt. % (e.g., organic) solvent.

[0213] The article obtained after the supercritical drying process can typically be characterized by at least one or more of the following properties: exhibiting N2 adsorption and / or desorption isotherms with hysteresis loops; N2 adsorption and desorption isotherm type IV according to IUPAC classification, as well as hysteresis loops; It shows type IV N2 adsorption and desorption isotherms with type H1 hysteresis loops according to IUPAC classification; In the p / p range of 0.70 to 0.99, it exhibits Type IV N2 adsorption and desorption isotherms with Type H1 hysteresis loops according to the IUPAC classification.

[0214] Heat treating of the aerogel or xerogel article to form a porous ceramic article can be carried out (typically in an oxygen-containing atmosphere) at a temperature of 70 degrees Celsius (°C) or higher, 80°C or higher, 90°C or higher, 100°C or higher, 125°C or higher, 150°C or higher, 175°C or higher, 200°C or higher, 250°C or higher, 300°C or higher, 400°C or higher, 500°C or higher, 600°C or higher, or 700°C or higher, and 1200°C or lower, 1100°C or lower, 1000°C or lower, 900°C or lower, or 800°C or lower. In other words, heat treating can be carried out at a temperature between 70°C and 1200°C.

[0215] In some embodiments, the porous ceramic article has a sulfate ion equivalent of less than 5 ppm and / or a chloride ion equivalent of less than 5 ppm. For example, raw materials used to prepare zirconia sols often contain chloride and sulfate ion impurities. Thousands of ppm (by weight) of these ions can be present in the porous ceramic article. If not removed, these impurities can volatilize at the temperatures used for sintering and become trapped as pores in the sintered body. The chloride and sulfate ion impurities can be removed prior to sintering, for example, using an ion exchange process. The ion exchange is optionally carried out by infiltrating the porous ceramic article with an aqueous ammonia solution, covering it with sand overnight, and then exchanging the ammonia solution with water several times. During this process, ammonia reacts with the chloride and sulfate ion impurities to form soluble ammonium salts, which are removed by diffusion into the water. These impurities can also be removed by adjusting the heating profile of the heat treatment used to form the porous ceramic article to ensure sufficient volatilization.

[0216] The sintering step is carried out to obtain a ceramic article having a final density of 94% or more, 95% or more, 96% or more, 97% or more, 98% or more, 99% or more, 99.5% or more, or 99.9% or more of the theoretical density. Sintering of porous ceramic articles is typically carried out under the following conditions: Temperature: 900°C to 2300°C, 100°C to 2000°C, 2050°C to 2300°C, 1800°C to 2100°C, or 1000°C to 1300°C; or 900°C or higher, 1200°C or higher, 1400°C or higher, 1600°C or higher, or 1900°C or higher; and 2300°C or lower, 2250°C or lower, 2200°C or lower, 2150°C or lower, 2100°C or lower, 2050°C or lower, or 2000°C or lower; Atmosphere: air or inert gas (e.g., nitrogen, argon); Pressure: ambient pressure (e.g., 1013 mbar); and Time: Until the final density of the material reaches 94%-100% density.

[0217] Sintering may be carried out at elevated or reduced pressure instead of ambient pressure. [Example]

[0218] Objects and advantages of the present disclosure are further illustrated by the following examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit the present disclosure.

[0219] Unless otherwise specified, all parts and percentages are by weight, all water is deionized water, and all molecular weights are weight average molecular weight. Furthermore, unless otherwise specified, all experiments were conducted at ambient conditions (23° C., 1013 mbar).

[0220] [Table 1]

[0221] method Crystal structure and size method (XRD analysis) Dried zirconia samples were crushed by hand using a mortar and pestle. A loose amount of sample was applied with a spatula to a glass microscope slide with a section of double-sided adhesive tape attached. The sample was pressed into the adhesive on the tape surface by pressing the spatula blade against the adhesive. Excess sample was removed by scraping the sample area with the edge of the spatula blade, leaving a thin layer of particles adhered to the adhesive. Loosely attached material remaining after scraping was removed by tapping the microscope slide firmly against a hard surface. Corundum (Linde 1.0 μm alumina polishing powder, lot number C062, Union Carbide, Indianapolis, IN) was prepared in a similar manner and used to calibrate the X-ray diffractometer for instrumental broadening.

[0222] X-ray diffraction scans show reflection shapes, copper K αThe data were obtained using a Philips vertical diffraction system with proportional detector registry for emitted and scattered radiation. The diffractometer was equipped with a variable incident beam slit, a fixed diffraction beam slit, and a graphite diffraction beam monochromator. Survey scans were recorded from 25 to 55 degrees two-theta (2θ) using a 0.04 degree step size and an 8 second dwell time. X-ray generator settings of 45 kV and 35 mA were used. Data for the corundum standard were collected at three separate areas on several individual corundum mounts. Similarly, data were collected at three separate areas on the thin-layer specimen mounts.

[0223] Observed diffraction peaks were identified by comparison with reference diffraction patterns contained within the International Center for Diffraction Data (ICDD) Powder Diffraction Database (Set 1-47, ICDD, Newton Square, PA, USA). The diffraction peaks of the samples were attributed to either the cubic / tetragonal (C / T) or monoclinic (M) forms of zirconia. For zirconia-based particles, the (111) peak of the cubic phase and the (101) peak of the tetragonal phase could not be separated, and therefore these phases were reported together. The amount of each zirconia form was evaluated on a relative basis, and the zirconia form with the most intense diffraction peak was assigned a relative intensity value of 100. The strongest lines of the remaining crystalline zirconia forms were scaled against the strongest line and assigned values ​​between 1 and 100.

[0224] The peak widths of the diffraction maxima observed due to corundum were measured by profile fitting. The relationship between the average corundum peak width and the corundum peak position (2θ) was determined by fitting a polynomial to these data to generate a continuous function that was used to estimate the instrumental width at any peak position within the corundum test range. The peak widths of the diffraction maxima observed due to zirconia were measured by profile fitting the observed diffraction peaks. Depending on the zirconia phase found to be present, the following peak widths were estimated: Cubic / tetragonal (C / T):(1 1 1) Monoclinic (M): (-1 1 1) and (1 1 1)

[0225] K α1 and K. α2 A Pearson VII peak shape model with wavelength components and a linear background model was used for all measurements. Widths were calculated as peak full width at half maximum (FWHM) with units of degrees. Profile fitting was accomplished using the capabilities of the JADE diffraction software suite. Sample peak widths were evaluated for three separate data collections obtained on the same thin-layer sample mount.

[0226] Sample peaks were corrected for instrumental broadening by interpolation of instrumental width values ​​from a corundum instrument calibration, and the corrected peak widths were converted to units of radians. Primary crystallite size was calculated using the Scherrer equation. Crystallite size (D) = Kλ / β(cosθ)

[0227] In the Scherrer equation, K is the form factor (here 0.9), λ is the wavelength (1.540598 Å), β is the calculated peak width (in radians) after correction for instrumental broadening, and θ is equal to half the peak position (scattering angle). β is equal to [calculated peak FWHM - instrumental width] (converted to radians), where FWHM is full width at half maximum. The cubic / tetragonal (C / T) average crystallite size was measured as the average of three measurements using the (1 1 1) peak:

[0228]

number

[0229] Methods for Photon Correlation Spectroscopy (PCS) Particle size measurements were performed using a light scattering particle size analyzer (available under the trade name "ZETA SIZER-Nano Series, Model ZEN3600" from Malvern Instruments Inc., Westborough, MA) equipped with a red laser with a light wavelength of 633 nm. Each sample was analyzed in a 1-centimeter polystyrene sample cuvette. The sample cuvette was filled with approximately 1 gram of deionized water, and then a few drops (approximately 0.1 grams) of zirconia-based sol were added. The composition (e.g., sample) in each sample cuvette was mixed by drawing the composition into a clean pipette and pumping the composition back into the sample cuvette several times. The sample cuvette was then placed in the instrument and equilibrated at 25°C. The instrument parameters were set as follows: dispersant refractive index 1.330, dispersant viscosity 0.8872 MPa-sec, material refractive index 2.10, and material extinction value 0.10 units. An automated size measurement procedure was then performed. The instrument automatically adjusted the laser beam position and attenuator settings to obtain the best particle size measurement.

[0230] The light scattering particle size analyzer illuminated the sample with a laser and analyzed the intensity fluctuations of the light scattered from the particles at an angle of 173 degrees. To calculate particle size, the instrument used the method of Photon Correlation Spectroscopy (PCS). PCS uses the fluctuating light intensity to measure the Brownian motion of particles in a liquid. The particle size is then calculated as the diameter of a sphere moving at the measured velocity.

[0231] The intensity of light scattered by a particle is proportional to the sixth power of the particle diameter. The Z-average size or cumulant mean is an average calculated from the intensity distribution, and this calculation is based on the assumption that the particles are unimodal, monodisperse, and spherical. Related functions calculated from the fluctuating light intensity are the intensity distribution and its mean. The mean of the intensity distribution is calculated based on the assumption that the particles are spherical. Both the Z-average size and the intensity distribution mean are more sensitive to larger particles than to smaller particles.

[0232] The volume distribution indicates the percentage of the total volume of particles that corresponds to particles within a given size range. The volume average size is the size of particles that corresponds to the mean of the volume distribution. This distribution is less sensitive to larger particles than the Z-average size because the volume of a particle is proportional to the cube of its diameter. Therefore, the volume average is usually smaller than the Z-average size.

[0233] How to measure oxide content The oxide content was measured by thermogravimetric analysis (obtained under the trade name "TGA Q500" from TA Instruments, New Castle, DE, USA). A sample (approximately 50 mg) was loaded into the TGA and the temperature was brought to 900°C in air. The oxide content of the sample was equal to the residual weight after heating to 900°C.

[0234] Sol batch preparation Zirconia-based sols, Sol-I(a) to Sol-IV(a), were prepared as described in WO2016191534 (Examples section - Processing: Preparation of Sol-S1), except for the feed composition changes. The target compositions of Sol-I(a) to Sol-IV(a) are listed in Table 1 below.

[0235] [Table 2]

[0236] Sol-I(a) through Sol-IV(a) were characterized using the methods described above. Table 2 below summarizes the crystallite size from the XRD analysis, as well as the PCS data, including the volume average size and Z-average size.

[0237] [Table 3]

[0238] Sol-I(a) through Sol-IV(a) were further treated to increase their concentration and / or remove acetic acid (AcOH). One or more combinations of ultrafiltration, diafiltration, and distillation were used. Diafiltration and ultrafiltration were performed using membrane cartridges (obtained from Spectrum Laboratories Inc., Rancho Dominguez, CA under the trade name "M21S-100-01P"). Distillation was performed using rotary solvent evaporation.

[0239] Diethylene glycol monoethyl ether-based sols, Sol-I(b) through Sol-IV(b), were prepared from Sol-I(a) through Sol-IV(a) by adding 2-[2-(2-methoxyethoxy)ethoxy]acetic acid (MEEAA) (3.5 wt% to 7.2 wt% based on the gram of oxide in the sol) and an appropriate amount of diethylene glycol monoethyl ether (adjusted to the intended final oxide concentration in the sol, e.g., 55 wt%) and concentrating each sol by rotary solvent evaporation. The resulting weight percentages of oxide, acetic acid (AcOH), and 2-[2-(2-methoxyethoxy)ethoxy]acetic acid (MEEAA) in each sol are shown in Table 3.

[0240] [Table 4]

[0241] To prepare precursor sol S1, 1303.4 grams of sol I(b) was placed in a 1 L bottle and combined with acrylic acid (77.66 grams) and diethylene glycol monoethyl ether (125.75 grams).

[0242] To prepare precursor Sol S2, 147.87 grams of Sol-II(b), 7.28 grams of Sol-III(b), and 2.15 grams of Sol-IV(b) were placed in a 250 mL bottle and combined with 2-[2-(2-methoxyethoxy)ethoxy]acetic acid (MEEAA) (0.16 grams), acrylic acid (9.19 grams), and diethylene glycol monoethyl ether (11.09 grams).

[0243] Preparation of printing sol Preparation of printing sol PS1 To prepare printing sol PS1, a portion of precursor sol S1 (500 grams) was placed in a 1-liter bottle and combined with diethylene glycol monoethyl ether (33.5 grams), hydroxyethyl acrylate (HEA) (2.2 grams), trimethylolpropane triacrylate ("SR351H") (47.1 grams), and two different urethane acrylates: CN975 (15.7 grams) and CN9031 (7.8 grams). Prior to printing, OMNIRAD 819 (0.1 wt. % based on the weight of the sol), butylated hydroxytoluene (BHT) (0.1 wt. % based on the weight of the sol), and isatin (0.05 wt. % based on the weight of the sol) were dissolved in the sol. The printing sol was then passed through a 1 μm filter.

[0244] Preparation of printing sol PS2 To prepare printing sol PS2, a portion of precursor sol S2 (100 grams) was placed in a 250 mL bottle and combined with diethylene glycol monoethyl ether (6.7 grams), hydroxyethyl acrylate (HEA) (0.44 grams), trimethylolpropane triacrylate ("SR351H") (9.42 grams), and two different urethane acrylates: CN975 (3.14 grams) and CN9031 (1.56 grams). Prior to printing, OMNIRAD 819 (0.1 wt. % based on the weight of the sol), butylated hydroxytoluene (BHT) (0.1 wt. % based on the weight of the sol), and isatin (0.05 wt. % based on the weight of the sol) were dissolved in the sol. The printing sol was then passed through a 1 μm filter.

[0245] How to do Layer-by-Layer 3D Printing The following procedure was used to print an object from a ceramic sol using layer-by-layer DLP stereolithography 3D printing. A build tray was assembled using a fluoropolymer release film. Approximately 50 mL of sol was loaded into the build tray at room temperature. Care was taken to prevent light exposure by performing the procedure in a UV-filtered room (yellow light) or in low-light conditions if a UV filter was not available. The build platform was sanded with sandpaper and cleaned with IPA as needed. The STL file was loaded into the software, and support structures were applied as needed. The settings for printing on an ASIGA MAX-X43 UV stereolithography printer (Asiga, Sydney, Australia) are listed in Table 4 below.

[0246] [Table 5]

[0247] After the build, the gel samples were immediately removed from the build platform and immersed in two used and one fresh diethylene glycol monoethyl ether solvent baths. The cleaned parts were post-cured in a Clearstone Technologies CA3200 inert UV curing chamber under nitrogen with a 385 nm LED exposure at 20% power for 1 minute. The parts were then placed in a sealed container until further processing.

[0248] Supercritical Fluid Extraction Methods The printed gel bodies were dried by supercritical fluid extraction, for example, as described in the method for supercritical extraction of gels in the Examples section of WO 2016 / 191534 (Mayr et al.).

[0249] Burnout and pre-sintering methods The dried gel body was placed on a bed of zirconia beads in an alumina crucible, which was covered with an alumina plate and then fired in air according to the following schedule: 1- Heat from 20°C to 220°C at a rate of 18°C / hour 2- Heat from 220°C to 244°C at a rate of 1°C / hour Heats from 244°C to 400°C at a rate of 3-6°C / hour 4- Heat from 400°C to 1020°C at a rate of 60°C / hour 5- Cool from 1020℃ to 20℃ at a rate of 120℃ / hour

[0250] Ion exchange method The pre-sintered body was placed in a 118 ml glass jar containing 1.0 N NH4OH to a depth of approximately 2.5 cm and soaked for at least 16 hours. The NH4OH was then discarded and the jar was filled with distilled water. The body was soaked in the distilled water for 1 hour. The water was then replaced with fresh distilled water. This process was repeated until the pH of the soaking water was equal to the pH of the fresh distilled water. The body was then dried at 90°C to 125°C for a minimum of 15 minutes.

[0251] Sintering Method The pre-sintered ion-exchanged bodies were placed on a bed of zirconia beads in an alumina crucible. The crucible was covered with an alumina plate and sintered in air according to the following schedule: 1- Heat from 20℃ to 1020℃ at a rate of 500℃ / hour 2- Heat from 1020°C to 1225°C at a rate of 120°C / hour 3- Hold at 1225℃ for 2 hours 4- Cool from 1225°C to 20°C at a rate of 500°C / hour

[0252] How to measure Archimedes density The density of the sintered material can be measured by the Archimedes technique. Measurements can be made on a precision balance (identified as "XSE204" manufactured by Mettler-Toledo, LLC, Columbus, OH, USA) using a density determination kit (identified as "Density Determination Kit for Excellence XP / XS Analytical Balances" manufactured by Mettler-Toledo, LLC, Columbus, OH, USA). The sample can be first weighed in air (A) and then immersed in water and weighed (B). The water can be distilled and deionized. Three drops of wetting agent (obtained under the trade name "PERVITRO 75%" from Mettler-Toledo, LLC, Columbus, OH, USA) can then be added to 250 ml of water. The density can be calculated using the formula ρ = (A / (AB))(ρ - ρ L )+ρ L (where ρ is the density of water, and ρ L is the density of air (0.0012 g / cm 3 The relative density can be calculated using the equilibrium density function (ρ) in terms of the theoretical density of the material. t ) and ρ 参照 =(ρ / ρ t )*100.

[0253] Method for measuring the flexural strength of ceramic articles Flexural strength can be determined in accordance with ISO 6872 (2008). The printed ceramic specimens are shaped into flexible bars with dimensions of approximately 1 millimeter (mm) x 4 mm x 12 mm after sintering. The parallel large faces of the flexible bars can be polished to a 15-micron surface finish using diamond lapping film (668X Diamond Lapping Film PSA, 3M, St. Paul, MN) in a water-lubricated Beta Grinder-Polisher (Buehler, Lake Bluff, IL) operating at 100 rpm. Each of the four edges along the length of the flexible bar can be chamfered, meaning that a bevel is created on the specimen edge along its length to a 45-degree angle. A three-point beam bending test configuration with a span of 10.0 mm can be used. The crosshead test speed is 1 mm / min. An Instron 5954 test frame (Instron Corporation, Canton, MA) can be utilized for testing.

[0254] Method for measuring opacity of ceramic articles The opacity of ceramic articles can be evaluated using the following procedure. After sintering, the dimensions of printed ceramic specimens can be approximately 1 mm ± 0.03 mm thick x 13 mm x 13 mm. The parallel large faces of the specimen can be polished to a surface finish of 15 micron grade diamond lapping film (668X Diamond Lapping Film PSA, 3M, St. Paul, MN) in a water-lubricated Beta Grinder-Polisher (Buehler, Lake Bluff, IL) operating at 100 rpm. The polished specimen can be measured in reflectance mode using a spectrophotometer (X-Rite Color i7, Grand Rapids, MI, USA). The optical transmittance (T) was determined according to T = 1 - RB / RW, where RB is the reflectance through a ceramic specimen on a black substrate and RW is the reflectance through the same specimen on a white substrate. A higher optical transmittance value indicates higher light transmission and lower opacity. Therefore, the opacity (O) is determined by the formula O=100-T.

[0255] Examples 1 to 3 Ceramic specimens were printed according to the layer-by-layer 3D printing method, dried according to the supercritical fluid extraction method, and subsequently processed according to the burnout and pre-sintering method, ion exchange method, and sintering method to form fully dense ceramic articles.

[0256] Example 1 Example 1 partially shows the incisal node feature within the cusp receptacle, exhibiting a thickness of less than 300 microns in the central region away from the proximal edge. Three separate veneer samples from a single batch had thicknesses of 198 microns, 195 microns, and 200 microns at their thinnest points. The samples were produced as described above using printing sol PS1. The gelled article is shown in Figure 15, while the sintered veneer is shown in Figure 16.

[0257] Example 2 Example 2 shows a region away from the proximal edge with a thickness of less than 300 microns. The exact thickness varies across the surface. Three separate veneer samples from a single batch had thicknesses of 278, 274, and 258 microns at their thinnest points. The veneers were produced as described above using printing sol PS2. The resulting article, including the support sprue, is shown in Figures 12C and 12D.

[0258] Example 3 Example 3, shown in Figure 5, illustrates a central inset area with greater surface roughness than the surrounding surface. The area of ​​greater surface roughness illustrates a 3M brand reproduction. The above sample was produced as described above using printing sol PS2.

[0259] The patents, patent documents, and patent applications cited herein are incorporated by reference in their entirety, as if each were individually incorporated by reference. It will be apparent to those skilled in the art that various changes and modifications may be made without departing from the inventive concepts described above. Thus, the scope of the present disclosure should not be limited to the structures described herein. Those skilled in the art will appreciate that numerous changes may be made to the above-described embodiments and implementation details without departing from the underlying principles thereof. Furthermore, various modifications and alterations of the present invention will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. Therefore, the scope of this application should be determined solely by the following claims and their equivalents.

Claims

1. an incisal edge, a cervical edge, a body extending between the incisal edge region and the cervical edge, and an opposing proximal edge; Labial surface and opposite tooth-facing surface, and a cusp receptacle adjacent the incisal edge; A monolithic veneer comprising: the body includes one or more structural features selected from the group consisting of an incisal tubercle at least partially within the cusp receptacle, a concave depression at least partially within the cusp receptacle, an engineered surface texture, and a relief feature; the thinnest part of the body within the central window area is 400 microns or less; Monolithic veneer.

2. The veneer of claim 1 , wherein the tooth-facing surface substantially matches the contour of the patient's labial tooth surface.

3. The veneer of claim 1 , wherein the engineered surface texture comprises one or more channels complementary to circumferential striations on the patient's labial tooth surfaces.

4. The veneer of claim 3 wherein the channels have a depth of 100 microns or less.

5. The veneer of claims 1-3, wherein the cusp receptacle includes one or more incisal tubercles.

6. A veneer according to any one of claims 1 to 5, wherein the cusp receptacle comprises a surface of the body having a series of concave depressions.

7. 8. The veneer of claim 7, wherein each indentation in the series of indentations has a radius of 100 microns or less, and wherein the indentations are configured to align with one or more features on the surface of the patient's tooth.

8. The veneer of any one of claims 1 to 7, wherein the cusp receptacle comprises a lingual wall surface opposite the tooth-facing surface of the body.

9. The veneer of claim 9 , wherein at least a portion of the structural feature is disposed on a lingual wall of the cusp receptacle.

10. 10. The veneer of any one of claims 1 to 9, wherein the veneer is monolithically formed from a sol containing ceramic particles, the sol including at least one of zirconia particles and silica particles.

11. A veneer according to any one of claims 1 to 10, wherein the sol comprises zirconia particles.

12. A veneer according to any one of claims 1 to 11, wherein the body comprises one or more translucent regions.

13. 13. The veneer of any one of claims 1 to 12, wherein the central window area of ​​the body has a cross-sectional thickness of 200 microns or less.

14. 14. The veneer of any one of claims 1 to 13, wherein an outer surface of the veneer comprises a plurality of support sprues, the plurality of support sprues being located on the incisal surface or the cervical surface.

15. 15. The veneer of any one of claims 1 to 14, wherein the support sprue comprises a shaft adjacent the veneer having a cross-sectional thickness not exceeding 100 microns.

16. 16. The veneer of any one of claims 1 to 15, exhibiting a flexural strength of at least 100 megapascals (MPa), 200 MPa or more, 300 MPa or more, 400 MPa or more, 500 MPa or more, 600 MPa or more, 700 MPa or more, 800 MPa or more, 900 MPa or more, 1000 MPa or more, 1100 MPa or more, or 1200 MPa or more.

17. The veneer of claim 1 , wherein the structural feature comprises a repeating pattern of surface texture elements, the elements being arranged in a unit cell.

18. A veneer according to any one of claims 1 to 17, exhibiting a density of 98% or more of the theoretical density of the ceramic material.

19. 1. A method of making a dental veneer, comprising: an incisal edge, a cervical edge, an opposing proximal edge, and a body extending between said edges; Labial surface and opposite tooth-facing surface, and a cusp receptacle on the incisal edge. receiving a design for a dental veneer; fabricating the dental veneer in a single piece from a ceramic sol using additive manufacturing, wherein the thinnest portion of the central window area of ​​the veneer is 400 microns or less, and the veneer exhibits a density of 94% or greater of the theoretical density of the ceramic material. A method comprising:

20. 20. The method of claim 19, wherein the veneer exhibits a density of 98% or greater of the theoretical density of the ceramic material.

21. 20. The method of claim 19, further comprising receiving a model of a patient's tooth surface and designing the veneer to substantially match at least a portion of the model.

22. The method of claim 19, wherein the model is a 3D model.

23. The method according to any one of claims 19 to 22, wherein the ceramic sol is a zirconia sol.

24. 24. The method of any one of claims 19 to 23, wherein the thinnest part of the additively manufactured veneer has a thickness of less than 200 microns.

25. The method of any one of claims 19 to 24, wherein the incisal edge of the veneer design includes a hollow cusp receptacle.

26. The method of any one of claims 19 to 25, wherein the cusp receptacle comprises one or more incisal tubercles.

27. 27. The method of any one of claims 19 to 26, wherein the body includes one or more structural features selected from the group consisting of an incisal tubercle at least partially within the cusp receptacle, a concave depression at least partially within the cusp receptacle, an engineered surface texture, and a relief feature.

28. additively manufacturing the veneer; a) obtaining a photopolymerizable sol comprising a plurality of ceramic particles dispersed therein, the ceramic particles having an average particle size of 1 nanometer (nm) to 100 nm; b) selectively polymerizing the photopolymerizable sol using actinic radiation and successive passages of a build substrate through the photopolymerizable sol to form a gelled article; c) extracting the solvent from the gelled article to form an aerogel or xerogel article; d) heat treating the aerogel or xerogel article to form a porous ceramic article; e) sintering the porous ceramic article to form a sintered ceramic article. The method of any one of claims 19 to 27, comprising:

29. 29. The method of any one of claims 19 to 28, wherein the body comprises one or more structural features selected from the group consisting of an incisal tubercle at least partially within the cusp receptacle, a concave depression at least partially within the cusp receptacle, an engineered surface texture, and a relief feature, and wherein creation of the features occurs prior to step (e).

30. A kit comprising: A plurality of veneers, each veneer being an incisal edge, a cervical edge, an opposing proximal edge, and a body extending between said edges; Labial surface and opposite tooth-facing surface Including, the body includes one or more structural features selected from the group consisting of an incisal nodule, a concave depression, a patterned surface texture on the tooth-facing surface, and a relief feature printed on the tooth-facing surface; the thinnest part of the thickness of the veneer at the proximal edge is 300 microns or less; Multiple veneers and a bonding agent for securing at least one veneer to the tooth surface; Includes a kit.

Images