Method for producing opalescence in dental restorations

Abstract

Disclosed are methods for creating opalescence in dental materials and restorations, compositions used in such methods, and the resulting dental materials and restorations. More specifically, opalescence can be created by directly embedding opalescent particles into a matrix material. In some embodiments, photonic crystals are embedded in the dental material to achieve the opalescent effect. Photonic crystal particles can be embedded in a dental material matrix, such as a ceramic, composite, or polymer, to generate opalescence in the material. In some embodiments, disclosed are compositions for applying opalescence to dental restorations.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to U.S. Patent Application Serial No. 62 / 806,192, filed February 15, 2019, entitled "Method for Producing Opulence in Dental Restorations," the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to dental materials and restorations, and methods for producing opalescence in such dental materials and restorations. More specifically, opalescence can be created by directly embedding opalescent particles into a matrix material. In some embodiments, photonic crystals are embedded in the dental material to achieve the opalescent effect. Photonic crystal particles can be embedded in a dental material matrix, such as a ceramic, composite, or polymer, to produce opalescence in the material. [Background technology]

[0003] Opalescence is a term that describes the optical characteristics of opal. The term refers to the change in color that can be seen when an opal is viewed in different lighting conditions; opal appears one color in reflected light and its complementary color in transmitted light. That is, light reflected from the opal's surface is one color, and light that passes through the opal is its complementary color.

[0004] Natural teeth have opalescence due to light scattering caused by hydroxyapatite nanocrystals. When incident light penetrates a tooth, blue light is preferentially scattered back to the illuminated side, giving the tooth a bluish-white appearance. However, in thin areas, light can pass through the tooth and is opalescent, so the areas through which the light penetrates appear red to orange in color. The opalescence of natural teeth comes from both the enamel and dentin, but the enamel is the primary source of opalescence.

[0005] Similarly, an opal effect can be created in dental materials by carefully controlling how light is scattered by that material. There are several known methods for achieving this effect, most of which require nanoscale particles to scatter the light.

[0006] One method of creating opalescent materials is through the nucleation and growth of nano-sized crystals in a matrix phase. By controlling the size of the crystals, the wavelength (and therefore color) of the scattered light can be modulated. However, achieving opalescence with this method requires very precise control of the temperature and hold time in the nucleation and growth cycle and subsequent thermal cycle; otherwise, the opalescent effect will be lost. Therefore, this method is not suitable for all situations where an opalescent material may be required.

[0007] Another method involves mixing nanoparticles with a matrix material. This method presents its own challenges: the nanoparticles must be well dispersed within the matrix, and they easily agglomerate during mixing or heat treatment. The agglomerated particles cause random scattering of light, resulting in a white, opaque material rather than the desired opalescence.

[0008] A different approach to producing opalescent materials, especially ceramic materials, uses nanoparticles as starting materials. With this technique, nanosized powders are compressed and sintered like conventional ceramic powders. Opalescent ceramics can be produced if the ceramic's optical properties are appropriate and the final grain size can be kept below 400 nm. However, maintaining a small and uniform grain size using conventional sintering processes is very difficult. Non-conventional sintering techniques, such as hot isostatic pressing or plasma-assisted sintering, are usually required, which are performed at lower temperatures with shorter hold times than conventional sintering.

[0009] Applicant has invented a new, efficient and effective method for achieving opalescence in dental materials, and dental materials and restorations having such opalescent properties. This new method offers distinct advantages over the prior art. All of the above methods require much more careful control of manufacturing parameters such as time, temperature, and particle size distribution than the method disclosed herein.

[0010] Furthermore, all of the above methods achieve opalescence through highly controlled scattering of light by either second phase particles or grain boundaries, which increases the opacity of the material. As a result, it is not possible to achieve the opalescent effect in very thin sections of translucent material using these methods. The present invention is particularly well suited to creating translucent materials that exhibit opalescence at very thin (0.1 to 0.5 mm) thicknesses, such as those used in aesthetic dental restorations. Summary of the Invention

[0011] In the present disclosure, opalescence is achieved by incorporating photonic crystal particles into dental materials. Previously, opalescence was imparted to dental materials by controlling scattering through careful distribution of second phases or by precisely controlling the microstructure. The embodiments described herein do not rely on either of these ideas, but instead utilize photonic crystal particles that reflect light of specific colors rather than scattering light over a wide range of wavelengths. The intensity of the reflected light by photonic crystals is much stronger than can be achieved by scattering. Therefore, strong opalescence can be achieved even in very thin films, such as layers of glaze ceramic applied to dental restorations.

[0012] Some embodiments provide a dental material comprising one or more dental matrices; and one or more photonic crystals.

[0013] In some embodiments, the one or more dental matrices comprise a dental glaze, a dental porcelain, a dental ceramic, a dental composite, a dental resin, a dental polymer, or a combination thereof.

[0014] In some embodiments, the dental ceramic comprises at least one of alumina, zirconia, glass ceramic, leucite-reinforced glass, glass-infiltrated ceramic, or a mixture or solid solution of two or more thereof.

[0015] In some embodiments, the photonic crystal is a synthetic opal.

[0016] In some embodiments, the photonic crystal is a synthetic opal that is partially or fully infiltrated with a ceramic material, an organic material, an organic-inorganic hybrid material, or a mixture of two or more thereof.

[0017] In some embodiments, the infiltrative ceramic material comprises one or more of alumina, zirconia, titania, silica, yttria, zinc oxide, hafnia, tin oxide, indium oxide, ceria, niobium oxide, tantalum oxide, germanium oxide, gallium oxide, and scandium oxide.

[0018] In some embodiments, the infiltrative ceramic material comprises one or more materials that can be converted to alumina, zirconia, titania, silica, yttria, zinc oxide, hafnia, tin oxide, indium oxide, ceria, niobium oxide, tantalum oxide, germanium oxide, gallium oxide, scandium oxide, or a mixture or solid solution of two or more thereof when subjected to chemical treatment, heat treatment, light treatment, pressure treatment, or a combination of two or more treatments.

[0019] In some embodiments, the organic-inorganic hybrid material comprises one or more materials that can be converted to alumina, zirconia, titania, silica, yttria, zinc oxide, hafnia, tin oxide, indium oxide, ceria, niobium oxide, tantalum oxide, germanium oxide, gallium oxide, scandium oxide, or a mixture or solid solution of two or more thereof upon chemical treatment, heat treatment, light treatment, pressure treatment, or a combination of two or more treatments. In some embodiments, the organic material of the organic-inorganic hybrid material consists of one or more monomers or polymers, or a mixture of at least one monomer and one polymer.

[0020] In some embodiments, the photonic crystal is an inverse opal.

[0021] In some embodiments, the inverse opal is made of a ceramic material, an organic material, an organic-inorganic hybrid material, or a mixture of two or more thereof.

[0022] Some embodiments provide a method of making a dental material that includes combining one or more photonic crystals with one or more dental matrices.

[0023] In some embodiments, the one or more dental matrices are dental glazes, dental porcelains, dental ceramics, dental composites, dental resins, dental polymers, or combinations thereof.

[0024] In some embodiments, the dental ceramic comprises at least one of alumina, zirconia, glass ceramic, leucite-reinforced glass, glass-infiltrated ceramic, and mixtures or solid solutions of two or more thereof.

[0025] Some embodiments provide a composition for imparting opalescence to a dental restoration, the composition comprising a ceramic component, an opal component, and a liquid component.

[0026] In some embodiments, the composition comprises about 50-85% by weight of a ceramic component; about 1-20% by weight of an opal component; and the balance, a liquid component.

[0027] In some embodiments, the ceramic component is ceramic-based and is present at about 50-85% by weight.

[0028] In some embodiments, the opal component is present at about 2-6% by weight.

[0029] In some embodiments, the opal component is present at about 6-12% by weight.

[0030] In some embodiments, the ceramic component is a glaze base present at about 50-65% by weight.

[0031] In some embodiments, the opal component is present at about 6-15% by weight.

[0032] Some embodiments include less than about 2% by weight of a viscosity modifier.

[0033] Some embodiments include less than about 1% by weight of a fluorescent agent.

[0034] Some embodiments comprise less than about 2% by weight of a viscosity modifier; and less than about 1% by weight of a fluorescent agent. [Brief explanation of the drawings]

[0035] [Figure 1a] Figure 1a shows the light scattering effect of various materials. [Figure 1b] Figure 1b shows the light scattering effect of various materials. [Figure 1c] Figure 1c shows the light scattering effect of various materials. [Figure 1d] FIG. 1d illustrates the effect achieved by the methods and materials herein. DETAILED DESCRIPTION OF THE INVENTION

[0036] According to the methods described herein, opalescence can be created by directly embedding opalescent particles into a matrix material. In particular, photonic crystals can be embedded in dental materials to achieve the opalescent effect. This disclosure relates to the use of photonic crystals as opalescent agents in dental materials.

[0037] Photonic crystal particles can be embedded in a dental material matrix, such as a ceramic, composite, or polymer, to produce opalescence in the material.

[0038] A crystal is a material in which atoms or molecules are arranged periodically.

[0039] A photonic crystal is a regular structure whose refractive index varies periodically on a length scale comparable to the wavelength of the light of interest. Light experiences a periodic potential as it propagates through a photonic crystal, much like electrons experience a periodic potential in a conventional crystal. The periodic potential in a photonic crystal is due to a dielectric lattice, not atoms or molecules. Light in a photonic crystal is prohibited from propagating in certain directions within certain energies. In other words, light is reflected in certain directions. For white light, only light within a certain wavelength range is reflected. The angle and wavelength range are controlled by the effective refractive index and the periodicity. Depending on the number of dimensions in which the photonic crystal has periodicity, there are one-dimensional, two-dimensional, and three-dimensional photonic crystals.

[0040] Photonic crystals formed from colloidal particles are called colloidal crystals or synthetic opals. Synthetic opals can be made by packing colloidal particles into ordered structures. Packing can be achieved by sedimentation, controlled drying, selective deposition on pre-patterned sites, pouring droplets of a colloidal suspension into air or other immiscible liquids followed by drying, or centrifugation of the colloidal suspension. Centrifugation is the fastest method for making photonic crystals in large quantities. Silica and polymer spheres are most often used for synthetic opals.

[0041] In addition to synthetic opals, there are other types of photonic crystals that can be used to create opalescence. For example, synthetic opals can be used as a framework to create what are called "inverse opals." Inverse opals are created by infiltrating synthetic opals with a different material (e.g., titania, silica, zirconia, or a polymer) and then removing the silica or polymer lattice by chemical dissolution or thermal decomposition.

[0042] A third type of photonic crystal can be created by partially or completely infiltrating the lattice of a synthetic opal with a different material, such as titania, silica, zirconia, or a polymer, but without inverting the structure by removing the synthetic opal.

[0043] The characteristic reflection color of a photonic crystal depends on the effective refractive index of the crystal and the periodicity of the lattice. Therefore, by infiltrating synthetic opal or inverting the opal, the effective refractive index can be altered to change the characteristic reflection color of the crystal. Similarly, the periodicity of the crystal can be controlled by changing the diameter of the spheres used to create the crystal. Equation (1) is the reflection peak equation for synthetic opal, partially or fully infiltrated opal, or inverse opal with a face-centered cubic lattice.

[0044]

number

[0045] where d is the lattice spacing, n eff is the effective refractive index, D is the particle diameter, Φ is the particle volume fraction, n p and n m is the refractive index of the particle and the medium filling the void. This formula provides guidance on how a desired reflected wavelength can be achieved by choosing the material and size of the sphere.

[0046] As described herein, synthetic opals and infiltrated synthetic opals were used to demonstrate the use of photonic crystals as opalescent agents in dental applications such as ceramics, composites, and polymers. The synthetic opals were formed by centrifugation of silica sphere suspensions.

[0047] General procedure for producing synthetic opal.

[0048] Silica spheres with either approximately 180 nm or 220 nm size (other sizes can be used) and ethanol were added to each centrifuge tube to create a 20 wt% ethanol suspension of silica spheres. Because the size of the silica spheres affects the periodicity, which affects the wavelength of reflected light, silica spheres of any size can be selected based on the desired light. For example, silica spheres range in size from approximately 140 nm to approximately 370 nm.

[0049] The size and reflectivity of the silica spheres determine the reflected wavelength (i.e., reflected color). The suspension was sonicated to break up the silica sphere agglomerates. The suspension was centrifuged at low speed to remove large agglomerates. The supernatant suspension was decanted and transferred to another centrifuge tube. It was sonicated again and centrifuged at high speed to form synthetic opal. The ethanol was decanted, and the synthetic opal was dried at room temperature. The dried synthetic opal was heated at 600°C for 4 hours to consolidate the opal. The synthetic opal was then further processed to prepare opalescent dental materials.

[0050] In its most general sense, the method herein incorporates synthetic opals, ie, photonic crystals, into dental materials through blending and other techniques.

[0051] Some methods involve the use of glazing powders, which are unstained, transparent glazing porcelains with an appropriate firing temperature. Any glazing powder suitable for use in dental restorations can be used. In some cases, synthetic opal can be incorporated into the glaze paste product.

[0052] In some embodiments, the photonic crystals can be mixed with a glazing powder, to which an organic liquid can be added later to obtain a paste.

[0053] In other embodiments, photonic crystals can be added to existing paste glaze products.

[0054] Glazing powder or paste glaze products, including but not limited to layering materials, glazing materials, and structure-building materials, are suitable for use in dental restorations.

[0055] In some embodiments, the photonic crystal powder can be incorporated into any dental ceramic, polymer, resin, composite, or other dental material.

[0056] Examples 1 and 5 below describe methods for creating glazes that can impart opalescence when applied to zirconia restorations and fired. Heat-treated opal, obtained using the general procedure, was ground into a powder. Opal powders smaller than 63 μm were further ground into smaller particles in an ethanol suspension. The particles were dried. The opal powder and glazing powder were mixed in a ratio of approximately 1:9 parts by weight. A range of approximately 1:1 to approximately 1:199 by weight can be used. In some embodiments, the range is approximately 1:2 to approximately 1:99. In some embodiments, the range is approximately 1:3 to approximately 1:49. The mixed powders were made into a paste and applied to the zirconia restoration. The glaze layer containing the opal particles was fired according to the glaze firing schedule.

[0057] In Examples 2 and 6, heat-treated opal chunks (i.e., agglomerates) were infiltrated with titania using the following procedure: The chunks were soaked in titanium isopropoxide for 2-10 hours and then dried. In some embodiments, the chunks were left in isopropoxide for approximately 4 hours. The dried chunks were heated at 600°C for 1 hour to obtain titania-infiltrated opal chunks. The titania-infiltrated opal chunks were crushed into powder. Titania-infiltrated opal powder smaller than 63 μm was further crushed in an ethanol suspension to produce smaller particles. The particles were dried. The titania-infiltrated opal powder and glazing powder were mixed in a ratio of approximately 1:9 parts by weight. A range of approximately 1:1 to approximately 1:199 by weight can be used. In some embodiments, the range is approximately 1:2 to approximately 1:99. In some embodiments, the range is approximately 1:3 to approximately 1:49. The mixed powder was formed into a paste and applied to the zirconia restoration. The glaze layer containing the opal particles was fired according to the firing schedule for the glaze.

[0058] In Examples 3 and 8, heat-treated opal chunks were subjected to double titania infiltration. The heat-treated opal chunks were infiltrated with titanium isopropoxide for 2 to 10 hours and then dried. In some embodiments, the chunks were left in isopropoxide for approximately 4 hours. The dried chunks were heated at 600°C for 1 hour to obtain titania-infiltrated opal chunks. The titania-infiltrated opal chunks were then subjected to a second titania infiltration process. In some embodiments, the infiltration step can be repeated 2 to 5 times. The double-infiltrated chunks were ground into powder. Opal powders smaller than 63 μm were further ground in an ethanol suspension to produce smaller particles. The particles were then dried. The titania-infiltrated opal powder and glazing powder were mixed in a ratio of approximately 1:9 parts by weight. A range of about 1:1 to about 1:199 by weight can be used. In some embodiments, the range is about 1:2 to about 1:99. In some embodiments, the range is from about 1:3 to about 1:49. The mixed powders were made into a paste and applied to the zirconia restoration. The glaze layer containing the opal particles was fired according to the firing schedule for the glaze.

[0059] In Examples 4 and 8, the heat-treated opal chunks were subjected to dual titania infiltration and titanium isopropoxide hydrolysis prior to post-heat treatment. The heat-treated opal chunks were infiltrated with titanium isopropoxide for 2-10 hours and allowed to dry. In some embodiments, the chunks were left in the isopropoxide for approximately 4 hours.

[0060] The dried chunks were soaked in water to hydrolyze the titanium isopropoxide and then heated at 600°C for 1 hour to produce titania-infiltrated opal chunks. Hydrolysis of titanium isopropoxide prevents the generation of carbon residue after heat treatment. The titania-infiltrated opal chunks were subjected to another titania infiltration and hydrolysis process.

[0061] In some embodiments, the infiltration step may be repeated two to five times. The doubly infiltrated chunks were ground into a powder. Opal powders smaller than 63 μm were further ground in an ethanol suspension to form smaller particles. The particles were dried. The titania doubly infiltrated opal powder and glazing powder were mixed in a ratio of about 1:9 parts by weight. A range of about 1:1 to about 1:199 by weight can be used. In some embodiments, the range is about 1:2 to about 1:99. In some embodiments, the range is about 1:3 to about 1:49. The mixed powders were made into a paste and applied to the zirconia restoration. The glaze layer containing the opal particles was fired according to the glaze firing schedule. [Example]

[0062] Example 1: 180 nm Milled Opal Powder with Dental Glazing Powder Seven grams of silica spheres with a size of approximately 180 nm and 28 grams of ethanol were added to each centrifuge tube to prepare a 20% by weight suspension of silica spheres in ethanol. This suspension was sonicated to break down silica sphere agglomerates. Centrifuged at low speed to remove large particles from the suspension. The supernatant suspension was decanted and transferred to another centrifuge tube. The suspension was sonicated again and centrifuged at high speed to form synthetic opal. The ethanol was decanted, and the synthetic opal was dried at room temperature. The dried synthetic opal was heated at 600°C for 4 hours to consolidate the opal. The heat-treated opal obtained by the general procedure was crushed into powder. Opal powder smaller than 63 μm was further crushed in an ethanol suspension to produce smaller particles. The particles were dried. Five grams of opal powder was mixed with 45 grams of glazing powder. The mixed powder was made into a paste and applied to the zirconia restoration. The glaze layer containing the opal particles was fired according to the glaze firing schedule.

[0063] Example 2: Titania penetration of synthetic opal - 180 nm A 20 wt% suspension of silica spheres in ethanol was prepared by adding 7 g of silica spheres with a size of approximately 180 nm to a centrifuge tube. This suspension was sonicated to break down silica sphere agglomerates. Centrifuged at low speed to remove large particles from the suspension. The supernatant suspension was decanted and transferred to another centrifuge tube. The suspension was sonicated again and centrifuged at high speed to form synthetic opal. The ethanol was decanted, and the synthetic opal was allowed to dry at room temperature. The dried synthetic opal was heated at 600°C for 4 hours to consolidate the opal. Chunks of heat-treated opal were infiltrated with titania using the following procedure: The chunks were soaked in titanium isopropoxide for 4 hours and dried. The dried chunks were heated at 600°C for 1 hour. The titania-infiltrated chunks were then crushed into powder. Titania-infiltrated opal powders smaller than 63 μm were further crushed in an ethanol suspension to produce smaller particles. The particles were dried. 5 g of titania-infiltrated opal powder was mixed with 45 g of glazing powder. The mixed powder was made into a paste and applied to the zirconia restoration. The glaze layer containing the opal particles was fired according to the glaze firing schedule.

[0064] Example 3: Dual titania infiltration of synthetic opal A 20 wt% suspension of silica spheres in ethanol was prepared by adding 7 g of silica spheres with a size of approximately 180 nm to a centrifuge tube. This suspension was sonicated to break down silica sphere agglomerates. Centrifuged at low speed to remove large particles from the suspension. The supernatant suspension was decanted and transferred to another centrifuge tube. The suspension was sonicated again and centrifuged at high speed to form synthetic opal. The ethanol was decanted, and the synthetic opal was allowed to dry at room temperature. The dried synthetic opal was heated at 600°C for 4 hours to consolidate the opal. The heat-treated opal chunks were infiltrated with titania as follows: The chunks were immersed in titanium isopropoxide for 4 hours and then dried. The dried chunks were heated at 600°C for 1 hour. The titania-infiltrated chunks were subjected to a second titania infiltration process. The doubly infiltrated chunks were then crushed into powder. Opal powders smaller than 63 μm were further ground in an ethanol suspension to produce smaller particles. The particles were dried. Five grams of the dried titania-doubly infiltrated opal powder was mixed with 45 grams of glazing powder. The mixed powder was made into a paste and applied to the zirconia restoration. The glaze layer containing the opal particles was fired according to the glaze firing schedule.

[0065] Example 4: Dual titania infiltration of synthetic opals and hydrolysis of titania precursors prior to post-heat treatment A 20 wt% suspension of silica spheres in ethanol was prepared by adding 7 g of silica spheres with a size of approximately 180 nm to a centrifuge tube. This suspension was sonicated to break down silica sphere agglomerates. Centrifuged at low speed to remove large particles from the suspension. The supernatant suspension was decanted and transferred to another centrifuge tube. The suspension was sonicated again and centrifuged at high speed to form synthetic opal. The ethanol was decanted, and the synthetic opal was allowed to dry at room temperature. The dried synthetic opal was heated at 600°C for 4 hours to consolidate the opal. Chunks of the heat-treated opal were infiltrated with titania as follows: The chunks were immersed in titanium isopropoxide for 4 hours and then dried. The dried chunks were soaked in water for 4 hours to hydrolyze the titanium isopropoxide, and then heated at 600°C for 1 hour. The titania-infiltrated chunks were subjected to the titania infiltration and hydrolysis process again. The doubly infiltrated chunks were ground to a powder. Opal powder smaller than 63 μm was further ground in an ethanol suspension to produce smaller particles. The particles were dried. Five grams of the dried titania doubly infiltrated opal powder was mixed with 45 grams of glazing powder. The mixed powder was made into a paste and applied to the zirconia restoration. The glaze layer containing the opal particles was fired according to the glaze firing schedule.

[0066] Example 5: 220 Milled Opal Powder with Dental Glazing Powder A 20 wt% suspension of silica spheres in ethanol was prepared by adding 7 g of silica spheres with a size of approximately 220 nm to a centrifuge tube and 28 g of ethanol. The suspension was sonicated to break down silica sphere agglomerates. Centrifuged at low speed to remove large particles from the suspension. The supernatant suspension was decanted and transferred to another centrifuge tube. The suspension was sonicated again and centrifuged at high speed to form synthetic opal. The ethanol was decanted, and the synthetic opal was dried at room temperature. The dried synthetic opal was heated at 600°C for 4 hours to consolidate the opal. The heat-treated opal was crushed into a powder. Opal powder smaller than 63 μm was further crushed in an ethanol suspension to produce smaller particles. The particles were dried. 5 g of opal powder was mixed with 45 g of glazing powder. The mixed powder was made into a paste and applied to the zirconia restoration. The glaze layer containing the opal particles was fired according to the glaze firing schedule.

[0067] Example 6: Titania penetration of synthetic opal - 220 nm A 20 wt% suspension of silica spheres in ethanol was prepared by adding 7 g of silica spheres with a size of approximately 220 nm to a centrifuge tube and 28 g of ethanol. This suspension was sonicated to break down silica sphere agglomerates. Centrifuged at low speed to remove large particles from the suspension. The supernatant suspension was decanted and transferred to another centrifuge tube. The suspension was sonicated again and centrifuged at high speed to form synthetic opal. The ethanol was decanted, and the synthetic opal was allowed to dry at room temperature. The dried synthetic opal was heated at 600°C for 4 hours to consolidate the opal. Chunks of heat-treated opal were infiltrated with titania using the following procedure: The chunks were soaked in titanium isopropoxide for 4 hours and dried. The dried chunks were heated at 600°C for 1 hour. The titania-infiltrated chunks were then crushed into powder. Titania-infiltrated opal powders smaller than 63 μm were further crushed in an ethanol suspension to produce smaller particles. The particles were dried. 5 g of titania-infiltrated opal powder was mixed with 45 g of glazing powder. The mixed powder was made into a paste and applied to the zirconia restoration. The glaze layer containing the opal particles was fired according to the glaze firing schedule.

[0068] Example 7: Dual titania penetration of synthetic opal - 220 nm A 20 wt% suspension of silica spheres in ethanol was prepared by adding 7 g of silica spheres with a size of approximately 220 nm to a centrifuge tube and 28 g of ethanol. This suspension was sonicated to break down silica sphere agglomerates. Centrifuged at low speed to remove large particles from the suspension. The supernatant suspension was decanted and transferred to another centrifuge tube. The suspension was sonicated again and centrifuged at high speed to form synthetic opal. The ethanol was decanted, and the synthetic opal was allowed to dry at room temperature. The dried synthetic opal was heated at 600°C for 4 hours to consolidate the opal. The heat-treated opal chunks were infiltrated with titania as follows: The chunks were immersed in titanium isopropoxide for 4 hours and then dried. The dried chunks were heated at 600°C for 1 hour. The titania-infiltrated chunks were subjected to a second titania infiltration process. The doubly infiltrated chunks were then crushed into powder. Opal powders smaller than 63 μm were further ground in an ethanol suspension to produce smaller particles. The particles were dried. Five grams of the dried titania-doubly infiltrated opal powder was mixed with 45 grams of glazing powder. The mixed powder was made into a paste and applied to the zirconia restoration. The glaze layer containing the opal particles was fired according to the glaze firing schedule.

[0069] Example 8: Dual titania infiltration of synthetic opals and hydrolysis of titania precursors before post-heat treatment - 220 nm A 20 wt% suspension of silica spheres in ethanol was prepared by adding 7 g of silica spheres with a size of approximately 220 nm to a centrifuge tube. This suspension was sonicated to break down silica sphere agglomerates. Centrifuged at low speed to remove large particles from the suspension. The supernatant suspension was decanted and transferred to another centrifuge tube. The suspension was sonicated again and centrifuged at high speed to form synthetic opal. The ethanol was decanted, and the synthetic opal was allowed to dry at room temperature. The dried synthetic opal was heated at 600°C for 4 hours to consolidate the opal. Chunks of the heat-treated opal were infiltrated with titania as follows: The chunks were soaked in titanium isopropoxide for 4 hours and then dried. The dried chunks were soaked in water for 4 hours to form titanium isopropoxide, and then heated at 600°C for 1 hour. The titania-infiltrated chunks were subjected to another titania infiltration and hydrolysis process. The doubly infiltrated chunks were ground to a powder. Opal powder smaller than 63 μm was further ground in an ethanol suspension to produce smaller particles. The particles were dried. Five grams of the dried titania doubly infiltrated opal powder was mixed with 45 grams of glazing powder. The mixed powder was made into a paste and applied to the zirconia restoration. The glaze layer containing the opal particles was fired according to the glaze firing schedule.

[0070] The opals described above can be incorporated into dental products that are applied to restorations to achieve desired aesthetics. In particular, these formulations can achieve desired aesthetics at significantly thinner thicknesses than conventional materials.

[0071] Some embodiments provide a composition for imparting opalescence to dental restorations, the composition comprising about 50-85 wt. % ceramic component; about 0-2 wt. % of a viscosity modifier; about 2-15 wt. % opal component; about 0-1 wt. % fluorescent agent; and the balance liquid component.

[0072] In some embodiments, the ceramic component is ceramic-based and is present at about 50-85% by weight.

[0073] In some embodiments, the opal component is present at about 2-6% by weight.

[0074] In some embodiments, the opal component is present at about 6-12% by weight.

[0075] In some embodiments, the ceramic component is a glaze base present at about 50-65% by weight.

[0076] In some embodiments, the opal component is present at about 6-15% by weight.

[0077] In some embodiments, such dental products are structure-building compositions comprising: Approximately 50-85% by weight of base ceramic; about 0-2 wt. % viscosity modifier; approximately 2-12% by weight of opal; Approximately 0-1% fluorescent agent; and the remaining liquid component.

[0078] In some embodiments, such dental products are structure-building compositions comprising: Approximately 50-85% by weight of base ceramic; about 0-2 wt. % viscosity modifier; Approximately 2-6% by weight of opal; approximately 0-1% of fluorescent agent; and the remaining liquid component.

[0079] Another embodiment is a traditional glaze that does not add substantial structure, such dental products include: Approximately 50-85% by weight of glaze base; about 0-2 wt. % viscosity modifier; approximately 6-16% by weight of opal; Approximately 0-1% fluorescent agent; and the remaining liquid component.

[0080] The base ceramic is an unpigmented, unopacified dental porcelain of a firing temperature appropriate for the system being used. This corresponds to the dental matrix described above.

[0081] The glaze base is an unpigmented, transparent glazing porcelain with a firing temperature appropriate to the system being used. It corresponds to the glazes described above.

[0082] The viscosity modifier is any thickening agent suitable for use in the system being used. A viscosity modifier can be optionally added to control the consistency of the paste. The addition of the viscosity modifier aids in the formation of the paste and, if necessary, helps to impart flow properties such as shear thinning, thixotropy, and / or shear thinning. The viscosity modifier can be selected from one or more of precipitated silica, fumed silica, polyethylene glycol, polyacrylic acid, salts of polyacrylic acid, polyvinyl alcohol, gums, saccharides, and organosilicones.

[0083] Opal component refers to synthetic opal as described herein.

[0084] The liquid component provides a vehicle for the glaze base and is removed during the baking process. Suitable liquid components include at least one liquid selected from C1-C6 monoalcohols, C1-C6 diols, C1-C6 triols, tripropylene glycol, polyethylene glycol, polypropylene glycol, and water.

Claims

1. 1. A composition for imparting opalescence to dental restorations, the composition comprising: a ceramic component that is about 50-85% by weight of a glaze base; an opal component; and a liquid component, wherein the opal component is a colloidally assembled silica synthetic opal that is partially or completely infiltrated with one or more of titania, zirconia, alumina, yttria, zinc oxide, hafnia, tin oxide, indium oxide, ceria, niobium oxide, tantalum oxide, germanium oxide, gallium oxide, and scandium oxide.

2. about 50-85 wt. % of said ceramic component; about 1-20% by weight of said opal component; and remaining liquid components; The composition of claim 1 comprising:

3. The composition of claim 1, wherein the opal component is present at about 2-20% by weight.

4. 4. The composition of claim 3, wherein the opal component is present at about 2-6% by weight.

5. 10. The composition of claim 1, wherein the opal component is present at about 6-20% by weight.

6. 6. The composition of claim 5, wherein the opal component is present at about 6-12% by weight.

7. 10. The composition of claim 1, wherein the opal component is present at about 6-15% by weight.

8. 10. The composition of claim 1, further comprising less than about 2% by weight of a viscosity modifier.

9. 10. The composition of claim 1, further comprising less than about 1% by weight of a fluorescent agent.

10. less than about 2% by weight of a viscosity modifier, and 10. The composition of claim 1, further comprising less than about 1% by weight of a fluorescent agent.

11. 10. The composition of claim 1, wherein the opal component is a colloidally assembled silica synthetic opal partially infiltrated with one or more of titania, zirconia, alumina, yttria, zinc oxide, hafnia, tin oxide, indium oxide, ceria, niobium oxide, tantalum oxide, germanium oxide, gallium oxide, and scandium oxide.

12. 12. The composition of claim 11, wherein the opal component is a colloidally assembled silica synthetic opal partially infiltrated with titania.

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