Dental compositions containing nanoparticles that provide a refractive index difference between a polymerizable resin and a filler

Abstract

Dental compositions and methods of formulating dental compositions are described. In one embodiment, the dental composition comprises a polymerizable resin containing one or more ethylenically unsaturated monomers or oligomers and nanoparticles. The nanoparticles have a refractive index of at least 1.600 and an average discrete particle or aggregate size of 100 nm or less. The dental composition further comprises an inorganic metal oxide filler having an average discrete particle or aggregate size of at least 200 nm. The nanoparticles are present in a concentration that results in a refractive index difference between the hardened polymerizable resin and the inorganic metal oxide filler, such that the dental composition has a contrast ratio of at least 40.

Description

Summary of the Invention

[0001] Dental compositions typically contain pigments to obtain desired opacity (e.g., contrast ratio) and aesthetic shade. It has been found that the inclusion of pigments, especially titania, can hinder cure depth. Although various dental hardenable compositions have been described, the industry would benefit from compositions with improved properties, such as high cure depth combined with high contrast ratio.

[0002] In one embodiment, a dental composition is described that includes a polymerizable resin containing one or more ethylenically unsaturated monomers or oligomers and nanoparticles. The nanoparticles have a refractive index of at least 1.600 and an average discrete particle or aggregate size of 100 nm or less. The dental composition further includes an inorganic metal oxide filler having an average discrete particle or aggregate size of at least 200 nm. The nanoparticles are present in a concentration that results in a refractive index differential between the cured polymerizable resin containing the nanoparticles and the inorganic metal oxide filler, such that the dental composition has a contrast ratio of at least 40.

[0003] In a preferred embodiment, the refractive index difference is balanced to maximize the contrast ratio while still providing a cure depth of at least 3.5 mm.

[0004] In another embodiment, a dental composition is described that includes a polymerizable resin that includes one or more ethylenically unsaturated monomers or oligomers and is substantially free of bisphenol-derived monomers. The polymerizable resin further includes high-refractive-index nanoparticles, as previously described. The concentrations of the polymerizable resin and nanoparticle components are selected so that the cured polymerizable resin containing the nanoparticles has a refractive index that differs from the refractive index of the (e.g., inorganic metal oxide) filler by at least 0.005, 0.006, 0.007, 0.008, 0.009, or 0.010.

[0005] In another embodiment, a dental composition is described that includes a polymerizable resin containing at least one bisphenol-derived monomer and high refractive index nanoparticles (as described immediately above). The concentrations of the polymerizable resin and nanoparticle components are selected so that the cured polymerizable resin containing the nanoparticles has a refractive index that differs from the (e.g., inorganic metal oxide) filler by at least 0.010, 0.011, 0.012, 0.013, 0.014, or 0.015.

[0006] Methods for treating tooth surfaces, dental articles, and methods for making dental compositions are also described. DETAILED DESCRIPTION OF THE INVENTION

[0007] The (hardenable) dental compositions described herein include a polymerizable resin and a (eg, inorganic metal oxide) filler.

[0008] Polymerizable resins typically contain at least one ethylenically unsaturated monomer or oligomer because they are curable by exposure to actinic radiation (e.g., light). In typical embodiments, such as dental composites, the polymerizable resin contains at least one polyfunctional ethylenically unsaturated monomer. The phrase "polyfunctional ethylenically unsaturated" means that each monomer contains at least two ethylenically unsaturated (e.g., free-radical) polymerizable groups. The ethylenically unsaturated groups are typically (e.g., terminal) free-radical polymerizable groups, such as (meth)acrylics, such as (meth)acrylamide (HC=CHCON- and HC=CH(CH)CON-), and (meth)acrylates (CHCHCOO- and CHC(CH)COO-). Other ethylenically unsaturated polymerizable groups include vinyls (HC=C-), such as vinyl ethers (HC=CHO-). Preferably, the ethylenically unsaturated terminal polymerizable group is a (meth)acrylate group, especially for compositions that are hardened by exposure to actinic radiation (e.g., UV or blue light). Furthermore, methacrylate functionality is typically preferred over acrylate functionality in dental hardenable compositions.

[0009] A variety of ethylenically unsaturated (eg, (meth)acrylate) monomers are known in the art for use in dental compositions, some of which are described below.

[0010] The polymerizable resin further comprises nanoparticles (e.g., inorganic metal oxides). Such nanoparticles, or "nanoscopic fillers," can be used as viscosity and thixotropy modifiers. Such nanoparticles can also partially contribute to the mechanical properties of the dental hardenable composition. Due to their size, such nanoparticles also contribute to the refractive index of the polymerizable resin.

[0011] In some embodiments, inorganic oxide nanoparticles have a primary particle size of 100 nm or less. Primary particle size typically refers to the size of non-aggregated, discrete particles. In other, less common, embodiments, nanoparticles may be aggregates of two or more particles bonded (e.g., fused or covalently) together, with the aggregates having a particle size of 100 nm or less. The average particle size can be determined by cutting a thin section sample of the solidified dental composition, measuring the particle sizes of approximately 50-100 particles using transmission electron micrographs at 300,000 magnification, and calculating the average. The nanoparticles can have a unimodal or multimodal (e.g., bimodal) particle size distribution. In some embodiments, (e.g., zirconia) nanoparticles have an average particle size of at least about 2, 3, 4, or 5 nanometers (nm). In some embodiments, (e.g., zirconia) nanoparticles have an average particle size of about 50, 40, 30, 25, 15, or 10 nanometers (nm) or less.

[0012] In a preferred embodiment, the dental composition contains nanoparticles (e.g., inorganic metal oxides) with a relatively high refractive index. The refractive index of the nanoparticles is typically greater than the refractive index of the individual organic components (e.g., (meth)acrylate monomers, etc.) of the polymerizable resin, as well as the refractive index of the mixture of organic components. Thus, the inclusion of high-refractive-index nanoparticles can increase the refractive index of the polymerizable resin. In typical embodiments, the high-refractive-index nanoparticles have a refractive index of at least 1.60, 1.65, 1.70, 1.75, 1.80, 1.85, 1.80, 1.85, or 2.00. Typical high-refractive-index inorganic metal oxide nanoparticles include alumina, which has a refractive index of 1.766, zirconia, which has a refractive index of 2.208, and titania, which has a refractive index of 2.614. In some embodiments, the nanoparticles can include a single inorganic oxide, which further contains minor amounts of other materials, such as other metal oxides. For example, in some embodiments, the nanoparticles comprise zirconia and up to about 5% by weight of another metal oxide, such as yttria. In other embodiments, the nanoparticles comprise appreciable amounts of two or more metal oxides, such as a mixed metal oxide of zirconia and silica. In some embodiments, the inorganic metal oxide nanoparticles have a refractive index of 2.4 or 2.3 or less, such as in the case of zirconia.

[0013] The dental composition optionally further comprises nanoparticles (e.g., inorganic metal oxides) having a relatively low refractive index, such as silica. The inclusion of low refractive index nanoparticles can reduce the refractive index of the polymerizable resin. Suitable silica nanoparticles are commercially available from Ecolab (St. Paul, MN) under the trade name NALCO COLLOIDAL SILICAS. For example, preferred silica particles can be obtained using NALCO products 1034A, 1040, 1042, 1050, 1060, 2327, and 2329.

[0014] Silica nanoparticles are preferably prepared from an aqueous colloidal dispersion (i.e., sol or aquasol) of silica. Colloidal silica is typically present in the silica sol at a concentration of about 1 to 50 weight percent. Colloidal silica sols with different colloidal sizes that can be used are commercially available; see Surface & Colloid Science, Vol. 6, ed. Matijevic, E., Wiley Interscience, 1973. Preferred silica sols for use in preparing fillers are supplied as dispersions of amorphous silica in aqueous media (e.g., Nalco colloidal silica from Ecolab) and those with low sodium concentrations that can be acidified by admixture with a suitable acid (e.g., Ludox colloidal silica from EI Dupont de Nemours & Co., or Nalco 2326 from Ecolab).

[0015] In some embodiments, the dental composition comprises at least 0.5, 1, 1.5, or 2 wt. % low refractive index (e.g., silica) nanoparticles. The amount of low refractive index (e.g., silica) nanoparticles is typically no more than 30, 25, 20, 15, or 5 wt. % of the dental composition. In other embodiments, the dental composition comprises less than 1, 0.5, 0.25, 0.1, or 0.005 wt. % low refractive index (e.g., silica) nanoparticles, or is substantially free of low refractive index (e.g., silica) nanoparticles.

[0016] When low-refractive-index (e.g., silica) nanoparticles are included in a dental composition, the concentration of the low-refractive-index (e.g., silica) nanoparticles is generally less than the concentration of the high-refractive-index (e.g., zirconia) nanoparticles. Thus, the weight or volume concentration of the high-refractive-index (e.g., zirconia) nanoparticles is typically greater than the weight or volume concentration of the low-refractive-index (e.g., silica) nanoparticles. In some embodiments, the weight or volume ratio of the high-refractive-index (e.g., zirconia) nanoparticles to the low-refractive-index (e.g., silica) nanoparticles is at least 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, or 2:1. In some embodiments, the weight or volume ratio of the high-refractive-index (e.g., zirconia) nanoparticles to the low-refractive-index (e.g., silica) nanoparticles is at least 2.1:1, 2.2:1, 2.3:1, or 2.4:1. In some embodiments, the weight or volume ratio of high refractive index (eg, zirconia) nanoparticles to low refractive index (eg, silica) nanoparticles is 100:1, 75:1, 50:1, 25:1, 10:1, or 5:1 or less.

[0017] Some suitable low refractive index (e.g., silica) nanoparticles and high refractive index (e.g., zirconia) nanoparticles are disclosed in U.S. Pat. Nos. 6,387,981 (Zhang et al.) and 6,572,693 (Wu et al.), as well as PCT International Publication Nos. WO 01 / 30304 (Zhang et al.), WO 01 / 30305 (Zhang et al.), WO 01 / 30307 (Zhang et al.), WO 03 / 063804 (Wu et al.), U.S. Pat. Nos. 7,090,721 (Craig et al.), 7,090,722 (Budd et al.), 7,156,911 (Kangas et al.), U.S. Pat. No. 7,241,437 (Davidson et al.), and U.S. Pat. No. 7,649,029 (Kolb et al.).

[0018] The dental compositions described herein preferably contain an appreciable amount of inorganic metal oxide filler. Fillers used in dental applications are typically ceramic in nature.

[0019] The filler can be selected from one or more of a wide range of materials suitable for incorporation into compositions used for dental applications, such as fillers currently used in dental composites and dental articles (e.g., crowns). Fillers are generally non-toxic and suitable for use in the oral cavity. Fillers can be radiopaque, radiolucent, or non-radiopaque. In some embodiments, the filler typically has a refractive index of at least 1.500, 1.510, 1.520, 1.530, or 1.540.

[0020] To increase radiopacity, it is common to include up to about 5% by weight of a component such as YbF. In some embodiments, the radiopacity of the hardened dental composition is at least 3 mm thick aluminum.

[0021] The filler may be either particulate or fibrous in nature. Particulate fillers may generally be defined as having a length-to-width ratio or aspect ratio of 20:1 or less, more commonly 10:1 or less. Fibers may be defined as having an aspect ratio of greater than 20:1, or more commonly greater than 100:1. The shape of the particles may vary, ranging from spherical to ellipsoidal, or more planar, such as flakes or discs. Macroscopic properties may be highly dependent on the shape of the filler particles, particularly the uniformity of the shape.

[0022] The dental composition described herein comprises inorganic metal oxide filler material that is larger in size than nanoparticles.As described above, nanoparticles are typically non-agglomerated, discrete particles with a particle size of 100 nm or less.In contrast, inorganic metal oxide fillers are particulate or fibrous materials with at least one dimension greater than 100 nm, such as at least 150 nm or at least 200 nm.For particulate fillers, the average particle size of the non-agglomerated, discrete particles or agglomerated particles is at least 200 nm.Inorganic metal oxide fillers are very effective for improving wear properties after curing.

[0023] In some embodiments, the hardened dental composition exhibits a flexural strength of at least 120, 130, or 140 MPa, and typically no more than 200 MPa or 250 MPa. In some embodiments, the hardened dental composition exhibits a flexural modulus of at least 3, 4, 5, 6, 7, 8, 9, or 10 GPa, and typically no more than 15 or 20 GPa.

[0024] In some embodiments, the filler may comprise a crosslinked organic material that is insoluble in the polymerizable resin, and may optionally be filled with inorganic fillers. Examples of suitable organic filler particles include filled or unfilled ground polycarbonates, polyepoxides, poly(meth)acrylates, and the like.

[0025] In some embodiments, the dental compositions described herein contain an acid-reactive filler, provided that the dental composition does not contain a component, such as a carboxylate, that appreciably reacts with the acid-reactive filler. Acid-reactive metal oxide fillers include, for example, barium oxide, calcium oxide, magnesium oxide, and zinc oxide. Acid-reactive glasses include borate glasses, phosphate glasses, and fluoroaluminosilicate ("FAS") glasses. However, in typical embodiments, the dental composition contains a non-acid-reactive filler, and the dental composition is substantially free of acid-reactive fillers (less than 1, 0.5, 0.25, 0.1, or 0.005 wt. %).

[0026] In some embodiments, the dental compositions described herein include non-acid-reactive fillers such as quartz, fumed silica, non-vitreous particulates of the type described in U.S. Pat. No. 4,503,169 (Randklev), and nanocluster fillers, such as those described in U.S. Pat. No. 6,730,156 (Windisch et al.), U.S. Pat. No. 6,572,693 (Wu et al.), and U.S. Pat. No. 8,722,759 (Craig).

[0027] In some embodiments, the filler comprises nanoclusters, i.e., nanoparticles, in the form of groups of two or more particles held together by intermolecular forces that are relatively weak but sufficient to cause the particles to agglomerate even when dispersed in a hardenable resin. Preferred nanoclusters may include lightly agglomerated, substantially amorphous clusters of non-heavy metal oxide (e.g., silica) particles and heavy metal oxides (i.e., having an atomic number greater than 28), such as zirconia. The zirconia may be crystalline or amorphous. In some embodiments, the zirconia may be present as particles. The particles forming the nanoclusters preferably have an average diameter of less than about 100 nm. However, the average particle size of lightly agglomerated nanoclusters is typically significantly larger.

[0028] Mixtures of fillers can also be used. When a mixture of fillers is used, a sufficient amount of the filler has a refractive index different from that of the cured polymerizable resin containing nanoparticles to provide the contrast ratio described herein. In some embodiments, at least 40, 50, 60, 70, 80, 90% or more by weight of the total filler mixture is a filler having a refractive index different from that of the cured polymerizable resin containing nanoparticles. Thus, a portion of the filler can be a filler having the same or a more similar refractive index as that of the cured polymerizable resin.

[0029] In some embodiments, the dental compositions described herein comprise at least 60, 61, 62, 63, 64, or 65 wt.% nanocluster filler, based on the total weight of the composition. The maximum amount of nanocluster filler is typically no more than 75% or 80%. In some embodiments, the total amount of inorganic metal oxide materials (i.e., nanoparticles and filler) is at least 70, 71, 72, 73, 74, or 75 wt.%. The maximum amount of inorganic metal oxide materials (i.e., nanoparticles and filler) is typically no more than 80% or 85%.

[0030] In some embodiments, the filler particles (e.g., nanoclusters) have a higher refractive index than the organic phase of the polymerizable resin. For example, the filler particles (e.g., nanoclusters) may have a refractive index of at least 1.530, 1.535, or 1.540, while the organic phase of the polymerizable resin (i.e., no nanoparticles present) has a refractive index of 1.500, 1.505, 1.510, 1.515, 1.520, or 1.525.

[0031] Due to the size of the fillers, they do not increase the refractive index of the polymerizable resin, rather, they act as a separate phase with respect to refractive index.

[0032] In some embodiments, the dental composition comprises a sufficient amount of high refractive index (e.g., zirconia) nanoparticles to provide a refractive index difference between the hardened polymerizable resin (i.e., containing the nanoparticles) and the inorganic metal oxide filler, such that the contrast ratio is at least 40, 41, 42, 43, 44, or 45.

[0033] As the concentration of high refractive index (e.g., zirconia) nanoparticles increases, the refractive index difference between the cured polymerizable resin containing the nanoparticles and the filler increases, which can result in a higher contrast ratio (opacity). However, even in the absence of (e.g., titania) pigment particles, the increased contrast ratio (e.g., opacity) reduces the depth of cure. Therefore, the concentrations of the polymerizable resin and nanoparticle components are selected to provide a synergistic balance of contrast ratio and depth of cure. In some embodiments, the refractive index difference and contrast ratio are maximized for a depth of cure of at least 3.5 mm or 4 mm.

[0034] The refractive index difference that can result in a contrast ratio of at least 40 can vary depending on the composition of the polymerizable resin. In typical embodiments, the refractive index difference is at least 0.005, 0.006, 0.007, 0.008, 0.009, and in some embodiments, even in the absence of a (e.g., titania) pigment, is at least 0.010, 0.011, 0.012, or 0.013.

[0035] In some embodiments, such as in the case of dental compositions containing little or no bisphenol-derived monomer, the refractive index difference may be 0.025, 0.024, 0.023, 0.021, or 0.020 or less. In other embodiments, such as in the case of dental compositions containing appreciable amounts of bisphenol-derived monomer, the refractive index difference may be 0.055, 0.054, 0.053, 0.052, 0.051, 0.050, 0.049, 0.048, 0.047, 0.046, or 0.045 or less. If the difference is too large, even in the absence of a (e.g., titania) pigment, the depth of cure may disadvantageously be less than 3.5 mm (or, in other words, 4 mm according to the ISO 4049 standard).

[0036] In some embodiments, the refractive index of the uncured polymerizable resin containing nanoparticles is less than the refractive index of the filler. In other embodiments, the refractive index of the uncured polymerizable resin containing nanoparticles is equal to or greater than the refractive index of the filler. In typical embodiments, the refractive index of the cured polymerizable resin containing nanoparticles is greater than the refractive index of the filler. In some embodiments, the refractive index of the filler is between (e.g., midway between) the refractive index of the uncured polymerizable resin containing nanoparticles and the cured polymerizable resin containing nanoparticles.

[0037] The contrast ratio can be achieved even in the absence of pigment and at lower pigment concentrations because it is provided by the refractive index difference between the cured polymerizable resin (i.e., containing nanoparticles) and the inorganic metal oxide filler. The pigment concentration can also vary depending on the composition of the polymerizable resin. The pigment particles typically have a discrete particle or aggregate size of at least 150 nm.

[0038] In some embodiments, such as dental compositions containing little or no bisphenol-derived monomers, the dental composition can include 0.05, 0.04, or 0.03 wt. % or less of pigment particles, such as high refractive index (e.g., titania) pigment particles. In other embodiments, such as dental compositions containing appreciable amounts of bisphenol-derived monomers, the dental composition can include 0.07, 0.06, or 0.05 wt. % or less of pigment particles, such as high refractive index (e.g., titania) pigment particles.

[0039] In some embodiments, such as for dental compositions containing little or no bisphenol-derived monomer, the contrast ratio (even in the absence of (e.g., titania) pigment) is typically no greater than 60, 59, 58, 57, 56, 55. In other embodiments, such as for dental compositions containing appreciable amounts of bisphenol-derived monomer, the contrast ratio (even in the absence of (e.g., titania) pigment) is typically no greater than 70, 69, 68, 67, 66, 65, 64, 63, 62, 61, 60, 59, 58, 57, 56, or 55.

[0040] In some embodiments, such as dental compositions containing little or no bisphenol-derived monomers, the dental composition typically comprises at least 2, 2.5, 3, 3.5, or 4 weight percent high refractive index (e.g., zirconia) nanoparticles, and the amount of high refractive index (e.g., zirconia) nanoparticles is typically no more than 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, or 10 weight percent of the dental composition.

[0041] In other embodiments, such as those containing appreciable amounts of bisphenol-derived monomers, the dental composition typically comprises at least 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10 weight percent high refractive index (e.g., zirconia) nanoparticles, and the amount of high refractive index (e.g., zirconia) nanoparticles is typically no more than 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, or 10 weight percent of the dental composition.

[0042] The concentrations of high refractive index nanoparticles just described are preferred for zirconia. If the high refractive index nanoparticles have a higher refractive index than zirconia, such as titania, a lower concentration of nanoparticles will be used. Furthermore, if the high refractive index nanoparticles have a lower refractive index than zirconia, such as alumina, a higher concentration of nanoparticles will be used.

[0043] In typical embodiments, the (e.g., high refractive index) inorganic metal oxide nanoparticles and inorganic oxide fillers include a surface treatment to enhance the bond between the nanoparticles and inorganic oxide fillers and the resin. Various surface treatments have been described in the art, including, for example, organometallic coupling agents and carboxylic acids, such as those described in U.S. Pat. No. 8,647,510 (Davidson et al.).

[0044] Suitable copolymerizable organometallic compounds have the general formula: CH2=C(CH3) m Si(OR) n or CH2=C(CH3) m C=OOASi(OR) nwhere m is 0 or 1, R is an alkyl group having 1 to 4 carbon atoms, A is a divalent organic linking group, and n is 1 to 3. The organometallic coupling agent may be functionalized with reactive curing groups such as acrylate, methacrylate, vinyl groups, and the like. Preferred coupling agents include gamma-methacryloxypropyltrimethoxysilane, gamma-mercaptopropyltriethoxysilane, gamma-aminopropyltrimethoxysilane, and the like.

[0045] In some embodiments, a combination of surface modifiers may be useful, with at least one of these agents having a functional group that is copolymerizable with the hardenable resin. Other surface modifiers that do not generally react with the hardenable resin may be included to enhance dispersibility or rheological properties. Examples of this type of silane include, for example, aryl polyether, alkyl, hydroxyalkyl, hydroxyaryl, or aminoalkyl functional silanes.

[0046] The surface modification can be carried out either subsequent to or after mixing with the monomer. Typically, it is preferred to combine the organosilane surface treatment compound with the nanoparticles before incorporation into the resin. The amount of surface modifier required depends on several factors, such as particle size, particle type, molecular weight of the modifier, and type of modifier. Generally, it is preferred to deposit approximately a monolayer of modifier on the surface of the particles.

[0047] It is known that the refractive index of a mixture of components can be calculated by determining the sum of the refractive indices of each component multiplied by the volume fraction of such component in the mixture. The equation is as follows:

number

[0048] As one skilled in the art will appreciate, all components can be used in this calculation, but typically it is sufficient to use all polymerizable (e.g., monomeric and oligomeric) components and nanoparticles. The volume of a material can be calculated from the known mass and density of the material. Furthermore, if the refractive index of the mixture is known and the volumes of the components are known, the unknown refractive index of a known volume of a material in the mixture can be calculated by the same equation if the refractive index of the other components is known.

[0049] The amount of surface treatment relative to the total volume of the filler is generally relatively small, so that the presence of the surface treatment has a negligible effect on the refractive index of the filler.Other components that generally have a negligible effect include initiators and additives.However, in the case of nanoparticles, the amount of surface treatment relative to the total volume of inorganic metal oxide nanoparticles is important and is included in the calculation.

[0050] The refractive index and density of various components commonly used in dental hardenable compositions are reported in the literature or provided by suppliers of such materials.For components not reported in the literature, density and refractive index values ​​can be measured using known and established techniques.For example, mercury porosimetry can be used to measure density, and refractive index can be measured according to the method described in the examples below.The refractive index and density of some representative components are as follows: [Table 1]

[0051] This allows the refractive index of the uncured polymerizable resin containing the nanoparticles to be calculated.

[0052] In some embodiments, the refractive index of the uncured polymerizable resin comprising the surface-modified nanoparticles differs from the refractive index of the inorganic oxide filler by more than 0.020. For example, this difference may be at least 0.021, 0.022, or 0.023. In other embodiments, the refractive index of the uncured polymerizable resin comprising the surface-modified nanoparticles (e.g., surface-modified nanoparticles) differs from the refractive index of the inorganic oxide filler by an amount of 0.020 or less. In some embodiments, the refractive index of the uncured polymerizable resin comprising the surface-modified nanoparticles differs from the refractive index of the inorganic oxide filler by at least 0.015, 0.016, 0.017, 0.018, or 0.019.

[0053] As can be determined by one skilled in the art, the refractive index of an uncured polymerizable resin generally increases with the densification (shrinkage) of the polymerizable monomer, on the order of about 0.030 to about 0.040. Therefore, the refractive index of a cured polymerizable resin can be approximated from the calculated refractive index of the uncured polymerizable resin, and vice versa.

[0054] In one embodiment, a method of formulating a dental composition is described that includes preparing the refractive index of one or more ethylenically unsaturated monomers of a polymerizable resin, preparing the refractive index of at least one filler, calculating the refractive index of the polymerizable resin and the filler, and adjusting the refractive index of the polymerizable resin with nanoparticles to obtain a sufficient refractive index difference (as described above) such that the hardened dental composition has a contrast ratio of at least 40. This method can then be used to "design" a dental composition with desired refractive index characteristics, and therefore contrast ratio.

[0055] In one embodiment, the polymerizable resin (including the surface-modified nanoparticles) is designed to have a refractive index less than that of the filler before curing and greater than that of the filler after curing. Without intending to be bound by theory, it is speculated that such a polymerizable resin (including the surface-modified nanoparticles) increases in transparency during curing as its refractive index approaches that of the filler. This contributes to a high cure depth. Furthermore, the same polymerizable resin (including the surface-modified nanoparticles) decreases in transparency during curing as the refractive index of the polymerizable resin (including the nanoparticles) exceeds that of the filler, increasing the contrast ratio. In some embodiments, the polymerizable resin (including the surface-modified nanoparticles) is designed so that the refractive index of the filler is near the midpoint between the refractive index of the uncured polymerizable resin (including the nanoparticles) and the refractive index of the cured polymerizable resin.

[0056] A variety of ethylenically unsaturated monomers can be used in dental compositions. The ethylenically unsaturated monomers of dental compositions are typically stable liquids at about 25°C, meaning that the monomers do not substantially polymerize, crystallize, or otherwise solidify when stored at room temperature (about 25°C) for a typical shelf life of at least 30, 60, or 90 days. The viscosity of the monomers typically does not change (e.g., increase) by more than 10% of the initial viscosity.

[0057] In particular, for dental restorative compositions, ethylenically unsaturated monomers generally have a refractive index of at least 1.50. In some embodiments, the refractive index is at least 1.51, 1.52, 1.53, or higher. The inclusion of a sulfur atom and / or the presence of one or more aromatic moieties can increase the refractive index (compared to a monomer of the same molecular weight that does not contain such substituents).

[0058] In an exemplary embodiment, the polymerizable resin comprises at least one monomer containing at least two ethylenically unsaturated (e.g., (meth)acrylate) groups, such as a bisphenol-derived monomer, a (e.g., aromatic) low volume shrinkage resin, or a combination thereof.

[0059] Preferred dental compositions described herein include one or more low volume shrinkage monomers such that the compositions exhibit a Watts Shrinkage of less than about 2%. In some embodiments, the Watts Shrinkage is 1.90% or less, or 1.80% or less, or 1.70% or less, or 1.60% or less.

[0060] Low volume shrinkage monomers include compounds described in U.S. Pat. No. 8,710,113; isocyanurate monomers such as those described in International Publication No. WO 2011 / 126647; tricyclodecane monomers such as those described in European Patent Application No. 10168240.9, filed July 2, 2010; polymerizable compounds having at least one cyclic aryl sulfide moiety such as those described in U.S. Patent Application Publication No. 2008 / 0194722; methylenedithiepane silanes such as those described in U.S. Pat. No. 6,794,520; oxetane silanes such as those described in U.S. Pat. No. 6,284,898; and di-, tri-, and / or tetra-(meth)acryloyl-containing materials such as those described in International Publication No. WO 2008 / 082881, each of which is incorporated herein by reference.

[0061] In some preferred embodiments, a majority of the (e.g., unfilled) polymerizable resin composition comprises one or more low volume shrinkage monomers, for example, at least 50%, 60%, 70%, 80%, 90%, or more of the (e.g., unfilled) polymerizable resin may comprise low volume shrinkage monomers.

[0062] In one embodiment, the dental compositions described herein include low-volume shrinkage monomers, such as those described in U.S. Patent No. 8,710,113. Such monomers contain a single backbone unit (U) having 6 to 20 carbon atoms, at least 6 of which form an aromatic or aliphatic cyclic moiety, and the remaining carbon atoms are either part of a substituent pendant from the cyclic moiety or part of a bridging group to a spacer unit, with one or more of the remaining carbon atoms optionally replaced by an oxygen atom. This backbone unit typically does not contain a bisphenol structure and preferably does not contain a halogen atom (e.g., F, Cl, Br).

[0063] The monomer further comprises one or two units (S) connected to the backbone unit (U) via ether bonds, wherein at least one spacer unit (S) comprises a -CH-CH-CH-CH-O-CH-CH(Q)-OG chain or a -CH-CH(OG)-CH-OM residue, or a mixture of these two spacer types within a single spacer unit (wherein G is attached to the spacer unit (S) via a urethane moiety, each G group comprises at least one polymerizable moiety, M comprises at least one group selected from acryloyl, methacryloyl, aryl, mixtures and combinations thereof, and Q comprises at least one group selected from hydrogen, methyl, phenyl, phenoxymethyl, mixtures and combinations thereof). In such compounds, at least two G groups are present. Furthermore, when only one unit (S) is present, the G group is not part of the unit (S) but is located on a substituent pendant from the unit (U), and the unit (U) has two substituents, each bearing a G group.

[0064] In some embodiments, the backbone unit (U) may comprise a moiety selected from: [ka]

[0065] The polymerizable moiety G is a moiety selected from: [ka] and combinations thereof.

[0066] Various representative structures are described in U.S. Patent No. 8,870,113. One such compound is as follows: [ka] where Q=hydrogen, methyl, phenyl, or phenoxymethyl; a, b, c, and d=0 to 3; (a+b)=1 to 6, (c+d)=1~6.

[0067] Another compound is as follows, where U and G are as defined above: [ka]

[0068] One representative compound is as follows: [ka]

[0069] The linking group of a low-shrinkage monomer typically has a molecular weight low enough that the monomer is a stable liquid at 25°C. However, the linking group typically has a molecular weight higher than the oxygen atom of, for example, 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl]propane ("BisGMA"), a common monomer utilized in dental compositions that links a (meth)acrylate group to an aromatic ring. The molecular weight of the linking group of the described monomers is typically at least 50 g / mol or 100 g / mol. In some embodiments, the molecular weight of the linking group is at least 150 g / mol. The molecular weight of the linking group is typically about 500 g / mol or less. In some embodiments, the molecular weight of the linking group is 400 g / mol or 300 g / mol or less.

[0070] In some embodiments, the molecular weight (i.e., calculated) of the low shrinkage monomer is typically 2000 g / mol or less. In some embodiments, the molecular weight of the monomer is about 1500 g / mol, or 1200 g / mol, or 1000 g / mol or less. The molecular weight of the monomer is typically at least 600 g / mol.

[0071] Increasing molecular weight without forming solids at 25° C. can be achieved by a variety of synthetic approaches. In some embodiments, the monomer has one or more pendant (e.g., polymerizable) substituents. In other embodiments, the monomer contains at least one aliphatic cyclic moiety and / or one or more aromatic moieties.

[0072] The multifunctional low shrinkage monomer is a (e.g., highly) viscous liquid, yet flowable, at about 25° C. The viscosity, as can be measured with a Haake RotoVisco RV1 device, as described in European Patent Application No. 10168240.9, filed July 2, 2010, is typically at least 300, or 400, or 500 Pa. * s and 10,000 Pa *In some embodiments, the viscosity is 5000 or 2500 Pa. * s or less.

[0073] In some embodiments, the dental composition comprises at least 5%, 10%, or 15% by weight, and typically no more than 30%, 25%, or 20% by weight, of low-volume shrinkage monomers. Mixtures of low-volume shrinkage monomers can be improved, some of which are exemplified in International Publication No. WO 2012 / 112350, which is incorporated herein by reference.

[0074] In other embodiments, the polymerizable resin comprises a bisphenol-derived monomer, such as ethoxylated bisphenol A dimethacrylate (BisEMA6), bisphenol A diglycidyl dimethacrylate (bisGMA), and mixtures thereof. In this embodiment, the dental composition comprises at least 5%, 10%, or 15% by weight of the bisphenol-derived monomer, and typically no more than 30%, 25%, or 20% by weight.

[0075] In some embodiments, the dental composition further comprises a low viscosity reactive (i.e., polymerizable) diluent. The reactive diluent typically has a viscosity of 300 Pa or less, as measured with a Haake RotoVisco RV1 device, such as that described in European Patent Application No. 10168240.9, filed July 2, 2010. * s or less, and preferably 100 Pa * s, or 50 Pa * s, or 10 Pa * In some embodiments, the reactive diluent has a viscosity of 1 or 0.5 Pa.s or less. * The reactive diluents have a viscosity of 0.05 wt. s ​​or less. Reactive diluents are relatively low in molecular weight, typically having a molecular weight of less than 600 g / mol, or 550 g / mol, or 500 g / mol. Reactive diluents typically contain one or two ethylenically unsaturated groups, such as in the case of mono(meth)acrylate or di(meth)acrylate monomers.

[0076] Some representative reactive diluents include 1,12-dodecanediol dimethacrylate (DDDMA), urethane dimethacrylate (UDMA), triethylene glycol dimethacrylate (TEGDMA), glycerol dimethacrylate (GDMA), ethylene glycol dimethacrylate, neopentyl glycol dimethacrylate (NPGDMA), and polyethylene glycol dimethacrylate (PEGDMA).

[0077] Various mixtures of reactive diluents can be utilized. In some embodiments, the dental composition comprises at least 0.5, 1, or 2 wt. % of the reactive diluent. Typically, the concentration of the reactive diluent is no more than 10, 9, 8, or 7 wt. % of the total dental composition.

[0078] In some embodiments, the dental composition includes at least one addition cleavage agent. The addition cleavage agent includes at least one ethylenically unsaturated end group and a backbone unit including an α,β-unsaturated carbonyl. The addition cleavage agent is cleavable by a free radical.

[0079] The addition cleavage agent is preferably of the formula: [ka] [In the formula, R 1 , R 2 , and R 3 are each independently Z m -Q-, a (hetero)alkyl group, or a (hetero)aryl group, provided that R 1 , R 2 , and R 3 At least one of them is Z m -Q-, Q is a linking group having a valence of m+1; Z is an ethylenically unsaturated polymerizable group, m is 1 to 6, preferably 1 to 2; Each X 1 are independently -O- or -NR4 -, where R 4 is H or C1-C4 alkyl, and n is 0 or 1].

[0080] Addition-cleavage agents according to Formula I are described in US Pat. No. 9,056,043, which is incorporated herein by reference.

[0081] In a preferred embodiment, an addition-cleavage material ("AFM") is added to a dental composition comprising at least one ethylenically unsaturated monomer or oligomer. Without intending to be bound by theory, it is speculated that the inclusion of such an addition-cleavage material reduces polymerization-induced stress, such as by the mechanism described in PCT Publication No. WO 2012 / 112304. In embodiments where the AFM is multifunctional and comprises at least two ethylenically unsaturated groups (e.g., Z is 2 or greater in Formula I), the material may function as a crosslinker, in which case the crosslinks are unstable.

[0082] The ethylenically unsaturated portion Z of the monomer can include the following structures, including but not limited to (meth)acryloyl, vinyl, styrene, and ethynyl, which are more fully described below with reference to the preparation of the compounds. [ka] In the formula, R 4 is H or C1-C4 alkyl.

[0083] In some embodiments, Q is —O—, —S—, —NR 4 -, -SO2-, -PO2-, -CO-, -OCO-, -R 6 -, -NR 4 -CO-NR 4 -, NR 4 -CO-O-, NR 4 -CO-NR 4 -CO-OR 6 -, -CO-NR 4 -R6 -, -R 6 -CO-OR 6 -, -OR 6 -, -SR 6 -, -NR 4 -R 6 -, -SO2-R 6 -, -PO2-R 6 -, -CO-R 6 -, -OCO-R 6 -, -NR 4 -CO-R 6 -, NR 4 -R 6 -CO-O-, and NR 4 -CO-NR 4 wherein each R 4 is hydrogen, a C1-C4 alkyl group, or an aryl group, and each R 6 is an alkylene group having 1 to 6 carbon atoms, a 5- or 6-membered cycloalkylene group having 5 to 10 carbon atoms, or a divalent arylene group having 6 to 16 carbon atoms, with the proviso that QZ does not contain a peroxide bond.

[0084] In some embodiments, Q is a group of formula -C r H 2r In other embodiments, Q is an alkylene such as -CH2-CH(OH)-CH2-, where r is 1 to 10. In some embodiments, Q is an aryloxy-substituted alkylene. In some embodiments, R 5 is an alkoxy-substituted alkylene.

[0085] R 1 -X 1 -group (and optionally R 2 -X 2- group) is typically H2C=C(CH3)C(O)-O-CH2-CH(OH)-CH2-O-, H2C=C(CH3)C(O)-O-CH2-CH(O-(O)C(C H3)=CH2)-CH2-O-, H2C=C(CH3)C(O)-O-CH(CH2OPh)-CH2-O-, H2C=C(CH3)C(O)-O-CH2CH2-N(H )-C(O)-O-CH(CH2OPh)-CH2-O-, H2C=C(CH3)C(O)-O-CH2-CH(O-(O)CN(H)-CH2CH2-O-(O)C(CH 3)C=CH2)-CH2-O-, H2C=C(H)C(O)-O-(CH2)4-O-CH2-CH(OH)-CH2-O-, H2C=C(CH3)C(O)-O-CH2- CH(O-(O)CN(H)-CH2CH2-O-(O)C(CH3)C=CH2)-CH2-O-, CH3-(CH2)7-CH(O-(O)CN(H)-CH2CH2- O-(O)C(CH3)C=CH2)-CH2-O-, H2C=C(H)C(O)-O-(CH2)4-O-CH2-CH(-O-(O)C(H)=CH2)-CH2-O- and H2C=C(H)C(O)-O-CH2-CH(OH)-CH2-O-, H2C=C(H)C(O)-O-(CH2)4-O-CH2-CH(-O-(O)C(H)=CH2)-CH2-O-, and CH3-(CH2)7-CH(O-(O)CN(H)-CH2CH2-O-(O)C(CH3)C=CH2)-CH2-O-.

[0086] The addition-cleavage agent may comprise a single monomer or a blend of two or more addition-cleavage agents. The total amount of addition-cleavage agent in a filled, hardenable (i.e., polymerizable) dental composition is typically 5% by weight, or 4% by weight, or 3% by weight, or 2% by weight or less. As the concentration of the addition-cleavage monomer increases, the stress deflection and Watts shrinkage typically decrease. In some embodiments, the dental compositions described herein typically exhibit a stress deflection of 15, 14, 13, 12, 11, or 10 micrometers or less (e.g., cusp). However, if the amount of addition-cleavage agent is greater than the optimum amount, the mechanical properties or depth of cure may be insufficient.

[0087] Addition-cleavage agents are generally cleavable by free radicals. Although photopolymerization is one mechanism for generating free radicals, other curing mechanisms also generate free radicals. Thus, addition-cleavage agents do not require irradiation with actinic radiation (e.g., photocuring) to result in stress reduction during cure.

[0088] Although low-shrinkage monomers are preferred, the refractive index difference as described herein can also be utilized to improve other dental compositions with higher shrinkage. Thus, the hardenable components of dental hardenable compositions can include a wide variety of other ethylenically unsaturated compounds (with or without acid functionality), epoxy-functional (meth)acrylate resins, vinyl ethers, and the like.

[0089] The (e.g., photopolymerizable) dental composition may include free-radically polymerizable monomers, oligomers, and polymers having one or more ethylenically unsaturated groups. Suitable compounds contain at least one ethylenically unsaturated bond and are capable of undergoing addition polymerization. Examples of useful ethylenically unsaturated compounds include acrylic acid esters, methacrylic acid esters, hydroxy-functional acrylic acid esters, hydroxy-functional methacrylic acid esters, and combinations thereof. Such free radically polymerizable compounds include mono-, di-, or poly-(meth)acrylates (i.e., acrylates and methacrylates), such as methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-hexyl (meth)acrylate, stearyl (meth)acrylate, allyl (meth)acrylate, glycerol tri(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,3-propanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, 1,2,4-butanetriol tri(meth)acrylate, 1,4-cyclohexanediol di(meth)acrylate, pentaerythritol tetra(meth)acrylate, sorbitol hexa(meth)acrylate, and the like. acrylate, tetrahydrofurfuryl (meth)acrylate, bis[1-(2-acryloxy)]-p-ethoxyphenyldimethylmethane, bis[1-(3-acryloxy-2-hydroxy)]-p-propoxyphenyldimethylmethane, ethoxylated bisphenol A di(meth)acrylate, and trishydroxyethyl-isocyanurate tri(meth)acrylate; (meth)acrylamides (i.e., acrylamide and methacrylamide), such as (meth)acrylamide, methylene bis-(meth)acrylamide, and diacetone (meth)acrylamide; urethane (meth)acrylate; bis-(meth)acrylate of polyethylene glycol (preferably having a molecular weight of 200 to 500); and vinyl compounds, such as styrene, diallyl phthalate, divinyl succinate, divinyl adipate, and divinyl phthalate.Other suitable free-radically polymerizable compounds include siloxane-functional (meth)acrylates. Mixtures of two or more free-radically polymerizable compounds can be used if desired.

[0090] The dental hardenable composition may also contain a monomer having a hydroxyl group and an ethylenically unsaturated group in a single molecule.Examples of such materials include hydroxyalkyl (meth)acrylates, such as 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate; glycerol mono- or di-(meth)acrylate; trimethylolpropane mono- or di-(meth)acrylate; pentaerythritol mono-, di-, and tri-(meth)acrylate; sorbitol mono-, di-, tri-, tetra-, or penta-(meth)acrylate; and 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane (bisGMA).Suitable ethylenically unsaturated compounds are available from a wide range of commercial suppliers, such as Sigma-Aldrich, St. Louis. However, in some embodiments, the dental composition is substantially free (less than 1, 0.5, 0.25, 0.1, or 0.005% by weight) of monomers having a hydroxyl group and an ethylenically unsaturated group in a single molecule.

[0091] The dental compositions described herein may include one or more hardenable components in the form of an ethylenically unsaturated compound having acid functionality. Such components contain both an acid group and an ethylenically unsaturated group in a single molecule. When present, the polymerizable component optionally includes an ethylenically unsaturated compound having acid functionality. Preferably, the acid functionality comprises an oxyacid (i.e., an oxygen-containing acid) of carbon, sulfur, phosphorus, or boron. However, in some embodiments, the dental composition is substantially free (less than 1, 0.5, 0.25, 0.1, or 0.005 wt. %) of an ethylenically unsaturated compound having acid functionality.

[0092] As used herein, the term "ethylenically unsaturated compound having acid functionality" is intended to include monomers, oligomers, and polymers having ethylenic unsaturation and acid and / or acid precursor functional groups. Acid precursor functional groups include, for example, anhydrides, acid halides, and pyrophosphates. Acid functional groups can include carboxylic acid functional groups, phosphoric acid functional groups, phosphonic acid functional groups, sulfonic acid functional groups, or combinations thereof.

[0093] Examples of ethylenically unsaturated compounds having an acid functional group include α,β-unsaturated acidic compounds, such as glycerol phosphate mono(meth)acrylate, glycerol phosphate di(meth)acrylate (GDMA-P), hydroxyethyl (meth)acrylate (e.g., HEMA) phosphate, bis((meth)acryloxyethyl)phosphate, ((meth)acryloxypropyl)phosphate, bis((meth)acryloxypropyl)phosphate, bis((meth)acryloxy)propyloxyphosphate, (meth)acryloxyhexyl phosphate, bis((meth)acryloxyhexyl)phosphate, and (meth)acryloxyoctyl phosphate. Examples of compounds that can be used as components include bis((meth)acryloxyoctyl)phosphate, (meth)acryloxydecylphosphate, bis((meth)acryloxydecyl)phosphate, caprolactone methacrylate phosphate, citric acid di- or tri-methacrylate, poly(meth)acrylated oligomaleic acid, poly(meth)acrylated polymaleic acid, poly(meth)acrylated poly(meth)acrylic acid, poly(meth)acrylated polycarboxyl-polyphosphonic acid, poly(meth)acrylated polychlorophosphonic acid, poly(meth)acrylated polysulfonate, poly(meth)acrylated polyboric acid, and the like. Monomers, oligomers, and polymers of unsaturated carbonic acid, such as (meth)acrylic acid, aromatic (meth)acrylated acids (e.g., methacrylated trimellitic acid), and their anhydrides can also be used.

[0094] The dental composition may include an ethylenically unsaturated compound having an acid functional group with at least one P-OH moiety. Such compositions are self-adhesive and non-aqueous. For example, such compositions may include at least one (meth)acryloxy group and at least one -OP(O)(OH) x A first compound comprising a group, wherein x=1 or 2, and at least one —OP(O)(OH) x a first compound, wherein the at least one (meth)acryloxy group and at least one —O—P(O)(OH) group are linked together by a C1-C4 hydrocarbon group; and x a second compound comprising a group, where x=1 or 2, and at least one —OP(O)(OH) x The group and at least one (meth)acryloxy group may include a second compound linked together by a C5-C12 hydrocarbon group; an ethylenically unsaturated compound without acid functionality; an initiator system; and a filler.

[0095] The initiator is typically added to the mixture of polymerizable components. The initiator is sufficiently miscible with the resin system so as to be readily soluble in (and prevent separation from) the polymerizable composition. Typically, the initiator is present in the composition in an effective amount, such as from about 0.1 weight percent to about 5.0 weight percent, based on the total weight of the composition.

[0096] In some embodiments, the mixture of monomers is photopolymerizable, and the composition contains a photoinitiator (i.e., a photoinitiator system) that initiates polymerization (or solidification) of the composition upon irradiation with actinic radiation. Such photopolymerizable compositions may be free-radically polymerizable. Photoinitiators typically have an effective wavelength range of about 250 nm to about 800 nm. Photoinitiators (i.e., photoinitiator systems comprising one or more compounds) suitable for polymerizing free-radically photopolymerizable compositions include two-component and three-component systems. Typical three-component photoinitiators include an iodonium salt, a photosensitizer, and an electron donor compound, as described in U.S. Pat. No. 5,545,676 (Palazzotto et al.). Iodonium salts include diaryliodonium salts, such as diphenyliodonium chloride, diphenyliodonium hexafluorophosphate, and diphenyliodonium tetrafluoroborate. Some preferred photosensitizers include monoketones and diketones (e.g., alpha diketones) that absorb some light within the range of about 300 nm to about 800 nm (preferably about 400 nm to about 500 nm), such as camphorquinone, benzil, furil, 3,3,6,6-tetramethylcyclohexanedione, phenanthraquinone, and other cyclic alpha diketones. Among these, camphorquinone is typically preferred. Preferred electron donor compounds include substituted amines, such as ethyl 4-(N,N-dimethylamino)benzoate.

[0097] Other photoinitiators suitable for polymerizing free radically photopolymerizable compositions include the class of phosphine oxides, which typically have an effective wavelength range of about 380 nm to about 1200 nm. Preferred phosphine oxide free radical initiators with an effective wavelength range of about 380 nm to about 450 nm are the acyl and bisacyl phosphine oxides.

[0098] Commercially available phosphine oxide photoinitiators capable of free radical initiation when irradiated in the wavelength range from greater than about 380 nm to about 450 nm include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (IRGACURE 819, Ciba Specialty Chemicals, Tarrytown, NY), bis(2,6-dimethoxybenzoyl)-(2,4,4-trimethylpentyl)phosphine oxide (CGI 403, Ciba Specialty Chemicals), and a 25:75 by weight mixture of bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide and 2-hydroxy-2-methyl-1-phenylpropan-1-one (IRGACURE 1700, Ciba Specialty Chemicals). Chemicals), a 1:1 mixture by weight of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 2-hydroxy-2-methyl-1-phenylpropan-1-one (DAROCUR 4265, Ciba Specialty Chemicals), and ethyl 2,4,6-trimethylbenzylphenylphosphinate (LUCIRIN LR8893X, BASF Corp., Charlotte, NC).

[0099] Tertiary amines may be used in combination with acylphosphine oxides. Illustrative tertiary amines include ethyl 4-(N,N-dimethylamino)benzoate and N,N-dimethylaminoethyl methacrylate. When present, the amine reducing agent is present in the photopolymerizable composition in an amount of about 0.1 weight percent to about 5.0 weight percent, based on the total weight of the composition. In some embodiments, the dental hardenable composition may be irradiated with ultraviolet (UV) light or blue light. In this embodiment, suitable photoinitiators include those available from Ciba Specialty Chemical Corp., Tarrytown, NY under the IRGACURE and DAROCUR tradenames, including 1-hydroxycyclohexyl phenyl ketone (IRGACURE 184), 2,2-dimethoxy-1,2-diphenylethan-1-one (IRGACURE 651), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (IRGACURE 819), 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one (IRGACURE 2959), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone (IRGACURE 369), 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (IRGACURE 369), and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (IRGACURE 369). 907), and 2-hydroxy-2-methyl-1-phenylpropan-1-one (DAROCUR 1173).

[0100] Photopolymerizable compositions are typically prepared by mixing the various components of the composition. In embodiments where the photopolymerizable composition does not cure in the presence of air, the photoinitiators are combined under "safe light" conditions (i.e., conditions that do not lead to premature solidification of the composition). If desired, a suitable inert solvent may be used in preparing the mixture. Examples of suitable solvents include acetone and dichloromethane.

[0101] Solidification occurs by exposing the composition to a radiation source, preferably a visible light source. Light sources that emit actinic light in the range of 250 nm to 800 nm (particularly blue light with wavelengths of 380 nm to 520 nm), such as quartz halogen lamps, tungsten halogen lamps, mercury arcs, carbon arcs, low, medium, and high pressure mercury lamps, plasma arcs, light-emitting diodes, and lasers, are conveniently used. Generally, useful light sources have a radiation intensity of 0.200 to 6000 mW / cm. 2 for 20 seconds with an intensity in the range of 1000mW / cm 2 The intensity of the light can generally provide the desired cure. A variety of conventional lights for solidifying such compositions can be used.

[0102] In typical embodiments, the dental composition is substantially free of redox cure systems and is therefore substantially free of polyacids and oxidizing agents (less than 1, 0.5, 0.25, 0.1, or 0.005 wt. %). In some embodiments, the dental composition is also free of reducing agents, as known in the art.

[0103] Optionally, the composition may contain solvents (e.g., alcohols (e.g., propanol, ethanol), ketones (e.g., acetone, methyl ethyl ketone), esters (e.g., ethyl acetate), other non-aqueous solvents (e.g., dimethylformamide, dimethylacetamide, dimethyl sulfoxide, 1-methyl-2-pyrrolidinone)), and water. In some embodiments, (e.g., one-component) dental compositions typically contain water in an amount of 5% or less by weight of the total dental composition.

[0104] If desired, the composition can contain additives such as indicators, dyes such as photobleachable dyes, pigments, inhibitors, accelerators, viscosity modifiers, humectants, buffers, radical and cationic stabilizers (e.g., BHT), and other similar ingredients that will be apparent to those skilled in the art.

[0105] In addition, pharmaceuticals or other therapeutic substances can be optionally added to the dental composition. Examples include, but are not limited to, fluoride sources, whitening agents, anticaries (e.g., xylitol), calcium sources, phosphorus sources, remineralizing agents (e.g., calcium phosphate compounds), enzymes, breath fresheners, anesthetics, coagulants, acid neutralizers, chemotherapeutic agents, immune response modifiers, thixotropic agents, polyols, anti-inflammatory agents, antibacterial agents (in addition to the antibacterial lipid component), antifungal agents, xerostomia treatment agents, desensitizing agents, and the like, of the type often used in dental compositions. Combinations of any of the above additives may also be used. Those skilled in the art can select the selection and amount of any one of such additives to achieve the desired results without undue experimentation.

[0106] Dental hardenable compositions can be used to treat oral surfaces, such as teeth, as is known in the art. In some embodiments, the composition can be solidified by curing after application of the dental composition. For example, when the dental hardenable composition is used as a restorative material, such as a dental filling, the method generally includes applying the hardenable composition to an oral surface (e.g., a cavity) and allowing the composition to harden. In some embodiments, a dental adhesive may be applied before applying the hardenable dental restorative material described herein. Furthermore, the dental adhesive is typically hardened by curing simultaneously with the hardening of the highly filled dental restorative composition. The method of treating an oral surface can include preparing a dental article and adhering the dental article to an oral (e.g., tooth) surface.

[0107] In other embodiments, the composition may be hardened (e.g., polymerized) into a dental article before application. For example, dental articles such as crowns can be preformed from the dental hardenable compositions described herein. Dental composite (e.g., crown) articles can be made from the hardenable compositions described herein by casting the hardenable composition in contact with a mold and allowing the composition to harden. Alternatively, dental composite (e.g., crown) articles can be made by first hardening the composition, forming a mill blank, and then mechanically cutting the composition into the desired article.

[0108] Another method for treating a tooth surface includes preparing a dental composition described herein, the composition being in the form of a (partially solidified) hardenable, self-supporting, malleable structure having a first semi-finished shape; placing the dental hardenable composition on a tooth surface in a subject's mouth; customizing the shape of the dental hardenable composition and solidifying the dental hardenable composition. This customization can be performed in the patient's mouth or in a model outside the patient's mouth, as described in U.S. Patent No. 7,674,850 (Karim et al.), which is incorporated herein by reference.

[0109] As used herein, "dental composition" refers to a material, including a filler, that is capable of adhering or bonding to an oral surface. Dental hardenable compositions can be used to bond dental articles to tooth structures, to form coatings (e.g., sealants or varnishes) on tooth surfaces, as restoratives that are placed directly in the oral cavity and allowed to harden in place, or alternatively, to create prostheses extraorally that are then bonded in the oral cavity.

[0110] Dental hardenable compositions include, for example, adhesives (e.g., dental and / or orthodontic adhesives), cements (e.g., one-component cements), primers (e.g., orthodontic primers), liners (applied to the base of cavities to reduce tooth sensitivity), coatings such as sealants (e.g., pit and fissure sealants), and varnishes; as well as resin restoratives such as dental fillings (also called direct composites), and articles for crowns, bridges, and dental implants. Highly filled dental compositions are also used in mill blanks from which crowns can be milled. Composites are highly filled pastes designed to be suitable for filling substantial defects in tooth structure. Dental cements are somewhat less filled and less viscous materials than composites, and typically act as bonding agents for additional materials such as inlays, onlays, and the like, or as filling materials themselves when applied and hardened as a layer. Dental cements are also used to permanently bond dental restorations such as crowns or bridges to tooth surfaces or implant abutments.

[0111] As used herein, "dental article" refers to an article that can be adhered (e.g., bonded) to a tooth structure or a dental implant. Dental articles include, for example, crowns, bridges, veneers, inlays, onlays, fillings, orthodontic appliances and devices.

[0112] "Orthodontic appliance" refers to any device intended to be bonded to tooth structure, including, but not limited to, orthodontic brackets, buccal tubes, lingual anchoring devices, orthodontic bands, mouth gag devices, buttons, and cleats. The appliance has a base that receives an adhesive, and the base may be a flange made of metal, plastic, ceramic, or a combination thereof. Alternatively, the base may be a custom base formed from a hardened adhesive layer (i.e., a single or multi-layer adhesive).

[0113] "Oral surfaces" refers to soft or hard surfaces in the oral environment. Hard surfaces typically include, for example, dental structures, including natural and artificial tooth surfaces, bone, and the like.

[0114] "Solidifiable" and "curable" describe materials or compositions that can be cured (e.g., polymerized or crosslinked) by heating to induce polymerization and / or crosslinking; by irradiating with actinic radiation to induce polymerization and / or crosslinking; and / or by mixing one or more components to induce polymerization and / or crosslinking. "Mixing" can be performed, for example, by combining and mixing two or more components to form a homogeneous composition. Alternatively, two or more components can be provided as separate layers, and the layers can be intermixed at their interface (e.g., spontaneously or by application of shear stress) to initiate polymerization.

[0115] "Solidified" refers to a material or composition that has hardened (e.g., polymerized or crosslinked).

[0116] "Solidifier" refers to something that initiates the solidification of a resin and can include, for example, a polymerization initiator system, a photoinitiator system, a thermal initiator system, and / or a redox initiator system.

[0117] "(Meth)acrylate" is shorthand for acrylate, methacrylate, or a combination thereof, "(meth)acrylic acid" is shorthand for acrylic acid, methacrylic acid, or a combination thereof, and "(meth)acrylic" is shorthand for acrylic, methacrylic, or a combination thereof.

[0118] As used herein, "a," "an," "the," "at least one," and "one or more" are used interchangeably.

[0119] Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed within that range (eg, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

[0120] The following examples further illustrate these objects and advantages, 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 this invention. All parts and percentages are by weight unless otherwise specified. [Example]

[0121] The following examples are provided to illustrate, but not to limit, the scope of the present invention. As used herein, unless otherwise specified, all parts and percentages are by weight, all water is deionized water, and all molecular weights are average molecular weights. Unless otherwise specified, materials can be obtained from Sigma-Aldrich, Milwaukee, WI.

[0122] Test Method Depth of Cure (DOC) Test Method Depth of cure (i.e., cure depth) was measured as described in ISO 4049 using a cylindrical stainless steel curing mold as the test fixture, except that the cylindrical cavity had dimensions of 4 mm in diameter and 20 mm in depth (to accommodate the larger cure depth). Specifically, the test fixture was placed on top of a flat polyester film, and the cylindrical cavity was filled with the sample to be light-cured. A second polyester film was placed on the fixture, and the filled test fixture was pressed down to flatten the sample surface. The filled test fixture was placed on a white background, and the composition was irradiated for 20 seconds using a dental curing light (e.g., ELIPAR FREELIGHT 2, ELIPAR S-10, or ELIPAR DEEP CURE, available from 3M Oral Care, St. Paul, MN). After irradiation, the sample was removed from the test fixture and any uncured sample was removed within approximately 1 minute of irradiation (e.g., by scraping the uncured material from the bottom of the sample, opposite the side exposed to the curing light). The thickness of the remaining cured material was measured. The reported cure depth is the actual cured sample thickness in millimeters divided by 2 and is from a single measurement unless otherwise noted.

[0123] Contrast Ratio (CR) Test Method and Color Test Method Uncured samples were formed into 1 mm thick x 30 mm diameter disks using a stainless steel mold and a Carver press (10,000-15,000 psi). These disks were then illuminated with an LED array (455 nm wavelength, 850 mW / cm intensity) for 20 seconds on one side of the disk. 2The discs were cured by exposing them to illumination by a reflective black background. The contrast ratio (or opacity) of the discs was measured using a modification of ASTM-D2805-95 (Hiding Power of Paints by Reflectometry). The Y tristimulus values ​​of the cured composite discs were measured with a Color i7 spectrophotometer (X-Rite, Grand Rapids, MI, USA) at a 25 mm aperture using distinct white and black backgrounds. All measurements were taken in reflection mode with D65 Illuminant without a filter. A 10-degree viewing angle was used. The contrast ratio was calculated as the ratio of the Y tristimulus value of the cured sample on a black substrate to the Y tristimulus value of the same sample on a white substrate (CR = R B / R W The contrast ratios were calculated as reflectance (i.e., reflectance is defined as equal to the Y tristimulus value) as a function of the Y tristimulus value (x100). Reported contrast ratio values ​​are from a single measurement unless otherwise noted, with lower values ​​indicating greater translucency (i.e., light transmission). Color data (L * a * b * ) were collected 2-10 minutes after curing in the same spectrophotometer (25 mm aperture against a white background, reflectance mode, using D65 illuminant, no filter, 10 degree viewing angle, to exclude specular reflection).

[0124] Refractive index measurement For uncured samples, the refractive index was measured on a Bausch & Lomb refractometer at 25°C using the sodium "D" line (approximately 589 nm).

[0125] For the cured samples, the refractive index was measured as follows: The backside of each sample was roughened with 1200-grit sandpaper and then mounted on a glass slide with double-sided tape. Reflectance spectral ellipsometry (RSE) data was acquired using an RC-2 ellipsometer for angles of incidence θ = 55° → 75°, Δ = 10°, and λ = 193 nm → 1000 nm. The data was analyzed for angles of incidence θ = 55° → 75°, Δ = 10°, and λ = 350 nm → 1000 nm. The samples were modeled as monolithic Cauchy materials.

[0126] Test method for bending strength and bending modulus The uncured samples were extruded into 2 mm x 2 mm x 25 mm quartz glass molds to form test bars. The samples were then cured through the molds using two standard dental curing 3M ELIPAR S-10s. The samples were cured by placing one light in the center of the sample bar and curing for 20 seconds, then curing both ends of the bar simultaneously for 20 seconds, flipping, and repeating.

[0127] Samples were stored (16-24 hours) immersed in deionized water at 37°C prior to testing. The flexural strength and flexural modulus of the bars were measured in accordance with ANSI / ADA (American National Standard / American Dental Association) Standard No. 27 (1993) using an Instron testing machine (Instron 4505 or Instron 1123, Instron Corp., Canton, Mass.) at a crosshead speed of 0.75 mm / min. Results are reported in megapascals (MPa) for flexural strength and in GPa for flexural modulus.

[0128] Stress Test Method To measure the stresses generated during the curing process, a slot was machined into a rectangular 15 x 8 x 10 mm aluminum block. The slot was 8 mm long, 4 mm deep, and 4 mm wide, positioned 2 mm from the edge to form a 2 mm wide aluminum cusp adjacent to a 4 mm wide cavity containing the dental composition to be tested. A linear variable displacement transducer (model GT 1000, used with an E309 analog amplifier, both from RDP Electronics, United Kingdom) was positioned as shown to measure the cusp displacement when the dental composition was light-cured at room temperature. Prior to testing, the slot in the aluminum block was sanded using Rocatec Plus Special Surface Coating Blasting Material (3M Oral Care), treated with RelyX Ceramic Primer (3M Oral Care), and finally treated with a commercially available dental adhesive (e.g., Adper Easy Bond or Scotchbond Universal, each available from 3M Oral Care). A substantially similarly machined aluminum block and test fixture is depicted in Figures 1 and 2 of US Patent No. 9,056,043.

[0129] The slots were thoroughly filled with the mixtures shown in the table, and the materials were irradiated with a dental curing light (ELIPAR S-10, 3M Oral Care) for 1 minute in near contact (less than 1 mm) with the material in the slot, and then the cusp displacement in microns was recorded 9 minutes after the light was turned off.

[0130] Watts shrinkage strain test method The Watts Shrinkage Strain (Watts) test method measures the shrinkage of a test sample in terms of its volume change after curing. Sample preparation (90 mg uncured composite test sample) and test procedure were performed as described in the following reference: Determination of Polymerization Shrinkage Kinetics in Visible-Light-Cured Materials: Methods Development, Dental Materials, October 1991, pp. 281-286. Results are reported as % shrinkage, or in other words, absolute volume loss (after 5 minutes of curing).

[0131] ACTA 3 Body Wear Test Method ACTA three-body wear testing of test samples compared to FILTEK Z250 Universal Restorative (3M Oral Care) was performed substantially as described in U.S. Patent No. 7,156,911, except that the wheel had 10 slots and the sample dimensions were 15 mm long, 10 mm wide, and 5 mm deep. Further details regarding this method can be found by reference: Influence of Shearing Action of Food on Contact Stress and Subsequent Wear of Stress-bearing Composites, P. Pallav, et al., Journal of Dental Research, January 1993.

[0132] Radiopacity Test Method Radiopacity was measured using a Heliodent Plus dental X-ray device (Sirona, X-ray tube voltage: 60 kV, exposure time: 0.06 seconds). Radiopacity measurements are in millimeters (mm) of equivalent aluminum.

[0133] material Polymerizable resin monomers "AFM-1" is an addition-cleavage monomer that can be prepared as described in U.S. Pat. No. 9,056,043, column 46, line 58 to column 47, line 27 ("Preparation of AFM-1"). "BisGMA" refers to 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl]propane (also known as bisphenol A diglycidyl ether methacrylate), available from Sigma-Aldrich Corp. (St. Louis, MO). "DDDMA" refers to 1,12-dodecanediol dimethacrylate, available from Sartomer Co., Inc. (Exton, PA) under the trade designation "SR-262." "ERGP-IEM" refers to 2-propenoic acid, 2-methyl-,1,1'-[1,3-phenylenebis[oxy-2,1-ethanediyloxy[1-(phenoxymethyl)-2,1-ethanediyl]oxycarbonylimino-2,1-ethanediyl]] ester, which can be prepared as described in U.S. Pat. No. 8,710,113, column 77, lines 33-40 ("Synthesis of ERGP-IEM"). "TEGDMA" refers to triethylene glycol dimethacrylate, available from Sartomer Co., Inc. (Exton, PA). "UDMA" refers to diurethane dimethacrylate, available from Rohm America LLC (Piscataway, NJ) under the trade designation "ROHAMERE 6661-0," and also available from Dajac Laboratories (Trevose, PA).

[0134] Filler particles Red, yellow, and black iron oxide pigments were obtained from Elementis Pigments Inc. (East St. Louis, IL). Titanium dioxide (R690 TiO2) pigment (white) was obtained from DuPont and had a measured average particle size of approximately 214 nm. "AEROSIL R972" refers to a hydrophobic fumed silica available from Evonik, Germany. "S / T Silica / Zirconia Cluster" refers to a silane-treated silica-zirconia nanocluster filler, which is prepared generally as described in U.S. Pat. No. 6,730,156 at column 25, lines 50-63 (Preparatory Example A) and column 25, lines 64 to column 26, line 40 (Preparatory Example B), with minor modifications, including adjusting the pH to about 8.8 with aqueous NH4OH (instead of adjusting the pH to 3-3.3 with trifluoroacetic acid), performing the silanization in 1-methoxy-2-propanol (rather than water), and obtaining the nanocluster filler by gap drying (rather than spray drying).

[0135] nanoparticles "S / T 20 nm Silica" refers to a silane-treated silica nanoparticle filler having a nominal particle size of approximately 20 nanometers, prepared substantially as described in U.S. Pat. No. 6,572,693, column 21, lines 63-67 ("Nano-sized Particle Filler, Type #2"). "S / T nanozirconia" refers to a silane-treated zirconia filler prepared from a zirconia sol substantially as described in U.S. Pat. No. 8,647,510, column 36, line 61 to column 37, line 16 (Example 11A-IER). The zirconia sol was added to an equal weight of 1-methoxy-2-propanol containing GF-31 (1.1 mmol of GF-31 per gram of nanozirconia to be surface-treated). The mixture was heated to approximately 85°C with stirring for 3 hours. The mixture was cooled to 35°C, the pH was adjusted to approximately 9.5 with aqueous NH4OH, and the mixture was reheated to approximately 85°C with stirring for 4 hours. The resulting material was washed with excess water, and the solvent was removed by gap drying, isolating the S / T nanozirconia as a dry powder. As used herein, "S / T nanozirconia" also refers to silane-treated zirconia filler that has been solvent-exchanged into a resin (and paste) without isolating the S / T nanozirconia in the form of a dry powder (e.g., by adding an S / T nanozirconia sol to a methacrylate-containing resin followed by concentration under reduced pressure and / or heating to remove volatile materials associated with the sol, as further detailed in the Examples herein).

[0136] Coupling Agent / Surface Treatment "GF-31" refers to 3-methacryloxypropyltrimethoxysilane, available from Wacker Chemie AG (Munich, Germany).

[0137] Other components "YbF3" refers to ytterbium fluoride, which has a particle size of approximately 100-105 nm and a refractive index of 1.52, and is available from Sukgyung AT Co. Ltd., (Korea). "BHT" refers to butylated hydroxytoluene (2,6-di-tert-butyl-4-methylphenol), available from Sigma-Aldrich Corp. (St. Louis, MO). "BZT" refers to 2-(2'-hydroxy-5'-methacryloxyethylphenyl)-2H-benzotriazole, available as "TINUVIN® 796" from Ciba, Inc. (Tarrytown, NY), and also available from Sigma-Aldrich Corp. (St. Louis, MO). "CPQ" refers to camphorquinone. "DPIHFP" or "DPIPF6" refers to diphenyliodonium hexafluorophosphate, available from Johnson Matthey, Alfa Aesar Division (Ward Hill, MA). "EDMAB" refers to ethyl 4-(dimethylamino)benzoate, available from Sigma-Aldrich Corp. (St. Louis, MO).

[0138] Concentrate A (S / T nano-zirconia in BisGMA / TEGDMA) Aqueous acetic acid-stabilized nanozirconia sol (99.9992 g, 32.68 wt. % nanozirconia, 4 wt. % zirconia, with yttria for phase stabilization, prepared generally as described in Example 11A-IER of U.S. Pat. No. 8,647,510) was combined with 1-methoxy-2-propanol (200.003 g) and GF-31 (8.741 g). The mixture was heated at 80°C for 6 hours, after which a 50 / 50 wt. mixture of BisGMA / TEGDMA (48 g) was added. The resulting mixture was rotary evaporated under reduced pressure at approximately 60-85°C to remove volatile materials (e.g., water, acetic acid, 1-methoxy-2-propanol) to yield Concentrate A (i.e., S / T nanozirconia in BisGMA / TEGMA resin) as a clear, slightly opalescent liquid. Concentrate A contained approximately 44.68 wt% S / T nano-zirconia.

[0139] pigment dispersion White, red, black, and yellow liquid pigment dispersions were prepared by standard paint grinding and mixing procedures on a roller mill. Table 1 summarizes the pigment dispersions used for the shading and opacification studies. [Table 2]

[0140] Resin 1 to 4 Concentrate A is diluted by adding a 50 / 50 mixture of BisGMA / TEGDMA and a photoinitiator package (CPQ, EDMAB, and DPIHFP) to obtain Resins 1-4. The compositions of photoinitiated Resins 1-4 are summarized in Tables 2a and 2b. [Table 3] [Table 4]

[0141] Low stress resin A Low Resin A was prepared with 68.83 wt% ERGP-IEM, 18.77% UDMA, 8.66% DDDMA, 1.50% AFM-1, 0.30% DPIHFP, 1.1% EDMAB, 0.28% CPQ, 0.05% BHT, and 0.50% BZT. This was the base resin used in making Pastes 12–17. The expected change in refractive index of these pastes upon curing is expected to be similar to that of the base resin.

[0142] The refractive index values ​​of Resins 1 to 4 and Resin A were measured before and after photocuring. The measured refractive index values ​​are summarized in Table 3. [Table 5]

[0143] After curing, polymerizable resins 2 to 4 have a difference of at least 0.010.

[0144] Paste 5-8 (uncolored) Sufficient S / T silica / zirconia clusters were mixed with each of Resins 1-4 to obtain Pastes 5-8, respectively. Each paste had a total S / T nanozirconia + S / T silica / zirconia cluster content of 75 wt%. The compositions of unpigmented Pastes 5-8 are summarized in Tables 4a and 4b. [Table 6] [Table 7]

[0145] The contrast ratio and depth of cure measurements for each of the light-cured pastes 5–8 are summarized in Table 5. Table 5 shows that the contrast ratio of the cured disks increases as the refractive index mismatch between (i) the refractive index of the S / T silica / zirconia clusters and (ii) the composite refractive index of the resin and S / T nanozirconia mixture increases. [Table 8] ￥ ELIPAR S-10 Pastes 5 to 8 meet the ISO 4049 standard.

[0146] Comparative pastes 9-11 (white colored, no S / T nano zirconia) A duplicate (larger) batch of Resin 1 was made by taking 250 g of a 50 / 50 wt% blend of BisGMA and TEGDMA and adding 0.549 g of CPQ, 2.499 g of EDMAB, and 0.748 g of DPIFHP (no nanozirconia). From this resin, a paste with 75 wt% S / T silica / zirconia clusters and 25 wt% starting resin was made and pigmented with white pigment from the white pigment dispersion to approximate the contrast ratio of Pastes 5-8. The composition of the pigmented paste is listed below. [Table 9] [Table 10] * The concentration of pigment is 15% of the amount of dispersion as reported in Table 1. The amount of pigment is reported in parentheses below the amount of dispersion.

[0147] The contrast ratio and ISO 4049 depth of cure were measured for each of Pastes 9-11 and Comparative Paste 18, as reported in Table 7 below. [Table 11] ￥ ELIPAR S-10 Pastes 9-11 and 18 meet the ISO 4049 standard.

[0148] Paste 12-17 Pastes 12-17 were all made from dry powder components and resins more suitable for bulk-fill applications (lower stress), demonstrating a more convenient method of manufacturing to achieve similar results. They were made using a speed mixer (SPEEDMIXER, available from Flacktek, Inc., Landrum, SC). All components were mixed together as a one-component system. Component concentrations in grams are reported in Tables 8a and 8b. Component concentrations in weight percent are reported in Tables 9a and 9b. Note that Paste 15 uses much less white pigment. Paste 17 cures deeply but has a lower contrast ratio. [Table 12] [Table 13] [Table 14] [Table 15] * The pigment concentration is 15% of the dispersion volume for WPD and 5% of the dispersion volume for RPD, BPD, and YPD, as reported in Table 1. The amount of pigment is reported in parentheses below the amount of dispersion.

[0149] The contrast ratios and cure depths measured for Pastes 12 to 17 were as follows: [Table 16] ￥ ELIPAR DEEP CURE or FREELIGHT 2 ** The calculated values ​​and the cured resin values ​​include nanoparticles.

[0150] Pastes 12, 13, 14, and 16 are pigmented. For example, when comparing Pastes 12 and 14, there is a significant increase in cure depth, which can be achieved by incorporating higher levels of S / T nanozirconia. Upon curing, the resins are estimated to shift upward in refractive index by 0.03 to 0.04 units based on Resins 1-4, depending in part on the intrinsic shrinkage of the resin upon curing. Pastes 15 and 17 lack pigmentation and are less aesthetically pleasing because the lower refractive index material of Paste 17 requires a contrast ratio of only 34 to achieve the high cure depth in this comparative example. Paste 15, without pigmentation, provides a higher contrast ratio than Paste 17, achieving a cure depth of over 4.5 mm. Paste 16 is fully pigmented to an A3 shade, with a contrast ratio of 49 (acceptable for many restorative materials). Paste 16 also has a cure depth of over 4 mm, due to the lower pigmentation required to achieve the desired contrast ratio for the final cured material.

[0151] Paste 18 A commercially available bulk-cure flowable composite (Paste 18) was analyzed and tested. The composition of the commercial composite included barium glass, ytterbium trifluoride, and a copolymer with a filler loading of 71 wt% and an inorganic content of 68.2 wt%. The filler particles ranged in size from 0.1 to 30 microns, with an average particle size of 5 microns. The resin contained a mixture of BisGMA (approximately 19%), ethoxylated bisphenol A dimethacrylate (approximately 69%), and dimethyloltricyclodecane dimethacrylate (approximately 11%), plus "other ingredients" presumed to be initiators and pigments.

[0152] Mechanical property testing: Pastes 16, 17, and 18 were tested for the mechanical properties of flexural strength and modulus, three-body abrasion resistance, Watts shrinkage strain, radiopacity, and cusp deflection. [Table 17]

[0153] As can be seen, the strength, radiopacity, wear rate, and shrinkage rate of pastes 16 and 17 are improved over the commercially available paste 18.

[0154] Paste 19-25 Pastes 21–25 were prepared from two “stock” pastes (Paste 19, pigmented with only RPD and WPD, and Paste 20, pigmented with only RPD) made from all dry powder components and resins more suitable for bulk-fill applications (lower stresses) to demonstrate a simple laboratory method for investigating the effects of contrast ratio and depth of cure on a set of formulations with varying WPD content. All resin, filler, and pigment components were set as shown in Table 12a and reported as weight percent compositions. These stock pastes are useful because they can be pigmented to multiple shades while having acceptable contrast ratios and a depth of cure of at least 3.5 mm due to their optimized nanozirconia content. Pastes 21–25 were prepared from stock Pastes 19 and 20 by mixing the reported weights of Pastes 19 and 20, as shown in Table 12b. All were prepared using a speed mixer (SPEEDMIXER, available from Flacktek, Inc., Landrum, SC). All components were mixed together as a one-component system. Table 12b clearly shows that, provided the appropriate base formulation, a cure depth of 3.5 mm and a contrast ratio of 60 can be achieved using 0.045 wt.% white pigment. [Table 18] * The resin contents, in weight percent, are ERGP-IEM 68.83, UDMA 18.77, DDDMA 8.66, AFM-1 1.50, EDMAB 1.10, DPIHFP 0.30, CPQ 0.28, BHT 0.05, and BZT 0.50. [Table 19] ** Elipar Deep Cure S, curing time 20 seconds

Claims

1. one or more ethylenically unsaturated monomers or oligomers; formula: 【Chemical 1】 [In the formula, R １ , R ２ , and R ３ are each independently Z ｍ -Q-, a (hetero)alkyl group, or a (hetero)aryl group, provided that R １ , R ２ , and R ３ At least one of ｍ -Q-, Q is a linking group having a valence of m+1; Z is an ethylenically unsaturated polymerizable group; m is 1 to 6; Each X １ are independently —O— or —NR ４ -, where R ４ is H or C １ ~C ４ alkyl, and n is 0 or 1. an addition cleavage agent having the formula: nanoparticles having a refractive index of at least 1.600 and an average particle size of discrete particles or aggregates of 100 nm or less; a polymerizable resin comprising: an inorganic metal oxide filler having a refractive index of at least 1.500 and an average particle size of the discrete particles or aggregates of at least 200 nm, and present in an amount of at least 60% by weight; A dental composition comprising: the polymerizable resin in an uncured state is characterized by a refractive index that is lower than the refractive index of the inorganic metal oxide filler; the difference in refractive index between the polymerizable resin and the inorganic metal oxide filler in the uncured and cured states is 0.020 or less; and The dental composition having the polymerizable resin in a hardened state is characterized by a contrast ratio of at least 40.

2. 1000mW / cm ２ 10. The dental composition of claim 1, having a cure depth of at least 3.5 mm after light curing at an intensity of 1000 ppm for 20 seconds.

3. 3. The dental composition of claim 1, wherein the inorganic metal filler comprises a nanocluster filler, the nanocluster filler comprising agglomerated particles of heavy metal oxide and silica nanoparticles having a refractive index of at least 1.

600.

4. 4. The dental composition of claim 1, wherein the nanoparticles comprise an inorganic metal oxide and further comprise silica nanoparticles, the nanoparticles having a refractive index of at least 1.600 having a first weight, the silica nanoparticles having a second weight, and the first weight being greater than the second weight.

5. The dental composition in its hardened state has the following properties: i) a Watts shrinkage of less than 2%; ii) a flexural strength of at least 120 MPa; iii) a flexural modulus of at least 8 GPa; and v) Radiopacity of aluminum at least 3 mm thick The dental composition according to any one of claims 1 to 4, wherein the composition exhibits any one of the following properties or a combination thereof:

6. The dental composition according to any one of claims 1 to 5, wherein the polymerizable resin is substantially free of bisphenol-derived monomers.

7. The dental composition of any one of claims 1 to 6, wherein the dental composition having the polymerizable resin in a hardened state is characterized by a contrast ratio of 70 or less.

8. The dental composition of any one of claims 1 to 7, wherein the refractive index difference between the polymerizable resin and the inorganic metal oxide filler in the hardened state is at least 0.

005.

9. The dental composition of any one of claims 1 to 8, wherein the refractive index difference between the polymerizable resin and the inorganic metal oxide filler in the hardened state is at least 0.

010.

10. The one or more ethylenically unsaturated monomers or oligomers are represented by formula (II): 【Chemistry 2】 [In the formula, Each G is independently: 【Chemistry 3】 is selected from each Q is independently hydrogen, methyl, phenyl, or phenoxymethyl; U is as follows: 【Chemistry 4】 is selected from each a, b, c, and d is an integer independently selected from 0 to 3, and a+b=1 to 6, and c+d=1 to 6. The dental composition according to any one of claims 1 to 9, wherein the low-shrinkage monomer is represented by the formula:

11. 11. The dental composition according to claim 10, wherein the low-shrinkage monomer represented by formula (II) is present in the polymerizable resin in an amount of 50 to 70% by weight.

12. The dental composition according to claim 10 or 11, wherein the low-shrinkage monomer represented by formula (II) is present in the dental composition in an amount of 15 to 20% by weight.

13. 13. The dental composition of any one of claims 1 to 12, wherein the one or more ethylenically unsaturated monomers or oligomers comprise a low viscosity polymerizable diluent selected from 1,12-dodecanediol dimethacrylate (DDDMA), urethane dimethacrylate (UDMA), triethylene glycol dimethacrylate (TEGDMA), glycerol dimethacrylate (GDMA), ethylene glycol dimethacrylate, neopentyl glycol dimethacrylate (NPGDMA), polyethylene glycol dimethacrylate (PEGDMA), and combinations thereof.

14. The dental composition of claim 13, wherein the low viscosity polymerizable diluent is present in the dental composition in an amount of 2 to 10 weight percent.

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