MXPA00001821A - Optimum particle sized hybrid composite - Google Patents

Abstract

The present invention provides a dental composite which has the high strength required for load bearing restorations, yet maintains a glossy appearance, even after substantial wear. Through the use of particles having a mean particle size between about 0.05&mgr;m, and about 0.50&mgr;m, the composite is useful in stress bearing restorations and in cosmetic restorations. The structural filler used is typically ground to a mean particle size of less than 0.05&mgr;m and also includes a microfill having a mean particle size less than 0.05&mgr;m to improve handling and mechanical characteristics. The preferred dental composites maintain their surface finish even after substantial use and also have the strength properties of hybrid composite resins. The structural filler is ground, typically by agitator milling, to the preferred particle size.

Description

HYBRID COMPOSITION AND THE OPTIMAL PARTICLE SMOOTH Field of the Invention The present invention relates generally to a composite resin material used for dental restoration, and more particularly to a universal composite resin material, suitable for all dental restorations and incorporating a reinforcing particle of Uniformly dispersed submicron size, which provides high strength, better wear resistance and gloss retention in clinical use.

BACKGROUND OF THE INVENTION In dentistry, practitioners use a variety of restorative materials to create crowns, veneers or veneers, direct fillings, inlays, overdentures and splints. Composite resins are a type of restorative material, which are suspensions of reinforcing agents, such as mineral fillers in a resin matrix. These materials can be reinforced in dispersion, reinforced with particles or hybrid compositions. The dispersion-reinforced compositions include a reinforcing filler of, for example, fuming silica having an average particle size of about 0.05 μm or less, with a filler loading of about 30% -45% by volume. of small particle and large surface area of the filler, the filler loading on the resin is limited by the resin's ability to wet the filler, consequently, a filler is limited to approximately 45% by volume. , the filler particles are not substantially in contact with each other Thus, the main reinforcement mechanism of such dispersion-reinforced compositions is by the displacement of cracks in the matrix around the filler. The resin matrix contributes significantly to the total strength of the composition.In dentistry, resins comp Scattered reinforced beads or icrorellens are typically used for cosmetic restorations because of their ability to retain surface luster. Typically, these micro-refill resins utilize free-radically polymerizable resins such as methacrylate monomers, which, after polymerization, are much weaker than the dispersed filler. Despite the dispersion reinforcement, the microfill resins are structurally weak, limiting their use to low stress restorations. An example of a dispersion-reinforced composition is HELIOMOLAR®, which is a dental composition that includes fuming silica particles of the order of an average particle size of 0.05 μm and rare earth fluoride particles of the order of a particle size. average less than 0.2 μm. HELIOMOLAR® is a composition of the radiopaque micro-refill type. Rare earth fluoride particles contribute to both frictional resistance and radiopacity. Particle reinforced compositions typically include a reinforcing filler having an average particle size greater than about 0.6 μm and a filler load of about 60% by volume. At these high filler loads, the filler particles are in contact with each other and contribute substantially to the reinforcing mechanism to the interaction of the particles with each other and to the disruption of cracks by the particles themselves. These composite resins reinforced into particles are stronger than the microfilled resins. As with the dispersion reinforced compositions, the resin matrix typically includes methacrylate. However, the filler in the particle-reinforced compositions has a greater impact on the overall strength of the composition. Therefore, compositions reinforced with particles are typically used for stress-bearing restorations. Another class of metal compositions, known as hybrid compositions, include the characteristics and advantages of dispersion reinforcement and those of particle reinforcement. The hybrid composite resins comprise fillers having an average particle size of 0.6 μm or greater with a micro-filler having an average particle size of about 0.05 μm or less. The HERCULITE® XRV (Kerr Corp.), is an example of those. The HERCULITE is considered by many as an industry standard for hybrid compositions. It has an average particle size of 0.84 μm and a filler load of 57.5% by volume. The filler is produced by a wet grinding process that produces fine particles that are substantially free of contaminants. Approximately 10% of this filler exceeds 1.50 μm in average particle size. In clinical use, the surface of the HERCULITE turns into a finished maté, which is unusually brittle over time. Because of this, the restoration may become distinguishable from the structure of the normal tooth when it dries, which is not desirable for a cosmetic restoration. Another class of compositions, fluid compositions, have a volume fraction of structural filler from about 10% to about 30% by volume. Those compositions fluids are mainly used in low viscosity applications to obtain good adaptation and to prevent the formation of gaps during the filling of a cavity. Several methods are available to form submicron particles, such as precipitation or solgel methods, available to produce particulate reinforcement fillers for hybrid compositions. However, these methods do not restrict the particle size above or below the wavelength of light to produce a stable bright surface. U.S. Patent No. 5,609,675 to Noritake et al., Shows an inorganic filler composition of 60% -99% by weight of spherical oxide particles having a diameter between 0.1- 25 1.0 μm, and 1% -40% by weight of oxide particles having an average particle diameter of less than 0.1 μm. This filler is manufactured by a solgel chemical process. The particle size range includes particle sizes up to 1.0 μm and thus the dental composition using such a filler will not provide a bright surface in clinical use. The particles formed by the sol-gel process are spherical as shown in FIGURES 2A and 2B. The described formulations are designed to improve the mechanical performance, wear and surface roughness of restorations, but do not provide retention of surface gloss in clinical use. Clinical studies of this material have shown high wear rates of 22.4 μm per year, which is not a stable surface (S. Inokoshi, "Posterior Restorations: Ceramics or Composites?" In Transactions Third International Xongress on Dental Materials Ed. H. Nakajima, Y. Tani JSDMD 1997). Grinding by a grinding method can be used to form submicron particles. The predominant types of milling methods are dry milling and wet milling. In dry grinding, air or an inert gas is used to keep the particles in suspension. However, the particles tend to agglomerate in response to van der Waals forces, which are the capabilities of dry milling. Wet grinding uses a liquid such as water or alcohol to control the agglomeration of fine particles. Therefore, wet milling is typically used for the grinding of submicron sized particles. A wet mill typically includes spherical means that apply sufficient force to break particles that are suspended in a liquid medium. The grinding devices are categorized by the method used to impart movement to the media. The movement imparted to the wet ball mills includes the tumbling, vibrating, planetary and agitation mills. Although it is possible to form submicron particles with each of those types of mills, the agitator ball mill or agitator is typically more efficient. The agitator ball mill, also known as a friction or agitated mill, has several advantages including high energy efficiency, handling of large solids, narrow particle size distribution of the output product, and the ability to produce homogeneous suspensions. The main variables in the use of an agitator ball mill are the speed of the agitator, the flow rate of the suspension, the time of the liquidity, the viscosity of the suspension, the solid size in the feed, the free size of grinding and the size of the desired product. . As a general rule, agitator mills typically grind particles at an average particle size of 1/1000 the size of the milling media in the most efficient operation. To obtain average particle sizes of the order of 0.05 μm to 0.5 μm, grinding media having a size smaller than 0.45 mm can be used. Grinding media with diameters of 0.2 mm and approximately 0.6 mm are also available from Tosoh Ceramics, Bound Brook, New Jersey. Thus, to optimize grinding, it is desirable to use grinding media of approximately 1000 times the size of the desired particle. This minimizes the time required for grinding. Previously, the use of a grinding process to achieve such fine particle sizes was difficult due to contamination of the suspension by the grinding media. By using zirconia stabilized with yttria (YTZ or Y-TZP, where TZP is polycrystalline tetragonal zirconia) the contamination by crushing the grinding media and abrasion of the mills is minimized. The Y-TZP has a fine grain, high strength and high tenacity to fracture. The YTZ is the hardest ceramic and due to this SfeTOireza, the YTZ will not degenerate structurally during grinding. The high strength Y-TZP is formed by sintering at temperatures of approximately 1550 ° C to form tetragonal grains having tetragonal grains of 1-2 μm mixed with 4-8 μm cubic grains and higher strength (1000 MPa) (1.01 x 104 kgf / cm2)), high tenacity at fracture (8.5 MPa (86.7 kgf / cm2)) and excellent wear resistance.

The use of the Y-TZP provides suitable grinding media to provide relatively pure structural fillers having average particle sizes of less than 0.5 μm. Despite some reduction in the contamination of the milled particle by the use of the YTZ grinding media, the currently available agitator ball mills still introduce an unacceptable level of contamination in the dental compositions containing the ground filler. No single current dental composition provides the high strength required to be used in the wide variety of repairs with the required brightness after substantial clinical use. To achieve those goals, current cosmetic dental restorations require the use of two or more layers of various composite materials to obtain the desired strength and appearance. The present invention eliminates the need for * multiple layers of various composite materials.

Brief Description of the Invention The present invention provides a dental composition containing resin that includes a structural filler of ground particles having an average particle size of between about 0.05 μm and about 0.5 μm, which has the high strength required for restorations that support loading, still maintaining a bright appearance of clinical use required for cosmetic restorations. In addition, because the structural filler particles are milled, the particles are not spherical, providing greater adhesion of the resin to the structural filler, thereby further increasing the overall strength of the composition. Although the use of structural filler particles that are ground and having an average particle size smaller than that of the wavelength of light, i.e. less than about 0.50 μm, the dental composition of the present invention provides the luster and translution required for cosmetic restorations. Specifically, since the size of the structural filler is less than the wavelength of the visible light, the surface of a dental restoration will reflect more in some directions than in others even after the composition has worn through brushing. The visible light waves do not substantially interact with the structural filler particles projecting out of the surface of the composition, and therefore, the optical clarity and luster of the surface is maintained even after substantial brushing. A known milling method, milling by stirring, has been adapted for use in the field of dental compositions. As adapted, this method is able to further reduce the average particle size of the HERCULITE® filler to an average particle size of between about 0.05 μm and 0.5 μm. The particle size is below the wavelength of light, which minimizes the interaction with light, thus producing a stable bright surface in clinical use. The particles are still large enough to reinforce the composition by the particle reinforcement mechanism, so that the restorations also support stress. The number of larger particles, above 0.5 μm in diameter, is also reduced to a minimum to help produce the stable glossy surface. * # * í¡ • 1. - Additionally, since the structural filler particles are milled at an average particle size of between about 0.05 μm and about 0.50 μm, the particles interact with each other to reinforce the composition, in a typical hybrid compositions form, to allow a The composition of the present invention is useful in stress-bearing restorations. In a preferred embodiment, the structural filler is milled, typically by agitator grinding, to the preferred average particle size. In contrast to the particles formed by the known sol-gel process, the crushing to the structural filler results in non-spherical particles, which due to their irregular shape interact with the polymerized resin to a much greater degree to increase the adhesion of the resin to the structural filler and therefore, increase the total resistance of the composition. The irregular shape of the particles is shown in FIGURES 1A and IB. Grinding with agitator with selected media and parameters used produces the particles of the required size, free of contamination in a narrow particle size distribution. This reduces the small percentage of small particles above 0.5 μm to produce a non-bright surface in clinical use. According to a further aspect of the invention, the microfilled particles having an average particle size of less than about 0.05 μm, preferably between about 1% by weight and about 15% by weight of the composition. The microfilled particles contribute to the dispersion reinforcement, fill the interstices between large structural filler particles reducing the clogged volume and provide a large surface area to be moistened by the resin to increase the strength. The microfilled particles also contribute to the flow properties of the uncured resin.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1A is a scanning electron micrograph, at an amplification of 20,000 X, of the ground particle of the present invention. FIGURE IB is a scanning electron micrograph, at an amplification of 5,000 X, of the ground particle of the present invention. FIGURE 2A is an electronic scanning micrograph, at an amplification of 20,000 X, of the filler particles of the prior art formed by the sol-gel process. FIGURE 2B is a scanning electron micrograph, at a magnification of 100,000 X, of the filler particles of the prior art formed by the sol-gel process.

Detailed Description of the Invention The present invention, in a preferred form, is a dental restoration composition, which includes a ground structural filler having an average particle size of between about 0.05 μm and about 0.50 μm and a micro-filler having a average particle size less than about 0.05 μm in a curable resin, preferably a photopolymerizable resin containing methylacrylate monomers. Such methylacrylate monomer resins are cured when exposed to blue visible light. The dental composition is applied to the teeth by the dental practitioner and exposed to a visible light source to cure the resin. The cured resin has a flexural strength greater than 100 MPa, which allows the use of resin in stress-supporting applications. To provide a ground structural filler having an average particle size of less than 0.5 μm, an extensive grinding step is required. The grinding is preferably carried out in a stirring mill and more preferably in a stirring mill designed to minimize contamination, such as that described in the Application US Patent Serial No., entitled "Agitator Mill and Method of Use for Low Crushing in Contamination", C. Angeletakis, filed on the same date as the present one and incorporated herein by reference in its entirety. The crushing de-agglomerates the structural filler particles separating the particles from the clumps, to decrease the size of the structural filler particles, eliminates large particles breaking and increases the specific surface area of the structural filler particles producing a large amount of very fine particles . The reduction in size with a stirring mill occurs due to a combination of impact with the grinding media, abrasion with the grinding media and friction of the particles. Structural fillers suitable for use in the present invention include barium magnesium aluminosilicate glass, barium aluminoborosilicate glass, amorphous silica, silica zirconia, silica-titanium, barium oxide, quartz, alumina and other oxide particles. organic.

EXAMPLES To prepare a structural filler for inclusion in a dental composition, the filler material to be milled, such as barium aluminoborosilicate glass (eg, type SP-345, Specialty Glass, Oldsmar FL), is loaded in a stirrer mill , such as an agitator mill with a total capacity of one liter of Draiswerk Inc., Mahwah, New Jersey, type PML-H / V, modified to include a transparent polyurethane stirrer and crushing chamber, a main seal of YTZ and a YTZ separator as described in the Patent Application American No '. Series, titled "Agitator Mill and Method of Use for Low Pollution Crushing" C. Angeletakis, presented on the same date as the present one and incorporated herein as a reference in its entirety. Three methods (A, B and C) were tested in which the agitator mill was filled to 70% of its volume with Y-TZP media. Method A used milling media with a size of 0.65 mm and Method B used milling media with a size of 0.40 mm.

A 20% z suspension included 700 grams of 345 mesh (20-30 μm) barium aluminosilicate glass in water (SP-345 available from Specialty Glass, Oldsmar, Florida) was circulated through the mill and into a cooled bath with external water at 20-30 liters per hour using a peristaltic pump. The agitator mill was operated at a tip speed of 10 m / sec for 3 hours. In Method C, the ground suspension of Method A was used, and the mill was then loaded with 70% of its Y-TZP grinding media volume of 0.20 mm, and the milling process was repeated for 1.5 hours. During the milling process, rough edges and facets were created on the structural filler particles by the impact with the grinding media, abrasion with the grinding media and friction of the particles. Each of these edges provides an adhesion site for the resin, which increases the total strength of the cured composition. When the 20% filler suspension is removed from the mill, the average particle size is measured, typically by laser diffraction. Laser diffraction is a method for measuring the average particle size by detecting the average relative angular intensity of the diffracted light. A beam of light 10 monochromatic with a uniform wavefront is directed to the sample, the light is diffracted or scattered by the particles and a detector is used to measure the relative average intensity of the light diffracted at various angles. The average particle size and the size distribution can then be calculated from the relative average intensity. One such laser diffraction device is described in U.S. Patent No. 5,610,712 to Schmitz et al., Incorporated herein by reference in its entirety. For the present example, an Analyzer was used. Average particle size of Horiba Laser Diffraction Model 2A-910. The particle size range of the structural filler was prepared by methods A, B and C as set forth in TABLE 1, as well as the particle size range for the hybrid composition PRODIGY (Kerr Corp.). TABLE 1 shows, for example, that for Method A, 10% by volume of the filler particles have an average particle size of less than 0.40 μm; 50% by volume of the filler particles have an average particle size of less than 0.92 μm; and 90% by volume of the filler particles have an average particle size less than 0.82 μm.

Average Particle Sizes in Microns The suspension was then dried at 110 ° C and the dried cake was sieved through a 100 mesh plastic screen (150 μm). The ground glass was then silanated by spraying in a V-blender with a solution hydrolyzed to 20% of gamma-methanoxypropyltrimethoxysilane in water to make the powder hydrophobic. The load of the silane in the filler was 2.5% by weight. The suitably sized structural filler was combined with colloidal sized particles, such as types of silica, alumina and silicates, for example silica-zirconia or silica-titanium, the particles having an average particle size of less than 0.05 μm. Typically, hydrophobic fuming silica was used in an amount of between 1-15% by weight of the »Final composition. Co? WS |? ## ft will show in TABLE 3, it is possible to use two types of fuming silica such as TS-530 which has an average particle size of 0. 02 μm and the OX-50 which has an average particle size of 0.40 μm. The structural filler and colloidal fillers are then combined with a light curable resin-based material, which may include commercially available monomers containing methacrylate groups. TABLE 2 lists the components of the resin that will be used in the later examples. Pigments such as titanium dioxide can be added to control the optical properties of the composition.

TABLE 2 COMPOSITION OF THE RESIN TABLE! P (continued) COMPOSITION DJ JEé- RESINA Other monomers may be used in the resin composition, such as diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,2-dodecanediol dimethacrylate, diurethane dimethacrylate (Rohamere) 6661-0, Huís America, Somerset, NJ), trimethylolpropane trimethacrylate, glyceryl dimethacrylate, neopentyl glycol dimethacrylate. The resin is introduced into a thermoregulated planetary mixer at 50 ° C. The planetary mixer is then started and the filler containing the physically mixed components listed in TABLE 3 is added slowly over a period of 3 hours. The composition is subsequently mixed for another hour and then under an attenuated oxygen pressure. Cured samples having the dimensions of 20 mm x 40 mm x 2 mm were then prepared. The extended clinical use of the material was simulated by abrasioning the samples with 600-degree silicon carbide sandpaper until a constant brightness value was obtained. The surface brightness was then measured using a microtrile apparatus (available from BYK-Gardner USA of Columbia, Maryland). The microtrill apparatus makes a photoelectric measurement of a light specularly reflected from a surface. The microtrill instrument was calibrated according to ISO 2813 with a measurement of 60 °. The results presented in TABLE 4 are the average of three measurements taken. The OX-50 particles are fumed silica AEROSIL "OX-50, commercially available from Degussa Corp., Ridgefield Park, NJ The particles of OX-50 have a surface area of 50 ± 15 m2 / g and an average particle size agglomerate The particle of the OX-50 has more than 99.8% by weight of Si02 with traces of A103, Fe203, Ti02 and HCl.The particles of OX-50 are then silanated by spraying in a V-blender with a hydrolyzed solution 20% gamma-methacryloxypropyltriralatelSiilane in water to make the powder hydrophobic The loading of the silane in the filler was 5% by weight The fumed silica treated CAB-O-SIL TS-530 is a high purity silica treated with hexamethyldiilase for make the particles extremely hydrophobic CAB-O-SIL particles are fuming silica produced by the hydrolysis of silicon tetrachloride vapor in a flame of hydrogen and oxygen. The CAB-O-SIL particles during the combustion process are reduced by a calcination (typically to less than 200 ppm of HCl). The colloidal filler particles contribute to the dispersion reinforcement, the filling of the interstices between larger structural filler particles, which reduces the occluded volume, provides a large surface area to be moistened by the resin and therefore increases the strength. The use of colloidal fillers reduces the shrinkage of the polymer and allows an equalization between the modulus of elasticity and the coefficient of thermal expansion of the composition with that of the teeth. The improved adhesion coupled with the control of polymer shrinkage, modulus of elasticity and coefficient of thermal expansion reduces the microinfiltration of bacteria along the bonding interface between the tooth and the cured dental composition. In the formation of a restoration using the composition of the present invention, the surface of the tooth is prepared by removing any portion of the tooth enamel, and if necessary the dentin, which is decomposed or damaged. A retaining groove is then formed in the dentin if necessary to maintain the restoration on the tooth. The practitioner then adds opacifiers and pigments to match the color of the composition with the color of the tooth. The composition then accumulates on the surface of the tooth to replace any lost material. Once the practitioner is satisfied with the appearance of the restoration, the composition is exposed to a visible light source to cure the resin and activate the adhesive by crosslinking the polymer matrix. After the composition has been cured, the surface is polished. The average particle size of the structural filler is limited to less than the wavelength of the light to prevent the structural filler from lowering the surface brightness after substantial brushing. However, it is expected that the particle size will be reduced below about 1 μm of the strength required for load-bearing restorations, due to the increase in the occluded volume of resin. Currently, it is believed that an average particle size of between about 0.05 μm and approximately 0.5 μm provides the best balance between optical and structural properties. The following examples were prepared using ground particles in the manner discussed above.

Example A: A resin composition was prepared by mixing: 27.6% by weight of Resin (Table 2); 63.7% by weight of silanated barium aluminoborosilicate structural filler (SP-345) having an average particle size of 0.62 μm prepared by Method A, discussed above; 5.0% by weight silica fumed silica OX-50 having an average particle size of 0.04 μm; and 3.7% by weight hydrophobic fumed silica TS-530 having an average particle size of 0.02 μm. The above components were mixed thoroughly as discussed above and samples prepared in the manner discussed below.

Example B: A resin composition was prepared by mixing: 28.2% by weight of Resin (Table 2); 64.7% by weight of silanated barium aluminoborosilicate structural filler (SP-345) having an average particle size of 0.47 μm prepared by Method B, discussed above; 3.1% by weight silica fumed silica OX-50 having an average particle size of 0.04 μm; and 3.9% by weight hydrophobic fumed silica TS-530 having an average particle size of 0.02 μm. The above components were mixed thoroughly as discussed above and samples were prepared in the manner discussed below.

Example C: A resin composition was prepared by mixing: 29.2% by weight of Resin (Table 2); 65.2% by weight structural barylate aluminum silicate filler (SP345) having an average particle size of 0.36 μm prepared by Method C, discussed above; and 2.3% on that silica fumed OX-50 silica having an average particle size of 0.04 μm; and 3.3% by weight hydrophobic fumed silica TS-530 having an average particle size of 0.02 μm. The above components were mixed thoroughly as discussed above and samples were prepared in the manner discussed below.

Test In the test of the resistance of the dental composition, methods were used, whenever possible, standard ISO methods, such as ISO 4049 for resin-based filling materials. The cured samples of the composite pastes were prepared with the dimensions of 20 x 40 x 2 mm. Samples were sanded with # 600 silicon carbide sandpaper under water until it obtained a constant brightness value. The gloss of the surface of the above compositions was measured using a Micro-tri-Gloss apparatus (BYK-Gardner USA, Columbia, MD) which effects a photoelectric measurement of the reflected light specularly of a surface. This instrument was calibrated according to ISO 2813. The measurement angle was 60 degrees. An average of three measurements was reported. ISO 4049 norm considered? "A value of 100% Al is the minimum value for a radiopaque composition, a value of 200% Al or greater is preferred by practitioners to properly determine the position of the restoration." In TABLE 3, the properties of The dental compositions of EXAMPLES A, B and C were compared with the hybrid PRODIGY composition.The hybrid composition (PRODIGY) has a flexural strength greater than 100 MPa, which allows its use in stress-bearing restorations. of EXAMPLES A, B and C each have flexural strength greater than 100 MPa, which approximates that of the PRODIGY composition, which allows them to be used in stress-bearing restorations, as can also be seen in TABLE 3 , the flexural modulus for the compositions of EXAMPLES A and C is 9248 MPa, which approximates the composition module PRODIGY The Rockwell hardness, which is similar for the four compositions reported in TABLE 3, is an average of 3 measurements on the surface of a cylindrical sample of 10 mm in diameter and 4 mm in height. The compositions were cured with light for 40 seconds and stored in water for 24 hours at 37 ° C before the hardness measurement. Despite the similarity in the mechanical properties of PRODIGY resaturation and the restorations of EXAMPLES A, B and C, after 24 hours of brushing, the shiny appearance of the material PRODIGY® was lost, leaving a matte finish as in normal clinical use. In TABLE 4, the properties of the dental composition of EXAMPLE B are compared with the commercially available products PALFIQUE ESTELITE® (from Tokoyama), HELIOMOLAR® (from Vivadent), SILUXPLUS® (from 3M), and DURAFIL® (from Kulzer) . Despite the high surface gloss and translucency, those commercial compositions do not have the strength required for load bearing restorations, while the composition of the present invention has sufficient strength.

TABLE 3 Physical Properties of Small Particle Compositions (SD) - fe »TABLE jp * (continued) Physical Properties of CpmpQ small particle (SD) determinations Physical Properties of Small Particle Compositions (SD) TABLE 4 Comparison of the Physical Properties of the Fine Particle Composition with Commercial Compositions (SD) TABLE 4 '"(continued) Comparison of the Physical Properties of Fine Particle Composition with Commercial Compositions (SD) Thus, the dental composition of the present invention provides a restoration having a high strength, useful for load-bearing restorations and also provides translucency and surface gloss, useful - ifc cosmetic restorations. The gloss is evident even after substantial wear and tear as can be seen on a 6 month or later appointment after the restoration is placed. Through the use of structural filler particles having an average particle size smaller than the wavelength of the light, although large enough to provide strength, the dental composition of the present invention provides the luster and translucency of the compositions reinforced by dispersion with the strength of the hybrid compositions. Although the present invention has been illustrated by a description of various embodiments and although those embodiments have been described in considerable detail, it was not the intention of the applicants to restrict or limit in any way the scope of the appended claims or such details. The advantages and additional modifications will be readily apparent to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details and representative compositions shown and described. This has been a description of the present invention, together with the preferred composition using the present invention as is now known. However, the invention itself will only be defined by the appended claims. It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.

Claims (18)

1. ? gKPlCATIONS Having described the invention as above, the content of the following claims is claimed as property. A dental composition, characterized in that it comprises: a resin base; and between about 10% by volume and about 70% of a ground structural filler having an average particle size of between about 0.05 μm and about 0.50 μm, where the ground structural filler contains less than 50% by volume of particles with a size of average particle with a diameter greater than 0.5 μm.
2. 2. The dental composition according to claim 1, characterized in that the composition has a flexural strength of at least 70 MPa.
3. 3. The dental composition according to claim 2, characterized in that the composition has a flexural strength of at least 100 MPa.
4. 4. The dental composition according to claim 1, characterized in that the composition maintains the surface gloss after wear.
5. 5. The dental composition according to claim 1, characterized in that the resin base comprises a polymerizable vinyl compound. The dental composition according to claim 1, characterized in that the ground structural filler contains less than 10% by volume of particles with an average particle size with a diameter greater than 0.8 μm. The dental composition according to claim 1, characterized in that it also comprises between about 1.0 and about 10.0% by volume of micro-filler having an average particle size of about 0.04 μm or less. The dental composition according to claim 7, characterized in that the micro-filler includes between about 0.5% by volume and about 5.0% by volume of particles having an average particle size of about 0.04 μm and between about 0.5% by volume and about 5.0% by volume of particles having an average particle size of about 0.02 μm. 9. The dental composition according to claim 1, characterized in that the composition has a gloss of approximately 45 or greater. 10. The dental composition according to claim 1, characterized in that it has a gloss of approximately 30 or greater in the composition. The dental composition according to claim 1, characterized in that the composition has a radiopacity of at least about 100% Al. 12. The dental composition according to claim 1, characterized in that the composition has a radiopacity of at least about 200% Al. 13. A dental composition, characterized in that it comprises: a resin base; and a filler that includes between about 10 and about 70% by volume of ground particles having an average particle size of between about 0.05 μm and about 0.50 μm and between about 1.0 and 10.0% by volume of micro-sized particles that have a size of particle approximately 0.04 μm or less in the resin base, where the composition has a flexural strength greater than about 100 MPa. 14. The dental composition according to claim 13, characterized in that the composition has a gloss of about 30% or greater and a flexural strength of about 105 MPa or greater. 15. The dental composition according to claim 14, characterized in that the composition has a gloss of about 45% or greater. 16. The dental composition according to claim 13, characterized in that the resin base includes a polymerizable vinyl compound. 17. The dental composition according to claim 13, characterized in that the resin base includes Bis-phenol-A-bis- (2-hydroxy-3-methacryloxypropyl) ether.; Triethylene glycol dimethacrylate; and ethoxylated Bis-phenol-A-dimethacrylate. 18. A dental composition, characterized in that it comprises: a resin base including Bis-phenol-A-bis- (2-hydroxy-3-methacryloxypropyl) ether, triethylene glycol dimethacrylate and ethoxylated Bis-phenol-A-dimethacrylate; between about 10% and about 70% by volume of filler particles having an average particle size of about 0.05 μm and about 0.5 μm between about 0.5% and about 5.0% by volume of filler particles having an average particle size of approximately 0.04 μm; between about 0.5% and about 5.0% by volume of particles having an average particle size of about 0.02 μm, the dental composition has a surface gloss of at least about 30% after simulated extended clinical wear. The present invention provides a dental composition, which has the strength required for load-bearing restorations, still maintains a shiny appearance, even after substantial wear. Through the use of particles having an average particle size of between about 0.05 μm and about 0.50 μm, the composition is useful in stress-bearing restorations and cosmetic restorations. The structural filler used is typically ground or crushed to an average particle size of less than 0.5 μm and also includes a microfiller having an average particle size of less than 0.05 μm to improve handling and mechanical characteristics. Preferred dental compositions maintain their surface finish even after substantial use and also have the strength properties of hybrid composite resins. The structural filler is milled or crushed, typically with an agitator mill, to the preferred particle size.