Polymerizable dental material.

The invention relates to a novel, polymerizable dental material with high transparency and good polishability.

Dental materials, particularly dental filling materials consist essentially of polymerizable liquid binders and organic and / or inorganic fillers. From DE-OS 14 92 040, for example, dental filling materials are known whose color adapts itself after curing the color of the natural tooth material. For this it is necessary that different refractive indices of the binder and filler slightly. As fillers, glass beads are used having a particle size in the range 18 to 40 microns, and glass fibers having a particle size in the range of 0.4 mm length and 13 microns in diameter. These are so-called macro-fillers.

The DE-PS 24 03 211 discloses dental materials which are in which exclusively microfine inorganic fillers (micro fillers) used in silica whose particle size in the 10 - 400nm. This gives surprisingly filling materials with good transparency and polishability and excellent physical properties.

To facilitate the incorporation of relatively large amounts of fumed or produced by the wet process silicas in polymerizable binder has been proposed to modify these fillers before their incorporation chemically or by heat treatment. The BET surface area is reduced thereby. (EP Patent No. 0,040,232, EP-OS 113 926).

The DE-PS 27 05 220 proposes transparent dental materials with high compressive strength before, in which a finely divided filler is used with such a particle size distribution that 70-95% of the particles have a particle size of 0.7 to 25 microns and 5 - 30% of particles have a particle size of 0.2 to 0.7 microns. Particles having a diameter less than 0.2 microns be used concomitantly at most in small quantities. The average grain size of the fine-particle fillers is 1 - 5 microns indicated. According to the examples of crude α-quartz is heated and milled for a particular method.

US Patent No. 4,220,582 discloses filling materials with improved radiopacity. In this case, a filler is used a barium-glass and amorphous silica, wherein the content of BaO in the glass must be at least 22.5 wt .-% amount.

The fillers of the DE-PS 32 47 800 are amorphous, spherical particles. They have a particle size from 0.1 to 1 micron, wherein the particles of silica and from 0.01 to 20 mol% consist of an oxide of at least one metal of Groups I, II, III and IV of the periodic table, and the components are chemically bonded to each other , These fillers are produced from hydrolysable compounds of silicon and metals by reaction with ammonia, as described in DE-PS 32 47 800 is described in more detail. The refractive index of the resulting fillers should be in the range from 1.35 to 1.70. The BET surface area of ​​the fillers can be decreased by calcination. Are given dental materials, containing such a filler, mixtures of said fillers or mixtures of fillers with a polymer filler.

U.S. Patent No. 4,503,169 describes radiopaque composites, which contain as filler special, non-vitreous microparticles. These are for example from an aqueous SiO₂ / ZrO₂ solution prepared which is subjected to heat treatment. The refractive index may affect the visual opacity of a composite.

Finally, EP-OS 238 025 radiopaque dental compositions are proposed which contain heavy metal fluorides. The transparency of the polymerized dental materials depends on the ratio of the refractive indices of the filler to the polymeric matrix. This publication can be further seen that produced with glasses dental filling materials are less abrasionstabil due to the low hardness of glass compared to quartz. It is not possible to grind the glasses so fine that you also get highly polished dental filling. Glasses which are ground so fine, be opaque by the grinding processes required for this purpose, which adversely affects the optical properties of the dental materials.

From the cited prior art it is apparent that there is still a need to improve the properties of dental materials, in particular their transparency while maintaining good polishing, the other physical properties, such as high compressive strength, low water absorption, high abrasion resistance , good bending strength, radiopacity, etc., should not be affected. If the micro-filled dental materials DE-PS 24 03 211 were pioneering in terms of polishing and transparency, it has been found that these materials still exhibit certain disadvantages. In particular, the incorporation of the fillers to be facilitated in the binder without the time consuming and labor intensive pretreatment of the inorganic filler is necessary, as stated for example in EP-HP 40 232nd

The invention is based, have a dental material with good transparency and polishability and other good material properties Ready Deliver, during its production, the inorganic fillers easy to work in the binder the task. Transparency is both to obtain the fullest possible hardening of the material during the photopolymerization, as well as the aesthetics of the finished product is crucial.

The invention provides a new dental material based on a polymerizable, ethylenically unsaturated monomer as binder, a catalyst for cold, hot and / or photopolymerization and 20 to 90 wt .-% of an inorganic filler, which is characterized in that it from as inorganic filler a mixture<ul><li>(A) amorphous, spherical particles of silicon dioxide and up to 20 mol% of an oxide of at least one element of groups I, II, III and IV of the periodic system with a refractive index of 1.50 to 1.58 and with an average primary particle size of 0 , 1 to 1.0 microns, and</li><li>(B) quartz, glass ceramic or glass powders or their mixtures with a refractive index of 1.50 to 1.58 and with an average particle size of 0.5 to 5.0 microns contains.</li></ul>

The term dental material are dental filling materials, materials for inlays or onlays understood, dental cements, facing materials for crowns and bridges, materials for artificial teeth or other materials for prosthetic, preservative and preventive dentistry.

In particular, the dental material is a composite according to the invention, ie, a dental filling material consisting of inorganic fillers and at least one ethylenically unsaturated polymerizable binder and a suitable catalyst system.

It was surprisingly found that it is possible by using a conventional binder and a targeted selection of the inorganic filler mixtures with very specific physical properties to provide a dental material having unexpected physical properties. In particular, it is surprising that the transparency and polishing are very good.

As the inorganic filler mixtures, mixtures of at least two different fillers can be used. The inorganic filler (A) is an amorphous, spherical material on the basis of silicon dioxide, that in addition contain an oxide containing at least one metal of the groups I, II, III and IV of the Periodic Table. Preferably, strontium and / or zirconium oxide is used. The average primary particle size is in the range of 0.1 to 1.0 .mu.m, in particular from 0.15 to 0.5 .mu.m. The refractive index of the inorganic filler (A) is 1.50 to 1.58, in particular 1.52 to 1.56. A particularly preferred value is 1.53 ± 0.01. There are also, filler possible, provided they meet the parameters regarding particle size and refractive index. Fillers of the type (A) are described in DE-PS 32 47 800th The filler of the type (A) can also be present as a sintered mixture of agglomerates having an average particle size of 1 to 30 microns.

When the inorganic filler (B) of the filler mixture is quartz, glass ceramic or glass powder. Glasses are preferred. The average primary particle size of the inorganic filler (B) is between 0.5 and 5.0 .mu.m, in particular between 1.0 and 2.0 microns and more preferably between 1.0 and 1.5 microns, while the refractive index values ​​between 1 should have 50 and 1.58, be-tween especially 1.52 and 1.56. It can also be used filler mixtures. The invention preferably Ba-silicate glasses with an average particle size in the range from 1.1 to 1.3 microns, and Sr silicate glasses with an average particle size in the range from 1.1 to 1.3 microns, and Li / Al-silicate glasses with a mean grain size from 1.0 to 1.6 microns used. Such powders can be for example &amp; bar, Cologne obtained by fine grinding with a RS-Ultrafeinstmühle of Reimbold.

Optionally, further fillers (C) may be used to achieve increased radiopacity, with an average primary particle 5.0 microns should not exceed. Such fillers are described for example in DE-OS 35 02 594th A particularly preferably used filler (C) is ytterbium.

Optionally, to adjust the viscosity, small amounts of micro-fine, pyrogenic or wet-precipitated silica (filler (D)) can be incorporated in the dental material, but not more than 5 wt .-%, based on the dental material.

The total filler amount, consisting of the fillers (A), (B) and optionally (C) and (D) in the dental material according to the invention is, depending on the intended use between 20 and 90%. the proportion by weight of filler (A) is preferably 5 - 60%, in particular 10 - 30%, the filler (B) 15 - 85%, in particular 30 - 70%, based on the total dental material.

The inorganic fillers are preferably silanated. Suitable adhesion promoters are, for example α-methacryloxypropyltrimethoxysilane is. The amount of adhesion promoter used depends on the type and the BET surface of the filler.

As polymerizable organic binders are all for a dental material binder, in particular monofunctional or polyfunctional methacrylates which can be used alone or in mixtures. As examples of these compounds are methyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, tetraethylene glycol dimethacrylate, triethylene glycol dimethacrylate, diethylene glycol dimethacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, butanediol dimethacrylate, hexanediol dimethacrylate, decanediol dimethacrylate, dodecanediol dimethacrylate, bisphenol A dimethacrylate, trimethylolpropane trimethacrylate, 2,2-bis-4 (3-methacryloxy 2-hydroxypropoxy) phenylpropane (bis-GMA) and the reaction products of isocyanates, in particular di- and / or triisocyanates and OH-group-containing methacrylates. Examples are the reaction products of 1 mol of hexamethylene diisocyanate with 2 moles of 2-hydroxyethylene methacrylate, 1 mole of tri (6-isocyanatohexyl) biuret with 3 moles of 2-hydroxyethylmethacrylate and 1 mol 2,2,4-trimethylhexamethylene diisocyanate with 2 moles of 2-hydroxyethyl methacrylate, which are hereinafter referred to as urethane dimethacrylates. The proportion of these mostly long-chain compounds in the dental material varies between 10 and 80 wt .-%.

The dental material can be polymerized according to the type of catalyst used hot, cold or light. The catalysts used for hot polymerisation the known peroxides such as dibenzoyl peroxide, dilauroyl peroxide, tert-butyl peroctoate or tert.-butyl perbenzoate can be used, as well as α, α'-azo-bis (isobutyroethylester), benzpinacol and 2,2'-dimethylbenzopinacol suitable ,

As catalysts for the photopolymerization such as benzophenone and its derivatives, benzoin and its derivatives can be used. Other preferred photosensitizers are α-diketones such as 9,10-phenanthrenequinone, diacetyl, furil, anisil, 4,4'-and 4,4'-dichlorobenzil dialkoxybenzil. Camphorquinone is particularly preferably used. The use of photosensitizers, together with a reducing agent is preferred. Examples of reducing agents are amines such as cyanethylmethylaniline, dimethylaminoethyl methacrylate, triethylamine, triethanolamine, N, N-dimethylaniline, N-methyldiphenylamine, N, N-dimethyl-sym.-xylidine and N, N-3,5-tetramethyl aniline, and 4-dimethylaminobenzoate.

As catalysts for the cold polymerization radical-supplying systems, for example benzoyl or lauroyl peroxide together with amines such as N N-dimethyl-sym-xylidine or N, N-dimethyl-p-toluidine used. It is also possible dual curing systems are used for the catalysis, for example, photoinitiators with amines and peroxides. As photocatalysts, mixtures of UV light-curing and curing in the visible light catalysts also come into consideration.

The amount of these catalysts in the dental material is typically between 0.01 to 5 wt .-%.

The dental material can also be incorporated into fine chip or bead polymers which may be homopolymers or copolymers of vinyl compounds already described. These homo- or copolymers can turn with the described inorganic fillers, also radiopaque, be filled. Further, the dental material contain conventional pigmenting agents and stabilizers.

Preferably, the dental material according to the invention is used as a dental filling material. Dental filling materials are prepared as two-component materials which cure cold after mixing. The composition is similar to the light-curing materials, except that instead of the photocatalysts into a paste, for example, benzoyl peroxide and the other paste, for example, N, N-dimethyl-p-toluidine incorporated. By mixing approximately equal parts of the two pastes obtained a dental filling material which hardens in a few minutes.

If the amine is omitted from the latter materials and used as a catalyst, for example benzoyl peroxide only, you get a hot-curing dental material which can be used for the manufacture of inlays and artificial teeth. For the manufacture of an inlay in the patient's mouth of the cavity, an impression is taken and made a plaster model. In the cavity of the plaster model, the paste is introduced and the whole is polymerized in a pressure pot under heat. The inlay is removed, worked and then cemented in the patient's mouth into the cavity.

The invention relates not only to the dental material, but also produced therefrom finished parts such as artificial teeth, shells, inlays etc.

The invention will be explained in more detail by way of examples. The comparative examples relate to dental materials which are not composed according to the invention, because they contain a higher proportion of microfine fumed silica instead of the filler component (A).

When used fumed silica AEROSIL® OX 50 sil. Degussa concerned it is a fumed silica having an average primary particle size of 40 nm and a BET surface area of ​​50 ± 15 m² / g, which is silanized.

In the examples used in the filler (A) it was such in accordance with DE-PS 32 47 800, namely an amorphous, spherical filler with an average primary particle size in the range 0.15 to 0.4 .mu.m and a refractive index of about . 1.53. The filler contains silica and 17.5 mol% of zirconium dioxide and is silanized.

The Ba-silicate glass used had a mean particle size of 1.2 microns and a refractive index of about 1.53, Sr-silicate glass has a mean particle size of 1.5 microns and a refractive index of about 1.525, the Li / Al-silicate glass an average particle size of 1.0 microns and a refractive index of about 1.538. The glasses mentioned above, there are inorganic fillers (B) in the sense of the invention. The desired particle size was obtained by fine grinding in an RS ultrafine mill. The powders were silanized.

The filler used in the examples (C) was ytterbiumtrifluoride with an average primary particle less than 1 .mu.m and a refractive index of about 1.53.

The incorporation of the filler mixtures according to the invention was carried out by conventional methods, for example by means of a kneader or a three-roll mill.

Of the materials of the examples, test pieces were prepared and polished with a rubber cup for 5 minutes. The surfaces were observed under a microscope.

The transparency was measured using the method described in EP-OS 189 540. The determination of the depth of cure was carried out according to ISO 4049, the test specimens were exposed for 40 seconds using a commercially available UV light (Heliomat® Vivadent), provided that a photocatalyst was present.

Examples

Comparative Example 1

(Filler: finely divided silanized Ba-glass, AEROSIL® OX 50 sil and ytterbium.).

In 18 g of a monomer mixture consisting of 27 wt .-% of an urethane prepolymer (reaction product of 1 mole of trimethylhexamethylene diisocyanate with 2 moles of hydroxyethylmethacrylate), 42.2 wt .-% bis-GMA, 30 wt .-% triethylene glycol dimethacrylate, 0.3 wt .-% camphor quinone and 0.5 wt .-% N, N-3,5-tetramethyl aniline, 16 g of silanized AEROSIL® OX 50, 15 g and 51 g of silanized ytterbiumtrifluoride Ba-silicate glass were incorporated. There was a solid, mouldable paste which was cured with light.<dl id="dl0001"><dt>Transparency:</dt><dd>27%</dd><dt>polishing:</dt><dd>Good</dd></dl>

Comparative Example 2

(Filler: finely divided silanized Ba-glass and AEROSIL® OX 50 sil.)

In 21 g of the monomer mixture described in Example 1 16 g of silanized AEROSIL® OX 50 and 63 g of silanized Ba-silicate glass were incorporated. There was a solid, mouldable paste which was cured with light.<dl id="dl0002"><dt>Transparency:</dt><dd>31%</dd><dt>polishing:</dt><dd>Good</dd></dl>

Comparative Example 3

(Dual-curing cement, filler fine mesh silanized Ba-glass and AEROSIL® OX 50 sil.)

a) Base paste:

In 31.5 g of a monomer mixture consisting of 80 wt .-% of an urethane prepolymer (reaction product of 1 mole of trimethylhexamethylene diisocyanate with 2 moles of hydroxyethylmethacrylate), 18.7 wt .-% dodecanediol dimethacrylate, 0.6 wt .-% camphorquinone and 0 , 7 wt .-% N, N-3,5-tetramethyl aniline, 7.5 g of silanized AEROSIL® OX 50, 10 g and 51 g of silanized ytterbiumtrifluoride Sr-silicate glass were incorporated. In addition, small amounts of color pigments were added so that a tooth-like appearance is obtained. There was a viscous cement paste.

b) catalyst paste:

In 31.5 g of a monomer mixture consisting of 80 wt .-% of an urethane prepolymer (reaction product of 1 mole of trimethylhexamethylene diisocyanate with 2 mol of hydroxyethyl methacrylate), 19.2 wt .-% and 0.8 wt .-% dodecanediol dibenzoyl peroxide, have been 7.5 g silanized AEROSIL® OX 50, incorporated 10 g and 51 g of silanized ytterbiumtrifluoride Sr-silicate glass. There was a viscous cement paste.

Both pastes were a dual-curing (self- and light-curing) mixed and cured cement.<dl id="dl0003"><dt>Transparency:</dt><dd>25%</dd><dt>polishing:</dt><dd>Good</dd><dt>curing depth:</dt><dd>3.6 ± 0.1 mm (steel mold, 40 sec, Heliomat®)</dd></dl>

example 4

In 18 g of a monomer mixture consisting of 49 wt .-% bis-GMA, 49 wt .-% dodecanediol, 2 wt .-% of dibenzoyl peroxide and 500 ppm of MEHQ, was added 15 g of ytterbium trifluoride, 15 g of silanized filler (A) and 52 g silanized Ba-silicate glass incorporated. There was a solid, translucent paste with good modeling properties.

The obtained dental material suitable as a tooth-colored, thermosetting inlay / onlay material.<dl id="dl0004"><dt>Transparency:</dt><dd>44%</dd><dt>polishing:</dt><dd>Good</dd></dl>

example 5

In 18 g of the monomer mixture described in Comparative Example 1, 15 g of ytterbium trifluoride, 16 g of silanized filler (A) and 51 g of silanized incorporated Sr-silicate glass. In addition, small amounts of color pigments were added so that a tooth-like appearance is obtained. There was a solid, translucent paste with good modeling properties.

The dental material obtained suitable as a tooth-colored, light-curing restorative material for the molar region as well as an inlay / onlay material.<dl id="dl0005"><dt>Transparency:</dt><dd>41%</dd><dt>polishing:</dt><dd>Good</dd><dt>flexural strength</dt><dd>139 ± 11 MPa</dd><dt>curing depth:</dt><dd>4.4 ± 0.1 mm (steel mold, 40 sec, Heliomat®)</dd></dl>

example 6

In 23 g of the monomer mixture described in Comparative Example 1 17 g were incorporated silanized filler (A) and 60 g of silanized Li-Al-silicate glass. In addition, small amounts of color pigments were added so that a tooth-like appearance is obtained. There was a solid, translucent paste with good modeling properties.

The dental material obtained suitable as a tooth-colored, light-cured crown and bridge veneering material and as a front tooth filling material.<dl id="dl0006"><dt>Transparency:</dt><dd>45%</dd><dt>polishing:</dt><dd>Good</dd></dl>

example 7

In 19 g of the monomer mixture described in Comparative Example 1, 15 g of ytterbium trifluoride, 16 g of silanized filler (A) and 50 g of silanized Li-Al-silicate glass incorporated. In addition, small amounts of color pigments were added so that a tooth-like appearance is obtained. There was a solid, translucent paste with good modeling properties.

The dental material obtained suitable as a tooth-colored, light-curing anterior restorative.<dl id="dl0007"><dt>Transparency:</dt><dd>44%</dd><dt>polishing:</dt><dd>Good</dd></dl>

example 8

a) Base paste:

Monomer mixture described in the 30.5 g in Comparative Example 3 (base paste) were incorporated 8.5 g of silanized filler (A), 10 g and 51 g of silanized ytterbiumtrifluoride Ba-silicate glass. In addition, small amounts of color pigments were added so that a tooth-like appearance is obtained. There was a viscous cement paste.

b) catalyst paste:

Monomer mixture described in the 31.5 g in Comparative Example 3 (Catalyst paste) were incorporated 8.5 g of silanized filler (A), 10 g and 51 g of silanized ytterbiumtrifluoride Ba-silicate glass. There was a viscous cement paste.

Both pastes were mixed to a dual-curing (self- and light-curing), translucent cement.<dl id="dl0008"><dt>Transparency:</dt><dd>42%</dd><dt>curing depth:</dt><dd>4.8 ± 0.1 mm (steel mold, 40 sec, Heliomat®)</dd></dl>