Dental restorative material

The present invention relates to a new dental restoration material which contains a special filler mixture.

Dental filling materials based on polymerizable compounds, so-called "composites", contain, in addition to one or more polymerizable monomers, activators, possibly polymerization catalysts and other constituents, a mineral filler.

The type and amount of this filler determine the physical properties of the filling made by the composite. The higher the proportion of filler and its particle sizes, the better for the physical properties, but generally the worse the polishability.

Attempts have therefore been made to improve the polishability of such materials by using fillers with small particle sizes between approximately 10 and 300 nm; however, this is at the expense of the mechanical properties.

These so-called "microfillers" are used predominantly or almost exclusively in the production of so-called light-curing composites, ie dental restoration materials which are in one phase and contain fillers, polymerizable compounds and a polymerization initiator which forms free radicals under the influence of light.

This is due in particular to the fact that these materials must have a certain curing depth which is not achieved with most fillers of larger particle sizes, the so-called "macrofillers".

Other macrofillers that do not have this disadvantage cause discoloration during the polymerization (= curing) of the filling. This applies in particular to the various types of glass which, when used alone, result in a greenish or grayish discoloration during the curing of the filling and, moreover, cannot be polished.

There was therefore a need to develop dental restoration materials, in particular light-curing materials, which do not have these disadvantages, but which can also be easily cured under the influence of light without polymerization catalysts, ie have a satisfactory depth of hardening, no discoloration, but have good physical properties, in particular with regard to reduced water absorption, shrinkage, a thermal expansion coefficient tending towards zero and improved mechanical properties, in particular with regard to hardness and diametric tensile strength.

In addition, it is desirable to achieve at least a certain degree of polishability.

It has now been found that a dental restorative material having the properties described can be produced if, in such an agent, an inorganic filling material in an amount of 60 to 90% by weight of the total composition is a mixture of at least one optionally silanized amorphous filler, in an amount of 50 to 90, in particular 50 to 75% by weight of the filler mixture, at least one optionally silanized crystalline filler is used in an amount of 10 to 50, in particular 25 to 50% by weight of the filler mixture, each with average particle diameters between about 0.3 and about 40 μm, preferably 0.3 and 20 μm, with this Mixture to improve the polishability up to about 10% by weight of an optionally silanized microfiller, especially finely divided silicon dioxide with an average particle diameter of less than 0.2 microns can contain.

Suitable amorphous filling materials are in particular various types of glass such as lithium aluminum silicate glass, powdered quartz, borosilicate glass, barium aluminum silicate, barium aluminum borate silicate or glass ceramic fillers with particle sizes between approximately 0.5 and approximately 40, preferably between 1 and 20 μm. These amorphous fillers as a component of the filler mixture used according to the invention can be X-ray transparent or X-ray opaque. A summary of such suitable filling materials can be found, for example, in RL Bowen, Journal of Dental Research, Vol. 58/5 (May 1979), pp. 1493-1501, in particular pp. 1495-1498.

Suitable radiopaque fillers are described in particular in US Pat. Nos. 3,801,344, 3,808,170 and 3,975,203 and DE-A-2,347,591.

A suitable crystalline constituent of the filler mixture according to the invention has in particular been found to be crystalline aluminum silicate, for example made from precipitated sodium feldspar. Other suitable crystalline filler components are, for example, lithium aluminum silicate such as beta-eucryptite, synthetic or natural calcium silicate, with an average particle size between approximately 0.3 and 40 11 μm, preferably approximately 0.3 or 0.5 and 20 or 10 μm.

From GB-A-1 544 776 dental restoration materials are already known (cf. in particular Example 3), which can contain a mixture of quartz and colloidal silicon dioxide as filler.

A reference to the combination of crystalline and amorphous fillers according to the invention in the particle size range between 0.3 and 40 ₁1m cannot be derived from this.

In order to improve the incorporability of the filler mixture according to the invention into the composition and the compatibility with the organic constituents, it is expedient to silanize these fillers with an organosilane. The silanization can be carried out using any suitable organosilane of the general formula<chemistry id="chem0001" num="0001"><img file="EP0091990B1_D0001.tif" /></chemistry>where R, R^l, R² and R³ represent the same or different organic radicals with the proviso that at least one radical is an OH group or a radical which can be converted into an OH group, for example by hydrolysis, in particular an alkoxy group. Preferred organosilanes are (meth) acroylpropyldihydroxymethoxysilane, (meth) acroylpropylhydroxidimethoxysilane, (meth) acroylpropyltrimethoxysilane or mixtures thereof; however, vinyl triethoxysilane or vinyl tri (methoxyethoxy) silane, for example, are also suitable silanizing agents.

In order to improve the polishability of the dental restoration material according to the application, a certain proportion of a microfiller, in particular a finely divided silicon dioxide with an average particle diameter below 200 nm, can also be present. However, in order not to influence the good physical properties of the cured material, the proportion of this microfiller should not be more than 10% by weight, preferably 4 to 8, in particular approximately 6% by weight, of the total filler content. This microfiller is also preferably silanized. A suitable silanized silicon filler material is described in EP-A-0 060 911.

A particularly suitable filler mixture is one that contains 50 to 75% by weight. optionally silanized amorphous lithium aluminum silicate with a particle size between about 1 and about 35 µm (average about 5 µm) and about 25 to about 50% by weight of an optionally silanized crystalline aluminum silicate with an average particle size between about 0.3 and about 20 µm, in particular 0.5 to 1 µm on average, preferably in a weight ratio of 3: 1.

As already stated, the dental restoration materials according to the invention are particularly suitable for use as light-curing products, ie products which are in one phase and polymerize under the action of light.

Such compositions contain one or more photopolymerization initiators. As such, in particular carbonyl compounds such as benzoin and its derivatives, in particular benzoin methyl ether, benzil and benzene derivatives, for example 4,4-oxidibenzil or other dicarbonyl compounds, e.g. B. diacetyl, 2,3-pentanedione or metal carbonyls, quinones or their derivatives. The proportion of photopolymerization initiator is 0.01 to 5% by weight of the total composition.

These light-curable, ie photopolymerizable, preparations preferably also contain so-called polymerization accelerators. These are substances that accelerate the polymerization reaction in the presence of polymerization initiators. Known accelerators are, for example, amines such as p-toluidine, N, N-dimethyl-p-toluidine, N, N-di (hydroxyethyl) -p-toluidine, trialkylamines such as trihexylamine, polyamines such as N, N, N ', N'-tetraalkylalkylenediamines , Barbituric acid and dialkyl barbituric acids and sulfimides, preferably in an amount of 0.01 to 5% by weight of the total composition. Suitable accelerators are for example from GM Brauer et. al. Journal of Dental Research, Vol. 58 / No. 10 (1979), S 1994-2000.

A preferred light-curable dental restoration material contains 60 to 90% by weight of the total composition of an inorganic filler mixture, which consists of 60 to 75% by weight (calculated on the filler mixture) of an optionally silanized amorphous filler, in particular lithium aluminum silicate, with a particle size between approximately 1 and approximately 20 µm, and 25 to 40% by weight⁰/ o of an optionally silanized crystalline filler, in particular aluminum silicate, with a particle size of about 0.5 to about 1 µm. If appropriate, this filler mixture can also contain up to 10, preferably up to 6% by weight of a preferably silanized, finely divided silicon dioxide which has an average particle diameter of less than 0.2 μm.

In principle, it is also possible to use the dental restoration materials according to the invention as two-phase preparations, one phase of which contains a polymerization catalyst, for example a peroxide, and the other phase an accelerator for this peroxide, for example an organic amine, the two phases being brought together immediately before filling the teeth and the polymerization takes place in the bored preferably occurs with a relining or a bonding material to be filled cavity.

Suitable peroxides, which decompose when the polymerization starts to form free radicals, are, for example, aryl peroxides such as benzoyl peroxide, cumene hydroperoxide, urea peroxide, tert-butyl hydroperoxide or perbenzoate and silyl peroxides, preferably in amounts of 0.01 to 5, in particular 0.5 to 2.5 % By weight of the total composition.

If one phase of the two-phase agent contains a polymerization initiator, an accelerator of the type described above, preferably an amine or barbituric acid or its derivatives, for example a dialkyl barbituric acid, is advantageously added to the other phase.

Polymerizable (meth) acrylic compounds can be used as polymerizable monomers in the dental restoration materials according to the invention. The known reaction products of bisphenols, in particular bisphenol A, and glycidyl methacrylate, known under the abbreviation bis-GMA, are particularly known here, the various alkanediol dimethacrylates such as 1,6-hexane-diol methacrylate, 1,4-butanediol dimethacrylate, tri- or tetraethylene glycol dimethacrylate, bis (2 methacroylpropyl) phthalate, isophthalate or terephthalate, trimethylolpropane di and trimethacrylate, and in particular the reaction products from diisocyanates and hydroxyalkyl methacrylates, as described, for example, in DE-A-No. 2,322,559, adducts of (di) isocyanates and 2,2-propane-bis- [3- (4-phenoxy) -1,2-hydroxypropane] -1-methacrylate according to US-A-No. 3,629,187 and in particular the adducts of isocyanates and methacroylalkyl ethers, alkoxybenzenes or alkoxycycloalkanes, as described in EP-A-44 352.

Of course, mixtures of suitable monomers can also be used.

Finally, it is expedient to add UV stabilizers to plastic-based dental filling materials in order to avoid darkening during the aging of the fillings. A particularly suitable UV stabilizer is 2-hydroxy-4-methoxybenzophenone. Another preferred material is 2- (2'-hydroxy-5'-methylphenyl) benzotriazole; however, in principle any physiologically inert UV absorbing agent is suitable for this purpose.

Hydroquinone, p-benzoquinone, p-butylhydroxytoluene and others are mentioned as examples. The latter compound can also act as an antioxidant in the filling, for example.

An overview of the substances commonly used in dental restorative materials can be found in the previously mentioned article by RL Bowen in the Journal of Dental Research, Vol. 58/5 (May 1979), pp. 1493 to 1503, as well as the associated supplements from JF Lann, pp. 1504 to 1506.

Composite materials also contain a small amount of dyes or pigments, if necessary, to give the filled tooth surfaces the most natural impression possible.

The following examples serve to explain the invention.

Mixture A

<tables id="tabl0001" num="0001"><img file="EP0091990B1_D0002.tif" /></tables>

Mix B

<tables id="tabl0002" num="0002"><img file="EP0091990B1_D0003.tif" /></tables>

Mixture C

<tables id="tabl0003" num="0003"><img file="EP0091990B1_D0004.tif" /></tables>

EXAMPLES

Examples I to III are compositions not according to the invention.

Example I

<ul id="ul0001" list-style="none"><li>Mixture A 100 parts by weight</li><li>Amorphous quartz powder (particle size ≈ 5 µm) 330 parts by weight Properties of the hardened material:<ul id="ul0002" list-style="none"><li>Hardening depth: 3.2 mm</li><li>Polishability: none.</li><li>Appearance: Unsatisfactory; too transparent with green tinge.</li></ul></li></ul>

Example 11

<ul id="ul0003" list-style="none"><li>Mixture B 100 parts by weight</li><li>Silanized amorphous quartz powder (particle size = 5 µm) 125 parts by weight of silanized silicon dioxide (particle size ≈20.5 nm) 45 parts by weight Properties of the hardened material:<ul id="ul0004" list-style="none"><li>Hardening depth: 2.5 mm</li><li>Polishability: Good.</li><li>Appearance: Moderate. The hardened material has a yellow tinge.</li></ul></li></ul>

Example 111

<ul id="ul0005" list-style="none"><li>Mixture C 100 parts by weight</li><li>Lithium aluminum silicate glass, particle size 1 to 35 microns, on average 4 microns 500 parts by weight</li><li>Properties of the hardened material:<ul id="ul0006" list-style="none"><li>Hardening depth: 5.0 mm</li><li>Polishability: none.</li><li>Appearance: Too transparent, with a gray cast.</li><li>Examples 1 to 7 are compositions according to the invention.</li></ul></li></ul>

example 1

<ul id="ul0007" list-style="none"><li>Mixture A 100 parts by weight</li><li>Silanized amorphous quartz powder (average particle size below 5 µm) 250 parts by weight</li><li>Crystalline lithium aluminum silicate (particle diameter 1 to 35 µm, on average 4 µm) 100 parts by weight Properties of the hardened material:<ul id="ul0008" list-style="none"><li>Hardening depth: 3.7 mm</li><li>Polishability: Good.</li><li>Appearance: very good; the optical properties of the hardened material correspond to those of the tooth structure without undesirable discoloration.</li></ul></li></ul>

Example 2

<ul id="ul0009" list-style="none"><li>Mixture B 100 parts by weight</li><li>Silanized borosilicate glass (particle size 0.5 to 35 µm, average 3 µm) 450 parts by weight</li><li>Silanized crystalline aluminum silicate (average particle size 0.5 to 1 µm) 150 parts by weight Properties of the hardened material:<ul id="ul0010" list-style="none"><li>Hardening depth: 4.0 mm</li><li>Polishability: Good.</li><li>Appearance: very good. The optical properties of the hardened material correspond to those of the tooth structure without undesirable discoloration.</li></ul></li></ul>

Example 3

<ul id="ul0011" list-style="none"><li>Mixture C 100 parts by weight</li><li>Lithium aluminum silicate glass (particle size 1 to 35 µm, on average 4 µm) 450 parts by weight</li><li>Silanized crystalline aluminum silicate (average particle size 0.5 to 1.5 µm) 150 parts by weight Properties of the hardened material:<ul id="ul0012" list-style="none"><li>Hardening depth: 4.2 mm</li><li>Polishability: Good.</li><li>Appearance: very good. The optical properties of the hardened material correspond to those of the tooth structure without undesirable discoloration.</li></ul></li></ul>

Example 4

<ul id="ul0013" list-style="none"><li>Mixture C 100 parts by weight</li><li>Silanized borosilicate glass (particle size 0.5 to 35 µm, 3 µm on average) 450 parts by weight of crystalline lithium aluminum silicate (beta-eucryptite) (average particle diameter 1 µm) 100 parts by weight Properties of the hardened material:<ul id="ul0014" list-style="none"><li>Hardening depth: 4.4 mm</li><li>Polishability: Good.</li><li>Appearance: very good. The optical properties of the hardened material correspond to those of the tooth structure without undesirable discoloration.</li></ul></li></ul>

Example 5

<ul id="ul0015" list-style="none"><li>Mixture B 100 parts by weight</li><li>Silanized amorphous quartz powder (particle size &lt;5 µm) 150 parts by weight</li><li>Silanized crystalline lithium aluminum silicate (beta-eucryptite) (average particle diameter 1 µm) 150 parts by weight</li><li>Silane is precipitated silicon dioxide (particle size 30 to 150 nm) 20 parts by weight</li><li>Properties of the hardened material:<ul id="ul0016" list-style="none"><li>Hardening depth: 3.6 mm</li><li>Polishability: Excellent.</li><li>Appearance: good; no noticeable discoloration.</li></ul></li></ul>

Example 6

<ul id="ul0017" list-style="none"><li>Mixture C 100 parts by weight</li><li>Lithium aluminum silicate glass (particle size 1 to 35 µm, on average 4 µm) 250 parts by weight</li><li>Crystalline aluminum silicate (average particle diameter 0.5 to 1 µm) 250 parts by weight</li><li>Properties of the hardened material:<ul id="ul0018" list-style="none"><li>Hardening depth: 3.1 mm</li><li>Polishability: Good.</li><li>Appearance: satisfactory; however slightly more opaque than the natural tooth structure.</li></ul></li></ul>

Example 7

<ul id="ul0019" list-style="none"><li>Mixture C 100 parts by weight</li><li>Lithium aluminum silicate glass (particle size 1 to 35 µm, on average 4 µm) 500 parts by weight</li><li>Crystalline lithium aluminum silicate (beta eucryptite) (average particle diameter 1 µm) 60 parts by weight Properties of the hardened material:<ul id="ul0020" list-style="none"><li>Hardening depth: 5.5 mm</li><li>Polishability: Satisfactory,</li><li>Appearance: satisfactory; however somewhat transparent.</li></ul></li></ul>

The depth of cure was determined with a curing lamp ("Translux") at an exposure time of 40 seconds. The light-induced discoloration was determined in accordance with ADA specification No. 27.

The results show the superior effect of the compositions according to the invention.