SE436684B - USE OF DIACRYLIC ACID OR DIMETACYRIC ACID ESTERS OF BISHYDROXIMETHYL TRICYCLO - Google Patents

Description

7804386-6 2 lack of hydroxyl groups unlike the pulps of U.S. Pat. No. 3,066,112, which due to their preparation by depositing bisphenol A on the epoxy groups of the glycidyl methacrylate contain two hydroxyl groups per molecule of the dimethacrylic acid compound.

These known bifunctional methacrylic acid esters are used in conjunction with radical-forming polymerization catalysts or initiators, especially in dentistry, as masses for dental fillings, where they have made a significant improvement over the previously used methyl methacrylates. They are polymerized quickly without leaving any residual monomers and, above all, show a markedly lower polymerization shrinkage. The cured material has high compressive strength, as evidenced by the investigations made by Henry L.

Lee et al. and J. Dent. Res. § 4, 526-535 (1969) and in H. Durner's work, published in Zahnärtzl. Welt / Reform, §l, p. 764 11972).

Despite the relatively good strength of the fillings and dentures obtained from the previously known bifunctional methacrylic esters, these pulps still do not meet all the requirements that can be placed on such pulps. Dental fillings and dentures are exposed to enormous chewing pressure and, in addition, abrasion phenomena through grinding. Therefore, despite the presence of these preparations, amalgam is still used for dental fillings by many dentists, even though this material suffers from shortcomings in terms of aesthetic oxygen and despite the fact that there are still concerns about its use due to the mercury content. Additions of fillers, in particular quartz powder or finely divided, amorphous silicic acid, have admittedly tried to further increase the strength and abrasion values of the polymeric masses, as is apparent from German publications 24 05 578, 24 32 013 and 24 38 411, wherein tri- or tetrafunctional methacrylic acid esters can also be used. However, these do not easily lead to satisfactory results.

In general, compressive strength values are achieved today, which are in the range 2200 - 2900 kp / cm2. Although in many cases these products are good enough, there is still a desire to produce even harder and more wear-resistant dental fillings and dentures, which are based on starting materials which can be easily obtained and which can then be rapidly polymerized by use of conventional polymerization catalysts and initiators and are completely cured in a short time already without any increase in temperature. It has surprisingly been found that diacrylic or dimethacrylic acid esters of bis-hydroxymethyltricyclo [É.2.1.02'§Y-decane constitute particularly suitable polymerizable components for dental fillings and dentures and the invention is thus directed to the use of such esters. for the manufacture of polymerizable dental pulps on the basis of bifunctional acrylic acid esters. They give extremely dimensionally stable and hard polymers. The diacrylic acid ester compounds can be readily prepared by esterifying dihydroxymethyltricyclodecan with acrylic acid or derivatives thereof by conventional methods.

Commercially available dihydroxymethyl tricyclo [2.1.02'§] - decane corresponds to the simplified formula given below Due to the usual procedure for the preparation of this tricyclo decane derivative, the hydroxymethyl residues can be in either 3- and 4-position as well as in 9 and 8-position in the tricyclodecan molecule. In general, these isomeric compounds are present side by side in the commercial product, the preparation of which e.g. is described in German Offenlegungsschrift 16 18 384. The compound has thus already been used for the production of polyadducts on the basis of triglycidyl isocyanurate, as is apparent from German Offenleged Ordinance 15 94 868.

The bifunctional bisacrylic acid or bismethacrylic acid esters of dihydroxymethyltricyclodecan are compounds which correspond to the general formula HH r / C \\ H / c (2) R -6 where R represents the methylene acrylate residue of the formula_ -cH -oco-c .__-_ C212 2.

R 1 wherein R 'may represent H or CH 3. In the general formula II, the statement CH (2) should indicate that at this C atom in the isomeric compound there may possibly be two H atoms, when the residue R is not there. They can be easily prepared by conventional methods by esterification of dihydroxymethyltricyclodecan with the free acrylic acids in the presence of suitable catalysts or by transesterification using acrylic acid esters of lower alcohols, e.g. methacrylic acid methyl ester. By the addition of polymerization inhibitors, such as p-methoxyphenol, in this case, ie during the esterification or transesterification, an undesirable polymerization can be prevented in the usual way at the elevated temperature.

The bifunctional acrylic esters of the formula II constitute colorless, thin-liquid oils which, due to their relatively low viscosity compared with the bifunctional methacrylic acid esters previously used in dentistry, offer an extremely easy-to-process alternative. The pulps used according to the invention may contain the conventional radical scavengers known for such polymerization purposes. Suitable polymerization catalysts are e.g. peroxides or azo compounds, in particular lauroyl peroxide, chlorobenzoyl peroxide, etc. For applications in which rapid polymerization at room temperature is necessary, especially in connection with dental filling materials, the known redox systems are preferably used, which usually consist of a peroxide and a reducing agent, e.g. amines, sulfinic acids, substituted sulfones, so-called CH-active compounds, such as barbituric acids or ß fl diketones. In general, redox systems which do not cause any color change are preferred, or, when using amine-containing redox systems, those amines which are relatively stable against color change are selected, in particular N, N-bis-hydroxyalkyl-3,5-xylidines or N , N-bis-hydroxyalkyl-3,5-di-t-butylanilines.

Due to the presence of compounds which, after the action of visible or ultraviolet light, initiate the polymerization, a rapid polymerization can be achieved upon irradiation, which is particularly advantageous for many uses. Masses containing suitable UV initiators are very stable in the dark, whereby the substances used according to the invention allow the preparation of ready-to-use one-component preparations. For this purpose, a conventional initiator for UV polymerization is dissolved in the bifunctional esters, e.g. benzoin, benzoin ethers,: Ä-substituted benzoins or benzoethanes, benzyl, benzyl ketals, halogenated aromatics, such as halomethylated benzophenones, etc. By adding small amounts of organic phosphites, the already very rapid polymerization can be further accelerated by the action of UV light.

One-component preparations which contain polymerization initiators which react to visible light are particularly easily cured.

These include e.g. combinations of quinones and aliphatic amines or of benzyl ketals, benzophenones or quinones and amines.

Preparations containing such initiator systems are sufficiently stable in the dark and, even during daylight irradiation or artificial irradiation of normal intensity, have a sufficiently long processing time. After irradiation with an intense light source, which provides visible light, rapid polymerization occurs.

In accordance with the invention, the bifunctional esters are used for dental pulps, ie raw materials in dentistry. This refers, for example, to dental fillers and preparations for the construction of removed tooth parts, coating and sealing compositions, materials for under-treatment of cavities, materials for crowns, bridges and coatings, compositions for the manufacture of artificial teeth, prosthetic materials and devices in orthodontics, ie. for braces.

In practice, the materials can be used to advantage wherever the use of plastic materials or polymerizable materials is common in dentistry.

The substances can then generally be used either as two-component systems, e.g. as a preparation, consisting on the one hand of monomers and on the other hand of filler material, containing the polymerization catalyst, or in the form of two liquids or two pastes, in which the two constituents of redox systems are in some way distributed between the two components . In addition, a use is in pre-dosed form, ie in plastic containers, which initially contain the two components separately and in which after combining the two components a mechanical mixing process takes place, without difficulties feasible with the according to the invention use the substances. Another advantageous application is the 7804336-6 burner area, which comprises polymerization by means of ultraviolet or visible light of dental filling and coating compositions, which are preferably present as one-component systems in ready-to-use form.

By means of the bifunctional methacrylic acid esters used according to the invention, an increase in the strength is achieved in comparison with the strength of traditional materials. Thus, for example, in the usual paste / paste preparations for dental fillings, it is possible to increase the compressive strength from about 2500 kp / cm 2 to about 4000 kp / cm 2 by a simple exchange of the known bifunctional methacrylic esters with the esters used according to the invention. na. In addition, curing occurs extremely quickly.

Especially with the use of conventional redox systems, the time from the beginning of the gel formation to the end of the curing is shortened to half and up to a quarter without thereby reducing the treatment time, ie the time until the beginning of the polymerization. This is especially important in connection with preparations to be applied in the mouth, especially when inserting dental fillings.

The bifunctional esters used according to the invention can be mixed with conventional, monofunctional acrylic esters and methacrylic esters. They can also be used together with the conventional, bifunctional methacrylic esters. Thus, in any way, an addition of bifunctional esters according to British Patent Specification 1,267,564, U.S. Patent Specification 3,923,740 or German Patent Specification 1,921,869, which are hydroxyl group-free, can serve to set a certain refractive index or can be used interchangeably. the use of such esters, as described in U.S. Pat. No. 3,066,112 and which contain hydroxyl groups, serve to set an admittedly low but intended water uptake of the polymers, which in many cases is desirable in order to avoid cracking at the edges. for dental fillings. The combinations of the substances according to the invention with these known, monomeric diacrylate or alkanediol diacrylate surprisingly give a strength of the polymers, which is hardly lower and in many cases even is higher than when using only the substances according to the invention. Such mixtures must contain at least 20% of the monomers according to the invention, based on the polymerizable monomer content in the pulps. Of the known bifunctional monomers, the new combination with the monomer compounds used according to the invention is particularly suitable, in particular the diacrylate or the diphthalate acrylate of the diol of bis-β-hydroxyethoxy-phenylpropylane or bis-¿. §- (β-hydroxy--propoxy-) phenyl7-propane. On the basis of such combinations, it is possible to produce particularly high-quality dental preparations, in particular dental filling and coating pellets, either on a paste-paste basis or as a one-component system. In the former, a substance according to the invention may be present in one paste and a known, monomeric substance in the second component, the peroxide being present in a paste and the activator in the other paste when using the redox catalyst system. The one-component systems contain mixtures of diacrylate according to the invention and known monomers, e.g. hexanediol dimethacrylate. After mixing the two pastes or after irradiating the pulps which contain light-demanding polymerization activators, curing to polymers with superior good hardness values occurs.

It is also possible to use conventional fillers and this is also suitable. Quartz, quartz glass and other glass materials, e.g. on the basis of aluminum silicate, as well as glass material, which gives the dentological materials a certain X-ray opacity, such as. barium or lanthanum glass material. Normally, these inorganic fillers are silanized according to known methods. The same applies to fibers, the addition of which may also be suitable for improving the mechanical properties, e.g. glass or quartz fiber. Even insoluble, inorganic salts or minerals, such as calcium fluoride, can be used as a filler. In addition, it may be advantageous to use or co-use only microfine fillers, in particular amorphous SiO 3 or Al 2 O 3 with average particle sizes between 10 "and 10" 3 mm, especially for consistency stabilization. is common in odontology and dentology, especially in the manufacture of dentures and teeth, is possible. Particularly relevant here are the usually in pearl form, tooth-colored polymethacrylic esters. Of course, the materials according to the invention can also be added with the usual pigments, soluble dyes, so-called "whitener" to achieve whiteness by fluorescence.

To prevent premature polymerization, it is convenient to add antioxidants, especially of a phenolic nature, such as e.g. p-methoxyphenol, hydroquinone or 2,6-di-t-butyl-p-cresol.

As stabilizers against discoloration by the action of light, the compositions may further contain UV light absorbing materials, e.g. benatotriazole, benzophenone or benzoic acid phenyl ester. The latter apply to special preparations which are not polymerized by the action of UV light.

The invention will be further elucidated below with the aid of a few examples, whereby bis-oxymethyl-tricycloane.2.l.02'É7 ¥ decane is designated as T-diol and its enter as T-diacrylate resp. T-dimethacrylate.

Example 1 Preparation of the bifunctional methacrylic ether of the T-diol, 98 g of T-diol, 129 g of methacrylic acid and 200 ml of gyclohexane were heated for 24 hours in the presence of 7 g of p-toluenesulfonic acid and 0.3 g of picric acid while distilling off the formed the water. Thereafter, the reaction product was washed repeatedly with 2N sodium hydroxide solution and water and then stripped off by treatment with AlO3.

For atabilization against premature polymerization, 10 mg of p-methoxyphenol were added and the cyclohexane used as solvent was finally distilled off in vacuo. ri nan obtained on this: act lan g dimethacrylate ester in farm of than almost colorless, thin liquid oil. viscous (25 ° c) = 1.1 P n§ ° = _ 1.5oo8 double bond equivalent: 170; 169 Example gel 2 Preparation of the bifunctional acrylic ester of the T-diol. 196 g of T-diol, 216 g of acrylic acid and N00 ml of hexane were heated for 6 hours in the presence of 14 g of p-toluenesulfonic acid and 0.7 g of picric acid while distilling off the water formed. After working up in the manner described in Example 1, 121 g of a colorless oil were obtained, which gave the following analytical values: viscosity (25 ° C); 1,2 P nšo: 0 n el, 50ü0 "_ WM double bond equivalent: l55§ 158 Example 3 Preparation of an acrylic-methacrylic mixture ester of the T-diol. 59 g Tediol, 22 g acrylic acid, 52 g methacrylic acid, 100 ml eyklohexane, H g of p-toluenesulfonic acid and 0.16 g of picric acid were heated together and the reaction mixture worked up: in the manner described in Example 1 above, 71 g of a colorless oil were obtained with the following values: viscosity (25%): 1, 2 P n§ ° = 1,5o2o double bond equivalent: 168; 172 g Approximately H0 I of the ester groups present were acrylic acid residues. Example gel Ä Comparative experiment (heat polymerization).

For comparison with a known product, the dimethacrylate derived from bisphenol-A was prepared according to Example 10 of German Patent Specification 1,921,869.

To determine the compressive strength of the polymers, this dimethacrylate and the T-dimethacrylate according to the invention were added with 0.6 Z of lauroyl peroxide, and the two solutions were each filled into 10 cylindrical molds with a diameter of 8 mm and a height of 8 mm, after which the molds were heated. 30 minutes to 130 ° C. The following average compressive strength values were obtained with these test specimens: with the pulp according to the invention: 1720 kplomz with the pulp according to Example 10 of German Patent Specification 1 921 869: ~ ll50 kp / cm 2 Example gel 5 ~ Comparative experiments (redox polymerization).

Two solutions were prepared, dissolving in T-dimethacrylate 0.8 N, N-bishydroxyethyl-3,5-di-t-butylaniline and 1.0 Z p-chlorobenzoyl peroxide. After mixing equal parts of the two solutions, the mixture was filled into molds lightly, as described in Example H above. After a few minutes, a hard, transparent polymer formed.

Analogously prepared analogous solutions of dimethacrylate of 2,2-bis-β- (Y-hydroxy-propoxy) phenyl7-propane, the synthesis of which is described in German Patent Specification 1921 869, and these were also processed into moldings of the same dimension.

The moldings were stored for 24 hours at 36 ° C. Subsequently, the following average compressive strength was determined: T-dimethacrylate 1640 kp / omg according to the state of the art: 1160 kp1cm2 Example gel 6 Paste / paste preparations for the preparation of dental fillings.

To prepare the two pastes, knead together: 7804506-6 I m 'A) g 2, ug g N, N-bis-hydroxyethyl-3,5-di-t-butylaniline, dissolved in 300 g Tedimethacrylate 1.8 g amorphous , silanated SiO 2 with an average primary particle size of 12 nm and 990 g silanated tooth-colored quartz powder (less than 60 μm) B) 300 g T-dimethacrylate 1.8 g of the S102 used in paste A 990 g silanated tooth-colored quartz powder (less than 60 μm) containing 6.0 g of p-chlorobenzoyl peroxide. - In a mixture of equal parts of the two pastes, a relatively flexible, easily applicable mass arose, which was introduced in the usual way into prepared tooth cavities and was cured there after about 3 minutes. The filling could then be ground and polished.

Example 7 Comparative experiments.

We ventured in the same manner as described in Example 6 and in turn manufactured 5-cylindrical moldings with the dimensions given in Example R.

For comparison with a known mass, two pastes were used, the composition of which corresponded to the data in Example 6, the Tedimethacrylate being replaced by the dimethacrylate given in Example 5 according to German Patent Specification 1921 869, and similar moldings were prepared. After 2 hours of storage at 36 ° C, the following average compressive strengths were obtained: Pastor on the basis of T-aimetacrylate = tj. uoso xp / ena Pastor according to the prior art: 2630 kplomz Example 8 - Pastel paste preparations for the preparation of dental fillings.

To prepare two pastes, kneaded together: A) 1.8 g of N, N-bis-hydroxyethyl-3,5-di-t-butylaniline, dissolved in 300 g of T-diacrylate 1.8 g of amorphous, silanated SiO 2 with an average primary particle size of 12 m nm and 990 g of silanate, tooth-colored quartz powder (less than 60 μl) B) 300 5 T-diacrylate - 1.8 g of the SiO2 used in paste A 7 990 g of silanated, tooth-colored quartz powder (less than 60 ¿Um), containing 0 6.0 g of p-chlorobenzoyl peroxide 11 If equal parts of the two pastes are mixed together, a processing time is obtained (from the beginning of the bop mixture) of about 1 minute 50 seconds at 24 ° C. Using a rheometer, the curing process was then followed. It was determined that the mass had already solidified and become stiff after a further 25 seconds.

With the paste / paste mixture used for comparison according to the prior art from Example 7, at the same processing time and temperature, about 90 seconds were required for the subsequent curing, which showed that the pulps according to the invention cured faster, so that the processing could be carried out earlier. The waiting time for patients and dentists, until the filling could be processed definitively, was thus shorter and thus advantageous in connection with the preparation according to the invention.

Example 9 Combination of a substance according to the invention with a dimethacrylate according to the prior art.

Paste A from Example 8 was used on the one hand and the peroxide-containing paste on the other hand on the basis of the known dimethacrylate of the 2,2-bis-β- (1-hydroxy-propoxy) -phenyl] -propane according to German Patent Specification 921 869 .

The pastes were mixed together in a ratio of 1: 1 and the compressive strength of the test specimens was determined in the manner described in Example H. The average measured value was 36ü0 kp / cm 2, i.e. significantly above the value of the conventional dentifrices, although only one of the two components was prepared on the basis of a substance according to the invention.

Example 10 Preparation for dental fillings in pre-dosed form.

According to the German public, were mixing containers used? 23 24 296. In foil pads, consisting of polypropylene casoated aluminum, 96 mg of T-diacrylate, containing 0.3 K N, N-bis-hydroxyethyl-3,5-di-t-butylaniline, were each ice-welded.

The foil pads were attached under the buckle which surrounded the main chamber.

Each main chamber weighed 330 mg of tooth-colored, silanated quartz powder (less than 60 .mu.m), containing 0.2% p-chlorobenzoyl. peroxide.

By means of a suitable device, pressure was applied to the buckle, so that the foil pads burst and their contents passed into the main chamber. Thereafter, the container was mechanically shaken in a shaker device. The resulting mass was immediately introduced into appropriately prepared dental cavities. The processing interval was about 2 minutes at 23 ° C, and the curing was then mainly completed after 1 minute.

Example ll s Comparative test (abrasion of dental fillings). The pastal paeta preparations mentioned in Examples 6 and 7 were used on the basis of T-dimethacrylate and the diester according to German Pat. No. 1,921,869, which were mixed in a ratio of 1: 1. To test the abrasion resistance, round test tubes with a diameter of 20 mm and a thickness of 1.5 mm were manufactured and weighed in suitable metal molds. To determine the abrasion resistance, the specimens were then processed under a suspension of calcium carbonate in water in a weight ratio of 1: 1, with motor-driven, controlled, cylindrical brushes with a diameter of 10 mm at 60 rpm. The weight load was 500 g. After drying, the weight loss was determined by weighing.

Wear: according to the invention: p 0.3 mg according to the prior art: 2.7 mg The already low wear of the preparation according to the prior art was thus further reduced by using a substance according to the invention by about a ten potency, so that the preparation had optimal properties for dental fillings. .

Example 120.

UV light polymerizable tooth filling material.

A UV light curable, ready-to-use dental filling mass was prepared by kneading 100 g of T-dimethacrylate, provided with 0.5 g of d- (2-cyanethylI-benzoin methyl ether, together with 5 g of that in Example 8). mentioned SiO2 powder and 345 g of ailanated, tooth-colored quartz powder (particle size less than 60 .mu.m).

Upon irradiation with a commercial UV polymerization apparatus, which gave a illumination effect of 70 ml, the pulp in a stock thickness of 2 mm was finally cured after 6 seconds. Example 13 _ With visible light polymerizable dental filling material.

By kneading 20 g of T-acrylate, 88 g of silanated, tooth-colored quartz powder (less than 60 .mu.m), 1 g of the SiO2 mentioned in Example 8, 0.8 g of methacrylic acid (4W, N-dimethylamino) -ethyl ester and H mg of phenanthrenequinone were obtained. a ready-to-use dental filling compound, which remained processable in an objection-free manner for longer than 5 minutes when irradiated in diffused daylight or in the light from an ordinary fluorescent tube (65 N).

For final curing, they were then irradiated with a halogen projector lamp (12 V, 75 W) with a cold light mirror. Using a filter inserted in front of the sample, light with wavelengths less than H00 nm was separated. After an irradiation time of 20 seconds, the pulp with a layer thickness of 2.5 mm was finalized.

Example «1ä coating or sealing compound for tooth enamel fissures.

Two solutions based on T-dimethacrylate were prepared, one containing 0.45 Z of N, N-bishydroxyethyl-p-toluidine and the other 0.4 l of chlorobenzoyl peroxide. Equal parts of the two solutions were then mixed together.

The coating composition prepared in this way was applied to tooth enamel, which before etching in the usual manner with 30 Zig of phosphoric acid.

The curing was started after about 1 minute, it was mainly completed after about 2 minutes. In this way, a smooth and abrasion-stable coating was obtained.

Example 15 UV light curable coating compositions for dental fillings by combining known diacrylates with substances according to the invention.

The resp. the diacrylates were mixed in the parts by weight given in the table below, and in the resulting mixture, 0.3% by weight of benzyl dimethyl ketal and 0.5% by weight were dissolved! didecylphenyl phosphite. 35% by weight of silanated, pyrogen-containing SiO2 was then introduced into the solution and distributed evenly. In this way spreadable coating compositions were obtained.

The compressive strength of coatings based on these masses was determined on moldings with the dimensions 2 x 2 x mm. The curing took place by irradiation with a commercial UV polymerization apparatus, which gave a lighting power of 70 mW. The values obtained are summarized in the Babylon below. Composition Compressive strength (parts by weight) (xp / omg) T-diacrylate T-dimeth-Hexanediol-Hexanediol-acrylate methacrylate-diacrylate_ v. 100 0 0 0 3,900 0 D 100 0 0 3,900 50 0 50 0 5,750- 7804586-6 ¿u Composition Compressive strength (parts by weight) (cplcna) T-diacrylate T-dimeth Hexanediol-Hexanediol-diacrylate methacrylate acrylate O 50 _ 50 0 G 030 0 66.7 _ 33.3 i 0 - 5 300 50 Q Surprisingly, the combination of the diester compounds used according to the invention with hexanediol di (the methacrylate in a weight ratio between 1: 1 and 2: 1 gave significantly higher values of the compressive strength than when using the substances according to the invention alone.) The use of a coating composition on on the basis of the pure hexanediol di (the methyl acrylate without the addition of substances according to the invention was practically impossible due to the enormous brittleness of the cured mass.) The combination according to the invention with the T-diester compound reduces the brittleness while simultaneously improving the compressive strength.

Example gel 16 g Preparation of a jacket crown.

In the ratio: 2: 3, the following were: T-acrylate-methacrylate (mixed ester, prepared according to Example 3) and solid polymethyl methacrylate in pearl form, which are commercially available in a variety of tooth color shades. The individual color shades of the bead polymer were premixed with 0.3 L of lauroyl peroxide. g On an insulated tooth stump model, the used color shades were applied in layers corresponding to the natural ñind color.

Each layer was briefly heated to about 120 ° C in a stream of hot air, and after completion of the crown, the alum was polymerized for 10 minutes at 150 ° C. A kgona with excellent abrasion resistance was obtained, which also came very close to the natural teeth in terms of cosmetics.

Example gel 17 * Coating of a precious metal bridge.

They used: T-dimethacrylate and polymethyl methacrylate bead polymer, which was dyed again in a tooth-like color shade and which was impregnated with 0.1 H 1 lauroyl peroxide.

The individual color shades were obtained in the same manner as in Example 15 by kneading the two components, in all cases in a ratio of 2: 3.

On it on. In the usual manner of retention, the position of the dental bridge was applied to the individual color shades in layers on the front, curing each layer as described in Example 16 above.

The coating was distinguished by excellent durability in the mouth; particularly by high abrasion resistance, and was unobtrusively cosmetic. '

Claims (3)

7804386-6 z _ _ lb Patent claim Use of diacrylic acid or dimethacrylic acid esters of bishydroxymethyl tricyclics. 2. 1 .oz 'Ü-aekan for the manufacture of polymerizable dental pulps, in particular for dental fillings and dentures, based on bifunctional acrylic acid esters. Use of the diacrylic or dimethacrylic acid esters according to claim 1 together with other known, polymerizable dimethacrylic acid esters, characterized in that the former are used in an amount of at least 20% by weight, based on the total amount of acrylic acid esters. Use according to claim 2, characterized in that the second dimethacrylic acid ester is a diacrylate or dimethacrylate of hexanediol, 2,2-bis - [- p- (hydroxy-ethoxy-) phenyl] -propane or 2,2- bis- [- p (Y-hydroxy-propoxy-) phenyl] -propane. r., ___-.- _ _ _v___