SE423395B - PROVIDED TO MANUFACTURE PLASTIC COMPOSITION, PREFERRED TO BE USED AS DENTAL MATERIAL - Google Patents

Description

8006575-e 2 properties of plastic composites in the above respects. According to the invention, this method of preparation is mainly characterized in that a mass, having inorganic particles containing an open, coherent and impregnable pore system with plastic material, which is wholly or partly impregnated with curable thermoplastic or polymerizable plastic material, is compressed or otherwise applied until the particles come into contact with each other and are bonded to each other by causing at least a portion of the curable plastic material to cure to form a plastic structure containing a continuous inorganic phase.

Plastic composition produced in this way also allows advantageous properties in manipulation in connection with the production of dental fillings. The method according to the invention also allows the use of plastics with better properties than has previously been possible, above all in that plastics with a higher average molecular weight and viscosity can be used.

The invention will be described in more detail below with reference to the accompanying drawing which illustrates a part of a plastic composite in 1000 times magnification produced by means of the method according to the invention.

The plastic composite illustrated in the figure has been prepared by compressing or otherwise applying a mass of exhibiting inorganic particles 1 containing an open, cohesive and impregnable pore system, fully or partially impregnated with curable thermoplastic or polymerizable plastic material 2 until the particles 1 reach into contact with each other and bond together with each other by causing at least a part of the curable plastic material 2 to cure to form a plastic structure containing a continuous inorganic phase 3. To give examples of how the invention can be practiced, the following experiments were performed: In Bis -GMAX (the reaction product of Bisphenol A and glycydyl methacrylate in U.S. Patent 3,006,122) was diluted with TEGDMA (triethylene glycol dimethacrylate) in given proportions (see table below). A photoinitiator (benzoin methyl ether, 0.8%) and a stabilizer (monomethyl ether of hydroquinone, 0.008%) were added to the monomer composition. Colloidal silicaxg was added in varying amounts (see table) to increase the content of inorganic constituents and control the monomer viscosity. x cFreeman Chemical Co., Port. Washington, Wi., USA, Lot 124 543 xx Aerosoil R R 972, Degusa, Frankfurt, Federal Republic of Germany. In the method according to the invention, different kinds of porous inorganic particles can be used, for example particles of a rigid three-dimensional network of inorganic fibers fused together in the contact points where the fibers abut each other (see SE patent specification 7603313-3). Such a network preferably consists of glass with a high X-ray density and is preferably made of extremely fine fibers such as those used in the following examples: A pair of square and plane-parallel press plates (l2xl2xl, 5 cm) were made of hydraulic cementx in stainless steel molds. One of the flat press surfaces was designed with small projections (hemispheres) along the periphery to obtain a minimum distance between the plates. The same plate was also provided with a thermocouple (Ni, Cr-Ni) with the measuring point centrally located and partially exposed in the press surface. The temperature was recorded in a printer. To allow even heating, the press plates were enclosed in a stainless steel box (wall thickness 5 mm) and just so large that the two press plates could be accommodated therein. This technique made it possible to keep the temperature differences below 10 ° C in the central area (65x65 mm) between the plates used for sintering.

A-glass type fiber dunxx (soda glass) with a fiber diameter of 2 microns was used. The same was placed between the plates in the given sintering area and compressed with 3kPa, which pressure was generated by the total weight of the upper press plate and the upper part of the steel box. The loaded box was placed in an electric oven automatically set at 800oC. Then after approx. 20 min. a temperature of 685É5 ° C was reached at the measuring point, the sintering was interrupted. The box was cooled at room temperature and at approx. 30,000 were opened and the sintered plate was removed.

Through the spacers in the press plate, the plate was then 775l25 microns thick.

The amount of fiberglass down required between the plates to obtain the desired porosity was calculated using a glass density of 2.5 g / cm 3. Two degrees of porosity were used, one that gave the plate an average glass content of approx. 40% and one that gave approx. 56% of the total volume.

The plates were crushed and ground by means of a mortar and pestle of porcelain. The powder was sieved through a series of standard sieves (Din 4188) and the fractions were labeled according to the size of the mesh openings (in microns) of the sieve in which they were collected x Secar R 250, Lafarge Aluminious Cement Co. Ltd., Essex, England. xx From Bilsom AB, Billesholm, Sweden. 800657646 C 4 plus the next larger size. Thus, a "coarse" fraction - (250 / l60), two "medium" (160/100, 100 / 7l) and a "fine" fraction (7l / / 40) were collected. The powders were treated with 1 M hydrochloric acid for 24 hours and then washed with distilled water and acetone.

A silane surface treatment of approx. 1/2%, of the weight of the powder was added in the form of silane dissolved in acetone. The powder was allowed to dry at room temperature and heated at 110 ° C for 45 minutes. If the powder, after gentle compression, did not allow the penetration of a drop of distilled water after standing for 5 minutes, the silane treatment was considered satisfactory. The plastics in powder and liquid form according to Table 1 were mixed by means of an agate spatula for dental use on a glass plate. For saturation, powder was added until dry particles began to appear in the mixture, indicating that excess monomer was no longer present in sufficient quantities to allow impregnation of additional particle marrow. i K The powder-plastic mixtures were filled into cylindrical cavities (diameter 4 mm, depth 2 mm) in acrylic rods with a square cross-section (1x1 cm).

For pressure application, an amalgam condensing instrument with a flat and circular end face (diameters 1.8 mm) was used. Applied force was measured by placing the acrylic rod on a single scale.

Condensation took place at right angles to the bottom of the cavities. The same started in the middle and the instrument was moved step by step over the surface until it was covered with overlapping markings. The procedure was repeated. The first time with relatively low pressure to obtain a primary gasket and a flat surface. When maximum pressure was applied (Table 1), this was kept constant for approx. one second. Parts that gave a l - 1.5 mm thick layer of condensed material were inserted at a time. Each layer was cured by being exposed to UV radiation for 60-80 seconds. reach The cavities were filled with a surplus of approx. 0.5 mm thickness to ensure complete removal of the oxygen-inhibited surface layer during the final treatment of the surface. Insertion and curing were performed at room temperature (22 ° C). the excess was removed and the samples were ground evenly with the surface of the acrylic rod on carborundum paper no. 600. Subsequent grinding was then performed on plaster linen with an aqueous suspension of corundum powder with a particle size of 0.3 microns. 'x' Silane A174, Union Carbide Co., Lot 803 080 174 xx Nuva-LiteR, L.D. Caulk Company, Canada. s 8006576-6 The samples for etching were divided in the middle plane and the exposed cross-sectional area was ground. The samples were then mounted with cold-hardened acrylic plastic and polished as before. The surface showing a cross section of the sample was etched with hydrofluoric acid (40%) for 1/2 hour and cleaned in distilled water.

The hardness was measured on the ground surface of the sample by means of Vickers hardness gauge and was performed in accordance with DIN 50133 with a load of 13kp. Before the samples were tested, they were stored for 1 week (22ilOC and 5015% relative humidity).

Etched surfaces were studied under a microscope in oblique incident light (x 40). With this method, the plastic / particle interface appeared well defined.

To test the polishability, the surfaces of the samples were sanded with alumina disc wax and then polished with a white rubber disc wax. Grinding and polishing were performed at low speed.

For all compositions used, the technique resulted in a composite with contact between the individual particles l. In most cases, they were brought into good intimate contact so that no zones between the particles could be distinguished. Varying hardness mainly represented only differences in inorganic content.

In all the compositions, the densified material had a solid surface which could be formed with an amalgam condenser tip. All surfaces polished with rubber discs showed a surface gloss that tended to increase with the hardness value.

Vickers hardness value for the polymer corresponding to the different liquid plastic compositions differed, as shown in a preliminary examination, only to a small and negligible extent. The hardness value therefore mainly reflects the concentration of the porous particles and the density of the individual particles.

The particle concentration was, as evidenced by both the hardness value and the microscopic appearance, more or less the same for the various liquid plastics used (composite 2-4). Nor was there a change when a "medium" particle fraction was incorporated (composite 5).

However, there was a significant increase in hardness when "high density particles" were used (composite 6). x ïyp Z3, ZA, Zwick & Go., Einsingen, üb Ulnvbonau, Federal Republic of Germany. xx Sof-Iexšï nrrüaxn, fine and super fine abrasive grains, 3M Co., St. Paul, Minnesota, US xxx IdentoflexR, type 1008, extrafin, Identoflex AG, Buchs, Switzerland. issoossve-e 6 In all the liquid plastics 2, the amount of solvent was small compared to what is normally used. The condensation technique was possible to implement even when the viscosity increased further by adding colloidal silica. This allows the choice of one or both of two options; partly to use a monomer with a higher average molecular weight than what normally happens and partly to increase the concentration of the inorganic component by adding a fraction of particles which are fine enough to penetrate the porous fiber network. For the latter purpose, particles of both colloidal and non-colloidal size and preferably with a high X-ray density can be used. Reduced shrinkage during polymerization can be achieved for example for Bis-GMA-based monomers with a higher average molecular weight (and thus also higher viscosity) than the conventional monomers normally used. Such an increase in molecular weight can be obtained by changing the amount and molecular weight of the solvent and / or by adding molecules larger than Bis-GMA. Reduced shrinkage during polymerization results in less generation of internal stresses and reduced pore formation. The mechanical strength also improves and the tendency to oxygen inhibition during polymerization decreases with increasing average molecular weight.

I. Experiments have also shown that it is possible to condense powder-monomer mixtures into the intended structure which contain considerable excess monomer in addition to what is required to fill in the porous particles 1. This is provided that the viscosity of the plastic is so low that at least some of the excess is pressed through the network structure in connection with the condensation. In these cases as well as in the absence of said excess, the condensation can be carried out so that most of the interfaces of the porous inorganic particles 1 are brought into contact, possibly in connection with a significant crushing of the surface layer of the particles. The particle crushing can be such that the particles adapt their shape to each other to such an extent that practically no spaces exist between the particles. Procedures for initiating the polymerization reaction other than those in the photoinitiation set forth in the example described may also be used. An example of such a process is heat curing, in which the free radicals required for the polymerization are formed by heating a monomer containing e.g. peroxide. In another process, the pulp is first divided into two parts, the first part in addition to a thermoset and inorganic constituents containing a catalyst for the thermoset, and the second part containing an activator for the catalyst. The polymerization then begins with the mixing of the two parts. The choice of the special catalyst and activator and the amounts thereof are close to the person skilled in the art, depending on the special plastic used and the amount thereof.

In the method according to the invention it is possible to also use porous inorganic particles 1 which only contain curable plastic material 2 in their outer portions and in the central part hardened plastic material. To improve the adhesion between the inorganic constituents and the plastic, the former can be pretreated with a silane binder as above. However, at least a part of the silane can also be added to the plastic material.

The porous inorganic particles 1 can be impregnated with thermoplastic material 2 and compression of the pulp in question can take place during heating so that the porous inorganic particles are bonded to each other. A The inorganic particles in the thermosetting plastic 2 consist of ceramic particles of preferably alumina or silica.

The curable plastic material 2 may consist of at least one monomer and / or polymer selected from the group consisting of acrylic plastic, vinyl chloride, cellulose acetate, styrene and acrylonitrile copolymer.

The thermosetting plastic may also consist of at least one acrylic monomer and / or polymer selected from the group consisting of ethyl methacrylate, ethyl acrylate or methyl methacrylate. The thermosetting plastic 2 can essentially consist of a copolymer of an acrylic monomer and another copolymerizable monomer. The copolymerizable monomer is selected from the group consisting of styrene, butadiene, ethylene and acrylic acid.

The thermosetting plastic 2 mainly comprises Bis-GMA or some other derivative of Bisphenol A and can be obtained by photoinitiating a polymerization reaction.

The method according to the invention is preferably used for these restoration works such as fillings, coatings, false teeth, prostheses and the like. In order to achieve such a dental restoration work with improved mechanical, physical and aesthetic properties as well as improved properties in terms of clinical manipulation, said method is characterized in that a dental plastic composite consisting mainly of porous inorganic particles, which are completely or partially impregnated with an at least partially polymerizable monomer and / or polymer and which are condensed or otherwise applied, so that the particles come into contact with each other and during polymerization are bonded together to form a plastic structure with a continuous inorganic.phase. 7 In laboratory and clinical experiments, it has been shown that with the described method it is possible to perform dental restoration work that exhibits mechanical, physical and aesthetic properties that closely correspond to the natural tooth structure. In addition, a negligible shrinkage upon polymerization achieves excellent polishability. In the prior art, the above-mentioned properties could not be achieved simultaneously.

The technique of mechanically packing and condensing a material in a dental cavity is previously known in connection with dental amalgam. It has known advantages in that it allows a close adaptation of the filling material to the cavity walls and also makes it possible to establish firm contacts between the repaired tooth and its neighbor. Furthermore, the condensability makes it possible to give the repair its final anatomical shape before curing. This avoids time-consuming and difficult final work with rotating instruments. These advantages are also achieved with the described method, which has not been possible before with tooth-like repair material. 80065 76-6äm fifi m: Qämm Hm eigï 32 Q ä »_ åmñw o N NNN JH J.- ... W 2 w J.- www w. : W NN .âšs så 3 ON 6332; Éämz 3 Nm .QQQQNNV ß ~ © ä v |: I. I. I |:. | w> ÛHÜ |: | m W ~ W l: | I .. I | = | | = | I. _I. flfifi N I-: l l = l 1:! mH w |: l l = | M: än .Sšb HE Eä fl mä 3 E cm fl mu äcoN .šïâë wš NNN mw fl ää mm fi J? J ... 3 w åö .... | N AN 3 .Éš fi N ON .o fi äwd Éäå xum fi 3 E. »ß Éßnox N ... mm fifi umm nwšøm .ÉQSNV äwäu wa EN Hwï fläm må C594 uma øßåz 3 N> oä RA N m m | m ¶ fšw fi v www å .ho fi æä å 3% m ëåmw wuqww fl ø wopwe à fl muäš u fl xošwm fl sölw fl m 380m m, »wåumm» xw fl moxwoämz Lwm fi nm fi m lwwwu fiflfi m NmÉo. ..

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Claims (28)

, 8006576-6 w Patent claims: 1. l. Methods of making plastic composites, preferably intended for use as dental materials including dental filling and coating materials, filling cements, crown and bridge materials as well as loose and denture materials, characterized in that a mass having inorganic particles OJ containing an open, cohesive pore system impregnated with plastic material, wholly or partially impregnated with curable thermoplastic or polymerizable plastic material (2), compressed or otherwise applied until the particles (1) come into contact with each other and are bonded together by at least a part of the the curable plastic material (2) is caused to cure to form a plastic structure containing a continuous inorganic phase (3). ' 2. a method according to claim 1, characterized in that the porous inorganic particles (1) are brought into contact with each other so that the majority of their interfaces reach contact with each other. 3. A method according to claim 1 or 2, characterized in that the porous inorganic particles (1) are brought into contact with each other so that they reach intimate contact by superficial crushing. 4. A method according to any one of the preceding claims, characterized in that the particle crushing is carried out so that the particles take shape one after the other to such an extent that practically no gaps between the particles remain. _ I 5. A method according to any one of the preceding claims, characterized in that the porous inorganic particles are impregnated with plastic material so that an excess of plastic material is formed. 6. A method according to any one of the preceding claims, characterized in that the porous inorganic particles have a diameter of less than 500 .mu.m and preferably less than 300 .mu.m. A method according to any one of the preceding claims, characterized in that 10--90% by weight of the porous inorganic particles (1) have a diameter of at least 10 Åm and at most 100 / on. IN A method according to any one of claims 1 to 6, characterized in that 10 to 40% by weight of the porous inorganic particles (1) have a diameter of at least 10 .mu.m and at most 100 .mu.m. 9. ¿A method according to any one of the preceding claims, characterized in that the porous inorganic particles consist of a rigid three-dimensional network of inorganic fibers fused together in the contact points where the fibers abut each other. 11 8006576-6 10. A claim according to claim 9, characterized in that the fibers are made of ceramic material, preferably glass, which preferably has a high X-ray density. 11. ll. A method according to claims 9 - 10, characterized in that the fibers in the network have a diameter of less than 100 μm, preferably less than 10 / km. 12. A method according to claim 11, characterized in that the fibers have a diameter between 1 and 4 .mu.m. 13. l3. A method according to any one of the preceding claims, characterized in that the curable plastic material has inorganic particles. 14. A method according to claim 13, characterized in that the inorganic particles in the curable material consist of ceramic particles preferably of alumina or silica or glass particles, the latter preferably having a high X-ray density. 15. A method according to any one of claims 13 to 14, characterized in that the inorganic particles in the curable plastic material have a size of less than 4 .mu.m, preferably between 0.005 and 2 .mu.m. 16. A method according to claim 14 or 15, characterized in that the inorganic particles in the thermosetting plastic material constitute 10 - 90% of the total weight of the particle / plastic mixture. 17. A method according to any one of the preceding claims, characterized in that the inorganic porous or non-porous particles are pretreated with a silane binder, preferably at least a part of the silane binder is incorporated in the plastic in an amount corresponding to 0.05 - 10% of the total weight of the composition. 18. A method according to any one of the preceding claims, characterized in that the porous inorganic particles contain 30 to 80% by volume of inorganic substance. 19. A method according to any one of the preceding claims, characterized in that the size of the porous inorganic particles is less than 300 .mu.m. 20. A method according to any one of the preceding claims, characterized in that the porous inorganic particles contain only curable plastic material in their outer portions and in the central part hardened plastic material. 21. A method according to any one of the preceding claims, characterized in that the porous inorganic particles are impregnated with 80055764- s g in 12 thermoplastic materials and that the mass is compressed during heating so that the porous inorganic particles are bonded to each other. ' A method according to any one of the preceding claims, characterized in that the curable plastic material consists essentially of at least one monomer and / or polymer from the group of acrylic plastic, polyvinyl chloride, cellulose acetate, styrene-acrylonitrile copolymer. 23. A method according to any one of claims 1 to 21, characterized in that the thermosetting plastic material consists of at least one acrylic monomer and / or polymer selected from the group consisting of ethyl methacrylate, ethyl acrylate and methyl methacrylate. 24. A method according to any one of claims 21, characterized in that the curable plastic material is essentially a copolymer of an acrylic monomer and another copolymerizable monomer. 25. A method according to any one of the preceding claims, characterized in that the thermosetting resin is a copolymer of an acrylic monomer Z and another copolymerizable monomer selected from the group consisting of styrene, butadiene, ethylene and acrylic acid. _ 26. A method according to any one of the preceding claims, characterized in that the curable plastic material consists essentially of Bis-GMA or another derivative of Bisphenol A. 27. A method according to any one of the preceding claims, characterized in that the curing of the plastic is achieved by photoinitiation of a polymerization process. '' 28. A method according to any one of the preceding claims, characterized in that a plastic composite consists mainly of porous inorganic particles which are completely or partially impregnated with an at least partially polymerizable monomer and / or polymer and which are condensed or otherwise methods are applied so that the particles come into contact with each other and during polymerization are bonded together to form a plastic structure with a continuous inorganic phase.