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Artificial Onlay Tooth Crowns and Inlays

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Artificial Onlay Tooth Crowns and Inlays Europaisches Patentamt 0 389 461 J European Patent Office (jO Publication number: A1 Office europeen des brevets EUROPEAN PATENT APPLICATION © Application number: 90850107.5 © mt.ci.5:A61C 5/10 @ Date of filing: 20.03.90 © Priority: 23.03.89 SE 8901049 © Applicant: SANDVIK AKTIEBOLAG © Date of publication of application: S-811 81 Sandviken 1(SE) 26.09.90 Bulletin 90/39 Applicant: Nobelpharma AB © Designated Contracting States: Box 5190 AT CH DE DK ES FR GB IT LI SE S-402 26 Gdteborg(SE) © Inventor: Oden, Agneta Bergstigen 26 S-182 74 Stocksund(SE) Inventor: Andersson, Marts Hammarstroms Tappa 2 S-443 39 Lerum(SE) © Representative: Ostlund, Alf Olof Anders et al Sandvik AB Patent Department S-811 81 Sandviken(SE) Artificial onlay tooth crowns and inlays. @ The present invention relates to artificial onlay increase. tooth crowns or inlays composed of a prefabricated core designed for preparations for onlay tooth crowns or inlays in natural teeth. The core is prefer- ably fabricated from a high strength densely sintered ceramic material by copy milling from a negative reproduction from the prepared cavity to a com- K pacted body or a presintered ceramic material. Dur- ing the copy milling the sintering shrinkage is con- *"sidered by enlargement of the copy milled com- ^pacted body or the presintered body corresponding ^to the sintering shrinkage. The onlay tooth crowns <Oand inlays are given the final shape by shaping the ^ surfaces outside the cavity of the compacted or the O> presintered body. After the final sintering the exter- material OOnal surface can be shaped before a veneer Fig.5 '"'is attached to the external surface of the core by e.g. O firing of dental porcelain. To manufacture onlay tooth the method of the ^ crowns or an inlay according to Uj invention decreases essentially the manufacturing time for onlay tooth crowns and inlays and at the same time the strength and the accuracy to shape Xerox Copy Centre EP 0 389 461 A1 Artificial onlay tooth crowns and inlays BACKGROUND OF THE INVENTION (porcelain, glass etc) in artificial tooth crowns is their brittleness, which often gives early fracture, This invention relates to accurately shaped ar- and these artificial crowns and inlays must be tificial all ceramic onlay tooth crowns and inlays as replaced more or less regularly. replacement for lost tooth structure. By starting from a negative reproduction of the prepared tooth and from this copy mill the surface which will fit OBJECTS AND SUMMARY OF THE INVENTION into the prepared cavity, a tooth crown or an inlay is obtained which is easier to produce and to lower One object of the present invention is to pro- cost. In addition, the onlay crown and inlay has w vide artificial tooth crowns and inlays, which are higher strength and a more accurate shape. Prefer- easier and accordingly cheaper to make and, in ably the coping is manufactured from a biocom- addition, have higher strength and accuracy to patible, high strength, ceramic material, which is shape. sintered to high density. Another purpose is to make an inlay or an Artificial tooth crowns and inlays made from a 75 onlay tooth crown by using densely sintered, high metal are today manufactured mainly in the follow- strength ceramic material, provided that the de- ing way: A dentist makes a preparation on a tooth, mand of high strength, accuracy to shape (that on which a dental construction is to be fixed in the means compensate for the shrinkage during sinter- mouth of a patient, an impression is made and with ing) can be combined with the demand on the this impression a copy of the preparation is made 20 application of porcelain concerning burning, adher- in gypsum. On this model a dental technician pre- ence, biocompatibility and esthetics. pares a crown in wax. The adjacent teeth must be considered, and the dental technician must have models from the two jaws. A sprue former in wax is BRIEF DESCRIPTION OF THE DRAWINGS fixed on one of the cusps of the wax crown. The 25 wax crown is loosened from the gypsum model. Fig 1 is a natural tooth with an artificial inlay The wax crown with the sprueformer are invested (dotted). This figure explains which cross sections in a metal ring with investment. The wax is burnt are shown by Fig.2 and Fig.3 out and a crown can be cast in a precious or non- Fig.2 is a cross section of a natural tooth precious metal. The cast crown can in certain 30 with an inlay cases be covered by a veneer made of porcelain in Fig.3 is a cross section of a root filled natural order to obtain a colour of the tooth crown similar tooth with an inlay. to the colour of natural teeth. Instead of porcelain Fig.4 is a natural tooth with an onlay tooth plastic material can be used. crown (dotted). This figure explains which cross The fabrication of tooth crowns in glass is very 35 sections are shown by Fig.5 and Fig 6. close to the technique described above with the Fig.5 is a cross section of anatural tooth with difference that after the casting a thin layer of an onlay tooth crown. porcelain is painted on the surface and fired, in Fig.6 is a cross section of a root filled order to give the tooth crown individual tooth col- tooth.with an onlay tooth crown. ours. 40 Tooth crowns fabricated mainly of porcelain DETAILED DESCRIPTION OF THE PREFERRED can be made with conventional dental porcelain EMBODIMENTS technique on a sheet made of a precious alloy. Porcelain crowns and inlays can also be made with Fig.1 shows an inlay in a tooth. In the figure conventional dental porcelain technique on a model 45 the border between the cavity and the inlay is of the abutment. The material in this model has no indicated as I, the axis of the tooth as X. changes in dimension on heating up to 1200° C. Fig.2 shows a cross section of an inlay in a natural When the tooth crown or the inlay is ready the tooth. In the figure.the veneer is indicated as A, the model of the abutment is removed by sand blast- core made from dense sintered ceramic as B, the ing. so cement as C, the copy milled surface of the core The above described complicated and time as D, the prepared surface of cavity as E, the pulp consuming methods are used to manufacture as F, and the natural tooth root as H. crowns and inlays, which will fit in individually Fig.3 shows a cross section of an alternative de- prepared cavities in natural teeth. sign for a root filled tooth, the same letters mean The problem with the material now used the same things as with Fig 2, while a root filling is EP 0 389 461 A1 indicated with G. tion. The contour outside the cavity is prepared Fig.5 shows a cross section of an onlay tooth manually with conventional dental technical ma- crown on a natural tooth, and chining practice. A negative reproduction can be Fig.6 shows a cross section of an alternative de- e.g. a Kerr impression, or a silicon impression. sign for an onlay tooth crown for a root filled tooth, 5 Preferably the core according to the invention the same letters mean the same things as with Fig is made from a biocompatible densely sintered, 2 and Fig.3. high strength ceramic material. On the core ob- In each of the Figures, the artificial onlay tooth tained the veneer is built up, so that the final crown or the inlay are the combination of the core product will be a tooth crown or an inlay fitting into B with the veneer A. They are fixed in the prepared w existing preparation and to the actual whole set of cavity E with cement C. teeth. According to the present invention, artificial on- As can be seen from Fig. 2 and Fig. 3 artificial lay tooth crowns and inlays are made in which the inlays are made as a core in densely sintered core is prefabricated from a biocompatible material ceramic (B) with veneer (A). They are fixed in the with part of the outer surface of the core D given 75 prepared cavity by e.g. cementing. The thin layer such dimensions as to fit into a preparation E, of cement (C) connects the prepared cavity walls which can be a preparation for an inlay or a prep- (E) with that part of the surface of the inlay or the aration for an onlay tooth crown or a preparation for onlay tooth crown, which has been made so that a tooth crown on a root canal pin. A biocompatible this surface (D) fits with great precision into the material for the core is a material which is not toxic 20 prepared cavity (E). The layer of cement can have and does not cause damage on oral tissues or a thickness < 200um preferably 25-75 urn. Artifi- does not give unwanted system effects. In addition cial onlay tooth crowns are made as a core in this material must not give any discolourations or densely sintered ceramic (B) with veneer (A). As otherwise give unwanted effects to the veneer ma- can be seen from Fig. 6 the preparation of a root terial. The onlay tooth crowns and the inlays are 25 filled tooth is extended down into the root canals in fixed by cementation in the cavities.
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