PRODUCTION OF METAL-CERAMIC DENTAL RESTORATIONS

摘要

1483362 Dental prosthesis NATIONAL RESEARCH DEVELOPMENT CORP 4 July 1975 [12 July 1974 8 Jan 1975] 30978/74 and 00804/75 Heading A5R [Also in Division B3] A porcelain-metal dental restoration is produced by firing porcelain on to a layer of metal oxide on a noble metal substrate, the oxide being wetted by the porcelain in the fused state. The invention is described with reference to jacket crowns, bridges and inlays. The substrate may be of platinum, rhodium, gold or silver, and the metal deposited thereon by electrodeposition or vapour deposition to form the oxide may be tin, indium or alloys thereof. The deposited metal may have a thickness of 0.2-2.0 microns, e.g. 0.5-1.0 microns, the substrate preferably being heated to diffuse some of the deposited metal into the substrate before the layer is converted to oxide electrolytically or by heating in air or oxygen. Dental porcelain may be used, e.g. as in Specification 1105111 which preferably contains 40- 50% by weight alumina, feldspar, glass fluxes and metallic pigments. The substrate and porcelain should have the same coefficient of linear expansion. A jacket crown may be made by swaging a platinum foil of 0.001-0.005" thickness around a model of a tooth stump. The foil may be supplied lacquered on the face to be applied against the model. After firing the lacquer is burnt off leaving a gap for cement to fix the crown to the stump. If the foil is not supplied with a pre-deposited metal or oxide layer one is now deposited. Moistened porcelain powder is built up on the oxide in several fired layers beginning with an opaque layer, followed by one or more translucent layers and a veneer layer. Alternatively, porcelain may be bonded to an oxide layer on a gold alloy cast to fit around a tooth model. In Example 4, tin-plated platinum foil is adapted to a silver die prepared from an impression. The foil is removed from the die and trimmed to the internal line angles of the preparation at the gingival floor. Untreated platinum foil of 0.001 mils thickness is now applied to the die to form a matrix which is trimmed just short of the cervical margin of the preparation so as to form a small apron around the preparation. The tin-coated foil is pushed on to the matrix. Alternatively, the inner foil may be layed down first and the outer foil layed over the inner foil. The outer foil is now oxidised, cooled and placed over the inner matrix and porcelain is applied which may be specified by the inclusion of 1-2% zirconium oxide. After staining and glazing, the inner foil is removed so as to allow a porcelain butt fit on the external cervical margin and provide space for cement. In Example 8 a posterior bonded crown is formed by adapting a 0.002 mils thick platinum foil to a silver die. The foil is removed, given a coating of tin, oxidised, re-adapted to the die and coated with porcelain. Varnish on the die provides space for cement. Example 6 applies the invention to repairing bridgework.