A new porcelain repair system was developed which uses a two-liquid primer, self-cured opaque resin, and light-cured composite. The primer consisted of two liquids. One component was 4% 3-trimethoxysilylpropyl methacrylate in methyl methacrylate, and the other component was 0.5% ferric chloride in ethanol. A self-curing opaque resin, 4-META/MMA-TBB opaque resin, was used as an adhesive to bind the porcelain and the composite. Adhesive opaque resin was applied on the roughened and primed porcelain. Light-cured composite was placed over the 4-META opaque layer. A shear test was performed for investigation of the strength and durability of the bonding. The result was that for all specimens after 20,000 thermocycles, fracture or crack propagation during the shear test occurred in the porcelain, rather than in the bond. This system may be used to repair fractured porcelain facings without removal of prostheses.

4-META and new phosphate-methacrylate resins adhere strongly to dental alloys. However, for strengthening the water durability of the adhesive interface, the oxidation of the alloy surface is indispensable. A new oxidation method using ion-sputtering was developed, and the effectiveness of this surface treatment on two dental alloys--a type IV gold alloy and Ni-Cr-Be alloy--was investigated. As an endurance test, thermocycling for a maximum of 100,000 cycles was adopted, and the tensile adhesive bond strength was then measured. Ion-coating the surface of the alloys resulted in strong bonds with adhesive resins, and after 100,000 thermocycles, a bond strength of above 20 MPa was maintained.

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The deficiency of the rigidity of the retainer causes the falling of the acid-etched fixed partial denture from the abutment teeth. It was reported in the previous paper that the adhesive strength of the bridge increased as the thickness of the retainer increasing and reached the plateau. Suitable thickness of the retainer, however, may be difficult to obtain due to the occlusal relation. The purpose of this study is to look for the proper shape of the retainer. The following conclusions were obtained. 1) Using cobalt-cromium alloy, the adhesive strength in the retainer of 1.0 mm thickness was better than that of 0.5 mm on the same shape. 2) The extension of proximal wing portions and adding ledge-form were effective to gain higher adhesive strength in using cobalt-cromium alloy and Au-Ag-Pd alloy.

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