[Study on retention of veneering materials to the facing crown made of hard-type resin. Application etching to Ni-Cr alloys].

In order to enhance adhesiveness between the resin and the metal in the facing crown made of hard-type resin, the bead application method has been widely utilized. A short-coming of this method is that the metal part of the facing must be made thicker for bead application. If, however, a retention is made beneath the surface of the metal part, the facing metal can be made thinner. The author studied the adhesiveness of metal to resin by producing pitting corrosion on the surface of four different kinds of Ni-Cr alloys, etching the surface with strong acid under various conditions, and compared the adhesiveness and failure conditions with those of the beaded specimens. The results were as follows: 1) The degree of corrosion of the surface of specimens was positively correlated with the duration of etching. However, the degree of corrosion differed depending on the kinds of etching solutions and specimen alloys. 2) In terms of adhesiveness, some of the etching groups were stronger than the beaded groups and some were weaker, depending on the kinds of alloys and etching conditions. 3) Condition of failure at the joint surface: in the beaded groups cohesive failure was the most prevalent type. In the etching groups, compound failure was the most prevalent. There was a positive correlation between adhesive strength and the amount of residual resin: the more residual resin, the greater the adhesive strength. 1) Electron microscopic observations: on the surface of specimens of the etching groups pitted roughness was observed, and the resin material was tightly attached to the metal surface. However, reciprocal diffusion of the elements from both materials was not indicated, nor was there any evidence of chemical bonding.