The evaluation of commercially available silane coupling agents for porcelain adhesion

We investigated the effectiveness of commercially available silane coupling agents on the adhesion between the composite resin and the porcelain. As silane coupling agents, we used Cosmotech primer. Clearfil porcelain bond. Porcelain liner M, and Scotchprime. As porcelain, we used Cosmotech porcelain DA2 which was etched either with hydrofluoric acid or with phosphoric acid gel. The tensile bond strengths between composite resin and the porcelain treated with silane coupling agents were measured after one day immersion in 37 degrees C water. Among the silane coupling agents, Clearfil porcelain bond gave the highest bond strength of about 175 kgf/cm2. When any of these silane coupling agents were used, the bond strengths were increased more by hydrofluoric acid etching than by phosphoric acid etching. Especially in the case of Scotchprime treatment, hydrofluoric acid etching was remarkably effective on the increase in the bond strengths. The value in hydrofluoric acid etching was 3 times higher than that in phosphoric acid etching. From SEM observation, hydrofluoric acid etching gave greater roughness to the porcelain surface, which resulted in greater mechanical interlocking of the resin. In the case of Cosmotech primer treatment, the combination with GC bonding agent did not increase the bond strengths, while combination with Clearfil new bond did. The phosphoric acid ester monomer in Clearfil new bond, which is known as strong acid, was supposed to catalyze the activation of silane coupling agent.