The effect of thermal cycling on metal–ceramic bond strength

ObjectivesThe aim was to evaluate the effect of thermal cycling on the metal–ceramic bond strength.MethodsFour different noble metal alloys were used. Specimens for the crack initiation test according to ISO 9693 were prepared to assess metal–ceramic bond strength (n = 10). The metal substrates were either air-borne particle abraded or polished prior to veneering. Bond strength was measured after veneering or after 6000 thermal cycles. With one alloy in addition long-term thermal cycling with 15,000 and 50,000 cycles was carried out. Statistical analysis was performed with one-way ANOVA followed by a post hoc Bonferroni test.ResultsPolished metal substrates showed a significantly lower bond strength compared to the air-borne particle abraded substrates. Treatment with 6000 thermal cycles did not significantly reduce the bond strength. Long-term thermal cycling resulted in an exponential decrease of bond strength for both polished and air-borne particle abraded specimens.ConclusionsAir-borne particle abrasion significantly increases metal–ceramic bond strength. Thermal cycling of metal–ceramic composites results in an exponential decrease of bond strength. The crack initiation test is a sensitive method for assessing the metal–ceramic bond strength.