EFFECTS OF DENTAL LABORATORY PROCESSING VARIABLES AND IN-VITRO TESTING MEDIUM ON THE PORCELAIN ADHERENCE OF HIGH-PALLADIUM CASTING ALLOYS

Purpose. This study assessed the effects of dental laboratory processi ng variables and testing medium on porcelain adherence of representati ve high-palladium alloys. Material and methods, The processing variabl es were recasting two and three times, porcelain stripping with hydrof luoric acid and rebuilding, and changing the recommended oxidation pro cedures. The testing medium was air for these four groups and the nont reatment group. In the last group, the specimens were stored and teste d in artificial saliva. The metal ceramic specimens were fractured wit h biaxial flexure in constant strain. The area fraction of adherent po rcelain (%) was calculated with a standardized spectrometric technique . A gold-palladium alloy served as the control. Results. Recasting wit hout adding new alloy negatively affected some high-palladium alloys. Porcelain stripping did not cause a decrease in adherence of the teste d alloys. The alternate oxidation treatment reduced significantly the porcelain adherence of the Au-Pd and one Pd-Cu-Ga alloy Storage and te sting in artificial saliva did not significantly affect the porcelain adherence of the alloys. The Au-Pd alloy exhibited the highest porcela in adherence.