PORCELAIN VENEERS - THE EFFECTS OF CONTAMINANTS AND CLEANING REGIMENSON THE BOND STRENGTH OF PORCELAIN TO COMPOSITE

An in-vitro study was carried out to investigate the effects of contam ination of the porcelain surface on the shear-bond strength of a dual- cure composite luting cement to etched, silanated porcelain. Furthermo re, the effects of different cleaning regimens were studied. A total o f 390 etched, silanated porcelain specimens were randomly divided into 13 groups of 30. Shear-bond strengths were measured for a control gro up and for specimens contaminated with saliva, die stone, and latex gl oves. Freshly contaminated samples were subject to three cleaning regi mens; water wash and dry, cleansing with acetone, and cleansing with 3 7% phosphoric acid gel. Bond strengths to the cleansed surfaces were m easured. Weibull analysis and analysis of variance were applied to the results. Saliva and latex glove contamination did not significantly a ffect shear-bond strength. Die stone contamination markedly reduced th e bond strength and cleaning did not restore the bond strength for the se specimens. Contact between porcelain veneers and stone models shoul d therefore be avoided. The wash/dry and phosphoric acid cleaning regi mens did not significantly improve or reduce bond strengths for contam inated specimens. Acetone cleaning produced a marked reduction in bond strength under all experimental conditions and should not be used.