Methods to Clean Residual Resin Cement from Lithium-Disilicate Glass-Ceramic.

Purpose: To compare the effect of different methods of cleaning residual composite cement from the surface of lithium-disilicate glass-ceramic on its bond strength.

Materials and methods: Blocks of lithium-silicate glass-ceramic (e.max CAD) were coated with composite cement. Blocks in a positive control (CO+) group received no cement; negative controls (CO-) received composite cement. After water storage (24 h), specimens were cleaned as follows (n = 20/group): BUR: grinding with a fine-grit diamond bur (20 s); ALUM: air abrasion with 50-µm alumina (10 s); GLASS: air abrasion with 50-µm glass beads (10 s); FURN: firing in ceramic furnace and cleaning with ethanol; SULF: immersion in sulfonic acid solution (1 h); HYFL: no additional treatment. All specimens were etched with hydrofluoric acid, aside from the CO- group, and treated with silane. A 1.5-mm diameter cement-filled tube was affixed to the specimens and light polymerized. Specimens were stored in 37°C water for 24 h (n = 10) or 90 days (n = 10). Shear bond strength was tested. Two-way ANOVA and post-hoc Tukey tests were performed. Specimens from each group were examined with SEM.

Results: Bond strength significantly differed according to surface cleaning method (p < 0.01) and storage time (p < 0.01), but their interaction was not significant (p = 0.264). Longer storage time decreased the bond strength. BUR, ALUM, GLASS, and FURN did not differ statistically significantly from CO+, but were significantly greater than CO-. SULF and HYFL did not differ statistically significantly from CO- and were significantly lower than CO+.

Conclusions: Cleaning composite cement with BUR, ALUM, GLASS, and FURN restored bond strengths to that of the positive control. However, only GLASS and FURN did not roughen the surface of the underlying lithium-silicate glass-ceramic.