In vitro effect of S. mutans biofilm on fluoride/MDPB-containing adhesive system bonded to caries-affected primary dentin.

Purpose: To evaluate the effect of storage in S. mutans culture or water on the durability of fluoride and MDPB-containing adhesive system on artificial caries-affected primary dentin. Methods: Dentin flat surfaces of primary molars were submitted to artificial caries development using S. mutans biofilm. CAPD cavities were restored with Adper Scotchbond Multi-Purpose (SBM) or Clearfil Protect Bond (CPB) and they were serially sectioned into sticks (1 mm(2) cross-sectional area) and stored in S. mutans biofilm for 3 days, in deionized water for 3 months and afterwards subjected to microtensile bond strength (mu TBS) test. A control group was submitted to immediate mu TBS testing. Two-way ANOVA and Tukey's tests were used. Failure sites were observed by SEM and classified as cohesive (dentin or resin) and adhesive failures. Results: The control group showed the highest mu TBS values (MPa) for both SBM (25.2 +/- 8.5) and CPB (15.6 +/- 6.1) adhesive systems. A significant decrease in mu TBS values after S. mutans biofilm and water storage was observed for SBM (18.7 +/- 5.7 and 17.4 +/- 4.1, respectively) and CPB (13.9 +/- 5.2 and 13.7 +/- 4.8, respectively), but no difference was found between them. The highest percentage of adhesive failure was observed for all groups. However, cohesive failure in dentin was observed in a higher percentage for SBM than CP.