Effect of Cariogenic Challenge on the Degradation of Adhesive-Dentin Interfaces

The aim was to evaluate, in vitro, the influence of pH cycling on microtensile bond strength (µTBS) and percentage of nanoleakage (%NL) in the dentin-adhesive interface. Flat dentin surfaces were obtained in 56 extracted third molars. The teeth were randomly divided into four groups (n=14): G1- Single Bond Universal (etch-and-rinse mode); G2- Single Bond Universal (self-etch mode); G3- Scotchbond Multi-Purpose; G4- Clearfil SE Bond. A block of composite was built on the adhesive area. Eight tooth/resin sets were cut parallel to the tooth's long axis to obtain 48 beams (0.8 mm2) for each group. Half of the beams were submitted to four cycles of pH cycling (demineralizing solution for 6 h and remineralizing solution for 18 h). The samples were submitted to µTBS test in a universal testing machine. Six tooth/resin sets were cut parallel to the tooth's long axis to obtain three slices of the central region (1.0 mm thickness). Half of the slices were submitted to pH cycling. The nanoleakage methodology was applied to obtain the %NL at the adhesive interfaces. According to two-way ANOVA, the interaction between factors (adhesive system x storage) was significant (p=0.0001) for µTBS and %NL. After pH cycling, there was a significant decrease in µTBS and a significant increase in %NL for all adhesives. The adhesives applied in the self-etch mode obtained lower %NL, differing significantly from the etch-and-rinse adhesives. It was concluded that the pH cycling negatively influenced the µTBS and %NL for all adhesives evaluated. However, self-etch adhesives allowed less %NL.