Different Chlorhexidine Concentrations on Adhesion to Normal versus Eroded Dentin

Objectives: The application of 2% chlorhexidine digluconate (CHX) benefits adhesion to normal or caries-affected dentin. It is unknown, however, if the results of this treatment, and also from that of lower concentrations of CHX, may also benefit adhesion to eroded dentin. The aim of this study was to investigate the immediate bond strength of a composite-resin to normal and eroded dentin treated with different concentrations (0.004% and 2%) of CHX. Methods: Forty two extracted caries-free human third molars had their occlusal thirds sectioned. Exposed flat dentin of 21 specimens was only submitted to a 600-grit SiC paper for 1 minute (normal dentin - N), and exposed flat dentin of the other 21 specimens were subsequently eroded by a regular cola soft-drink (5-minute immersion; 3x/day; 5 days - E). The dentin surfaces were, then, etched for 15 seconds with 37% phosphoric acid, washed and blot dried. Each third of N specimens were rehydrated with 1.5µL, respectively, of distillated water (control - NC); of 0.004% CHX (N0.004%); or of 2% CHX (N2%). The same was performed for E specimens (EC; E0.004%; E2%). Adper^TM Single Bond 2^® adhesive system was applied in all specimens and composite buildups were constructed incrementally with Filtek^TM Z350^®. After storage in deionized water for 24 hours at 37˚C, specimens were sectioned in beams (cross-sectional area of 0.81mm²) for microtensile bond strength testing (EMIC; 0.5mm/minute). Data were analyzed by two-way ANOVA and Bonferroni tests (p<0.05). Results: Mean values of bond strength (MPa±standard deviation) for experimental groups were: N (34.74±9.79); N0.004% (35.69±9.85); N2% (41.22±5.38); E (20.94±5.37); E0.004% (21.12±7.44); and E2% (15.97±5.17). Only the soft-drink represented a significant effect. Conclusions: Immediate bond strength to eroded dentin was lower than that to normal dentin. The application of any of the concentrations of chlorhexidine was not capable to influence them. Funding: FAPESP 09/14986-0.