Chlorhexidine Preserves Bond-Strength to Normal and Eroded-Dentin after 6-Months Aging

Objectives: Evidences have pointed out the positive effect of aqueous solutions of chlorhexidine digluconate (CHX) in preserving bond-strength (BS) of composites to normal or caries-affected dentin. The role of CHX on adhesion to eroded dentin is, in turn, unknown. Thus, this study aimed to evaluate the effect of the application of CHX in different concentrations on microtensile bond-strength (µTBS) of a composite to normal and eroded dentin.  Methods: Extracted caries-free human third molars (n=42) had their occlusal thirds sectioned and exposed flat dentin was only submitted to a 600-grit SiC paper/1min (normal dentin-N/n=21), or subsequently eroded by a regular-cola soft-drink (5-minute immersions; 3x/day; 5 days-E; n=21). They were, then, acid-etched (37%H₃PO₄; 15s), washed, blot dried, and rehydrated with 1.5µL, respectively, of distillated water (control-NC/n=7; EC/n=7); of 0.004%CHX (N0.004%/n=7; E0.004%/n=7); or of 2%CHX (N2%/n=7; E2%/n=7). Adper^TMSingle Bond 2^® was applied in all specimens and composite buildups were constructed incrementally with Filtek^TMZ350^®. After storage in deionized water (24h/37˚C), specimens were sectioned in beams, which were tested immediately or after 6-months aging (EMIC; 0.5mm/minute). Data were analyzed by three-way ANOVA and Tukey tests (α=0.05). Results: Mean µTBS values (MPa±sd; immediately/6-months) were: NC(34.74±9.79^Aa/20.77±14.35^Ab); N0.004%(35.69±9.85^Aa/23.10±8.13^Ab); N2%(41.22±5.38^Aa/34.64±6.62^Aa); EC(20.94±5.37^Ba/7.87±8.81^Bb); E0.004%(22.11±7.44^Ba/6.09±9.40^Bb); E2%(15.97±5.17^Ba/22.23±9.12^Ba). The erosive challenge negatively affected BS to dentin, and the application of any of the concentrations of CHX did not exert a significant effect immediately. After 6 months, only 2%CHX was able to prevent BS loss both to normal and to eroded dentin. Conclusions: The application of CHX solutions, at 2% but not at 0.004%, seems to be a promising strategy to conserve BS both to normal and to eroded dentin in the long term.