Carious and eroded dentin represent clinical challenges. The use of a universal bonding system, in a self-etching mode, associated with chlorhexidine (CHX) seems to not improve its longevity. This may be attributed to the competition for calcium between the bonding agent functional monomer and CHX.
The purpose of this study was to explore the interaction between two calcium-dependent agents: 10-methacryloyloxydecyl-dihydrogen phosphate (MDP) and 2% chlorhexidine (CHX) digluconate in association with a self-etching universal bonding system.
Flat dentin surfaces were obtained from 120 specimens (n=20/group) prepared from extracted sound human third molars and randomly divided into three groups according to the dentin substrate: sound ([S] control), artificial carious ([C] 6 h/demineralization + 18 h/remineralization for 5 days + 48 h/remineralization), and artificial eroded ([E] 3 cycles for 5 min/day for 5 days using orange juice). Before bonding procedures, one-half of the specimens from each group were pretreated with deionized water (W) and the other half with 2% chlorhexidine (CHX), forming six groups: S-W, S-CHX, C-W, C-CHX, E-W, and E-CHX. All specimens were restored with Adper Single Bond Universal (self-etching mode) and two increments of composite resin (Filtek Z-250), following the manufacturer’s instructions. Slices (0.8 mm) were obtained from the specimens and subjected to scanning electron microscopy (SEM) analysis and sticks (0.64 mm2) were obtained and subjected to a microtensile bond strength test (μTBS) in a universal testing machine (0.5 mm/min) after 24 hours and 6 months of storage. Failure modes were classified using optical microscopy (40×). Data was statistically analyzed by three-way ANOVA and Tukey tests (p<0.05).
Substrate type was a statistically significant factor (p<0.0001), whereas neither the pretreatment (p=0.189) nor time (p=0.337) were significant. No interaction considering all the factors was significant (p=0.453). Conclusions: Carious and eroded dentin substrates negatively interfered with the bonding potential of an MDP-based universal bonding system, regardless of the use of CHX. Likely, the reduction of available calcium impaired the effectiveness of the bonding system.