Longitudinal dentin bond strength evaluation using different application modes of a metalloproteinase inhibitor

Abstract

Objective: This study evaluated the influence of diluted chlorhexidine (CHX, wt %) in the dental unit waterline (DUWL) on dentin bond strength. Material and Methods: Eighty human molars were coronally sectioned and randomly assigned to five groups (n=10), as follows: (G1) 37% phosphoric acid etching (H3PO4) rinsed with distilled water (DW); (G2) H3PO4 rinsed with 2% CHX; (G3) H3PO4 rinsed with 5% CHX; (G4) H3PO4 rinsed with DW followed by 2% CHX application; and (G5) H3PO4 rinsed with DW followed by 5% CHX application. The adhesive system (Adper Scotchbond Multi-Purpose Plus) was applied, and composite resin blocks (Filtek Z350 XT) were incrementally built up. Teeth were sectioned to obtain microtensile specimens, which were tested for bond strength after 24 h or 12 months of storage. Fracture patterns were examined under a stereomicroscope (40×) and hybrid layer morphology was evaluated using scanning electron microscopy (SEM). Data were analyzed using two-way ANOVA and Tukey tests (α=0.05). Results: CHX in the DUWL did not reduce bond strength compared to the control group, regardless of concentration or storage time. Application of 5% CHX as a primer decreased immediate bond strength, although this effect was reversed after water-aging. No significant differences were observed among groups in the longitudinal evaluation. Failures were predominantly adhesive, and SEM analysis showed homogeneous hybrid layer formation without gaps or porosity. Conclusion: Diluted CHX in the DUWL does not adversely affect resin-dentin bond strength. Although a temporary reduction in bond strength was observed with 5% CHX primer application, this effect was mitigated over time.

KEYWORDS

Adhesive system; Bond strength; Chlorhexidine; Dentin; Metalloproteinase.