Potential of Acacia Extract as a Collagen Crosslinker and Stabilizer of the Resin-dentin Interface

The aim of this study was to investigate whether different concentrations of acacia extract could improve the biological stability of dentin collagen. Slice (n=3) and beam (n=5) samples of dentin obtained from human third molars were demineralized and treated with the following solutions: G1 (control)-deionized water; G2-1% acacia extract; G3-2% acacia extract; and G4-3% acacia extract. The dentin slices were analyzed by Fourier transform infrared (FTIR) spectrophotometry to observe their interactions with collagen. The beams were submitted to digestion with type I bacterial collagenase solution, and the percentage of weight was calculated to evaluate the resistance to enzymatic biodegradation. The Adper Scotchbond Multipurpose adhesive system was applied on the flat dentin surfaces according to the manufacturer's recommendations (G1). In groups G2, G3 and G4, acacia extract at concentrations of 1%, 2%, and 3%, respectively, were applied after acid etching. A resin composite block was built on the adhesive, and the teeth were cut to obtain beams (n=7 teeth; ~12 beams per tooth) with cross-sectional areas of approximately 0.8 mm2. Half of the specimens were submitted to the microtensile bond strength (µTBS) test in a universal testing machine at a crosshead speed of 0.5 mm/min, and the other half were submitted to the µTBS test after six months of storage in distilled water. FTIR analysis showed the interactions of the three concentrations of acacia extract with collagen. According to ANOVA and Tukey tests, G1 had the highest biodegradation rate (100%), which was significantly higher than the rates of G2 (24%), G3 (23%) and G4 (17%) (p<0.05). According to two-way ANOVA and Tukey tests, only G1 showed a significant decrease in µTBS after six months of storage (p<0.05). It was concluded that 1%, 2%, and 3% acacia extract all interacted with human dentin collagen, reduced collagen biodegradation and favored the stabilization of the bonding interface at the six-month evaluation.