Bonding of adhesive luting agents to caries-affected dentin

Abstract

Purpose: This study evaluated the bond strength of adhesive luting agents applied to caries-affected dentin (CAD). Methods and materials: Thirty-six non-carious human third molars were abraded to expose an occlusal dentin surface. Caries lesions were induced in half of the samples using a microcosm biofilm model. Biofilm was cultivated under an anaerobic atmosphere for 14 days in a medium enriched with mucin. The same medium containing 1% sucrose was alternated for 4h per day. Cylinders of resin cement (RelyX ARC, RelyX U200 or BisCem) were built up over the dentin substrate and submitted to shear bond load. The samples were then longitudinally sectioned. The hardness and elastic modulus of dentin was measured at depths of 10, 20, 30, 40, 50, 100, 150 and 200 m from the occlusal surface. A three-dimensional finite element simulation was performed to analyze the residual stress distribution for each experimental condition during the shear bond strength test. Bond strength data were analyzed by two-way ANOVA and hardness and elastic modulus by split-plot ANOVA. Multiple comparisons were performed with the Student–Newman–Keuls test (a=0.05). Results: Independent of the type of cement, the highest bond strengths were observed in sound dentin. Relyx ARC bond strength was similar to that of RelyX U200 for both substrates; BisCem had the lowest values. CAD had lower hardness values than sound dentin above a depth of 100 m. Elasticmodulus exhibited a similar trend, but above a depth of 150 m. Stress distribution during the bond strength test was similar under all experimental conditions. Conclusion: Impairment of the mechanical properties of dentin promoted by carious lesions reduced the bond strength of adhesive luting agents.