Hardness and microshear bond strength to enamel and dentin of permanent teeth with hypocalcified amelogenesis imperfecta.

ABSTRACT

BACKGROUND: Adhesive procedures are often required to restore teeth affected by hypocalcified amelogenesis imperfecta (HAI). AIM: To evaluate the hardness of enamel/dentin of teeth affected by HAI and the bond strength to these substrates, as well the influence of 5% NaOCl on bond strength. DESIGN: Permanent molars presenting HAI and sound third molars were used. Enamel surfaces were wet-flattened and Knoop hardness was assessed. The two-step, etch-and-rinse adhesive Single Bond 2 (3M ESPE) was applied and resin cylinders bonded to the surfaces and submitted to microshear testing. The subjacent medium dentin was then exposed by wet-grinding. Hardness readings and microshear testing were carried out again. The relationship between hardness and bond strength was assessed by nonlinear regression analysis. RESULTS: Hardness of normal enamel was higher than hardness of enamel affected by HAI, whereas dentin hardness did not differ from normal to HAI-affected teeth. Enamel and dentin hardness were similar for teeth affected by HAI. Higher bond strengths were obtained to the normal tooth tissues. Dentin bond strength was higher than enamel bond strength. NaOCl exposure did not influence bond strengths. A positive linear relationship between enamel hardness and bond strength was observed. CONCLUSION: HAI imposes challenges to bonding to enamel and dentin.