Effects of De- and Remineralization of Dentin on Bond Strengths Yielded by One-, Three-, and Four-step Adhesives

Purpose: To assess the effect of different peri- and intertubular dentin mineralization conditions and etching on shear bond strength in vitro. Materials and Methods: One hundred fifty crowns of extracted bovine incisors were embedded in resin and ground to expose the buccal coronal dentin. Sixty specimens were subjected to a demineralizing solution (DS) and another 60 teeth to a bacterial-based laboratory caries model (S. mutans, SM). Thirty specimens of each demineralization protocol (DS and SM) were randomly selected and remineralized (-R). Thirty sound dentin specimens served as control (C). Resin composite buildups (Tetric) were bonded after application of one of the following adhesives: a one-step self-etching adhesive (Xeno III), and a self-etching adhesive (Syntac Classic) without (three-step) and with prior additional 35% phosphoric acid etching (etch-and-rinse, four-step). Teeth were subjected to shear bond strength testing in a universal testing device at a crosshead speed of 0.5 mm/min (Ultradent method). Results: Bond strength value for group C ranged from 6.3 to 8.4 MPa (p > 0.05). DS and DS-R samples showed increased bond strength with the one-step adhesive (11.6 MPa, p 0.05), whereas the three-step adhesive with additional etching showed decreased bond strength (3.2 MPa, p 0.05). SM samples showed the lowest bond strength of all adhesive systems (range 1.1 to 1.5 MPa, p > 0.05). Remineralization showed no effect on the latter group. Conclusion: The degree of mineralization of the dentin is important for adhesion. Additional etching with phosphoric acid reduced bond strength of a three-step adhesive. Keywords: dentin, demineralization, S. mutans, adhesive, bond strength