Micro-shear bond strength of adhesives with different degrees of acidity: Effect on sound and artificially hypermineralized dentin

This study evaluates the bond strength of four self-etching adhesive systems with different acidity levels in normal and artificially hypermineralized dentin substrate. Healthy human molars were divided into groups: normal dentin—N (n = 36) and artificially hypermineralized dentin—H (n = 36). Self-etching adhesive systems Clearfil S3 Bond (n = 9), Optibond All in One (n = 9), Clearfil SE Bond (n = 9), and Adhese (n = 9) were used for both the N and H groups. Transparent cylindrical matrices were positioned on the treated dentin surfaces, filled with composite resin, and light-cured for 40 s. After the transparent cylindrical matrices were removed, the specimens were stored for 24 hr in a humid environment at 37°C and were subjected to a micro-shear bond strength test. For each group, a specimen was prepared and evaluated in scanning electron microscope for adhesive interface observation. Normality was confirmed and the two-way analysis of variance and Games–Howell post-tests were conducted (α =.05). The data demonstrated an interaction between the adhesive system and type of dentin substrate (p <.01). For normal dentin, all adhesive systems assessed were adequate; however, in the hypermineralized dentin, the Clearfil SE Bond two-step self-etching adhesive system with mild pH presented the highest immediate bond strength. There was a predominance of adhesive failures for all adhesive systems in the different dentin substrates evaluated. It was concluded that the self-etching adhesive systems evaluated were efficient for both substrates, and for the hypermineralized dentin, the Clearfil SE Bond presented a higher bond strength value.