Effect of Etching Time on Resin-Primary Dentin Adhesion and Degradation of Interfaces

Abstract

The purpose of this research was to evaluate the resin–dentin bond degradation in primary teeth after reducing the etching time. The dentin surfaces were bonded with: an etch and rinse adhesive (single bond-SB); a two step self-etching adhesive (Clearfil self etching bond-CSEB); and a one-step self-etching adhesive (one up bond F-OUB). For half the specimens, the recommended etching time was used (the manufacturer’s instructions); for the other half the etching time was reduced by 50%. The bonded teeth were divided according to different challenging procedures: (a) 24 h storage in distilled water and sectioned into beams (1.0 mm2); (b) immersion of the bonded beams in 10% NaOCl aqueous solution for 5 h; (c) load cycled (5000 cycles, 90 N) and then sectioned into beams. The micro-tensile bond strength (MTBS) was measured and fractographic analysis performed. The data were statistically analyzed using an analysis of variance (ANOVA) technique, together with multiple comparisons tests. The results showed that the OUB produced the lowest MTBS values, regardless of the challenging procedure. After NaOCl immersion, the MTBS decreased in all groups, with the Clearfil self etching bond (immersed for half the time) attained the highest MTBS. Following the instructions for each of the adhesive systems, after load cycling, no differences in MTBS were observed in the samples after 24 h. However when the etching time was shortened, a decrease in MTBS were observed for all groups. In conclusion, shortening the etching/conditioning time caused a significant change to the bond strength which was material dependent. The OUB produced the lowest bond strengths, regardless of other variables; and a reduced conditioning time resulted in an increased bond strength for CSEB adhesive.