Shortening the Etching Time for Etch-and-Rinse Adhesives Increases the Bond Stability to Simulated Caries-affected Primary Dentin

Purpose: To evaluate the influence of shortening the etching time on the bond degradation of one etch-and-rinse and one two-step self-etching adhesive system to sound (SD) and caries-affected (CAD) dentin of deciduous teeth. Materials and Methods: Flat dentin surfaces from 48 deciduous molars were assigned to 8 groups according to substrate (SD and CAD, pH cycling for 14 days), adhesive system (Adper Single Bond 2 [SB] and Clearfil SE Bond [CSEB]), and etching time (recommended by manufacturers and half the recommended etching time). Composite buildups were constructed and sectioned to obtain bonded sticks (0.8 mm2) to be subjected to microtensile testing immediately or after 12 months of water aging. Two sticks from each tooth at each time were immersed in silver nitrate solution to qualitatively assess nanoleakage. The microtensile bond strength (μTBS) values of each adhesive were submitted to three-way repeated measures ANOVA and Tukey's post-hoc tests (α = 0.05). Results: The etching time influenced the bond strength only for SB. The highest μTBS values and lowest silver nitrate uptake were observed when half the recommended acid-etching time was used, regardless of substrate. Water storage for 12 months reduced bond strengths, except to CSEB bonded to SD. The μTBS values obtained for CAD were lower than for SD, irrespective of adhesive system. Nanoleakage was more pronounced in CAD. Conclusion: The effect of shortening the etching time is material dependent and results in better bond stability for sound and caries-affected dentin of deciduous teeth when an etch-and-rinse adhesive system is employed. Parole chiave: deciduous teeth, caries-affected dentin, etching time, microtensile testing, nanoleakage, deterioration