Influence of NaOCl Irrigation and Water Storage on the Degradation and Microstructure of the Resin/Primary Dentin Interface

Purpose: To evaluate the influence of NaOCl irrigation and water storage on the degradation and microstructure of the resin/dentin interface of primary teeth bonded with three different adhesive systems using the microtensile bond strength test (µTBS) and scanning electron microscopy (SEM). Materials and Methods: Ninety sound primary molars were used. Eighteen groups were formed according to different adhesive systems (Adper Single Bond 2, SB; Clearfil Protect Bond, CP; Adper Prompt L-Pop, APL) with or without 0.5% NaOCl irrigation and water-storage time (24 h, 45 days, 90 days). The middle dentin was exposed. In the NaOCl group, NaOCl irrigation was performed for 30 min, and all groups were restored with composite (Charisma). Sticks with a 1-mm2 cross-sectional area were prepared for the µTBS test. The data were analyzed by ANOVA and Tukey's test (p 0.05). The failure modes, presence or absence of resin tags, and the resin/ dentin interface were evaluated by SEM, and data were analyzed using Cochran-Mantel-Haenszel statistics (p 0.05). Results: The µTBS of APL was significantly lower than the other groups regardless of treatment and storage time. A significant decrease of µTBS values after 90 days of water storage occurred only in the non-NaOCl irrigation groups. After 90 days of storage, resin tags partially disappeared in APL and CP, and in SB, 100% of the resin tags remained. Conclusion: The choice of adhesive system is one of the factors when bonding to primary dentin is considered. In this study, the etch-and-rinse and the two-bottle self-etching adhesive system produced the highest µTBS values irrespective of prior NaOCl irrigation even up to 90 days of water storage. Keywords: microtensile bond strength, NaOCl irrigation, adhesive systems, long-term bonding degradation, primary teeth