Background: Attempts to improve bond strength of self-etch adhesives can enhance the durability of composite restorations.
Aims: The aim of the present study was to evaluate the effect of collagen and smear layer removal with sodium hypochlorite solution (NaOCl) and EDTA on micro-tensile bond strength (μTBS) of self-etch adhesives to dentin.
Settings and design: It was an in-vitro study.
Materials and methods: Seventy-two teeth were divided into eight groups and their crowns were ground perpendicular to their long axis to expose dentin. The teeth were polished with silicon-carbide papers. The groups were treated as follows: No conditioning, 0.5-M EDTA conditioning, 2.5% NaOCl conditioning, NaOCl + EDTA conditioning. The surfaces were rinsed and blot-dried. Clearfil S3 and I-Bond were applied according to manufacturers' instructions and restored with Z100 composite. After 500 cycles of thermo-cycling between 5°C and 55°C, the samples were sectioned and tested for μTBS.
Statistical analysis: Data were analyzed by two-way ANOVA and Tukey-HSD test.
Results: The highest μTBS was recorded with Clearfil S3 + NaOCl + EDTA, and the lowest was recorded with I-Bond without conditioning. μTBS in EDTA-and EDTA + NaOCl-treated groups was significantly higher than the control and NaOCl-conditioned groups.
Conclusions: Application of EDTA or EDTA + NaOCl before one-step self-etch adhesives increased μTBS.
Keywords: Adhesives; laboratory research; smear layer; sodium hypochlorite.