San-jun Zhao, DDS, PhD, Ji-hua Chen, DDS, PhD, Yu Xiong, DDS, PhD, and Hui Wang DDS, PhD
Department of Prosthodontics, Stomatological College, The Fourth Military Medical University, Xi’an,
P. R. China
Purpose: To observe the effect of acid etching time on nanoleakage and microtensile bond strength (μTBS) of the adhesive-dentin bond with different total-etch adhesive systems.
Materials and Methods: Eighty human molars, whose occlusal enamel was removed to expose the dentin surfaces, were conditioned with phosphoric acid for 0 (control), 15, 30 or 60 s (n=20). Resin-dentin bonded specimens were produced using four one-bottle adhesives respectively; OptiBond Solo (OB), Single Bond (SB), One-Step (OS), and Prime & Bond NT (PB). Each specimen was then sectioned perpendicularly to the adhesive interface into eight beams. Four were used to measure the nanoleakage of adhesive-dentin interface by transmission electron microscope and four to conduct the μTBS test. The data was collected and statistically compared with analysis of variance and post-hoc test.
Results: Nanoleakage increased with increasing etching time (0, 15, 30, and 60 s; p<0.05). For the OS and PB groups, the highest μTBS were achieved after 15 s of etching, followed by 30, 60, and 0 s. For the OB and SB groups, the μTBS between 15 and 30 s etching time subgroups were not significantly different between them but significantly higher than those of 0 and 60 s etching time subgroups (p<0.05).
Conclusion: Increasing etching time demineralized the dentin surface to a depth greater than adhesives can penetrate, resulting in more nanoleakage and lower μTBS. (Int Chin J Dent 2006; 6: 29-37.)
Key Words: dentin, etching time, nanoleakage, microtensile bond strength.