Purpose: To investigate the effect of postextraction substrate aging on the microtensile bond strength (muTBS) of an adhesive system (Excite).
Materials and methods: Sixty sound human third molars were extracted for orthodontic purposes and prepared after the following storage periods in distilled water at 37 degrees C (n = 10): G1 - 1 h; G2 - 24 h; G3 - 7 days; G4 - 30 days; G5 - 1 year; G6 - 2 years. The occlusal surfaces were removed using diamond disks to expose middle dentin and a standardized smear layer was created by polishing with wet 600-grit sandpaper. The adhesive system was applied according to the manufacturer's instructions, and a resin composite block (5 mm in height, Tetric Ceram shade A2/Ivoclar Vivadent) was built in 1-mm increments, each one being light cured for 40 s (600 mW/cm2). After storage in distilled water at 37 degrees C for 24 h, teeth were sectioned to obtain stick-shaped specimens with a cross-sectional area of approximately 0.7 +/- 0.2 mm2. Specimens were submitted to muTBS test in a Kratos universal testing machine at a crosshead speed of 0.5 mm/min. Data were statistically analyzed using one-way ANOVA at a significance level of 5% (p < 0.05)
Results: The mean muTBS in MPa +/- SD were: G1 = 47 +/- 3.1; G2 = 42 +/- 5.1; G3 = 41 +/- 6.4; G4 = 43 +/- 9.8; G5 = 40 +/- 7.0; G6 = 52 +/- 5.7. No statistically significant difference was found among experimental groups.
Conclusion: Human teeth stored for long periods of time can be used to determine the in vitro muTBS of one-bottle adhesive systems.