Chronological Nano-hardness Change of the 2-bottle One-step Self-adhesives

Objectives: The purpose of this study was to evaluate a chronological nano-hardness change of 2-bottle one-step self-adhesives after light activating in water. Methods: Freshly extracted human molars were cut using a slow-speed diamond saw to expose the dentin surface, and the exposed dentin surfaces were polished with 600-grit silicone carbide paper. The dentin surfaces were treated with three kinds of 2-bottle one-step self-adhesives, AQ Bond Plus (AQP) (Sun Medical, Shiga, Japan), One-up Bond F Plus (OBF) (Tokuyama Dental, Tokyo, Japan) and Fluorobond Shake-One (FSO) (Shofu, Kyoto, Japan) following manufacturer's instructions. The adhesive was applied five times in order to create a thick bond layer. The surface of each adhesive was wiped with an alcohol cotton pellet to remove the unpolymerized layer. The nanohardness change of the adhesive surface was measured using ENT-1100a (Elionix, Tokyo, Japan) immediately after light activating (0), then again at 1 hour (1h), 1 day (1d), and lastly 10 months (10m). The specimens were stored in distilled water during the measurement period. Data was statistically analyzed by t-test, ANOVA and Tukey's test (a=0.05). Results: The nanohardness (MPa) and S.D. of each material was: AQP-0 10.1(3.8), AQP-1h 92.9(8.0), AQP-1d 111.8(17.0), AQP-10m 88.0 (13.5), OBF-0 19.3(11.9), OBF-1h 73.1(22.5), OBF-1d 105.1(44.1), OBF-10m 90.8(32.7), and FSO-0 32.5(10.3), FSO-1h 79.6(4.5), FSO-1d 91.9(4.6), FSO-10m 115.1(36.3). Conclusion: The nanohardness of the 2-bottle one-step self-adhesives had increased 1 hour after light activating. Statistically, there was no significant nanohardness change in the materials from the measurement at 1 hour, to the measurement at 10 months.