Four-year water degradation of a total-etch and two self-etching adhesives bonded to dentin

ObjectivesTo evaluate effect of direct and indirect water storage on the microtensile dentin bond strength of one total-etch and two self-etching adhesives.MethodsThe adhesive materials were: one total-etch adhesive; ‘Admira Bond’ and two self-etch adhesives; ‘Clearfil SE Bond’ and ‘Hybrid Bond’. Freshly extracted human third molar teeth were used. In each tooth, a Class I cavity (4 mm × 4 mm) was prepared in the occlusal surface with the pulpal floor extending approximately 1 mm into dentin. The teeth were divided into three groups (n = 18). Each group was restored with the resin composite ‘Clearfil APX’ using one of the tested adhesives. For each experimental group 3 test procedures (n = 6) were carried out: Procedure A: the teeth were stored in water for 24 h (control), then sectioned longitudinally, buccolingually and mesiodistally to get rectangular slabs of 1.0–1.2 mm thickness on which a microtensile test was carried out. Procedure B: the teeth were also sectioned; however, the slabs were stored in water at 37 °C for 4 years before microtensile testing (direct water storage). Procedure C: the teeth were kept in water at 37 °C 4 years before sectioning and microtensile testing (Indirect water storage). During microtensile testing the slabs were placed in a universal testing machine and load was applied at cross-head speed of 0.5 mm/min.ResultsFor the 24 h control, there was no significant difference in bond strength between the three tested adhesives. After 4 years of indirect water storage, the bond strength decreased but the reduction was not significantly different from those of 24 h. After 4 years of direct water storage, the bond strengths of all tested adhesives were significantly reduced compared to their 24 h results.ConclusionAll the tested adhesives showed no reduction in bond strength after indirect water exposure for 4 years. After 4-year direct water exposure, the bond produced by all tested adhesives was unable to resist deterioration.