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

Objectives: To evaluate effect of direct and indirect water storage on the microtensile dentin
bond strength of one total-etch and two self-etching adhesives.
Methods: The adhesive materials were: one total-etch adhesive; ‘Admira Bond’ and two selfetch
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-
1.2mm 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 8C for 4 years before microtensile
testing (direct water storage). Procedure C: the teeth were kept in water at 37 8C 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.
Results: For 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.
Conclusion: All 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.