Enamel sealing ability of self-etch adhesives

Objectives: To study the influence of acid-etching and thermal fatigue on the enamel sealing ability of 3 self-etch adhesives. Methods: Twenty-four bovine teeth were used in this study. Two preparations 6.0mmX3.0mmX1.5mm were made on the buccal surface of each tooth. The teeth were randomly assigned to one of 3 self-etch adhesives: Adper Prompt L-Pop (AP, 3M ESPE), Clearfil SE Bond (SE, Kuraray), and iBond (iB, Heraeus Kulzer) (n=8). For each tooth, one of the preparations was etched with 35% H₃PO₄ for 15 sec while the other was not etched. Preparations were restored with Filtek Z250 (3M ESPE). For each group, 4 teeth were thermocycled for 1,500 cycles (5^o-55^oC, 30 sec), while the other 4 teeth were left in water at 37 ^oC. Specimens were isolated with nail polish except for a 1.0 mm rim around the interface, and immersed in 50wt% ammoniacal silver nitrate for 24 h followed by 8h in photodeveloping solution. Observations were carried out under a Hitachi S700 FESEM equipped with a backscattered electron detector. Silver penetration was computed in ranks from 0-4 and analyzed with Kruskal-Wallis and Mann-Whitney non-parametric tests (P<0.05). Results: When data were pooled for thermal fatigue, thermocycled specimens leaked significantly more than non-thermocyled specimens (P<0.042). Acid-etching resulted in statistically less leakage than when adhesives were applied as per manufacturers' instructions (P<0.003). For AP, no-etching with thermocycling resulted in statistically higher silver penetration than the other 3 AP subgroups (P<0.045). For SE, acid-etching without thermocycling resulted in statistically lower silver penetration than the other 3 SE subgroups (P<0.029). For iB, acid-etching, regardless of thermal fatigue, resulted in statistically lower silver penetration (P<0.03). Conclusion: Enamel sealing provided by self-etch adhesives is influenced by phosphoric acid etching and thermal fatigue.