Effect of all-in-one adhesives on permanent and primary enamel

Objectives: Nowadays, etching of the enamel surface prior the self-etching adhesives application is not performed. However, questions have been raised regarding their reliability to achieve durable bonds to enamel especially when the prismless layer of enamel is thick such as in primary teeth. The aim of the present study was to evaluate the morphological changes obtained on ground and unground enamel of permanent and primary teeth after application of three all-in-one self-etching adhesives. Methods: The adhesives Clearfil S³ Bond (CS), iBond (IB) and G-Bond (GB) were evaluated. Phosphoric acid 37% (30 s) was used as a control. Labial surfaces of twenty primary (n=5) and twenty permanent canines (n=5) were divided into two halves. One half was cleaned with a rotating brush under water and the other one was ground with SiC paper (280grit). The phosphoric acid and the adhesives tested were placed on the enamel surfaces according to the manufacturers' instructions. Afterwards, the phosphoric acid was rinsed-off by water-spray and the adhesives by acetone to remove the uncured material. All specimens were observed before and after the enamel treatments under SEM, at 30 kV of accelerating voltage, at x1000 magnification. Results: Phosphoric acid produced well-defined etching pattern on primary and permanent enamel, which was uniform on unground and non-uniform on ground surfaces. No changes were noted after IB and GB placement on ground and unground enamel. CS appeared to be more effective causing a slightly porous surface actually on permanent teeth. Conclusion: The morphological changes verified on permanent and primary enamel surfaces after the application of the three all-in-one self-etching adhesives evaluated can not guarantee micromechanical retention of the resin composites.