Improving bonding effectiveness of mild self-etching adhesives by selective enamel acid etching

Objective. The aim of this study was to evaluate microleakage of class V resin composite restorations when using mild self-etching adhesives according to manufacturers’ instructions compared to modified application protocol by selective enamel acid etching using 37% phosphoric acid. Materials & Methods. Sixty human premolars with a standard Class V cavity were prepared at buccal surface, located across the CEJ. Cavity dimensions were 1.5 x 3.0 x 3.0 mm with a 45º bevel of 1.0 mm width at enamel margin. Specimens were divided into 6 groups. Three commercially available adhesives were investigated: Optibond FL, Clearfil SE Bond and Clearfil S3 Bond. Adhesives used according to manufacturers’ instructions were used as controls compared to the modified application protocol by selective enamel acid etching using 37% phosphoric acid. Placement of resin composite was performed incrementally. The specimens were kept in 100% humidity at 37 ºC for 24 hours followed by 5,000 thermal cycles between 5±1 ºC and 55±1 ºC. Microleakage test was performed by using silver nitrate as leakage indicator, and subsequently three longitudinal sections were made. All sections were evaluated for microleakage at enamel and dentin margins. The results were analyzed by Chi-Square test and Wilcoxon Signed Rank test with a 95% confidence level. Results. Clearfil SE Bond exhibited lower enamel leakage value, compared to control, when beforehand enamel was etched with phosphoric acid, but no statistically significant difference was shown. In contrast, the sealing ability of Clearfil S3 Bond at enamel margin of modified protocol group was found to be statistically better than manufacturer’s protocol group. Modified application of Optibond FL presented less leakage at dentin margin compared to that found in control group significantly. Conclusion. There was no difference in sealing ability at enamel margin of Clearfil SE Bond when used according to manufacturers’ instructions compared to modified protocol using selective enamel acid etching. In contrast to Clearfil S3 Bond, sealing ability of modified protocol was found to be better than that of manufacturer’s protocol. Double conditioning of enamel using phosphoric acid and Optibond primer did not compromise bonding effectiveness of Optibond FL group, however, double etching in dentin reduced dentin bonding quality.