Effect of dentin deproteinization on microleakage of class V composite restorations

The role of the collagen fibers in dentin adhesion has not clearly been est ablished. Therefore, this laboratory study evaluated the microleakage at re sin-dentin and resin-enamel interfaces of Class V composite restorations af ter etching enamel and dentin with phosphoric acid (H3PO4) or after etching with H3PO4 followed by deproteinization with 5% sodium hypochlorite (NaOCl ) to prevent the formation of a hybrid layer. Ten extracted human molars we re used to prepare standardized Class V cavities on both buccal and lingual surfaces. The teeth were randomly divided in two groups: 1) Class V caviti es that were etched with H3PO4 for 15 seconds; b) Class V cavities that wer e etched with H3PO4 for 15 seconds followed by collagen removal with 5% NaO Cl for two minutes. The cavities were restored using the Prime & Bond 2.1 b onding system and TPH resin composite. The specimens were stored in water f or 24 hours at 37 degreesC and thermocycled 500 times between water baths k ept at 5 degreesC and 55 degreesC. After thermocycling, specimens were imme rsed in a 0.5% aqueous solution of basic fuchsin for 24 hours. Three longit udinal sections of each restoration were obtained and examined with a stere omicroscope for qualitative evaluation of microleakage. The data were stati stically analyzed by Mann-Whitney U and Wilcoxon matched pairs signed ranke d tests. Extra specimens were analyzed with the scanning electron microscop e (SEM). Occlusal margins (enamel margins) resulted in statistical lower de gree of leakage than gingival margins (dentin/cementum margins) in both tre atment groups. For each type of margin, there were no statistically signifi cant differences between the etched and the etched and deproteinized groups . Under the SEM, occlusal surfaces showed no detachment between enamel and dentin, while dentin/cementum resulted in gap formation.