Effects of pre-etching in class V cavities restored with silorane and methacrylate-based composites Efekty wstępnego wytrawiania ubytków klasy V wypełnionych materiałami kompozytowymi na bazie siloranów i metakrylanów

Background. Self-etching adhesive (SEA) systems were recently introduced to simplify the bonding procedure and were initially considered a good replacement for the etch-and-rinse adhesive system that uses orthophosphoric acid (PA) for enamel and dentin etching. Siloranes, a new class of ring opening monomers, were synthesized to overcome the problems related to polymerization shrinkage. This new type of monomer is obtained from the reaction of oxirane and silorane molecules with a volumetric shrinkage determined to be 0.99%. Objectives. To assess the influence of preliminary phosphoric acid etching on the sealing ability of silorane- and methacrylate-based composites. Material and methods. Standard class V cavities were prepared on the buccal side of 48 extracted, sound, human premolars. The specimens were randomly divided in two groups: A) Silorane System®/Filtek Silorane®; B) Scotchbond Universal®/Filtek Supreme®. Each group was divided in two subgroups. A1) and B1): no preetching was performed. A2) and B2): selective, enamel pre-etching was performed. The interfacial sealing ability of the materials was evaluated by scoring the depth of methylene blue penetration through optical microscope observations. The differences in infiltration scores recorded for the tested materials were evaluated for statistical significance (Kruskal-Wallis ANOVA, Mann-Whitney U test, p < 0.05). Results. No groups showed a “0” score, and group B2 had the lowest individual score, reaching at least a “2” score. In the silorane groups, pre-etching decreased the infiltration score but the result was not statistically significant. No statistically significant differences emerged among the tested materials except for the Bis-GMA composite restored group where the pre-etching significantly reduced the interfacial leakage (p < 0.05). Conclusions. Selective enamel pre-etching significantly reduced the marginal infiltration in class V cavities, restored with Bis-GMA composite and a self-etching adhesive system. The low-shrinking silorane composite achieved better sealing ability