Solvent-free self-etch adhesive as a breakthrough in bonding technology: fact or fiction?

Objective The aim of this study was to compare the microshear bond strength (µSBS) and adhesive dentin interfacial ultramorphology of a solvent-free self-etch adhesive with those of a solvent-containing adhesive. Materials and methods Twenty caries-free third molars were used to prepare specimens of dentin surfaces. Ten specimens were prepared for each material. Specimen surfaces were further divided according to the prepared dentin surface into superficial and deep. The adhesives were applied on dentin surfaces according to the manufacturer’s instructions, after which Filtek Z250 XT composite resin was condensed through a polyethylene tube with a 0.75-mm internal diameter and 1-mm height attached firmly to the dentin surfaces and light cured. The bonded specimens were stored in distilled water at 37°C for 24 h before being tested. The µSBS values of the adhesives to dentin were evaluated and the collected data were analyzed statistically using one-way analysis of variance. In addition, in each experimental group, three specimens were prepared for analysis under scanning electron microscopy. Results There was a significant difference in µSBS between solvent-free self-etch adhesives and solvent-containing adhesives. Scanning electron microscopic findings confirmed the results. Conclusion Elimination of the solvent from a self-etch adhesive systems hindered the infiltration of adhesive components into dentin, which affects the bonding quality of resin composite to dentin