Microshear bond strength to dentin of self-adhesive flowable composite compared with total-etch and all-in-one adhesives

BACKGROUND/PURPOSE: Because of the lack of data on long-term survival of a flowable self-adhesive composite (SAC) restoration, the purpose of this study was to compare the microshear bond strengths (μSBSs) of flowable resin composites to dentin, either with self-adhesive ability or with the combined use of a total-etch adhesive and all-in-one adhesive, before and after thermocycling. MATERIALS AND METHODS: Coronal dentin specimens of 60 extracted sound third human molars were divided into three groups (n = 20) as follows: Group 1, flowable SAC (VF); Group 2, total-etch adhesive + flowable composite (FL); Group 3, all-in-one adhesive + flowable composite (AL). For each adhesive, half of the specimens were subjected to μSBS testing after 24-hour water storage, and the other half of the specimens were subjected to 5000 thermocycles followed by μSBS testing. The morphologies of the adhesive interfaces were evaluated under a scanning electron microscope. Data were analyzed using one-way analysis of variance (ANOVA) and independent t test. RESULTS: One-way ANOVA showed similar results for both 24-hour water storage and thermocycled groups. The FL group showed the highest μSBS values (P < 0.001). The VF and AL groups were not statistically significantly different. Thermocycling had no effect on μSBS values (P = 0.578). The interfacial observation revealed that VF had a gap at the resin–dentin interface. By contrast, both FL and AL specimens had distinct adhesive layers without any gap formation. CONCLUSION: The results from this study indicated that laboratory bonding effectiveness of flowable SAC was approximately that of all-in-one adhesive.