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.