Evaluation of micro-shear bond strength of a self-adhesive flowable giomer to dentin in different adhesive modes

Recently, self-adhesive flowable composite resins (SAFC) have been introduced to dental practice to simplify the clinical procedure and to reduce the treatment time but with limited data regarding their bonding performance to dentin. The aim of this in vitro study was to evaluate the micro-shear bond strength (μ-SBS) of a giomer SAFC (FIT SA F03 – FSA) bonded with different modes to dentin after artificial aging. Additionally, a qualitative evaluation of the hybrid layer formation after different adhesive modes was performed using scanning electron microscopy (SEM). A flowable giomer composite resin (Beautifil Flow Plus F03 – BFP) was used as control. Fifty sound human molars were used for providing the dentinal substrates. The experimental groups of the study were five; two for BFP, where the specimens bonded to dentin using etch-and-rinse (Optibond FL) and self-etch (Clearfil SE Bond 2) strategy, and three for FSA, where self-adhesive mode was also applied. The μ-SBS test was applied after 24 h and after thermocycling. Etch-and-rinse and self-etch modes exhibited significant higher μ-SBS compared to self-adhesive mode for FSA (p < 0.05) . Adhesive failures were predominant for both materials regardless of the adhesive mode and there was an increase in adhesive failures after thermocycling. Uniform hybrid layer was observed for the dental adhesives used, whereas visible gaps appeared when the self-adhesive mode was applied. FSA presented inferior behavior when bonded to dentin following the self-adhesive mode, while the best approach for BFP seemed to be the two step self-etch adhesive mode.