Self-adhesive flowable resin composite for occluso-proximal restorations in primary teeth: restorative time and fracture resistance analysis

Abstract

Restoring occluso-proximal cavities in primary molars is clinically challenging due to their anatomical characteristics and the difficulty of matrix adaptation. Although resin composites are widely used, their technique sensitivity has led to simpler alternatives, such as self-adhesive flowable composites, whose performance in primary teeth remains unclear. Objective:  This in vitro study evaluated the restorative time and fracture resistance of occluso-proximal restorations in primary molars using a self-adhesive flowable resin composite, a flowable resin composite, and a conventional resin composite. Methodology:  Thirty primary molars received two standardized occluso-proximal cavities and were randomly assigned to three groups (n=10): (1) self-adhesive flowable resin composite (Yflow SA), with the entire cavity restored; (2) universal adhesive (Scotchbond Universal) in self-etch mode + flowable resin composite (Filtek Z350 XT Flow), with the entire cavity restored; and (3) universal adhesive in self-etch mode + conventional resin composite (Filtek Z350 XT), inserted incrementally. Restoration time was measured using a digital chronometer, and all teeth underwent 14 days of pH cycling before the fracture resistance test. Mean fracture resistance values were analyzed using one-way ANOVA and Tukey's test. The Kruskal–Wallis and Dwass–Steel–Critchlow–Fligner tests were used to compare the restoration time among groups. Failure modes were analyzed descriptively. Results:  The self-adhesive flowable resin composite required the shortest restoration time, followed by the flowable resin composite and the conventional resin composite (p<0.001). Fracture resistance was significantly lower in the self-adhesive flowable resin composite group compared to the flowable and conventional resin composite groups (p<0.01). Adhesive failures predominated in the self-adhesive flowable resin composite group (45%), while mixed failures were more frequent in the other restorative approaches (70–75%). Conclusion:  In a laboratory setting, the use of a self-adhesive flowable resin composite for the entire cavity compromised the fracture resistance of occluso-proximal restorations in primary molars, despite reducing operative time.