Can preheated resin composite optimize bond strength and film thickness for indirect adhesive restorations?

Abstract Purpose Resin composite shows potential as a luting agent for indirect adhesive restorations, but its viability as an alternative to resin cement remains uncertain. This study aimed to evaluate the microtensile bond strength (µTBS) and film thickness of preheated resin composite used as a luting agent for indirect adhesive restorations. Materials and methods Fifteen extracted molars were randomly assigned to three groups ( N = 15): dual-cure resin cement (control group), room-temperature resin composite, and preheated resin composite. After the resin blocks were luted with dual-cure resin cement or resin composite, based on the assigned groups, the specimens ( n = 75) underwent µTBS testing. Film thickness evaluation ( n = 72) was performed by measuring the cement layer thickness of sections under a stereomicroscope. Data were analyzed using one-way ANOVA, Tukey, Kruskal-Wallis, and Dunn tests. Results The dual-cure resin cement exhibited higher bond strength than the room-temperature resin composite but showed bond strength comparable to that of the preheated resin composite. Both resin composite groups (preheated and room-temperature) showed similar bond strength values. The film thickness test revealed that the resin cement had the thinnest film layer, followed by the preheated resin composite. The highest film thickness was observed in the room-temperature resin composite. Although preheating did not significantly affect bond strength, it reduced the film thickness. Conclusion For the luting of indirect restorations, preheated resin composite exhibited bond strength comparable to that of dual-cure resin cement. Preheating reduced the film thickness of the resin composite luting layer; however, even when preheated, the film thickness remained above the clinically acceptable limit.