Impact of different resin materials and light-curing units on adhesive performance of fiber posts

This study evaluated the effect of different light-curing units on the conversion degree of resin materials used for luting glass fiber posts and the bond strength to root dentin. One hundred bovine roots received endodontic treatment and were randomly assigned to five groups (n = 10) according to the luting material: RelyX U200 (self-adhesive resin cement), RelyX Ultimate (adhesive resin cement), Filtek Bulk Fill Flow (bulk-fill flowable composite with camphorquinone), Tetric N-Flow Bulk-Fill (bulk-fill flowable composite with ivocerin), and Filtek Supreme Flowable (flowable composite resin). Light activation was performed using either an LED singlewave (Radii Plus) or a polywave LED (Valo Cordless), both at 1000 mW/cm². The degree of conversion was analyzed using Raman spectroscopy, and bond strength was assessed using the push-out test, followed by failure mode analysis. ANOVA and Tukey (α=0.05) demonstrated that RelyX Ultimate and Filtek Bulk Fill Flow provided higher strength values, different (p<0.05) from Tetric N-Flow Bulk-Fill, RelyX U200, and Filtek Supreme Flowable, which had the lowest values. Regarding light-curing units, LED polywave showed the highest bond strength difference (p<0.05) from LED singlewave. Adhesive failures were predominant across all groups, regardless of the material, light source, or root third. RelyX U200, RelyX Ultimate, and Filtek Bulk Fill Flow showed a higher degree of conversion than Tetric N-Flow Bulk-Fill and Filtek Supreme Flowable. Overall, both the choice of luting material and the light-curing unit influenced bonding effectiveness. RelyX Ultimate and Filtek Bulk Fill Flow showed superior performance, and the polywave LED generally produced better adhesion outcomes.