Effect of Preheating of Resin Luting Materials on Push-Out Bond Strength of Fiber Posts to Intraradicular Dentin

This study aimed to evaluate the effect of preheating on the push-out bond strength (PBS) and microhardness (HV) of fiber-reinforced flowable and injectable composites and to compare them with dual-cure resin–cement for post cementation. Fifty premolars were endodontically treated, and post spaces were prepared. Specimens were divided into five groups (n = 10) based on the resin luting material. After adhesive application, fiber posts were luted with dual-cure resin–cement (LinkForce), fiber-reinforced flowable composites (EverX Flow; non-heated/preheated), and injectable composites (G-aenial Universal Injectable; non-heated/preheated). After 24 h, roots were sectioned (coronal, middle, apical) for PBS testing (Instron). For HV, 10 specimens per resin luting material were prepared, and top/bottom microhardness was measured to assess the depth of cure. Data were analyzed with two-way ANOVA and post hoc Tukey tests (p < 0.05). Both types of resin luting material and preheating significantly affected PBS and HV (p = 0.0001). Preheated EverX Flow showed significantly higher PBS and HV than LinkForce, while G-aenial Injectable exhibited the lowest values (p < 0.05). Within each resin luting material, PBS significantly decreased from the coronal to the apical region (p = 0.0001). Preheated fiber-reinforced flowable composites demonstrate improved microhardness and adhesion, offering a reliable alternative to the dual-cure resin–cements for fiber post cementation.