Bond Strength and Failure Behavior at the Post–Core Interface of Prefabricated Metal Posts Associated with Surface Treatment and Core Composite Polymerization Mode: An In Vitro Study

Background: Post–core bonding plays a critical role in restoration longevity, and both the post surface treatment and core composite polymerization mode may influence interfacial performance. Methods: This in vitro study evaluated the effect of the post surface condition (no treatment vs. airborne-particle abrasion combined with an MDP-containing primer) and the composite polymerization mode (dual-, light-, and chemical-cure) on the pull-out bond strength and failure behavior of prefabricated metal post–core systems. A 3 × 2 factorial design was applied to 72 specimens (n = 12). After thermocycling, bond strength and failure modes were analyzed using two-way analysis of variance (ANOVA) and chi-square tests (p < 0.05). Results: The surface treatment significantly increased bond strength (p < 0.001; η2 = 0.49) and shifted failure modes toward predominantly non-adhesive patterns (p = 0.011). Although the core type also showed a significant effect (p < 0.001), its influence was comparatively smaller. The bond strength was ranked as light-cure > chemical-cure > dual-cure under both surface conditions. Conclusions: Within the limitations of this study, post surface treatment was the primary determinant of bond strength and failure behavior. Clinically, effective surface modification appears to be more decisive than core composite selection, while differences among core materials become more apparent after establishing a stable bonding substrate.