Effect of gutta-percha removal methods on fiber-post bond strength

Objectives: This study evaluated the effect of three root canal filling material (RCFM) removal techniques—mechanical, thermo-mechanical, and chemico-mechanical—on the micro push-out bond strength of fiber posts to root dentin in endodontically treated teeth.

Materials and Methods: Forty-five single-rooted human premolars were endodontically treated and randomly allocated into three groups (n = 15) according to the RCFM removal technique used during post-space preparation: mechanical, thermo-mechanical, or chemico-mechanical. Fiber posts were luted using a dual-cure resin cement. Roots were embedded in resin and sectioned into coronal, middle, and apical thirds. Micro push-out bond strength was measured using a universal testing machine. Failure modes were examined under a stereomicroscope and validated using scanning electron microscopy. Statistical analysis used two-way ANOVA and Chi-square tests (α = 0.05).

Results: Both the thermo-mechanical and mechanical groups showed significantly higher bond strength values than the chemico-mechanical group (p < 0.001). Across all groups, the coronal third recorded the highest bond strength, while the apical third presented the lowest values (p < 0.001). Adhesive failure at the dentin–cement interface was the most frequent failure mode.

Conclusions: The gutta-percha removal technique and the root canal region significantly influence fiber-post bond strength. Solvent-based chemico-mechanical methods may adversely affect adhesion quality. Clinical Relevance: Thermo-mechanical and mechanical removal techniques may provide more reliable post retention during retreatment procedures, improving adhesion and reducing the risk of post debonding in daily practice.