Bond Strength and Failure Modes of Fiber Versus Resin-based Posts with Different Lengths in Endodontically Treated Premolars: An In Vitro Study

Post-and-core systems are essential for restoring root canal–treated teeth, especially when damaged by trauma or decay. Fiber-reinforced posts remain the clinical standard, but newer all-resin posts have been proposed as alternatives. However, there is limited evidence comparing their bond strength and failure modes at different post lengths.

This in vitro study evaluated the effect of post material (fiber vs all-resin) and post length (10 mm vs 5 mm) on pull-out bond strength and classified failure modes in endodontically treated premolars.

Sixty extracted mandibular premolars were randomly divided into three groups (n = 20): Group A – fiber posts (10 mm); Group B – all-resin posts (10 mm); and Group C – all-resin posts (5 mm). Following standardized root canal treatment and post space preparation, posts were cemented using a dual-cure resin cement. Pull-out bond strength was tested using a universal testing machine at 0.5 mm/s. Failure modes were categorized, and representative samples were examined under Scanning Electron Microscopy (SEM). Data were analyzed using one-way ANOVA and Tukey’s post hoc test (p < 0.05).

Group B (10 mm all-resin posts) had the highest pull-out resistance, followed by Group A (10 mm fiber posts), while Group C (5 mm all-resin posts) demonstrated the lowest resistance. Statistically significant differences between Groups B and C, and between Groups A and C (p < 0.05) were observed; no significant difference was found between Groups A and B. Post material or length did not significantly influence failure mode.

The study showed that post material and length influence retention strength, with longer all-resin posts performing comparably to fiber posts. These findings suggest that 10 mm all-resin posts may provide a conservative alternative in clinical scenarios where fiber posts cannot be placed. However, resin posts of shorter length demonstrated insufficient retention, limiting their clinical applicability.

Fiber posts remain the standard and most accepted option for post-and-core restorations. However, 10 mm all-resin posts showed comparable pull-out bond strength and may be considered as a viable option for anatomically constrained cases. In contrast, 5 mm all-resin posts had significantly reduced retention and are not recommended in cases where the optimal retention is essential.