Three-Largest Dentin–Sealer Interfacial Gaps After Warm Vertical Obturation: An In Vitro SEM Study

Abstract

Direct comparisons of epoxy resin-, calcium silicate- and calcium hydroxide-based root canal sealers under an identical thermoplastic obturation protocol remain limited. This in vitro study compared the mean of the three largest visible dentin–sealer interfacial gaps (the three-largest-gap value) of ADSEAL, BioRoot Flow and Sealapex in the apical, middle and coronal root segments after a standardized warm vertical obturation protocol. Ninety single-rooted teeth were allocated to three groups (n = 30 per group) and obturated with down-pack and thermoplasticized backfilling; the three widest visible discontinuities per segment were measured by scanning electron microscopy and averaged. Generalized estimating equations with Bonferroni-adjusted post hoc comparisons were used. In the primary raw-scale analysis, sealer type significantly affected the three-largest-gap value (p < 0.001) and the sealer type × segment interaction was significant (p = 0.021), whereas root segment alone was not (p = 0.083). The only significant segment-specific difference occurred in the coronal segment, where BioRoot Flow (22.13 ± 16.06 µm) showed wider gaps than Sealapex (11.40 ± 4.34 µm). Sensitivity analyses indicated that the statistical significance of the sealer main effect and of the sealer × segment interaction was not fully invariant to outlier-exclusion criteria or to outcome transformation, although the ordering of the group means was unchanged. These findings indicate that interfacial gap behavior is better characterized at the product and root-segment level than by nominal material classification; however, they are morphological and should not be read as evidence of overall adaptation, leakage resistance or clinical superiority.