The ability of different compositions of calcium silicate and epoxy sealers to withstand gutta percha removal via in vitro pull-out testing

Root canal sealers are crucial for obturation quality. Epoxy resin-based AH Plus has long been considered the gold standard, with sealing largely dependent on adhesion. New formulations include BJM Root Canal Sealer, an epoxy-based sealer incorporating antibiofilm macromolecules (BioSafe). Tricalcium silicate-based (TCS) bioceramic sealers offer biocompatibility and handling advantages and achieve sealing partly through expansion and biomineralization, with radiopacifiers such as zirconium oxide. The newly launched AH Plus Bioceramic reportedly contains relatively low tricalcium silicate (5–15% wt) and high zirconium dioxide (50–70% wt), whereas Total Fill BC contains higher tricalcium (20–35% wt) and dicalcium silicate (7–15% wt) with lower zirconium oxide (35–45% wt). There is limited evidence on how such compositional changes, including adding macromolecules to epoxy sealers or altering TCS phase content, affect sealer performance. The study aims to evaluate how these compositional changes influence resistance to gutta-percha removal using an in vitro pull-out test as an indirect indicator of sealing ability.

Prior research identifies AH Plus epoxy resin sealer as a clinical benchmark, with sealing efficacy linked to adhesive properties. BJM RCS introduces antibiofilm macromolecules (BioSafe, 1.6–3.3% wt). Bioceramic/TCS materials improve handling and biocompatibility, replace MTA components (e.g., zirconium oxide as radiopacifier in sealers), and include calcium phosphate to promote biomineralization. Reported compositions differ: AH Plus Bioceramic has relatively low TCS content and high zirconium dioxide, while Total Fill BC has higher tri- and dicalcium silicate content and lower zirconium oxide. Micro-CT data showed that oval canals filled with AH Plus had fewer GP–sealer interface gaps than those with a TCS sealer (EndoSequence BC). However, data relating specific compositional changes (e.g., macromolecule addition to epoxy or altered TCS/zirconia proportions) to pull-out resistance have been lacking, motivating the present study.

Study design: In vitro pull-out test comparing sealers with differing compositions. Ethics: Conducted per Declaration of Helsinki; IRB approval #2243-2021 (04/21). Teeth: Fifty extracted mandibular and maxillary molars with similar distal (mandibular) or palatal (maxillary) canals, complete root formation, near-zero curvature, and initial canal diameter < size 20 K-file. Sample size based on prior in vitro studies and Winpepi calculations. Preparation: Teeth stored in 0.9% NaCl, sectioned at the CEJ with a 0.3 mm Horico disc for access. Canals prepared to ISO 45 using DC Taper rotary files to a standardized length of 8 mm from CEJ. Irrigation: 5 mL of 3% NaOCl per canal, final rinse with 2 mL 17% EDTA; canals dried with paper points. Groups: Five groups (n=10 canals each): (1) AH Plus (epoxy), (2) BJM RCS (epoxy with antibiofilm macromolecules), (3) Total Fill BC (bioceramic/TCS), (4) AH Plus Bioceramic, and (5) GP only (no sealer). Obturation: Single-cone technique using ISO size 45 GP cone with the designated sealer for groups 1–4; cones left uncut coronally. Controls: Two additional teeth per sealer group obturated with sealer only (no GP) to verify sealer setting prior to testing. Storage: 100% humidity at 37 °C for 10 days. Pull-out testing: Shimadzo Universal Testing Machine; tooth clamped in lower forceps, GP cone grasped by upper forceps and pulled at 1 mm/min until torn or completely removed. For each specimen, a force–stroke graph was recorded; the peak force (N) at removal or rupture was taken as outcome. For each specimen, the event (torn vs removed) was recorded. Blinding: Testing performed by a single operator blinded to group allocation. Statistical analysis: SPSS v27. Normality of force data confirmed (Kolmogorov–Smirnov p=0.085). Means ± SD reported. Group comparisons by one-way ANOVA with Bonferroni post hoc tests. Categorical outcomes (torn vs removed) compared by chi-square. Significance at P<0.05.

- Pull-out force was significantly higher for AH Plus, BJM RCS, and Total Fill BC versus AH Plus Bioceramic. Means ± SD: AH Plus 1.87 ± 0.53 N; BJM RCS 2.05 ± 0.47 N; Total Fill BC 1.63 ± 0.32 N; AH Plus Bioceramic 0.93 ± 0.48 N. - Pairwise comparisons: AH Plus vs AH Plus Bioceramic, P<0.001; BJM RCS vs AH Plus Bioceramic, P<0.001; Total Fill BC vs AH Plus Bioceramic, P=0.01. Total Fill BC did not differ significantly from epoxy sealers (ANOVA/Bonferroni: vs AH Plus P=1.00; vs BJM RCS P=0.291). - Event type: In AH Plus Bioceramic group, all cones (10/10) were completely removed (no ruptures), significantly different from each other sealer group (P=0.01) and from all sealer groups combined (P<0.001). Total removed counts: AH Plus 2/10, BJM RCS 3/10, Total Fill BC 5/10, AH Plus Bioceramic 10/10. - GP-only group: Required 0 N for cone removal, indicating negligible tensile contribution from GP alone.

Findings indicate that sealer composition critically affects resistance to GP pull-out. The AH Plus Bioceramic sealer, with reduced tri- and dicalcium silicate content and increased zirconium oxide, exhibited substantially lower pull-out resistance and complete cone removal in all cases, suggesting poorer adaptation to GP and/or diminished expansion-related sealing typical of higher TCS content. In contrast, Total Fill BC, with higher tri- and dicalcium silicate content, performed comparably to epoxy-based sealers and significantly better than AH Plus Bioceramic. The addition of antibiofilm macromolecules (BioSafe) to the epoxy-based BJM RCS did not adversely affect pull-out performance relative to AH Plus, supporting that macromolecule incorporation does not impair adhesion in this context. The results align with prior micro-CT observations of more interface gaps with certain TCS sealers versus epoxy in oval canals, potentially contributing to easier cone removal. Differences between torn versus removed cones may be influenced by variability in sealer layer thickness inherent to single-cone obturation in non-circular canals, patient-related dentin characteristics (age-related tubule density/diameter, mineral content), and unknown pre-extraction pulp status with possible biofilm remnants that could alter sealer interactions.

Adding BioSafe macromolecules to an epoxy sealer did not change its resistance to GP pull-out compared with AH Plus. AH Plus Bioceramic sealer showed significantly lower attachment/resistance than the other tested sealers, likely due to its lower tri- and dicalcium silicate content and higher zirconium oxide proportion. Composition-driven differences in bioceramic sealers materially affect pull-out resistance.

- Variability in sealer layer thickness due to the single-cone technique and non-round canal geometry. - Teeth sourced from different patients and age groups, potentially affecting dentinal tubule characteristics and dentin mineral content. - Unknown pre-extraction pulp conditions; residual biofilm may have influenced sealer performance. - In vitro design using extracted teeth and standardized 8 mm canal segments may limit generalizability to clinical conditions.