Influence of Obturation Technique on the Retreatability and Push-Out Bond Strength of Bioceramic Sealers: An In Vitro SEM Study

Bioceramic sealers have gained widespread acceptance in contemporary endodontics due to their favorable biological properties, dimensional stability, and bioactivity. However, their strong adhesion to dentinal walls and penetration into dentinal tubules may complicate removal during endodontic retreatment procedures. Additionally, the obturation technique may influence both the retreatability of root canal filling materials and the bond strength of sealers and resins to radicular dentin. Methods: One hundred extracted human single-rooted teeth were instrumented using the WaveOne Gold system and obturated with a bioceramic sealer using two techniques: single-cone (Group A, n = 50) and warm vertical compaction (Group B, n = 50). After sealer setting, retreatment procedures were performed using ProTaper Universal Retreatment files combined with passive ultrasonic irrigation. Scanning electron microscopy was used to evaluate smear layer removal and dentinal tubule obstruction. Eighty specimens were subsequently re-obturated with a bioceramic sealer and divided into four subgroups according to the obturation technique used before and after retreatment. A push-out bond strength test was performed on coronal, middle, and apical root sections. Statistical analysis was conducted using SPSS software with a significance level set at p ≤ 0.05. Results: No statistically significant differences were observed between the groups regarding the working time required for root filling removal (p > 0.05). However, significant differences were found in push-out bond strength values among the experimental groups (p < 0.05). Specimens obturated using warm vertical compaction showed significantly higher bond strength compared with the single-cone technique. Scanning electron microscopy observations revealed less residual bioceramic sealer on dentinal walls in the warm vertical compaction group. Conclusions: Within the limitations of this in vitro study, the warm vertical compaction technique demonstrated superior bonding performance and resulted in less residual bioceramic sealer after retreatment compared with the single-cone technique.