Retreatability of root canals filled with gutta percha and a novel bioceramic sealer- a scanning electron microscopy study

Objective: To compare effectiveness of 5% acetic acid, 10% formic acid, and chloroform used adjunctively with a rotary retreatment system in removing a premixed calcium-silicate sealer (Ceraseal) and gutta-percha from root canals, using scanning electron microscopy (SEM) to quantify residuals across canal thirds. Materials and methods: Thirty-six extracted single-rooted anterior teeth were instrumented, obturated (single-cone GP + Ceraseal), and stored for two weeks. Specimens were retreated with HyFlex Remover files and randomly assigned (n = 9/group) to: G1-5% acetic acid; G2- 10% formic acid; G3-chloroform; G4-distilled water (negative control). Two milliliters of test solution were used with repeated instrumentation until patency; canals were then irrigated with saline and dried. Roots were split; standardized SEM images (×1000) of coronal, middle, and apical thirds were scored. Results: Intragroup, residuals increased apically in all solvent groups: in G1, apical > middle > coronal (all p = 0.021); in G2, apical > coronal/middle (p = 0.021); in G3, apical > coronal (p = 0.021); G4 showed no significant intragroup differences. Intergroup, coronal third: G1 had significantly lower residuals than G3 and G4; G1 ≈ G2; G2 ≈ G3 ≈ G4. Middle third: G1 and G2 < G4 (p = 0.021); no other pairwise differences. Apical third: no significant between-group differences. Conclusions: When combined with HyFlex Remover files, 5% acetic and 10% formic acids enhanced removal of Ceraseal/gutta-percha, particularly in coronal third; 5% acetic outperformed chloroform coronally. In middle and apical thirds, acidic solvents, chloroform, and water yielded broadly comparable outcomes.