Comparative Evaluation of Apical Seal Integrity in Retrograde vs. Orthograde Filling Techniques during Endodontic Microsurgery: An in vitro SEM-Based Study

Background: Achieving a reliable apical seal is a critical determinant of success in endodontic microsurgery. Recent advances in bioceramic materials have prompted investigation into their sealing effectiveness when applied via orthograde or retrograde techniques. However, comparative data on their performance remains limited. Aim: To evaluate and compare the apical seal integrity of orthograde and retrograde filling techniques using bioceramic materials through scanning electron microscopy (SEM). Materials and Methods: An in vitro study was conducted on 52 extracted human maxillary central incisors, randomly assigned to four experimental groups (n = 13 per Group). Group 1 received retrograde filling with bioceramic putty; Group 2 received retrograde filling with bioceramic deep putty packing technique (sealer coat + putty). Groups 3 and 4 received orthograde fillings - Group 3 with a bioceramic putty, and Group 4 with a bioceramic deep putty packing technique (sealer coat + putty). Groups 1 and 2 were incubated after retrograde filling; Groups 3 and 4 were incubated before apical resection. All samples were incubated for 7 days at 37° C, then sectioned, and analyzed under SEM to assess number of internal gaps and ratio of marginal gaps in the sample. Statistical analysis was performed using Kruskal-Wallis tests (α = 0.05). Results: The results revealed no statistically significant differences between the orthograde and retrograde techniques in terms of the number of internal gaps or marginal gap ratio (p = 0.126 and p = 0.228, respectively), indicating that the orthograde approach achieved similar sealing performance to the retrograde method. Conclusion: Orthograde application of bioceramic putty demonstrated comparable apical sealing to retrograde techniques, with no statistically significant differences observed between groups. These findings suggest that both orthograde and retrograde approaches using bioceramic materials can provide similar sealing performance in endodontic microsurgery.