To evaluate structural loss during selective re-treatment of mandibular incisors between conventional and static guided technique using customized re-treatment bur - an in vitro study

Purpose: The present study aimed to compare and evaluate the extent of structural loss during selective endodontic retreatment of mandibular incisors using conventional burs versus customized retreatment burs.
Methods: Twenty-six extracted mandibular anterior teeth exhibiting two canals, confirmed through intraoral periapical radiographs in the mesiodistal dimension, were selected for the study. Access cavity preparation was selectively performed for buccal canal and lingual canal was intentionally missed. Bio-mechanical instrumentation and obturation was completed for buccal canal following copious irrigation with 5.25% sodium hypochlorite, 0.9% saline, and 17% EDTA. The lingual canals were intentionally left untreated. Access cavity was restored using composite resin. Preoperative cone-beam computed tomography (CBCT) scans were acquired for all samples. The specimens were then randomly allocated into two groups:
• Group A: Selective retreatment performed using a customized long-shank parallel round bur guided by a static 3D-printed template to locate the missed lingual canal.
• Group B: Selective retreatment carried out using a conventional small round bur (#1) under 10× magnification.
Following the retreatment procedures, postoperative CBCT scans were obtained. Volumetric substance loss was calculated using image analysis software by comparing pre- and postoperative scans.
Results: Group A exhibited significantly lower volumetric structural loss than Group B. The use of a customized guided bur enabled precise localization of the untreated canal with minimal removal of dentinal tissue.
Conclusion: Selective endodontic retreatment of mandibular anterior teeth with two canals, when performed using a guided endodontic approach with a customized bur, results in significantly reduced structural loss compared to the conventional technique. This method enhances accuracy and preserves tooth structure, offering a clinical advantage in retreatment cases.

Keywords: Mandibular anteriors with 2 canals, selective retreatment, static guided endodontics.