Anatomic determination of the mesiobuccal root resection level in maxillary molars.

Surgical endodontics involving root resection/apical fill are often performed when retreatment by orthograde endodontic procedures are not possible. Because of the potential presence of accessory canals within the root, a preferred minimal root resection level should be investigated for the removal of the majority of these canals. One hundred fifty-three extracted, uninstrumented, mesiobuccal roots from first and second maxillary molars were examined for the presence of accessory canals, canal isthmus, and canal wall thickness. Three hundred ninety accessory canals were identified, with 80% of these canals located within 3.64 mm of the apex of the tooth. Canal isthmus was often not evident until 3.12 mm of the root was resected, with canal wall thickness only approximating 1 mm thick. The observations here suggest a minimal resection level to 3.6 mm for accessory canal incidence, canal isthmus detection, and canal wall thickness and provide a better understanding of maxillary mesiobuccal (MB) root anatomy for retrograde root resection/apical filling.