Proximity of maxillary molar palatal roots to adjacent structures for endodontic microsurgery: a cone-beam computed tomography study.

[BACKGROUND] The surgical complexity associated with the palatal roots of maxillary molars was considerably elevated. Previous studies on the relationships between maxillary molar roots and the maxillary sinus or cortical plates have focused on individual root observation without considering the positional relationship between buccal and palatal roots or analysing the surgical pathway of maxillary molar palatal roots. This study aimed to investigate the relationship between maxillary molar palatal roots and adjacent anatomical structures to provide a reference for performing palatal roots endodontic microsurgery.

[METHODS] Anatomical characteristics of the maxillary molar roots were determined using cone-beam computed tomography (CBCT) imaging data from 250 patients. The relationship between the root apex plane (RAP) and the maxillary sinus floor (MSF) was categorized into two types (Type I and Type II) based on whether the RAP was higher than the MSF or not. There were also two subclasses for Type I and Type II, which included Type I-a (RAP was lower than MSF), Type I-b (RAP and MSF were on the same plane), Type II-a (root apex protruded into the maxillary sinus) and Type II-b (root apex did not protrude into the maxillary sinus, but the RAP was higher than the MSF). Distances from the root apexes to the MSF and the cortical bone surface were measured.

[RESULTS] Of 500 teeth, 1352 roots were evaluated. Buccal roots obstruction 3 mm from the palatal root apex were present in almost all maxillary molars. The proportion of Type II-b cases in the palatal roots of three-rooted maxillary molars was significantly higher than that in the mesiobuccal (MB) and distalbuccal (DB) roots (P < 0.01). The distance from the root apex to the MSF increased with age and was significantly longer in females than in males (P < 0.05). The average distance from the apexes of palatal roots to the buccal cortical plate was 10.12 mm for first molars and 10.53 mm for the second molars. When measured through the MB roots, the distance to the buccal cortical plate was significantly shorter than that through the DB roots in the first molars (P < 0.05); however, the opposite was observed in the second molars (P < 0.05).

[CONCLUSIONS] For determining the relationship between maxillary molar palatal roots and adjacent structures, CBCT provides reliable information, which acts as the basis for performing endodontic microsurgery of the palatal roots. Understanding the relationship between the roots of the maxillary molar and neighbouring anatomical structures helps surgeons evaluate potential difficulties, select optimal strategies, and reduce complications.

[CLINICAL TRIAL NUMBER] Not applicable.