A CBCT Evaluation of the Proximity of Mandibular Molar Roots and Lingual Cortical Bone in Various Vertical Facial Patterns and Factors Related to Root-Cortical Bone Contact

Abstract

The objective of this study was to assess the proximity of the mandibular molar roots and the lingual cortical bone in patients with various vertical facial patterns and determine factors related to root-cortical bone contact. A total of 145 patients (84 males, 61 females, mean age: 22.0 ± 1.76 years) were assigned to hypodivergent (36 patients), normovergent (80 patients) and hyperdivergent (29 patients) groups based on their facial height ratio. Cone-beam computed tomography (CBCT) images were used to measure the distance between the mandibular molar roots and the lingual cortical bone, and any instances of root-cortical bone contact were identified. The study investigated the correlation between the contact of the mandibular molar roots with the lingual cortical bone and several variables, including sex and cephalometric measurements. The distance between the mandibular molar roots and the lingual cortical bone was significantly shorter in the hyperdivergent group than in the hypodivergent group (p < 0.05). Of the total root-cortical bone contact, 87.6% was observed in the mandibular second molars, and the distal roots of the mandibular second molars had the highest contact rate at 43.1% in the hyperdivergent group (p < 0.05). Among the evaluated variables, only the distance between the distal root apex of the mandibular second molar and the mandibular plane was found to be associated with contact of the mandibular molar roots with the lingual cortical bone. An increase of 1 mm in this distance was associated with a 22% decrease in the likelihood of contact between the mandibular second molar roots and lingual cortical bone (p < 0.001). Given the proximity and high contact ratio between the mandibular molar roots and lingual cortical bone, it is recommended that these structures be evaluated using CBCT before planning molar distalization or intrusion in hyperdivergent patients.