Abstract:Objective To investigate the differences in anatomical structures of the mandibular mental foramen region in patients with bony class Ⅱand class Ⅲ malocclusions. Methods Preoperative CBCT images of 256 patients who underwent orthognathic surgery at the Affiliated Stomatological Hospital of Nanjing Medical University from January 2019 to December 2020 were included in the study to analyse the anatomical structure of the mental foramen region. All measurements were analysed using 3D analysis software. Results Ultimately, 466 hemimandibles from 247 patients were included, summing to 244 left and 222 right hemimandible imaging data, and including 176 male hemimandibles and 290 female hemimandibles, as well as 368 young adults and 98 non-young adult hemimandibles. There was no statistically significant difference in the number of left and right hemimandibles included in the study (P>0.05). The number of female patients exceeded male patients, and young adult patients outnumbered non-young adult patients (P<0.01=. The anterior extension length of anterior loop of the inferior alveolar nerve on the right and left sides in patients with bony class Ⅲ malocclusion [(2.31±1.70) mm, (2.22±1.36) mm] and the stretch downward length [(7.67±2.93) mm, (7.66±2.76) mm] were significantly greater than those in patients with bony classⅡ malocclusion [(1.56±0.52) mm, (1.54±0.52) mm] and [(5.93±2.52) mm, (5.95±2.35) mm]. There were also significant differences in the above indicators between patients of different genders (P<0.05). The differences of partial indexes among different age groups were statistically significant. Conclusion There are differences in the anatomy of the inferior alveolar nerve anterior loop of and other mental foraminal regions in patients with different types and genders of malocclusions. Sufficient attention should be paid during orthognathic surgery.