Retrospective comparison of mandibular canal and ramus morphology in skeletal class 1, class 2 and class 3 individuals

The aim of this retrospective study was to evaluate the differences in the morphology of the ramus and mandibular canal in sections obtained from CBCT images of individuals with skeletal class 1, class 2 and class 3 jaw relationships for diagnosis and planning before orthognathic treatment. The study included patients aged 18-50 years with skeletal class 2 (12 patients) or class 3 (12 patients) dentofacial deformity diagnosed by clinical and radiologic examination and patients with class 1 (12 patients) dentofacial relationship who presented for routine treatment. DICOM images obtained from pretreatment CBCT were evaluated in three dimensions using Materialise Mimics 25.0.0.550 software. In our study in which we accepted 4 mm above the lower border of the mandibular foramen as the lingula, the distance between the lingula and the mandibular notch was found to be significantly longer in the class 3 patient group compared to the other groups. In the patient group with class 1 skeletal classification, the distance of the canal to the buccal cortical bone, the amount of buccal cortical bone and buccal cancellous bone in the mandibular second molar region was higher than in the mandibular first molar region, while in the mandibular first molar region, the distance of the canal to the inferior cortical bone and the amount of inferior cortical bone were higher than in the mandibular second molar region. In the group of patients with class 2 skeletal classification; the distance of the canal to the inferior cortical bone and the amount of inferior cortical bone in the mandibular first molar region were significantly higher than in the mandibular second molar region. In the group of patients with class 3 skeletal classification, the amount of inferior cortical bone in the mandibular first molar region was significantly higher than in the mandibular second molar region. The distance from the most distal part of the second mandibular molar to the mandibular foramen and the anteroposterior length of the ramus at 4 mm above the lower border of the mandibular foramen were significantly greater in males than in females. At the mandibular first and second molar regions, the distance between the mandibular canal and the inferior cortical bone, and the thickness of cancellous bone buccal and inferior to the mandibular canal at the mandibular second molar region were significantly greater in males than in females.The morphologies of the ramus and mandibular canal in sections taken from CBCT images of individuals with skeletal class 1, class 2 and class 3 jaw relationships were examined and compared, especially for the SSRO technique. Patients with different skeletal structures and different genders may show different morphologic characteristics. Knowledge of these potential anatomical differences and risk factors between patients will help to prevent complications that may occur during surgical procedures and to perform operations faster, safer and more controlled. Key Words: CBCT, orthognathic surgery, mandibular canal morphology, ramus morphology, skeletal class 1, skeletal class 2, skeletal class 3