Evaluation of the relationship between mandibular symphysis morphology and lower incisor dentoalveolar compensation mechanism in skeletal class I and class III patients by cone-beam computed tomography

Aim: The aim of this thesis study is to examine the linear and angular aspect of the relationship between mandibular symphysis morphology and lower incisor alveolar bone support in adult Class III patients with the CBCT technique; to compare the morphological differences of the mandibular symphysis formed as a result of natural compensation with adult Class I patients. Matherial and Method: In our study, 15 patients (7 males, 8 females) in the Class I normodivergent group, 15 patients in the Class I hyperdivergent group (9 females, 6 males), 15 patients in the Class III normodivergent group (11 males, 4 females) and 15 patients in the Class III hyperdivergent group (7 females, 8 males) CBCT records of a total of 60 patients were reviewed retrospectively. The mean age of the patients was determined as 20.10±2.97. All measurements and drawings were performed on the midsagittal section of the right lower central tooth. The correlation between angular and linear morphology of the mandibular symphysis and alveolar bone thickness was evaluated in all groups. Results: There was no statistically significant difference between the groups in terms of alveolar bone thickness and linear measurement averages of the mandibular symphysis. Significant differences were observed between the groups in symphysis concavity, basal symphysis inclination, dentoalveolar symphysis inclination and IMPA values, which are angular measurements of the mandibular symphysis. Symphysial thickness, total symphysis height, dentoalveolar symphysis inclination and symphysis convexity angle were significant in the correlation between alveolar bone thickness and mandibular symphysis. Conclusion: There was a positive correlation between dentoalveolar symphysis thickness and alveolar bone thickness in all groups. Total symphysis height was negatively correlated with alveolar bone thickness only in Class I patients. There was no significant correlation between basal mandibular symphysis inclination and thickness and alveolar bone thickness. In conclusion; examination of mandibular symphysis morphology alone is not a sufficient parameter, it is only supportive in order to interpret alveolar bone thickness, especially in Class III patients. Key Words: cone-beam computed tomography, mandibular symphysis, alveolar bone thickness, Class I malocclusion, Class III malocclusion, symphysis inclination