Introducing Surface-To-Surface Matching Technique to Evaluate Mandibular Symmetry

Objectives: This study introduced a three-dimensional (3D) surface-to-surface matching technique to evaluate the mandibular symmetry of teenagers and adults with unilateral second molar scissor bite.<br><br>Methods: The targets came from 73 cone-beam computed tomography (CBCT) images with unilateral second molar scissor bite, including teenagers (n=30) and adults (n= 43). 73 images without scissor bite and matched in sex and age were selected as controls. The scans were developed into 3D mandible models and seven mandibular functional unit models. 3D deviation analysis and matching percentages calculation were performed to evaluate the mandibular symmetry.<br><br>Results: Comparisons were made between the study samples and control samples. For teenagers, statistically significant differences were observed in the mandibular body and condylar process. While the alveolar process, mandibular ramus, chin units, coronoid process, and mandibular angle showed no significance. For adults, units including the alveolar process, mandibular body, chin units, mandibular ramus, and condylar process showed significant differences. Only the coronoid process and mandibular angle showed no significance.<br><br>Conclusion: Mandibular asymmetry was observed in both teenagers and adults with unilateral second molar scissor bite. Moreover, compared with teenagers, more mandibular units of adult patients were affected.<br><br>ClinicalSignificance: Based on the surface-to-surface matching technique, the symmetric and morphological information of the mandible can be converted into visual color maps and quantitative descriptions. This method can bring convenience to the study of the growth of mandible, orthodontic treatment and orthognathic surgery design.<br><br>Funding Information: This work was supported by the National Natural Science Foundation of China [grant number 81873710]; the Guangdong Financial Fund for High-Caliber Hospital Construction [grant number 174-2018-XMZC-0001-03-0125/C-05]; the Science and Technology Planning Project of Guangdong Province, China [grant number 2020A0505100034], and the Natural Science Foundation of Guangdong Province, China [2021].<br> <br>Declaration of Interests: The authors declare that they have no competing interests.<br> <br>Ethics Approval Statement: The ethical approval was obtained from the ethics committee of the Affiliated Stomatology Hospital of Sun Yat-sen University, Guangzhou, China (Approval No. KQEC-2021-41-02). This study complied with all regulations and informed consents were obtained. All samples used in the experiment have been de-identified to protect patient privacy.<br>