• Natthacha Vamvanij, Chatchawarn Chinpaisarn, Rafael Denadai, Hyung Joon Seo, Betty C J Pai, Hsiu-Hsia Lin, and Lun-Jou Lo.
• Department of Plastic and Reconstructive Surgery and Craniofacial Research Center, Chang Gung Memorial Hospital, Chang Gung University, Taoyuan, Taiwan.
• J Formos Med Assoc. 2021 Sep 1; 120 (9): 1768-1776.

Background/PurposeThree-dimensional computer-assisted orthognathic surgery allows to simulate the space between the mandibular ramus segments, i.e. intersegmental gap, for the correction of facial asymmetry. The purposes of the study were to estimate the screws- and mandible bone-related changes from the early postoperative period to the period after the debonding and to measure the association between the intersegmental gap volume and the screws- and mandible bone-related changes.MethodsThis cone-beam computed tomography (CBCT)-assisted retrospective study assessed the stability of the bicortical positional screw fixations in maintaining the space between the mandibular ramus segments after bilateral sagittal split osteotomy in correction of 31 patients with malocclusion and facial asymmetry. The primary predictor variable was the CBCT-based intersegmental gap volume at early postoperative period (T1). The primary outcome variables were CBCT-based screws- and bone-related measurement changes between the T1 and T2 (at debonding) periods.ResultsNo significant differences were observed in screws-related linear and angular measurements between T1 and T2 virtual models. Some of mandible bone-related linear and angular measurements had significant differences (P < 0.05) between the T1 and T2 images, but with no clinical repercussion such as need of revisionary surgery. The gap volume and the screws- and bone-related changes had no significant correlations.ConclusionThis study contributes to the multidisciplinary-related literature by demonstrating that the bicortical positional screws-based fixation technique in maintaining the three-dimensional-simulated space between the mandibular ramus segments is a stable and clinically acceptable option for correction of facial asymmetry associated with malocclusion, regardless of intersegmental gap size.Copyright © 2021 Formosan Medical Association. Published by Elsevier B.V. All rights reserved.

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