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Comparison of Lip-Line Cant Change After 1-Jaw and 2-Jaw Surgery

Lee, Ui-Lyong DDS, PhD*; Nam, Ji-Hye DDS, MSD; Choi, Won-Cheul DDS, PhD; Kim, Hye-Won DDS, PhD; Kim, Hye-Jin DDS, MSD; Choi, Young-Jun DDS, PhD

doi: 10.1097/SCS.0000000000005556
Clinical Study: PDF Only

Objectives: The purpose of this study was to compare the lip line cant (LLC) changes after 1 and 2-jaw surgery, and to evaluate the correlations of the craniofacial factors affecting LLC.

Methods: The study subjects were selected (LLC amount within 1.5–6.0°) from among the patients diagnosed with Class III malocclusion who underwent one (n = 20) or 2-jaw surgery (n = 20). Cone beam computed tomography images were obtained immediately before the operation (T1) and 6 months after the operation (T2). Preoperative and postoperative craniofacial measurements were obtained.

Results: The study subjects showed 3.12° LLC on average before undergoing 1-jaw surgery, and their LLC changed to 1.27° after the surgery. As for 2-jaw surgery, the subjects showed 3.38° LLC on average before the surgery and 0.98° after the surgery. LLC at pre-treatment may be more affected by a cant of the occlusal plane in the mandible than maxilla. In the comparison of the value of changes of LLC, the value of 2-jaw surgery was bigger than the value of 1-jaw surgery but the difference was statistically insignificant.

Limitations: This study had a limitation in that the muscles were not considered. And the metal bracket or metal crown and bridge, however, can cause noise and blurring artifacts in CT, which can lead to a low resolution. And the limited number of the patients should be considered.

Conclusions: In correlation analysis, both pre-surgery LLC and change of LLC have correlation with almost all the craniofacial measurement. Lip-line cant of patients with facial asymmetry has higher correlation with mandibular cant than with other cants. To improve the LLC, a surgical plan should be established to minimize the mandibular cant using the computer simulation as well as the maxillary cant.

*Department of Oral & Maxillofacial Surgery

Department of Orthodontics, Dental Center, Chung-Ang University Hospital

Department of Oral & Maxillofacial Surgery, College of Medicine, Chung-Ang University, Seoul, Republic of Korea.

Address correspondence and reprint requests to Ui-Lyong Lee, DDS, PhD, Clinical Associate Professor, Department of Oral & Maxillofacial Surgery, Dental Center, Chung-Ang University Hospital. 224-1 Heukseok-dong, Dongjak-gu, Seoul, Republic of Korea; E-mail:

Received 19 March, 2018

Accepted 8 March, 2019

Ji-Hye Nam, and Ui-Lyong Lee contributed equally to this work.

Young-Jun Choi, Ji-Hye Nam, and Ui-Lyong Lee contributed equally to this work.

The authors report no conflicts of interest.

Supplemental digital contents are available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (

© 2019 by Mutaz B. Habal, MD.