Introduction  Lips play a fundamental role in facial attractiveness and in decisions pertaining to orthognathic surgery. Objective  To assess the upper lip changes following Le Fort I osteotomy for maxillary advancement and/or impaction. Methods  In the present retrospective non-randomized clinical trial, we evaluated 3 groups of patients who underwent Le Fort I osteotomy of the maxilla. Group 1 (n = 35) underwent maxillary advancement, group 2 (n = 14), maxillary impaction, and group 3 (n = 11) was submitted to both maxillary advancement and impaction. The lip thickness of all patients was measured preoperatively, and the participants in each group were categorized into two subgroups: thin (< 12 mm) and thick (> 12 mm) lip. The primary (before orthognathic surgery) and final (after orthodontic bracket removal) lateral cephalograms of the patients were analyzed using the Dolphin software. Comparisons were made using the paired t -test and linear regression in the IBM SPSS Statistics for Windows software. Results  The length of the upper lip increased by 1 mm ( p  = 0.012) on average following maxillary advancement, and it decreased by 0.43 mm ( p  = 0.24) on average following maxillary impaction. In the maxillary advancement group, the change in angulation of the incisors predicted the incisal display ( p  = 0.03). In the maxillary impaction group, skeletal changes in the vertical dimension predicted changes in upper lip length ( p  = 0.033). Conclusions  Le Fort I osteotomy for maxillary advancement significantly increases the length of the upper lip. The assessment of lip thickness prior to surgery can help predict the postoperative results. Changing the angulation of the incisors can predict the incisal display. In maxillary impaction, skeletal changes in the vertical dimension can predict the changes in the length of the upper lip.

BACKGROUND: Upper lip morphology is essential in diagnosis and treatment of orthodontics and orthognathic surgery. This study is aimed to evaluate the association between upper lip characteristics (ULCs) and skeletal patterns (SPs).
METHODS: 2079 patients were involved and grouped by sagittal and vertical. Class I, II, and III were identified by ANB angle, while normodivergent, hyperdivergent, and hypodivergent were identified by Facial Height Index and Sum of Angles. ULCs were evaluated by superior sulcus depth, nasolabial angle, upper lip length, basic upper lip thickness, and upper lip thickness. Confounders including demography, malocclusion, upper incisors, and upper lips were adjusted by multivariate linear regression to identify the association between ULCs and SPs. Group differences were evaluated with analysis of variance and Chi-square test.
RESULTS: The mean value of ULCs and prevalence of SPs were explored in the Western China population. ULCs were significantly different in various sagittal, vertical, and combined SPs. Superior sulcus depth was negatively related to Class II, and positively related to Class III and the hypodivergent pattern after adjusted by confounders.
CONCLUSIONS: ULCs significantly varied among different SPs, while only superior sulcus depth was independently associated with SPs, indicating superior sulcus depth is the only ULC that might be significantly corrected by intervention of skeletal growth.