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Updated: Sep 30, 2026
Quantification of Orofacial Phenotypes in Xenopus
Published on: November 6, 2014
Upper Lip Shape Is Associated With Its Underlying Hard Tissues: A Geometric Morphometric Analysis
Michael D Han1, Cameron Phen2, Alexander Munaretto3
1Associate Professor, Department of Oral and Maxillofacial Surgery, University of Illinois Chicago College of Dentistry.
Background:
Soft tissue prediction after orthognathic surgery is particularly challenging in the upper lip, due to its geometric complexity. Point-based or angle-based methods do not permit shape quantification, while others require substantial resources while still not being reliable for routine clinical dependence.
Purpose:
The purpose was to measure the relationship between the contours of the upper lip and the underlying dentoalveolar structures (DAs), and to measure the influence of sagittal maxillary position, maxillary surgery (MxS), age, sex, and lip thickness using geometric morphometrics.
Study Design, Setting, Sample:
This retrospective study with cross-sectional and cohort components involved subjects planned for orthognathic surgery at University of Illinois Chicago Department of Oral and Maxillofacial Surgery over a 19-month period. Inclusion criteria were presence of cone-beam computed tomography (CBCT) scans, and exclusion criteria were conditions affecting facial soft tissues and soft tissue distortion on CBCT. Upper lip and DA shape were defined by points digitized on CBCT.
Predictor Variable:
The primary predictor variable was DA shape, defined as the configuration of the digitized DA as a 5 × 2 matrix. The secondary predictor variable was MxS (yes/no).
Main Outcome Variables:
The outcome variable was upper lip shape, defined as the digitized upper lip configuration.
Covariates:
Covariates were sella-nasion-A point angle, age, sex, and lip thickness.
Analyses:
Generalized Procrustes and two-block partial least squares (PLSs) analyses were performed to calculate the PLS correlation coefficient (r-PLS) to indicate absent (0) to perfect (1) hard-to-soft tissue covariation (>0.70 defined as high). To measure the influence of the covariates, leave-one-out cross-validation and Spearman's correlation analyses were performed. Level of statistical significance was P < .05.
Results:
In 101 subjects, the mean age was 19.58 years (±5.69), and 67 (66.33%) were female. Covariation was high for the entire sample without MxS (r-PLS 0.77, P < .01) or after MxS (r-PLS 0.80, P < .01). Sella-nasion-A point angle, age, sex, and lip thickness had no association with covariation (P ≥ .2).
Conclusions And Relevance:
Upper lip shape is highly related to that of the DA, with or without MxS. Findings of this geometric morphometrics analysis can be utilized as adjuncts to augment shape-related prediction performances of existing systems.
