Three-dimensional evaluation of facial asymmetry and its association to occlusal and muscular imbalance in young women.

Background: Diagnosing asymmetries and restoring functional balance are challenges in facial rehabilitation and aesthetic procedures. This cross-sectional observational study aimed to evaluate whether occlusal imbalance and the electromyographic activity of the masseter and temporalis muscles in young women may be associated with facial asymmetry.

Material and methods: Fifty women (mean age ± standard deviation: 22.5 ± 2.7), without temporomandibular dysfunction and with balanced facial profiles, were divided into two groups categorized by receiver operating characteristic analysis: symmetric (n=25) and asymmetric (n=25). The variables included the evaluation of asymmetry through clinical examination, quantification of asymmetry using stereophotogrammetry through the root mean square method, asymmetry of occlusal contacts, and electromyographic activity of the masseter and temporal muscles in both latero-lateral and antero-posterior directions. The mean asymmetry indices were compared using Welch's t-test and the Mann-Whitney test. The impact of occlusal and muscular imbalance on facial asymmetry was assessed through linear regression analysis.

Results: A significant difference was observed between the groups in the asymmetry of occlusal contacts, with a considerable effect size (p<0.01 - Cohen's d=0.73). The imbalance in the electromyographic activities of the masseter and temporal muscles was considered a predictor of facial asymmetry (F=4.00, p<0.02, R²=0.15).

Conclusions: Occlusal imbalance and electromyographic activity of the masseter and temporal muscles are associated with facial asymmetry. Key words:Facial asymmetry, masticatory muscles, stereophotogrammetry, occlusion, electromyography.