Background/Objectives: Facial asymmetry is gaining an increasing diagnostic interest in many clinical contexts. Several three-dimensional surface-based methods have been proposed for its assessment; however, they might provide non-equivalent data. Since there is a lack of comparative studies in these terms, this study aims to compare three methods for assessing the asymmetry of the face and facial thirds, thus addressing whether the potential differences can be considered clinically acceptable or not. Methods: Two ‘maxillofacial’ methods based on the trigeminal nerve distribution and one ‘orthodontic’ method based on reference horizontal planes were used to identify the facial thirds on 3D facial models of 80 Italian healthy adults to calculate the asymmetry of the face, and the upper, middle, and lower thirds of the face differently selected by each method. As a measure of asymmetry, the Root Mean Square value was calculated through a mirroring surface-based registration. Intra- and inter-operator reliability was verified for each method. Differences and interchangeability between the methods were tested, respectively, by two-way repeated measures ANOVA (Analysis of Variance) and Bland–Altman and Similarity Percentage model analysis. Additionally, the time required to perform each method was assessed. Results: All methods demonstrated excellent intra- and inter-operator reliability. While the ANOVA analysis found significant differences (p < 0.001) for the majority of facial Regions of Interest between each method, the Bland–Altman analysis revealed that the differences were clinically acceptable (<0.50 mm) for all facial regions between the trigeminal methods, and for the face and the upper third of the face between the orthodontic method, which was revealed to be faster, and the trigeminal ones. The additional similarity percentage model provided visual support for the complete interchangeability of the two trigeminal methods, as evidenced by the lower Coefficient of Variation value. Conclusions: There is no best method for assessing facial asymmetry that applies to all types of clinical settings, as we have shown that different methods may not be completely interchangeable. However, we suggest that the methods based on the trigeminal subdivision can be used interchangeably in contexts where the morpho-functional analysis of maxillofacial regions with different embryological origins is considered. Thus, the clinical setting imposes the choice of one method over another and, as we have pointed out, the consequent comparison of data with those obtained with methods whose interchangeability has been demonstrated.

Purpose: Orthognathic surgery is a cornerstone therapeutic approach for correcting dentofacial deformities; however, its Impact on neuromuscular adaptation remains incompletely understood, particularly regarding different surgical strategies. The aim of this study was to evaluate and compare neuromuscular changes in patients undergoing monomaxillary or bimaxillary orthognathic surgery. Methods: Eighty adult patients treated with combined orthodontic–surgical therapy were included (37 monomaxillary; 43 bimaxillary). A control group of 20 healthy adult subjects with physiological occlusion and no history of orthodontic or orthognathic treatment was included. Surface electromyography (sEMG) of the masseter and anterior temporalis muscles and mandibular kinesiography were performed using standardized protocols at five treatment phases. Electromyographic symmetry indices (Percent Overlapping Coefficient—POC), muscle activity (µV), IMPACT values, and mandibular movement parameters were analyzed. Results: During the presurgical orthodontic phase, both groups showed comparable reductions in neuromuscular activity. Postoperatively, monomaxillary patients exhibited earlier stabilization of sEMG symmetry and a faster increase in IMPACT values, approaching physiological reference ranges at the final follow-up. In contrast, bimaxillary patients showed greater variability and slower functional recovery. Mandibular opening and lateral movements improved in all patients, with more stable kinesiographic patterns observed in the monomaxillary group. Conclusions: Within the limitations of this study, neuromuscular adaptation following orthodontic–surgical treatment appears to be associated with the surgical approach adopted, rather than representing a direct effect of surgical extent. These findings support the role of functional assessment as a complementary component in the management of orthognathic patients.