Mandibular Asymmetry, Generalized Joint Hypermobility, and Temporomandibular Disorders in Pre-Orthodontic Growing Individuals: A Cross-Sectional Clinical–Radiographic Study

Objective: This study aims to explore the relationship between mandibular asymmetry (MA), generalized joint hypermobility (GJH), and temporomandibular disorders (TMD) in pre-orthodontic growing individuals. Methods: This cross-sectional study included 74 pre-orthodontic individuals aged 8–16 years. Mandibular asymmetry was evaluated through posteroanterior cephalometric analysis, using menton deviation ≥ 4 mm as the threshold for asymmetry. GJH was assessed using the Beighton Score (BS ≥ 4 = GJH-positive), while TMD was diagnosed based on Axis I of the DC/TMD. Associations among the variables were tested using a chi-square test (p < 0.05; SPSS v.24). Results: The study included 74 patients (25.7% males; mean age 12.7 ± 2.16 years). The GJH-positive group (n = 41) showed a higher prevalence of TMD (85.4%) compared to the GJH-negative group (51.5%) (p = 0.002). MA was more frequent in the GJH-positive group (68.3% vs. 45.5%; p = 0.041). A significant association was also found between TMD and MA (71.2% vs. 27.3%; p < 0.001). In both groups, patients with TMD were more likely to present MA (GJH-negative p = 0.022; GJH-positive p = 0.046). Conclusions: MA emerged as a key factor associated with the presence of TMD, particularly when combined with GHJ. These findings indicate that MA alone is significantly related to the occurrence of TMD, regardless of joint hypermobility status. However, the risk appears to be amplified in individuals who also present with GJH. Effect size analysis indicated that most associations were small, with only the one between TMD and MA reaching a moderate level. This highlights the importance of evaluating statistical significance in the context of effect size to better assess clinical relevance.