Associations Between Different Types of Malocclusion, Functional Disturbances, and Temporomandibular Disorders: A Case–Control Study

Background: Temporomandibular disorders (TMDs) are multifactorial conditions frequently encountered in orthodontic practice, and the independent associations of occlusal and structural variables remain unclear. This case–control study constructed a multivariable model integrating clinical, cephalometric, panoramic, and functional variables to examine their associations with TMD, diagnosed according to the DC/TMD Axis I protocol. Fifty patients with TMD and 50 non-TMD controls were consecutively recruited between October 2024 and December 2025. Occlusal characteristics, lateral cephalometric measurements, and Kjellberg panoramic symmetry indices (SI1/SI2) were assessed using standardized protocols. Candidate variables were initially explored using univariable analyses with false discovery rate adjustment, followed by multivariable Firth penalized logistic regression to reduce small-sample bias and separation. Mandibular deflection (OR = 3.57, 95% CI 1.54–9.09) and deviation (OR = 4.35, 95% CI 1.69–12.50) demonstrated the strongest independent associations with TMD, while SI1 asymmetry (<90%) became significant after multivariable adjustment (OR = 3.57, 95% CI 1.08–14.29). The final model showed apparent discrimination within the study sample (AUC = 0.822; 95% CI: 0.742–0.902). However, this value was calculated using the same dataset and should not be interpreted as validated model performance or compared to other studies. The observed SI1 effect should be interpreted cautiously, as it may reflect model instability due to the relatively small sample size. Within the limitations of this case–control design, functional disturbances showed stronger associations with TMD than static structural variables; however, external validation is required before clinical application.