The effects of TMJ symptoms on skeletal morphology in orthodontic patients with TMJ disc displacement

Objective. The aim of this study was to investigate the effects of temporomandibular joint (TMJ) symptoms on skeletal morphologies of orthodontic patients with TMJ disc displacement (DD). Materials and methods. The sample consisted of 197 women seeking orthodontic treatment. The subjects were divided into two groups according to the presence of TMJ symptoms: the presence and absence of TMJ symptoms. Each group was sub-divided into three groups based on magnetic resonance images of bilateral TMJs: bilateral normal disc position (BN), bilateral disc displacement with reduction (DDR) and bilateral disc displacement without reduction (DDNR). Seventeen variables from lateral cephalograms were analyzed by two-way analysis of variance to identify differences in skeletal morphologies with respect to TMJ symptoms and TMJ DD status. Results. Patients with TMJ DD were more likely to have short ramus height, short mandibular body length and backward positioning of the ramus and mandible. These skeletal morphologies became more severe as TMJ DD progressed to DDNR. However, the skeletal morphologies associated with TMJ DD were not significantly different between symptomatic and asymptomatic patients. As a result, patients with TMJ DD had backward positioning and clockwise rotation compared to those with bilateral normal TMJs, irrespective of the presence of TMJ symptom. Conclusions. This study suggests that TMJ DD is associated with altered skeletal morphology, but TMJ symptoms do not significantly influence the relationships between TMJ DD and skeletal morphology.