Method: Subjects consisted of 213 adult female orthodontic patients. Before orthodontic treatment, lateral cephalograms and TMJ magnetic resonance imaging (MRI) was obtained and subjectvie histories of TMJ symptoms were recorded. Subjects were divided into two groups according to existence of TMJ symptoms. Each group was subdivied into three sub-groups based on TMJ DD status using TMJ MRI: bilateral normal disk position (BN), bilateral disk displacement with reduction (DDR), and bilateral disk displacement without reduction (DDNR). Two-way analysis of varience was used to analyze differences in dentofacial characteristics with respect to TMJ DD status and TMJ symptoms.
Result: : We found that more than half of asymptomatic patients had TMJ DD. Sixty-two % of asymptomatic subjects had TMJ DD and 26.5% of symptomatic subjects showed normal TMJ status. Regardless of clinical TMJ symptoms, subjects with TMJ DD had decreased ramus height, decreased mandibular body length, and backward rotation of the ramus. These dentofacial characteristics became more severe as TMJ DD progressed to DDNR.
Conclusion: This study showed that TMJ DD is associated with differences in dentofacial morphology, irrespective of the existence of TMJ symptoms.