Analysis of TMJ Structural Abnormalities in Patients With Different Types of Malocclusions

Objectives: Structural abnormalities of the temporomandibular joint (TMJ) will affect orthodontic treatment. So we analyzed common issues of TMJ structure among patients with different types of malocclusions.
Methods: 312 patients need orthodontic treatment were randomly selected, including 98 males and 214 females, ranged from 10 to 55 years old. Conventional anteroposterior, lateral cephalometric radiographs and panoramic radiographs before treatment were obtained for the study subjects. Magnetic resonance images of the subjects’ TMJs were acquired, and the subjects’ TMJ structures were assessed.
Results: Among the entire subject population of 312 patients, 206 patients (66.03%) presented with TMJ structural abnormalities. In particular, TMJ structural abnormalities were found in 57 of the 98 examined male patients (58.16%) but were significantly more common among female subjects, occurring in 149 out of the 214 examined female patients (69.63%). Sagittal analysis revealed that an abnormal TMJ structure was present in 60.71% of skeletal Class I patients, 72.97% of skeletal Class II patients, and 64.04% of skeletal Class III patients. Horizontal analysis indicated that an abnormal TMJ structure was present in 78.18% of patients with mandibular deviation to the left, in 60.87% of patients without mandibular deviation, and in 85.19% of patients with mandibular deviation to the right. Vertical analysis revealed that an abnormal TMJ structure was present in 77.12% of high-angle patients, 56.88% of average-angle patients, and 70.59% of low-angle patients.
Conclusions: TMJ structural abnormalities were present in a high proportion (approximately two-thirds) of orthodontic pretreatment patients. The incidence of structural TMJ abnormalities was significantly higher in female patients than in male patients. In the sagittal direction, the highest incidence of structural TMJ abnormalities occurred in skeletal Class II patients. In the horizontal direction, the lowest incidence occurred in patients without mandibular deviation. In the vertical direction, the lowest incidence occurred in the average-angle patients.