Disc position in clinically asymptomatic, pretreatment adolescents with Class I, II, or III malocclusion : A retrospective magnetic resonance imaging study.

OBJECTIVE: To test the null hypothesis that children with Class I, II, and III malocclusions who have not undergone orthodontic therapy present with displaced discs.

MATERIALS AND METHODS: This study relied on retrospective material consisting of 76 unilateral left sagittal-oblique temporomandibular joint (TMJ) magnetic resonance imaging (MRIs) and lateral cephalometric radiographs taken in maximum intercuspal position in patients with clinically symptom-free and orthodontically untreated Class I (n = 30; 19 girls and 11 boys), Class II (n = 26; 10 girls and 16 boys), and Class III malocclusion (n = 20; 5 girls and 15 boys). The mean ages of patients with Class I, II, and III malocclusions were 10.55 ± 0.81, 11.71 ± 0.31, and 8.98 ± 1.80 years, respectively. Study groups were compared with one-way ANOVA analysis or Welch ANOVA test. Differences were evaluated via the Tukey HSD or Games-Howell test.

RESULTS: Disc-condyle positions were almost within normal limits in Class I malocclusion. The disc was positioned anteriorly relative to the condyle (p < 0.05) and the condyle positioned posteriorly in the glenoid fossa in Class II malocclusion (p < 0.05). The disc was positioned slightly anteriorly relative to the condyle (p < 0.05) and the condyle was positioned posteriorly in the glenoid fossa in Class III malocclusion. Disc-condyle positions were observed to be almost identical in all three malocclusion classes.

CONCLUSION: Disc-condyle position was nearly normal in patients with Class I malocclusion. Nevertheless, a Class II malocclusion is more apt to reveal anterior disc displacement than a Class III malocclusion.