Relationship between fossa-condylar position, meniscus position, and morphologic change in patients with Class II and III malocclusion.

OBJECTIVE: To evaluate fossa-condylar-meniscus morphologic changes in patients with skeletal and dental Class III and Class II division 1 and 2 malocclusion to determine which type is related to internal derangement of the temporomandibular joint (TMJ) and whether the variation of TMJ structure is related to a particular type of malocclusion.

MATERIALS AND METHODS: Seventy-two pretreatment orthodontic patients, ranging in age from 10 to 27 years, underwent examination of the right and left TMJs with corrected Schöller's position radiographs. Bilateral TMJ relationships of the fossa-condyle were examined through subjective evaluation and linear and area measurements. In addition, in 20 of the 72 patients, meniscus positions and morphologic changes were imaged with a 0.5 T sagittal magnetic resonance imaging system on the right and left TMJ.

RESULTS: (1) The variation of condyle-fossa positions for identical types of malocclusion was very large. (2) Skeletal and functional Class III malocclusion patients demonstrated significantly more anteriorly positioned condyles. (3) Class II division 1 patients showed concentrically positioned condyles, but with slightly anterior displacement. (4) Class II division 2 patients demonstrated more posteriorly positioned condyles. (5) When condyles were in anterior or concentric positions, meniscus positions and morphology were normal and in concavoconcave shapes. (6) When condyles were in posterior positions, most meniscus positions were in normal or slightly anterior range and their shapes were also concavoconcave. The rest were significantly more anterior and their shapes were abnormal, as evidenced by thickened anterior bands.

CONCLUSION: Class III and Class II division 1 malocclusion demonstrated normal structure and function of the TMJ. Class II division 2 malocclusion was obviously associated with abnormal structure and function of the TMJ.