Magnetic resonance imaging on TMJ disc thickness in TMD patients: a pilot study.

Statement Of Problem: Studies of temporomandibular joint (TMJ) discs removed from autopsy specimens and in surgery indicate that they are often thicker in patients with temporomandibular disorders (TMDs). Disc thickness may also change when the condyle moves in and out of the joint fossa during opening and closing.

Purpose: The purpose of this pilot study was to test the hypothesis that the TMJ disc thickness is greater in TMD patients than in healthy subjects and is affected by the degree of jaw opening.

Material And Methods: Magnetic resonance images (MRI) were made of the TMJs in young volunteers, 9 asymptomatic subjects and 9 TMD subjects, at closed and at 10-, 20-, and 30-mm open positions. The thickness of the anterior and posterior bands of the discs and the intermediate zones was measured and compared between TMD and control groups, and between closed and opened positions, using the repeated-measures method in general linear model (alpha=.05).

Results: The hypothesis that the disc was thicker in the TMD than in the control group was supported with respect to the anterior band and intermediate zone (P<.046), but not with respect to the posterior band. The hypothesis that the thickness is affected by the degree of jaw opening was only supported for the posterior band, where it increased during opening in both groups (P<.005).

Conclusions: The results indicate that the anterior band and the intermediate zone of the TMJ discs are thicker in TMD patients than in healthy subjects. The posterior band thickness increases with mouth opening in both asymptomatic and TMD subjects.