Variation of coronal temporomandibular diskposition in asymptomatic volunteers using MRI

Objective: The assessment of the variation of normal coronal temporomandibular disk position relative to the condyle in asymptomatic volunteers using magnetic resonance imaging. Material and Methods: 30 symptom-free volunteers (15 women, max. age: 19-74 years, mean age: 32 and 15 men, 22-79 years, mean age: 38) without a history of temporomandibular disorders were examined using a standardized clinical examination protocol. Following this, bilateral magnetic resonance images in both the open and closed mouth position were acquired in the sagittal and angulated coronal planes. The coronal opened and closed mouth images were analysed with computer software. The medial and lateral edges of both disk and condyle were marked for this purpose, always using the slice through the posterior 3 mm of the disk. The distance between these points was measured automatically and was divided by the largest medio-lateral dimensions of the condyle. Results: 5 patients (17%) presented with anterior disk displacement and had to be excluded. Analysis of the coronal closed mouth disk position suggested that a peripheral (medial) position of the disk (relative to the condyle) may be physiological: 21% of the joints showed this kind of disk position. In the open mouth position, the peripheral location of the disk was even more frequent and more pronounced: 83% of the joints exhibited a medial position of the disk relative to the condyle in that plane. Conclusions: In both the closed and open mouth positions, a peripherally (medially) located disk seems to be within the normal range of variation. Additionally, the disk seems to shift even more medially when the mouth is opened.