Densities and sizes of main masticatory muscles in patients with internal derangements of temporomandibular joint obtained by computed tomography.

Computed tomography (CT), due to its excellent resolution capacity, is a suitable method to examine the soft and bony structures of the masticatory system. The aim of this study was to compare densities and sizes of the masseter and medial and lateral pterygoid muscles obtained by CT between the symptomatic and asymptomatic side in patients with internal derangement of the temporomandibular joint (TMJ). The aim was also to correlate these variables to sex and age, duration of the symptoms, diagnosis and dentition. The material consisted of 33 patients (26 women, 7 men, mean age 37 years, range 14-74 years) whose TMJs were examined by CT and whose coronal CT scans were available. Diagnosis in the symptomatic TMJ was confirmed in operation. No statistically significant difference was seen in mean densities and sizes of the masticatory muscles between the symptomatic and asymptomatic side. The duration of the symptoms, however, correlated positively to the density of the lateral pterygoid muscles in patients with complete dentition. The age of the patients in this group correlated negatively to the size of the masseter muscles. It can be concluded that patients with internal derangements of TMJ with a long duration of symptoms have structural changes in their masticatory muscles which are detectable by CT.