Thickness of the soft tissue layers and articular disk in temporomandibular joints with deviations in form

Abstract

115 right temporomandibular joints from Swedish subjects, aged 1 day to 93 years, were examined. Twenty-four of the 102 adult joints exhibited deviations in form. Twenty-two of these affected joints were examined histologically regarding the thickness of the soft tissue in the lateral and mediocentral parts of the condyle and temporal component as well as in the lateral, laterocentral, mediocentral and medial parts of the disk. The thickness of the soft tissue was measured microscopically on sagittal sections in the anterior, middle and posterior parts of the joint components. The soft tissue layers were thickest in the lateral parts of the condyle superiorly (0.6 mm) laterally on the anterior and posterior-inferior slopes of the articular tubercle of the temporal component (0.6 and 0.5 mm) and posteriorly in the mediocentral portion of the disk (3.2 mm). The measurements raised the question of shrinkage of the actual tissues. Therefore a small methodological investigation was undertaken to estimate the shrinkage of tissue due to treatment of specimens of the TMJ with conventional histological techniques. Shrinkage during passage from physiological saline to xylene was significant (p < 0.05), but was less than 10% with 95% certainty. A highly significant negative correlation was found between the amount of undifferentiated mesenchyme and the thickness of the soft tissue layer, a finding clearly suggesting that the undifferentiated mesenchyme is utilized for remodelling of the tissue layers with deviations in form as a result. The occurrence of undifferentiated mesenchyme and the total thickness of the soft tissue layers reflect the functional loading of the joint components.