Relationship of TMJ Articular Soft Tissue to Underlying Bone in Young Adult Condyles

Abstract

This investigation used a histological model to study the relationship of articular soft-tissue thickness and contour to the underlying bone in the TMJ condyle of young adults. The usefulness of selected dental and demographic factors in the prediction of the articular soft-tissue thickness and contour was also tested. One sagittal histological section was studied from the lateral, central, and medial thirds of 53 left mandibular condyles. Outline tracings of the articular and compact bone surface were divided into anterior, superior, and posterior sectors for the study of curvature measured by the overlaying of a template of a harmonic series of arcs. The thickness and composition of the articular tissues were measured in each sector by light microscopy. The fibrous connective tissue layer always maintained the articular surface, even in the absence of a cartilage layer. The histological character, including the presence or absence of cartilage, rather than the overall tissue thickness, was considered to be a more useful marker of functionally stimulated changes in the joint. Articular soft-tissue thickness was not related to surface deviation in form and was not correlated with age in this young adult sample. Reduced soft-tissue thickness in the anterior part of the condyle was more common in cases with lack of molar support. Dental attrition was not a useful predictor of soft-tissue thickness. Compact bone contour correlated with soft-tissue contour in the superior (r = 0.816) and posterior (r = 0.808) sectors, explaining only 64% of the variance, but not in the anterior sector (r = 0.265). Thicker or thinner articular soft tissue was not predictable by the underlying compact bone contour or thickness. Therefore, the clinician should not automatically assume that the radiographic osseous image represents the actual articular surface.