A histochemical survey of the human temporomandibular joint disc of patients with internal derangement without reduction.

This study describes, microscopically, the pathologic findings correlated to malpositioning of the human temporomandibular joint disc. The specimens studied consisted of 21 discs removed from patients affected by temporomandibular joint arthropathy. The specimens were cut longitudinally and were fixed overnight in 10% neutral-buffered formalin. They were embedded in paraffin with anatomic orientation preserved. Three- to 4-microm thick sections were cut according to routine procedures and mounted on slides. Then they were stained with Goldner-modified-Mallory staining used for morphologic study at light microscopy. Abnormal collagen fiber arrangements, fragmentation of collagen fibrils, new vessel formation, meniscal tears, mucoid degeneration of the disc matrix, chondrocyte-like cells proliferation, sometimes with clonal aggregation, and hyalinization were detected in temporomandibular joint disc specimens with internal derangement, although with a different extent. From our observations, it seems that in most cases, the temporomandibular joint disc responded to internal derangement without reduction with a fragmentation of collagen fibers because hyalinization of disc matrix occurred very rarely. Moreover, disc derangement without reduction is characterized also by a change in cell population phenotype.