The function of discomuscular relationships in the human temporomandibular joint.

The aim of this morphological study was to investigate whether muscle tissue attaches directly to the discus articularis of the human temporomandibular joint (TMJ) and to indicate the probable significance of such attachments for the function of this articulation. The macroscopic and microscopic findings were derived from fixed and unfixed human TMJ of varying ages and genders, whereby the functional maturity of the masticatory apparatus was taken into consideration. To date, the results of this study show that aside from fibers originating from the superior venter of the m. pterygoideus lateralis, additional muscle or connective tissue fibers from the perimysium of the m. masseter insert to varying extent in the disc. The same is true for the m. temporalis, which is also directly connected to the disc via muscular or fibrous elements, or indirectly via fibers from the m. masseter. The insertion of the m. pterygoideus lateralis is always in the medial portion of the discus articularis and those of the mm. temporalis and masseter, respectively, in the middle and lateral portions of the disc. It is highly probable that a direct force transfer through the mm. temporalis and masseter to the articular disc takes place, and that these muscles contribute to the movement of the disc during jaw movement, whereas the size and form of the muscle insertions are subject to a great deal of individual variation. Differences were observed between immature and mature TMJ as well as between partly and fully toothed masticatory apparatuses.