Amianthoid fibres in muscle tissue associated with temporomandibular joint ankylosis.

The masseter and temporalis muscles were studied ultrastructurally in 3 patients having extra and intra-articular ankylosis of the TMJ. Amianthoid fibres (thick collagen fibres) varying from 280-430 nm in diameter were found in the connective tissue of both muscles. These fibres appeared to form by fusion of collagen fibrils of normal thickness rather than representing an active dynamic process. The presence of amianthoid fibres in these muscles may account for the restricted mouth opening associated with TMJ ankylosis and could be of some value in future management of this condition.