Clinical study for the characteristics and treatment of masticatory muscle tendon-aponeurosis hyperplasia

Abstract

Masticatory muscle tendon-aponeurosis hyperplasia (MMTAH) is a new disease entity that is characterised by hard severely limited mouth opening without pain. Additionally, MMTAH may be frequently misdiagnosed as bilateral fibrous ankylosis of the temporomandibular joint (TMJ) by clinicians. This study aimed to identify the characteristics and treatment of MMTAH. We selected 22 patients who presented with limited mouth opening and underwent bilateral aponeurectomy and coronoidectomy and 10 healthy participants without limitations in mouth opening. All participants underwent mouth opening training following surgery, and follow-up assessments were performed every 3 months. Mandibular movements were recorded during maximal opening and excursion. Moreover, we conducted surface electromyography (EMG) of the masseter and anterior temporalis muscles during maximum voluntary teeth clenching and used a pressure-sensitive film to assess the occlusal load in the intercuspal position. There were no significant differences in the lateral and protrusive movements of the mandible between patients with MMTAH and their healthy counterparts. Both occlusal force and EMG activity were considerably higher in patients with MMTAH than in healthy participants. In addition, the EMG activity of the anterior temporalis muscle was significantly higher than that of the masseter muscle in these patients. Furthermore, the maximal opening increased markedly and the occlusal force decreased significantly after surgery. MMTAH is characterised by the large occlusal force and EMG activity of the masseter muscles and anterior temporalis, and surgery is a useful treatment for this disorder.