Changes in masseter inhibitory reflex responses in patients with diffuse sclerosing osteomyelitis of the mandible.

Masticatory inhibitory mechanisms were studied in 10 patients treated for diffuse sclerosing osteomyelitis of the mandible. Their masseter inhibitory reflex responses were provoked electrically by mental nerve stimulation during maximal clenching of the teeth. The masseter inhibitory reflex was normal in two patients and significantly abnormal in eight patients. The two patients with a normal masseter inhibitory reflex were free of complaints, whereas, of the eight patients with an abnormal masseter inhibitory reflex, two were free of complaints and six had moderate to severe symptoms. In three patients, spasms and involuntary bursts of electromyographic activity were found. The abnormal masseter inhibitory reflex consisted of a loss of early and late components in four patients or a loss of the late component with a normal early one in four patients. These findings seem to support the hypothesis that diffuse sclerosing osteomyelitis of the mandible is a chronic tendoperiostitis caused by muscle overuse. It is suggested that this overuse is caused by central hyperexcitability of trigeminal motoneurons.