Osteonecrosis in patients treated with definitive radiotherapy for squamous cell carcinomas of the oral cavity and naso-and oropharynx.

A group of 381 patients with squamous cell carcinoma of the oral cavity and naso-and oropharynx treated with definitive radiotherapy were analyzed with respect to the incidence and precipitating factors of mandibular osteonecrosis. Elective dental extraction prior to therapy increased the incidence, and dental conservation decreased it. Spontaneous osteonecrosis did not occur with doses less than 6,000 rads in 6 weeks, and was uncommon (1.8%) at doses under 7,000 rads in 7 weeks. At doses over 7,000 rads, osteonecrosis developed in 9%. The incidence was greater in patients with tumors near bone (9.4%) than in those with tumors not next to bone (2.1%).