In four cases the diagnosis was processed through intraoral bone exposure, relaxation and loss of synthesis material of mandible region, producing mobility of bone stumps and pain. The blades and screws were in the region for osteosínthesis of mandibulotomy used as access for surgery of resection of primary tumor of mouth floor. In one case there was pain and intraoral bone exposure. The average time between radiotherapy and osteoradionecrosis lesion appearing varied in 26.4 months.