Effects of therapeutic radiation on microstructure of the human mandible.

Mandibular bone from eight patients who had received therapeutic radiation (6,000-7,200 rads) for intra-oral cancer was obtained at surgery (1 month to 9 years after radiation) and compared histologically with non-irradiated mandibular bone from five subjects. Measurements made on the internal remodeling process of cortical bone included the extent of internal surface and the fraction indicating resorption, and the proportions of osteones which were incomplete (less than 3/4 filled with matrix), complete, and plugged. Appreciable differences were observed in all parameters except plugged osteones. The findings suggested early cessation of osteogenesis, and somewhat later cessation of resopriton, without subsequent resumption of either process. The histologic appearance of the osteoblasts, osteoclasts, and osteones was in accord. Microfractures found in the irradiated bone were not seen to have healed. Radiation damage to the osteoprogenitor cells is postulated.