Osteoradionecrosis (ORN) of the mandible: a laser Raman spectroscopic study.

Laser Raman spectroscopy has been used in this study to characterize mandibular bone samples from patients who had undergone radiation therapy for oral cancer. The paper discusses spectral changes resulting in osteoradionecrosis (ORN) of the mandibular bone, a serious complication that may occur after radiation therapy. Histopathological studies normally reveal the radiation damage on vascular canals and loss in bone cells, but will not reveal any structural or biochemical changes. All radiation-induced side effects are attributed to this hypovascularity and hypocellularity caused by early- and/or late-delayed effects. Our Raman studies on normal and ORN bone and on bone exposed to radiation, but not in the ORN state, show that irradiation produces immediate structural changes in the inorganic bone matrix with a slight loss in cells. ORN bone, in addition to the structural changes that had already occurred on radiation exposure, shows almost complete loss of cellular components. Since bone tissue is continuously being remodeled (dissolved and rebuilt) under normal conditions, our results suggest that the immediate structural changes in the calcium hydroxy apatite mineral part is not repaired in ORN, due to loss of the highly transient osteoblasts and osteoclasts resulting from destruction of stem cells. The spectral studies also show changes in the organic matrix, which is mostly type I collagen.