Cancer radiotherapy to the head and neck region results in short- and long-term radiation tissue injuries. Radiation bone injury is a long-term manifestation which could progress to osteoradionecrosis. A case of radiation tissue injury to the periodontium is presented. The possible pathogenesis of these events is described as they relate to the sequential radiographic changes observed over a period of 6 years until the involved teeth were exfoliated. The post-irradiation management of the teeth with advancing periodontal disease in the path of irradiation was by conservative means, including good personal oral hygiene care, scaling and root planing, periodic chlorhexidine irrigation, and topical fluoride application.