Patients who have had their jaws irradiated as part of management of head and neck malignancy are at risk of osteoradionecrosis (ORN) following tooth extraction. Thirty-seven patients with a history of irradiation to the jaws were managed during a four year period. Twenty-nine patients received hyperbaric oxygen therapy (HBO) consisting of 20 treatments before surgery and ten treatments a f t e r. Only one (4 per cent) developed ORN. Seven patients who did not have HBO and one who did (15 per cent) developed ORN. The need for prophylactic treatment with HBO is discussed. It is recommended that prophylactic HBO is used prior to surgery for irradiated facial bones.
Hyperbaric oxygen has shown consistent benefit in treating patients with delayed radiation injury. It has also had success in preventing radiation injury in some instances. Additional study in identifying patients at risk for injury and delivering hyperbaric oxygen with prophylactic intent to prevent these injuries appears to be promising. Additional approaches to applying hyperbaric oxygen as a radiosensitizer also deserve further study. No convincing evidence exists to support concerns that hyperbaric oxygen enhances or stimulates malignant growth.
Object Relationship Notation (ORN) is a declarative scheme that allows a variety of common relationship types to be conveniently specified to a database management system (DBMS), thereby allowing their semantics to be automatically enforced by the DBMS. ORN can be integrated into any data model that represents binary associations or DBMS that implements them. We give a brief description of ORN syntax and semantics and provide algorithms that can be used to implement ORN. These algorithms must deal with the presence of association cycles in the database. We explore in detail the problems caused by such cycles and how ORN and its implementation deal with them, and we show that ORN semantics are noncircular and unambiguous.