17. Osteonecrosis

Patients with cancer may be liable to either osteoradionecrosis or osteochemonecrosis.

Radiotherapy (RT) in high doses involving the oral cavity, maxilla, mandible and salivary glands may result in several undesired reactions, of which osteoradionecrosis (ORN) is probably the worst. ORN is defined as exposed irradiated bone tissue that fails to heal over a period of 3 months without a residual or recurrent tumour.

The pathogenesis of ORN is not completely understood but it appears in hypoxic, hypovascular and hypocellular tissue, where there is tissue breakdown leading to a non-healing wound. There is no infection, but teeth in the field of irradiation might be the portal of entry for micro-organisms. ORN, as a radiation-induced fibro-atrophic mechanism, involves free radical formation, endothelial dysfunction, inflammation, microvascular thrombosis, fibrosis and remodelling, and finally bone and tissue necrosis.

Risk factors for ORN include:

ORN is three times higher in dentate than in edentulous patients, which has led to a strategy of preventive extractions of all decayed and periodontally compromised teeth before jaw RT. However, since caries and periodontal disease are so common, there is controversy regarding whether such teeth should always be removed. Patients about to be treated with RT do need intensive preventive dental treatment but it is now generally accepted that teeth that really need to be extracted before RT are only those within the high-dose field that are unrestorable or have advanced periodontal involvement. The extractions must be done before RT, and patients who required multiple dental extractions or extensive surgical extractions, or both, can be given eight weeks of pentoxifylline 400 mg twice daily with tocopherol 1000 IU, starting a week before the procedure, as prophylaxis.