Radiotherapy-induced mandibular bone complications.

The mandible is among the bones most frequently affected by irradiation. The most severe post-radiation injury of the mandible is osteoradionecrosis (ORN). Conflicting data have been reported on the incidence of this complication, its aetiology and management. The incidence of mandibular ORN in head and neck cancer patients managed with radical or postoperative irradiation, has varied widely in the literature from 0.4% to 56%. The interpretation of data derived from particular series are difficult due to the different scoring methods and classification systems used for the evaluation of post-radiation bone damage. Although ORN occurs typically in the first three years after radiotherapy, patients probably remain at indefinite risk. The diagnosis of ORN is principally based on the clinical picture of chronically exposed bone. Radiological symptoms include decreased bone density with fractures, cortical destruction and loss of spongiosa trabeculation. Numerous factors that may be associated with the risk of ORN include treatment-related variables (for example, total radiotherapy dose, biologically effective dose, photon energy, brachytherapy dose rate, combination of external beam irradiation and interstitial brachytherapy, field size, fraction size, volume of the mandible irradiated with a high dose), patient-related variables (like deep parodontitis, pre-irradiation bone surgery, bad oral hygiene, alcohol and tobacco abuse, bone inflammation, dental extraction after radiotherapy) and tumour-related factors (tumour size or stage, proximity of the tumour to bone, anatomic tumour site). Primary management of post-radiation bone lesions include conservative modalities such as saline irrigations, antibiotics during infectious episodes, topically applied antiseptics, gentle sequestrectomy and removal of visibly loosened bone elements as well as treatment with hyperbaric oxygen (HBO). Surgery is reserved for persistent ORN and includes radical resection of the lesion(sequestrectomy, hemimandibulectomy etc.) with reconstruction. In recent years the introduction of preventive oral hygiene measures and meticulous dental evaluations before and after irradiation, improvement in radiotherapy techniques and the development of reliable diagnostic and therapeutic procedures have resulted in a decreased incidence of ORN. Nevertheless, given the severe impact of ORN on patient quality of life, research should be continued to further ameliorate this problem.