Genesis—progression of early jaw osteoradionecrosis in head and neck cancer survivors: dynamics of independent but interconnected factors

Purpose Long-term head and neck cancer survivors are few, but always exposed to a risk of mandibular osteoradionecrosis (ORN) despite the use of appropriate dose-volume constraints in today’s radiotherapy. Here, ORN development is approached from another look, in an attempt to explain its complexity. Definitions Early ORN is best defined by length of the mucosal defect (<2 teeth long) and radiological assessment of the depth of areas of bone resorption (lysis below the level of the inferior alveolar canal) in the radiotherapy volume. Technical improvements have greatly reduced the incidence of ORN, but a lifelong risk remains and requires long-term follow-up. Causal factors Pathogenic hypotheses have evolved over time from the “radiation-trauma-infection” triad to the 3H theory of “hypoxia-hypocellularity-hypovascularity”, and then radiation-induced fibro-atrophy of the bone. ORN is a dynamic process combining interacting causal factors that worsen each other over time: (a) radiation-induced fibro-atrophy of the bone and its related radiotherapy technical parameters; (b) periodontal disease/dental trauma and their related questions on optimal timing of pre- or post-radiotherapy extractions and how many teeth; (c) infection/oral microbiota and their related mechanically inaccessible bone sequestra (residual bacteria); (d) vascular factors from capillary network destruction to artery stenosis of irradiated branches and the carotid trunk. Conclusion Symptomatic medical care focusing on comorbidity parameters and devitalized tissue removal is not sufficient to protect patients against ORN. These new insights should help to treat early ORN through concomitant control of these causal factors and best dental care.