Osteoradionecrosis
The pathophysiology of ORN is fairly complex and involves drastic changes to bone tissue as a result of DNA damage and cell death caused by radiation treatment.
[6] Certain risk factors including the size and location of tumor,[7][8] history of smoking[2] or diabetes,[7] and presence of dental disease[3][9] can affect the chances of developing ORN.
Current prevention strategies are aimed at avoiding excess doses of radiation as well as maintaining excellent dental hygiene.
[12] However, excessive radiation doses can cause even normal cells to be overwhelmed by DNA damage and lead to local tissue changes and necrosis.
[3] In 1983, Robert E. Marx, a prominent oral and maxillofacial surgeon, refuted the notion that trauma and infection were requirements in the development of ORN.
[15] In addition, radiation causes injury to the endothelial cells of local vasculature, creating a hypovascular environment which leads to decreased oxygen delivery resulting in hypoxic tissues.
[3][15] Initial reports by Marx and others showing that treatment with hyperbaric oxygen (HBO) prevented ORN helped support this theory.
[17] However, later studies began to raise doubts about the effectiveness of HBO therapy and question whether Marx's theory was comprehensive enough to guide treatment.
[18] Current understanding is guided primarily by the work of Delanian and Lefaix, who proposed the radiation-induced fibroatrophic (RIF) process.
[3] In the constitutive organized phase, fibroblasts persist and are converted to myofibroblasts by these same cytokines, that begin to fibrous extracellular matrix (ECM) within the affected bone.
[19] Finally, during the late fibroatrophic phase, the affected bone becomes hypocellular as myofibroblasts begin to die and leave behind weak, fibrotic tissue.
[19] Ultimately, these tissues are fragile and susceptible to damage by trauma or infection with little ability to repair or defend themselves due to the lack of vasculature caused during the pre-fibrotic phase.
[19] Given this understanding of the pathophysiology of ORN, current treatments are targeted at decreasing inflammatory cytokines and reducing free radical damage to DNA.
[19][20] Risk factors for osteoradionecrosis include: The staging system can be useful as a baseline reference for management after a definitive diagnosis of ORN has been established.
Patients undergoing head and neck radiotherapy may experience a sore mouth, therefore a soft bristle toothbrush may be preferred.
[28] The patient’s oral condition needs to be taken into consideration and tailored accordingly as trismus may be present which would not allow the back of the mouth to be accessed by fluoride splints or trays.
[30] Patients will still be susceptible to radiation caries and periodontal disease, more so if they present with dry mouth or access difficulty when tooth brushing.
