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Osteoradionecrosis (ORN) is a serious long-term side effect of radiation therapy. The definition of osteoradionecrosis of the jaw has changed throughout the years and remains unclear given our limited knowledge of ORN. Nonetheless, currently, most consider ORN a condition characterized by the presence of exposed bone, which fails to heal after high-dose radiation (greater than 50-60 Gy). Although the time frame at which ONJ occurs is still unclear, it is considered a long-term side effect of radiation therapy, occurring between six months to one year after treatment, and the risk of ORN increases over time.
While the prevalence of ORN is difficult to ascertain, most literature estimates that it is approximately 5 percent. ORN is most often associated not with direct damage to the bone, but rather with trauma to tissues overlying the bone, including surgical procedures such as extractions. The condition has been found to occur more frequently in the mandible than in the maxilla, possibly because of the limited vasculature in the mandible. For some patients, however, ORN occurs spontaneously.
Wait, so how does this happen?
Good question. The pathophysiology is still not well understood, yet there are several postulated theories. Probably, the most popular and well-known hypothesis was proposed by Marx in 1983. Marx’s 3-H hypothesis states that radiation results in triad of tissue hypoxia, hypocellularlity and hypovascularity, which leads to tissue breakdown. However, currently, many support the radiation-induced fibrosis hypothesis. In this complex process, radiation induces cellular damage as well as an acute inflammatory response, and alters the normal functioning and turnover of osteoclasts and osteoblasts.
How do we diagnose ORN?
Diagnosis is not as straightforward as one might imagine. The classic clinical presentation involves exposed bone at an irradiated site. Symptoms usually include an area of exposed dead bone (sequestra), often accompanied by an ulceration that exhibits delayed healing or simply does not heal. In addition, patients may complain of fetor oris (also known as halitosis), numbness, or chronic pain. The area may also present swollen or as a fistula. Severe cases include cortical bone fracture and/or an oro-antral communications.
If the exact radiation dosage is not known, what are some signs that an area has received high doses of radiation?
There are several signs associated with high doses of radiation therapy to the head and neck. These include loss of facial hair growth, profound xerostomia (dry mouth), tissue induration, and taste loss. Patients sometimes experience mucosal telangiectasia, characterized by small dilated blood vessels along the mucosa inside the mouth. Often, a quick marker of where the radiation was delivered can be detected by noticing where a man’s beard line has stopped.
What are the risk factors?
Risk factors include high doses of radiation (50-60 Gy or more), the type of radiation delivered, and the anatomical location of the radiation. Although ORN occurs spontaneously, 60 percent of cases are linked to trauma to the jaw such as extractions or periodontal surgery. Thus, dentate patients are at an increased risk of developing ORN. Additionally, tobacco and alcohol usage are associated with an increased risk of ORN. ORN has a predilection for the male sex. Other risk factors include the use of vasoconstrictors such as epinephrine and poor health or nutritional status. The risk of ORN actually increases over time and is directly related to the dosage of radiation received. In other words, the higher the dosage, the greater the risk of developing ORN.
How is ORN treated?
Maintaining good oral hygiene cannot be stressed enough, and regular dental recall visits are key. Visiting a dentist regularly and frequently will minimize a patient’s risk for developing dental decay and thus the risk of dental infection and ORN. Before a patient receives radiation therapy, all questionable teeth should be extracted or restored at least 14 to 21 days before receiving radiation treatment. Post-radiation dental extractions should be strongly avoided. As stated earlier, the mandible presents a greater risk for developing ORN than the maxilla, and posterior sites present a greater risk than anterior sites; in other words, the lower back teeth present the highest risk for developing ORN, while the upper front teeth present the lowest risk.
Ideally, no extractions should be performed in the field of radiation because radiation dosage is linked to ORN (i.e. greater than 50-60 Gy). While extractions are absolutely advised against, some studies indicate that if an extraction is performed on a post-radiation patient, the use of prophylactic antibiotics may minimize bacterial invasion to the extraction site. The protocol includes administering penicillin VK to patients before and after the procedure.
Always minimize trauma when possible. If a tooth can be saved, it is ideal to save the tooth and perform root canal therapy over an extraction. If an extraction is performed, avoid using periosteal elevators, irrigate the site with saline, eliminate bony spicules, and try to create primary closure.
Given their increased risk for dental decay, patients should be prescribed a neutral sodium fluoride 1.1 percent (5,0000 PPM fluoride) toothpaste and apply this toothpaste nightly.
When radiation hits metal in a person’s mouth, the radiation scatters and may be associated with an increased risk for developing mouth sores. Thus, it is often recommended that patients wear custom radiation mouth guards when undergoing radiation if the metal in their mouth will be in the field of the radiation. The mouth guards do not eliminate the risk of developing mouth sores or ORN, but may help reduce the risk by preventing the soft tissue from directly touching the intraoral metal.
Minimizing hypovascularity after radiation treatment is also believed to be linked to a reduced risk of developing ORN. This means that when administering local intraoral anesthesia, an anesthetic with low or no epinephrine should be used.
Conservative measures, such as irrigating the exposed bone with saline or antimicrobial rinses (chlorhexidine gluconate 0.12 percent), are recommended. Additionally, it is important to direct patients on how to irrigate properly. Additional conservative measures include allowing the bony sequestra to exfoliate while epithelialization occurs underneath. In certain cases, however, surgical resection is indicated.