What Is Osteoradionecrosis

Introduction

Definition of osteoradionecrosis (ORN)

Osteoradionecrosis (ORN) is defined as bone death/necrosis, which is usually caused by radiation. It usually occurs due to a lack of blood supply, which hinders the maintenance of bone tissues. It is a rare condition that develops as a side effect of prolonged cancer treatments using radiation. It can be seen in around 3-10% of the patients who have undergone radiation therapy. It mostly affects the lower jaw (mandible), but can also affect the upper jaw ( maxilla). 

Occurrence and causes

Radiation therapy varies according to the type and grade of cancer. Patients who receive higher doses of radiation (around 7000 cGY) are more prone than those who get >6000 cGY. According to an epidemiology study, 9% of patients who get 7000 cGY and 2% of patients who get >6000 cGY of ionising radiation are diagnosed with ORN. It is also more likely to show up in patients above the age of 55 years and those who have aggressive tumours, leading to higher radiation values.

Understanding osteoradionecrosis

How radiation therapy contributes to ORN

Osteoradionecrosis is a complication due to radiation therapy. Radiation causes the death of cells and is mainly targeted towards cancer cells. However, due to the wide range of beams, there is a possibility of cell death in other regions. It leads to the uprooting of the vascular system in the jaw. The vascular system is necessary for supplying oxygen and nutrients to tissues, but if this is disrupted, then tissues start dying. As a result of this, bones in the jaw also lose their ability to heal quickly.

Common sites affected

Osteoradionecrosis is seen throughout the mandible and other parts of the face. Radiation exposure  to the head and neck leads to loss of bone tissue.As a result, there is a loss of mobilityof bones in the jaws.

Symptoms and diagnosis

Clinical manifestations

Patients with early ORN are generally asymptomatic despite the exposed bone and ulcerated mouth. Patients can experience bad breath, painful eating and lodging of food particles in the exposed crevices leading to infections. Furthermore, the jaw region can swell up in case of an infection which makes chewing and swallowing food very hard. This is also paired with a numbing sensation due to loss of nerves in the jaw.

Diagnostic procedures

Procedures like CT scans and MRIs can be used for an early diagnosis of ORN. Computed Tomography (CT) scan can be used to determine the location of prominent bone damage such as sclerosis and cortical thinning. Whereas, Magnetic Resonance Imaging (MRI) scans are employed to understand loss of bone marrow through weak signals in a jaw MRI. This indicates a significant damage to bone tissues. Plain radiography also helps to identify the location of decalcification in the mandible. 

A culmination of these tests alongside a biopsy is integral in diagnosing ORN. The biopsy is an additional test to ensure there is no cancer/tumour that has been overlooked after radiation therapy before beginning ORN treatment.

Risk factors and prevention

Factors influencing ORN development

The factors that influence ORN development include all aspects of the tumour present in the individual. Hence, the location and stage of the tumour are important to consider when evaluating the chances of bone tissue decay. Apart from these, it's essential to understand the proximity of the tumour to bone tissues and the doses of radiation received. The type of radiation therapy is crucial to identify the damage caused to blood vessels. Lastly, the patient's oral hygiene techniques also contribute to the chances of bone death. The stronger their teeth and bones, the less likely they are to be affected by radiation.

Strategies for prevention

Since this disease is very hard to treat, it's essential to take measures to prevent it from progressing into irreversible damages. One of the measures that can help reduce the chances of tooth decay involves the use of high fluoride toothpaste. Fluoride intercepts acid attack on the enamel. It also helps with mineral build up of the teeth making them stronger and less prone to decay. 

Another method used to prevent the onset of this disease involves the use of hyperbaric oxygen therapy. Through this procedure, patients are supplied with increased amounts of pure oxygen (100%) stored in clear chambers. The increased oxygen content in the body helps to repair damaged tissues. Additionally, this allows for improved blood flow to tissues that are prone to necrosis, preventing further irreversible damage. To prevent any complications, these sessions are limited to a maximum of 2 hours and the pressure within the chamber is also kept lower than normal atmospheric pressure.

Thirdly, platelet rich plasma is supplied to regions that are prone to decay post radiation therapy. This is carried out to allow growth of new and rejuvenated tissues in the jaw. Although there have been research studies conducted on these methods, it is necessary to point out that none of these have a 100% success rate and are just supplements to prevent the progression of ORN.

Treatment approaches

Conservative management

Conservative management of ORN includes using saline irrigation to combat inflammation and irritation of the mouth. Subsequently, this is coupled with oral hygiene instructions like regular cleansing of the mouth, brushing teeth with high-fluoride toothpaste and more to prevent infections. However, if an infection develops due to the exposed bone tissue, doctors can prescribe antibiotics to control and reduce the impact of the bacterial infection. 

Surgical interventions

Surgical interventions are generally associated with a diagnosis of severe osteoradionecrosis. One of these is debridement, which is the removal of thickened skin and necrotic tissue to prevent the spread of decay. Additionally, sequestrectomy is a method used by surgeons to remove dead bone tissues and could be coupled with soft tissue reconstruction in some cases. Depending on the extent of the defect, reconstruction can include local flaps or free tissue transfer. These techniques allow for the regeneration of the lost tissue and try to restore the functions of the jaw with minimal pain so the patients can lead a normal life post-treatment.

Novel therapies and emerging treatments

Intensity-modulated radiation therapy is one of the novel techniques that is being used to treat head and neck cancers. By using this technique, doctors can shape the radiation beams to effectively target the tumour site. This prevents any adverse effects radiation could have on normal bone tissue and teeth. 

Apart from this, the treatments mentioned below have also become more frequent and are constantly being improved to have a higher success rate in preventing the development of ORN in patients.

Complications and long-term effects

Some of the chronic consequences of this condition include the constant development of mouth ulcers and lesions that are quite painful. This makes everyday tasks like eating and drinking hard to carry out as the range of motion of the mouth is limited. There can be development of fractures in the jaw due to weakened bone tissues. Subsequently, if not cleaned and managed regularly, there is a high chance of systemic infections that can lead to sepsis. In terms of physical features, there can be increased swelling of the face along with exposed jaws and loose teeth. Some of these can be controlled with prescription drugs; however, it's unlikely they can be completely cured.

Prognosis and outlook

Factors for understanding the course of Osteoradionecrosis in patients include looking at their medical history, such as diabetes, age, sex, and alcohol/drug use. Apart from these, it's essential to recognise the tumour site, grade and level of treatments available. Additionally, in terms of the dental health of the patient, one needs to analyse their teeth structure, regeneration rate and extraction probabilities. These variables will help indicate the likelihood for developing ORN as well as the treatment methodologies that can be employed to improve the state of the patient.

Summary

• Osteoradionecrosis is a condition that occurs in patients receiving radiation therapy, which is usually targeted at the head and neck.
• It relates to the necrosis/death of bone tissue and tooth decay
• Higher amounts of ionising radiation and old age increases the chances of developing this condition
• There is no exact treatment for it, but there are many preventive measures and surgical techniques that can be used to reduce its effects
• Preventative treatments include hyperbaric oxygen therapy, intensity-modulated radiation therapy (novel discovery) and better oral hygiene techniques 
• Some factors that lead to the development of ORN include tumour size, grade and extent, as well as dental hygiene
• Generic factors that are important to understand the chances of ORN include age, sex, alcohol usage and diet
• It can be diagnosed using CT Scans, MRI and biopsy before beginning a treatment process for ORN
• Treatments can involve saline irrigation in the early stages, but as the condition progresses, surgical intervention would be more effective in alleviating patient symptoms. This would involve removing necrotic tissue to prevent more decay in the jaw
• There can be difficulty in eating and swallowing due to facial inflammation as well as dental issues like loose teeth and infected gums that make everyday tasks challenging