Xerostomia is the medical term for the sensation of dry mouth. Hyposalivation signifies a reduction in salivary flow and is an objective, measurable entity. Radiation therapy affecting the head and neck where the salivary glands are in field of radiation is associated with salivary gland atrophy. Radiation doses of 25 Gy or greater are associated with hyposalivation, reduced salivary flow and function. In addition to reduced flow, the saliva produced is ropey, thick and predominantly mucus. The extent of hyposalivation and xerostomia felt is linked to the dosage of radiation received as well as the location of the field of radiation. As saliva acts as a natural buffer in the mouth, bathing and lubricating the teeth and oral tissues, reduced salivary flow leaves patients prone to an increased risk for dental decay. Additionally, xerostomia is associated with taste alterations, difficulty swallowing and difficulty speaking.
Trismus is the medical term for limited or reduced opening of the jaw. Trismus is often seen three to six months after radiation therapy due to radiation fibrosis (in other words the muscles become fibrotic and contract). The degree of trismus varies depending on the radiation dosage, the location of the radiation as well as the patient's medical history and age. Nasopharyngeal and oropharygneal carcinoma treatment appears to be more commonly associated with trismus than other head and neck cancers. Trismus may also result from surgical resections.
Depending on the location of the radiation, some patients may experience a sore throat. Although you may be tempted to dissolve on lozenges throughout the day, it is important to dissolve sugar-free lozenges to prevent rapidly developing rampant dental decay. The extent of the sore throat and duration is related to the radiation dosage and field of radiation.
Mucositis, literally inflammation of the mucosa, is characterized by mouth sores, intraoral mucosal redness, tissue sloughing and a burning sensation. It is an acute side effect and is also associated with chemotherapy. Not all patients experience mucositis. Additionally, the extent and degree of mucositis varies among patients. Traditionally, mucositis is most commonly seen in the second week of radiation therapy, and patients experience resolution weeks after completing radiation treatment.
Hypogeusia means a reduced taste sensation, while dysgeusia means an altered sense of taste. It is very common to experience taste alterations or loss of taste sensation while undergoing treatment. Many patients state that the first taste bud to change is that which is responsible for sweetness. The extent of taste loss and the duration of taste alteration depend on several factors including radiation dosage, location of the radiation field, and the salivary flow. Saliva enhances the body's ability to detect taste. Radiation doses of 60 Gy or higher may be associated with permanent taste alterations depending on the location of the tongue within the radiation field.
Osteoradionecrosis of the jaw is an area of exposed bone in maxillofacial area that was previously irradiated. It is a complicated and involved pathological process discussed in more detail in this post. Essentially, ORN is a late side effect of radiation therapy, occurring six months to one year after treatment and is associated with radiation doses of greater than 60 Gy. It is most commonly associated with trauma to the tissues overlying the bone rather than direct trauma to bone such as extractions or periodontal (gum) surgery. Nonetheless, ORN can occur spontaneously. Regular dental visits may help minimize the risk for developing ORN. Additionally, prior to receiving radiation therapy, it is advisable to visit a dental oncologist for a pre-radiation dental evaluation. Prior to receiving radiation to the head and neck, any non-restorable teeth that will be in the field of radiation should be extracted. Extractions of teeth in the field of radiation (if the total radiation dosage was greater than 50-60 Gy) after radiation therapy should be avoided.
Nutritional deficiencies may occur as a result of the loss of taste sensation, dry mouth and mouth sores. Despite these side effects, it is important to increase or maintain caloric intake to prevent weight loss.
How do we manage these conditions?
This post discusses management of oral conditions associated with head and neck radiation therapy.