Dental and oral complications
The likelihood is high that aggressive cancer treatment will have toxic effects on normal cells as well as cancer cells. The gastrointestinal tract, including the mouth, is particularly prone to damage. This is true whether the treatment is radiation or chemotherapy. Most patients being treated for head and neck cancer will experience some oral complications, and while most of these are manageable, complications can sometimes become severe enough that treatment must be completely stopped. In addition, surgical solutions to tumor removal may lead to oral and nutritional problems as well.
The most common oral problems occurring after radiation and chemotherapy are mucositis (an inflammation of the mucous membranes in the mouth), infection, pain, and bleeding. Other possible complications might include dehydration and malnutrition, commonly brought on by difficulties in swallowing (dysphagia). Radiation therapy to the head and neck may injure the glands that produce saliva (xerostomia), or damage the muscles and joints of the jaw and neck (trismus). These treatments may also cause hypovascularization (reduction in blood vessels and blood supply) of the bones of the maxilla or mandible (the bones of the mouth). In addition, treatments may affect other forms of dental disease (caries, or soft tissue complications), or even cause bone death (osteonecrosis).
By identifying patients at risk for oral complications, health care providers are able to start preventive measures before cancer therapy begins, reducing the occurrence of problems brought about by different treatment modalities. The most important risk factors leading to problems are oral or dental disease that already exists, and poor oral care during cancer therapy. Other risk factors include the type of cancer, the chemotherapy type and schedule used, the area irradiated and how much radiation is given, how low blood counts are decreased and for how long, the patient's age, and the general condition of the patient's health pre-treatment.
Pre-existing oral conditions may increase the risk of infection or other problems. Problems such as calculus and tartar on the teeth, broken teeth, the condition and quality of existing dental repairs such as crowns or fillings, periodontal disease, and appliances such as bridges, partial dentures, or other removable fixtures can make therapy more difficult later on. Bacteria and fungi can live in the mouth, and may develop into an infection when the immune system is not working well, or when white blood cell counts are low. Both of these factors can be caused by the treatment methods used. Where the gums (gingiva) or other soft tissues are irritated, tissues can thin and waste away, causing sores in the mouth. These complications can result in a significant reduction in the quality of life for the patient.
Overview of complications and patient coping mechanisms
CE course on complications for dentists from Dentaltown.com
Radiation issues
One way in which radiation therapy kills cancer cells, is by shrinking blood vessels in the affected area. Fast growing tumor cells require more oxygen and nutrients than normal cells, and they are "oxygen starved" to death. Additionally, both radiation therapy to the head and neck and chemotherapy drugs affect the ability of cells to divide, an efficient manner in which to kill cancer cells. This however, also makes it difficult for tissues in the mouth to repair themselves in the treated sites. Therefore, people being treated with radiation therapy for head and neck tumors, frequently have side effects associated with the radiation itself, or with the decreased blood flow. The mucus membranes, or soft tissues inside our mouth and throat, are tender to this lifesaving treatment; salivary glands are especially sensitive as well. The damage to these tissues and glands depends on the amount and kind of radiation used, the total dose, and the size of the area irradiated. Damage caused by radiation therapy affects the tissues for the rest of the patient's life. These hard and soft tissues are more easily damaged after treatment has been completed, and normal methods of cell repair do not work as well once cells have been exposed to radiation. It is of extreme importance that the patient's dentist is aware and educated in the issues regarding radiation therapy. The special dental considerations surrounding post-treatment care last forever.
Chemotherapy issues
Chemotherapy kills cancer cells by taxing some aspects of their life cycles more than it taxes the life cycle of most normal cells. However normal cells in the body can be susceptible to the stress of chemotherapy. When the white blood cell count is lowest, oral tissues are most prone to damage. The mouth is able to recover only when the white blood cell count returns to normal. The lips, tongue, floor of the mouth, inside of the cheeks, and soft palate (the upper back of the mouth) are more affected by chemotherapy drugs than are the hard palate (the upper front of the mouth) and the gingiva surrounding the teeth. Some chemotherapy drugs are more likely to cause problems in the mouth, especially when they are given in high doses, in repeating schedules, or when given simultaneously with radiation therapy. Spicy foods, abrasive foods, and alcohol should be avoided so as not to aggravate the sore tissues, and water should be consumed in high volume to maintain the moistness of tissues and the body's fluid balance. During and shortly after chemotherapy, an oncologist should be consulted before any dental care is performed. With white blood counts and clotting factors at low levels, dental treatment should be postponed until after a blood test confirms a return to normal levels. Chemotherapy can also lead to neurotoxicity, a persistent, deep pain that mimics a toothache, but that has no dental or mucosal source.
Surgical issues
Patients who undergo a surgical solution to the removal of their cancer may have unique problems related to the oral structures which are now missing. While necessary in some cases, surgery can be deforming. Reconstructive surgery may be employed during the primary surgery or afterwards as a secondary procedure.
Alterations to the structures of the oral cavity and face result in complications which frequently require prosthetic reconstruction after completion of the healing process. Read more information on reconstruction and rehabilitation.The use of dental and facial implants may be employed in achieving the final solution.
The success rates of these osteointegrated implants, is well substantiated. Implants to replace teeth and to hold maxillofacial prosthesis, have been placed successfully even in irradiated tissues, though with lower success rates.
Mucositis and oral infection
Mucositis, which can be caused by radiation or chemotherapy, results from the mitotic death of the basal cells of the mucosal epithelium. Portions of the gastrointestinal tract become inflamed, and red, burn-like or ulcer-like sores appear throughout the mouth.
Patients being treated with chemotherapy for tumors anywhere in their bodies, or by radiotherapy, are often plagued with mucositis. Severity depends on the quality of dental hygiene, the treatment schedule, the irradiated area and the amount of radiation given, as well as the age of the patient. Late effects can be characterized by thinning of the mucosa (the soft tissues of the oral cavity), and submucosal ulceration and necrosis. Oral mucositis is made worse by infection. The mouth can become infected, and the loss of soft tissues in the mouth can allow disease-causing organisms to enter the bloodstream. Once the mouth is affected by treatments, even the normal, good bacteria that exist as part of the natural flora of our mouth, can cause infections, as well as disease-causing organisms picked up from other sources. As the white blood cell count decreases as a result of treatments, the frequency and seriousness of infection increases. Patients who have low white blood cell counts over a long period of time, are at more risk of developing serious infections. Antibiotics used over a long period of time can change the number of normal, beneficial bacterial organisms in the mouth. Their decreased numbers may allow an excessive growth of fungi. Steroids given at the same time as treatments can also make the problem worse. Most oral infections in patients with solid tumors are caused by yeast and other fungi, while the rest are caused by viruses (such as herpes) and bacteria.
Mucosal healing should be complete within three to six weeks after radiation therapy, and mucositis should begin to resolve at the same time.
Radioprotectors may also be employed to reduce the negative biological effects of radiation therapy, and they may prove useful in reducing tissue toxicity. A dentist or oncologist may prescribe viscous topical anesthetics such as lidocaine to reduce discomfort, or a "Miracle Mix" (a tissue coating agent and numbing agent) to aid in oral comfort, if the symptoms are especially bad. While an uncomfortable aspect of treatment, mucositis will heal by itself shortly after treatment is completed.
More information about mucositis
More about the treatment of mucositisfor dentists
Xerostomia
Xerostomia information for dentists
Xerostomia (dry mouth) changes the ability of the mouth to neutralize acid, clean the teeth and gums, and protect the mouth from infection. Saliva is needed for taste, swallowing, and speech. Xerostomia is the thickening of, or reduction in volume of saliva. Symptoms include dryness, a sore or burning feeling (especially on the tongue), cracked lips, cuts or cracks at the corners of the mouth, changes in the surface of the tongue, and difficulty wearing dentures. An extremely dry mouth will also impair proper speaking, and the swallowing of foods. Saliva contains important protective enzymes which aid in the prevention of tooth decay and periodontal disease. To protect against tooth decay during and after treatments, patients with xerostomia should apply fluoride to the teeth daily to protect them. Besides a reduction in salivary volume, treatments can cause saliva to become thick, stringy, and annoying to the patient. Once saliva is thickened or reduced in volume, minerals can be lost from the teeth (demineralization), and needed minerals (calcium, phosphorus) are not redeposited on the teeth. Plaque becomes heavy and thick, and the acids produced after eating sugary foods can cause additional mineral loss. All this contributes to dental decay. It is essential that once salivary function begins to diminish that attention to oral hygiene must be increased. It is not uncommon for post treatment individuals to visit their dental hygienist at rates far more frequently than what is recommended for the general public. Quarterly for cleanings would not be too often, and some patients go even more frequently because even with the most diligent program at home they are unable to prevent the accumulation of plaque and calculus on the teeth. Xerostomia is typically not reversible, and the chronic effects may persist for months or years, with recovery depending on the area radiated, the total dose, and the individual patient. Obviously when the salivary glands are directly in the field of radiation, the condition is unavoidable. New developments in the manner in which radiation is delivered such as IMRT treatments, More about IMRT and radio-protective drugs such as Amifostine may reduce the effects of radiation induced xerostomia.
Synthetic saliva solutions and saliva substitute lubricants are helpful in many patients with dry mouth, and some favorable reports have been published. Oral Balance®, an over-the-counter gel, also available as a liquid which can be carried easily in the pocket, is a good example. In some patients in whom the salivary complaint is related to the "thickness" (excess mucous-type secretions), guaifenesin (Organidin NR®) as a liquid or tablet may help as a mucolytic agent (200-400 mg, 3 to 4 times daily). There are a variety of over the counter products that contain this active ingredient - read labels. During the treatment phase of these moisture changes in the mouth the thickening of saliva and mucous production can be problematic. OTC products such as Mucinex which contain the same active ingredient, may be helpful in this area.
Management of xerostomia in oral cancer patients during and after treatments Mary Brosky, DMD, University of MinnesotaDemineralization
Demineralization of the teeth and the breakdown of tooth structure can also occur as a result of treatment. This is not necessarily the result of the teeth being in the direct field of radiation therapy. Demineralization may also result when the parotid and/or submandibular/sublingual salivary glands are included in the field of radiation, and are damaged. A diminished supply of saliva, or a change in the quality of saliva, particularly of the resting flow from the submandibular/sublingual glands, deprives the oral cavity of the protective components of saliva, and the calcium and phosphate ions necessary to maintain the hydroxyapatite content of tooth enamel and dentin. Demineralization may contribute to dental caries, or hypersensitive teeth.
Scrupulous hygiene must be maintained indefinitely; daily topical fluoride applications are effective as a means of combating the tendency of oral cancer patients to develop dental caries which can be a by-product of demineralization.
Loss of taste
With radiation therapy, a loss of taste (dysgeusia) may also occur due to damage of the taste bud cells. These cells occur primarily in the tongue papilla and are very sensitive to radiation. These cells usually are capable of repopulating within four months following treatment, but some permanent impairment may remain. There are essentially four tastes; sweet, sour, bitter, and salty. Patients are unique, and different tastes will return at different rates after treatment, and in different amounts. The degree to which taste returns is highly variable and varies from patient to patient. Xerostomia and mucositis also contribute to dysgeusia.
Speech and swallowing
Complications from treatment also have a profound effect on speech and swallowing. The two go hand in hand, as the same coordinated movement of the structures in the mouth and throat that is essential for the production of intelligible speech, are also necessary for a person to swallow normally. The effects of a cancer on speech and swallowing depend on the location and size of the growth. Both speech and swallowing may also be compromised by surgical interventions, and to a lesser extent by radiation treatments. A sore or lump on the lips, for example, may restrict movement, resulting in unclear production of labial sounds, and the patient's ability to hold food in their mouth while eating may also be reduced. A lesion on the tongue may affect the intelligibility of some lingual sounds, and limit the ability to move food around the mouth or push food back toward the throat during swallowing. A growth on the roof of the mouth (soft palate) or in the throat may change the nasal quality of the voice. The size of the cancerous growth does play a role in how speech and swallowing abilities are affected. After surgery there are other important factors which determine the extent of complications such as; the amount of tissue removed, the removal of portions of speech and swallowing related anatomy such as the tongue, the availability and frequency of speech/swallowing therapy post-treatment, and the motivation of the patient. Reconstructive surgery and the use of prosthetic devices have become very sophisticated, and current techniques have been shown to restore oral functioning to near normal levels. Frequently, evaluation and treatment by a speech-language pathologist is essential to restore speech intelligibility and swallowing skills. Speech-language specialists are integral parts of the hospital-based cancer team and perform both pre and post surgical assessments, as well as post treatment therapy.
More on speech and swallowing issues - dysphagia
Trismus
This is essentially the inability to open the mouth properly. Trismus is another complication that may develop after radiation treatment. Trismus occurs as a result of fibrotic changes to the muscles of mastication and the temporomandibular joint capsule, when they are included in the radiation field. The full extent of trismus usually becomes evident three to six months after the end of radiation treatment. The patient's limited ability to open the mouth properly, combined with impaired salivary production, may interfere with the ability to maintain adequate oral hygiene, speech, and the ability to sustain adequate nutrition. Stretching exercises are important during the treatment process to minimize post treatment trismus.
Osteoradionecrosis
Perhaps the most severe side effect of radiation therapy is osteoradionecrosis (ORN), or bone death. This condition occurs in three to ten percent of patients. Osteoradionecrosis develops as irradiation diminishes the bone's ability to withstand trauma and avoid infection, and it can be facilitated by poor nutrition and hygiene. This process may be spontaneous or result from trauma, leading to non-healing soft tissue and bone lesions, followed by bone necrosis. The non-healing bone may become secondarily infected. All patients who are to receive chemo-radiation therapy should have unsalvageable teeth removed, periodontal health maximized, and fluoride therapy instituted prior to treatment. Osteoradionecrosis is an extremely serious complication for patients requiring tooth extraction after radiation therapy, and the risk does not appear to diminish with time (for the rest of his/her life the patient should never allow a dentist to extract a tooth after radiation therapy without consulting a radiation oncologist). The ability of the bony tissues to heal is compromised by hypovascularization. 
Essentially, the radiation destroys some of the very small blood vessels within the bone. These blood vessels carry both nutrients and oxygen to the living bone. A reduction in these vessels correlates to a reduction in the bone's ability to heal itself.
All patients who require extraction of teeth in a previously irradiated field should be considered at risk of developing osteoradionecrosis. The traumatic fracture of a maxillary bone or the mandible post treatment in an accident can also result in severe consequences. Such a problem when complicated by ORN, can cause massive destruction of the jawbones. Treatment for ORN may include hyperbaric oxygen treatments in which the bone is subjected to saturation with oxygen in a pressure chamber, not unlike those used to treat divers for the bends. More about hyperbaric treatments When the severity of these post treatment ORN complications is considered, aggressive dental treatments such as extractions before radiation therapy become understandable. More about ORN hereNutritional problems
All of these factors, in addition to the nausea and vomiting that can follow treatment, have an effect on the patient's nutrition, and can lead to eating deficiencies. The inability to maintain adequate nutritional health is a particularly common problem for persons with oral cancer, and it is a major cause of morbidity and mortality. A healthy diet is of the utmost importance when undergoing therapy. Anorexia is the most common symptom that may occur early in the disease process, or later as the tumor grows and metastasizes. Cachexia is a clinical wasting syndrome evidenced by weakness and a marked and progressive loss of body fat and muscle tissues. Anorexia and cachexia frequently occur together, but cachexia may occur in individuals who are ingesting adequate calories and protein but experience malabsorption of the nutrients. During and after treatment, there may be less enjoyment in eating and drinking, or embarrassment or isolation in social situations. Sometimes the patient simply may not want to eat, but it is very important to maintain a nutritious diet, particularly when undergoing treatment. It is integral to health and the recovery process.
For patients who lose a significant amount of weight during treatments or have compromised eating abilities afterwards, the use of a feeding tube must be considered.
Photo credit: hncancer
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