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By Philip C. Fox, DDS, FDS, RCSEd
Xerostomia (dry mouth) is the subjective feeling of oral dryness. It is important to recognize that xerostomia is not a diagnosis, but a symptom with multiple possible causes. Although dry mouth is most frequently associated with altered salivary gland function, there are other etiologies for this oral issue. It is important to perform a complete evaluation of the patient with dry mouth, determining, if possible, the cause of the xerostomia so that appropriate management can be instituted in a timely manner. The patient with xerostomia who has salivary gland hypofunction is at risk for many oral complications and it is critical to institute appropriate preventive measures. Xerostomia may also be a consequence of systemic disease, and early recognition may aid in treatment. This monograph will review methods of evaluation for xerostomia and practical measures for management of the patient with dry mouth.
Epidemiology and Etiology of Xerostomia
Xerostomia is a common oral concern for many patients. It is estimated that up to 10 percent of the general population experiences persistent oral dryness.1,2 Xerostomia is more frequent with increasing age, and over 25 percent of elders complain of daily dryness.3 That percentage is even higher in institutionalized elders. However, it should be recognized that xerostomia is not a result of aging per se, and should not be dismissed as such. Salivary function in healthy, non-medicated elders does not vary significantly from younger individuals. It is believed that the increased frequency of dryness complaints with aging is a result of systemic disease and medication use, both more common in elders and both associated with xerostomia.4
As noted earlier, there are non-salivary causes of xerostomia. These include conditions in which there are alterations of oral mucosal sensation or central cognitive changes, such as following a cerebral vascular accident (stroke). Dryness has been associated with depression, even in the absence of recognizable changes in salivary function. The most common causes of xerostomia, however, are conditions or circumstances that result in alterations in salivary gland function, either quantitative or qualitative.1
The most frequent cause of dry mouth complaints is the use of prescription drugs. There are hundreds of pharmaceuticals that have xerostomia as a side effect.5,6 The salivary glands are stimulated strongly by cholinergic agents. Therefore, anti-cholinergic medications, such as antihistamines, are most likely to cause decreased salivary output and xerostomia.5 However, many other classes of medications, including sedatives, antipsychotics, antidepressants and diuretics are associated with xerostomia. Interestingly, many herbal preparations may induce complaints of oral dryness, and patients should always be questioned about non-prescription drug use.7 Examples of commonly used preparations include members of the Labiatae family (specifically all the salvias), capsicum, garlic, Ginkgo biloba, and St. Johns Wort (Hypercicum perforatum). Herbal preparations with strong diuretic properties, such as stinging nettle (Urtica dioica) and dandelion (Taraxacum officinale) also may lead to complaints of dry mouth. Caffeine is well recognized as a cause of xerostomia.8 As many as 25 million persons in the United States may experience xerostomia as a result of medication use.
The most frequent cause of dry mouth complaints is the use of prescription drugs.
There are also medical therapies that result in xerostomia. Radiotherapy to the head and neck region that includes the salivary glands in the treatment fields can lead to significant and persistent dry mouth. This is an expected complication at exposure levels above 5200 cGy.9,10 Systemically administered radionuclides, such as 131I for treatment of thyroid cancer, are a recognized cause of dry mouth, particularly when re-treatment is required.11 Bone marrow transplantation also may have xerostomia as a side effect, due to the salivary gland involvement in graft-versus-host disease.12
Another major cause of xerostomia is systemic disease. There are a large number of conditions that can affect salivary gland function and lead to complaints of dryness, including diabetes, thyroid disorders, cystic fibrosis and connective tissue diseases.13 The most prominent of the connective tissue diseases is Sjögrens syndrome, an autoimmune condition that may affect up to 4 million people in the United States. Xerostomia is one of the hallmark symptoms in Sjögrens syndrome, experienced by over 95 percent of patients.14 Patients experience a number of dryness complaints in addition to xerostomia. These include eye, nose, throat, skin and vaginal dryness. Since complaints of oral dryness typically do not appear until salivary function has been reduced by approximately 50 percent,15 more than a single gland must be affected for xerostomia to manifest. This emphasizes that dryness resulting from salivary dysfunction is usually indicative of systemic involvement. Table I provides a fuller listing of systemic conditions with xerostomia as a possible symptom.
Table I. Systemic Conditions that May Have Xerostomia as a Symptom
- Autoimmune connective tissue disorders
- Sjögrens syndrome, primary and secondary
- Granulomatous diseases
- sarcoidosis, tuberculosis
- Graft-versus-host disease
- Cystic fibrosis
- Bells palsy
- Diabetes (poorly controlled)
- Human immunodeficiency virus infection
- Thyroid disease
- hypo- and hyper-thyroidism
- Late stage liver disease
- Affective disorder
- Eating disorders and malnutrition
- anorexia, bulemia, dehydration
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