Dry Mouth

Dry mouth is a lack of moisture in the mouth.

Saliva is the fluid that keeps the mouth moist. Saliva lubricates the teeth, gums, and tongue and helps wash debris from the mouth. It helps people taste, digest, and swallow foods. It also contains substances that kill microorganisms. Saliva is produced by the salivary glands. There are three main pairs of salivary glands plus many tiny glands throughout the mouth.

Many older people have a dry mouth. Although aging itself affects moisture in the mouth only slightly, it does make people more susceptible to conditions that dry the mouth.

For many people, a dry mouth is only an occasional annoyance. For others, it is a persistent problem (called xerostomia), which interferes with tasting, chewing, swallowing, speaking, and wearing dentures. Persistent dry mouth also increases the risk of tooth decay and periodontal disease. Persistent dry mouth is usually a symptom of a disorder or a side effect of a drug.

Causes

The mouth becomes dry when too little saliva is produced or when the saliva changes so that it moistens less well. When there is too little water in the body (as occurs in dehydration), less saliva is produced, and the mouth becomes drier. Breathing through the mouth can cause dryness. Low humidity in the air can make the mouth drier.

Drugs are the most common cause of dry mouth among older people. Dry mouth can be a side effect of more than 400 drugs. The drugs most likely to cause dry mouth include

• Antihistamines
• Tricyclic antidepressants (used to treat depression)
• Certain antipsychotics (used to treat loss of touch with reality)
• Certain drugs used to treat cancer
• Many drugs used to lower blood pressure or treat heart failure (including diuretics, which cause the kidneys to excrete more water and salt)

Many disorders can cause persistent dryness of the mouth. They include Sjögren's syndrome (which also causes dry eyes), Alzheimer's disease, sarcoidosis, hypothyroidism, and diabetes. Radiation used to treat cancers of the mouth, head, or neck causes the mouth to be permanently dry.

The mouth may become dry because stones or tumors develop in the tubes that lead from the salivary glands to the mouth (salivary ducts). Stones or tumors can block the flow of saliva. Infection or inflammation of the salivary glands can cause occasional or persistent dryness.

Dentures themselves do not cause dry mouth. If dentures cover the roof of the mouth, they may cover some salivary glands. As a result, the mouth may feel dry.

Symptoms and Diagnosis

Persistent dry mouth may cause bad breath. Chewing and swallowing food may become difficult. Sometimes undernutrition results. The dry tongue may stick in the mouth, making speaking difficult. Wearing dentures may become uncomfortable. The lips and tongue can become cracked and feel as if they are burning. The gums may become tender and bleed, suggesting gingivitis. A tooth may ache if tooth decay occurs.

A doctor or dentist usually suspects xerostomia after listening to a person's description of symptoms. Occasionally, dryness is noticed during a routine examination.

A doctor or dentist tries to determine the cause of the dryness. The drugs the person is taking are reviewed to determine whether any could be the cause. The mouth is carefully inspected. The doctor or dentist feels (palpates) the inside of the mouth to check for swelling or blockage in the salivary glands. The openings of the salivary ducts are inspected for evidence of blockage. Computed tomography (CT) or magnetic resonance imaging (MRI) is sometimes done to confirm the presence of inflammation or a blockage. If Sjögren's syndrome is suspected, the eyes are examined. Blood tests are done to confirm the diagnosis. Or a dentist or doctor may remove a tissue sample from a salivary gland and examine it under a microscope (biopsy).

Prevention and Treatment

Drinking enough fluids helps prevent dehydration, one cause of dryness. People with dry mouth should not drink fluids that contain sugar to reduce the risk of developing cavities. If people breathe mainly through their mouth during sleep, they can use a humidifier by the bedside to prevent the mouth from becoming dry.

If a dry mouth is caused by dehydration, a person is usually given fluids, which can reverse the dryness. If a dry mouth is a side effect of a drug, a doctor reduces or discontinues the drug if possible.

If a blockage in the salivary glands or ducts is the cause, the blockage is removed. If inflammation or infection of the salivary glands is the cause, taking a prescription drug may lessen or relieve dryness. Inflammation can be treated with drugs such as ibuprofen. An infection is usually treated with antibiotics such as amoxicillin.

Dry mouth caused by certain disorders is not relieved by treatment. In such cases, sucking on sugarless candy (including mints) and chewing sugarless gum may slightly stimulate production and flow of saliva. Saliva substitutes, usually used as sprays, are available. They must be used frequently.

Two prescription drugs, pilocarpine and cevimeline, can stimulate the salivary glands to produce more saliva. These drugs help relieve dryness, particularly during mealtime. Occasionally, they have side effects such as sweating and diarrhea.

Measures, including drugs, that stimulate saliva flow can help improve a person's ability to chew and speak. They may improve the way the mouth feels.

Some nonprescription products are made especially for people with dry mouth. These products contain the substances that kill bacteria normally present in saliva. They also contain ingredients that help keep the mouth moist and prevent cavities. These products are available as toothpastes, mouth rinses, oral gels, and chewing gums.

People with a dry mouth have to take extra care to prevent tooth decay and gingivitis. They must brush their teeth or dentures carefully after each meal. Frequent dental examinations are needed to check for and treat tooth decay and periodontal disease.