Dry mouth is caused by a reduced or absent flow of saliva. This condition can cause discomfort, interfere with speech and swallowing, make wearing dentures difficult, cause bad breath (halitosis), and worsen oral hygiene by causing a decrease in the acidity of the mouth and an increase in bacterial growth, which contributes to the development of cavities. Longstanding dry mouth can result in severe tooth decay and candidiasis of the mouth. Dry mouth is a common complaint among older people.
Dry mouth occurs when the salivary glands (glands in the mouth that produce saliva) malfunction and thus decrease saliva production. There are many causes, including dehydration and mouth breathing (see table Some Causes of Dry Mouth).
The most common causes of dry mouth are
Drugs are the most common cause overall. About 400 prescription drugs and many nonprescription (over-the-counter) drugs cause a decrease in saliva production. The most common classes of drugs include the following:
Many commonly used drugs have anticholinergic effects. Dry mouth is only one among many anticholinergic side effects.
Many chemotherapy drugs cause severe dryness and mouth sores (stomatitis) while they are being taken. These problems usually end after the drugs are stopped.
Other common drugs that cause dry mouth include certain antihypertensives (drugs used to lower high blood pressure), antianxiety drugs (drugs used to treat anxiety disorders), and antidepressants (drugs used to treat depression).
Illegal methamphetamine use has resulted in a disorder called meth mouth, which is severe tooth decay caused by methamphetamine-induced dry mouth. The damage is worsened by the tooth grinding and clenching caused by the drug, the heat of the inhaled vapor, and probably elevated intake of sugary beverages and poor oral hygiene while using this drug. This combination causes very rapid destruction of teeth and a lifetime of dental problems for younger people.
Tobacco use usually causes a decrease of saliva.
Radiation therapy for head and neck cancer can severely damage the salivary glands, often causing permanent dryness. Even low doses of radiation can cause temporary drying.
Not all people with a dry mouth need to be immediately evaluated by a doctor. The following information can help people decide whether a doctor’s evaluation is needed and help them know what to expect during the evaluation.
In people with dry mouth, certain symptoms and characteristics are cause for concern. They include
Doctors first ask questions about the person’s symptoms and medical history. Symptoms of dry or irritated eyes, dry skin, rash, and/or joint pain raise the possibility of Sjögren syndrome. Doctors also ask about a history of past or current radiation treatment, head and neck trauma, and a diagnosis of or risk factors for HIV infection. Doctors need to know all the drugs a person is taking to find out whether any are causing the dry mouth.
Doctors then do a physical examination. The physical examination is focused on the mouth, to see the degree of dryness. If the degree of dryness is unclear, doctors can hold a tongue depressor against the inside of the cheek for 10 seconds. If the tongue depressor falls off immediately when released, the flow of saliva is considered normal. If there is difficulty removing the tongue depressor, the flow of saliva is not normal. In women, the lipstick sign, where lipstick sticks to the front teeth, may be a useful indicator of dry mouth.
Doctors also examine the mouth for the presence of any sores caused by the fungus Candida albicans and check the condition of the teeth (for instance, whether there are any cavities in unusual places). Unexpectedly severe and rapid tooth decay may be a sign of illicit drug use, particularly methamphetamines.
What doctors find during the history and physical examination often suggests a cause of the dry mouth (see table Some Causes of Dry Mouth) and the tests that may need to be done. If the dry mouth began shortly after a new drug was started, doctors often try stopping the drug to see whether symptoms go away.
Some Causes of Dry Mouth
Sometimes, doctors test how well the salivary glands are functioning by measuring the flow of saliva (a test called sialometry). People chew paraffin or apply citric acid to the tongue to stimulate the flow of saliva, and then doctors collect the saliva. Measuring the flow of saliva can help doctors determine whether the dry mouth is getting better or worse.
If doctors are unable to determine the cause of dry mouth, people should usually undergo a biopsy (removal of a sample of tissue for examination under a microscope) of a minor salivary gland on the lower lip to detect Sjögren syndrome, sarcoidosis, amyloidosis, tuberculosis, or cancer. They may also consider HIV testing.
When possible, the cause of dry mouth is treated. For people with drug-related dry mouth whose current drug cannot be stopped or changed to another drug, drugs should be taken in the morning rather than at night, because nighttime dry mouth is more likely to cause cavities. For all drugs, easy-to-take formulations, such as liquids, should be considered. Drugs that need to be placed under the tongue should be avoided. People should drink water before swallowing capsules and tablets or before placing nitroglycerin under the tongue. People also should avoid decongestants and antihistamines.
Treatment that helps control the symptoms of dry mouth consists of measures that
Drugs that increase saliva production include cevimeline and pilocarpine. The main side effect of cevimeline is nausea. The main side effects of pilocarpine include sweating, flushing, and excreting large volumes of diluted urine (polyuria).
Sipping sugarless fluids frequently and chewing gum that contains xylitol helps stimulate saliva flow. Using an over-the-counter saliva substitute containing carboxymethylcellulose, hydroxyethylcellulose, or glycerin may also help.
Petroleum jelly can be applied to the lips and under dentures to relieve drying, cracking, soreness, and trauma of the lining of the mouth. A cold-air humidifier may aid mouth breathers, who typically have their worst symptoms at night.
Meticulous oral hygiene is essential. People should brush (using a commercial or prescription fluoride toothpaste) and floss regularly (including just before bedtime) and use fluoride rinses or gels daily. Newer toothpastes with added calcium and phosphates also may help prevent cavities. People should see their dentist more often for preventive dental care and plaque removal. The most effective way to prevent cavities is to use custom-fitted mouth trays filled with prescription toothpaste for at-home fluoride application, especially at night. People may prefer to apply prescription fluoride toothpaste to the teeth without using a tray. In addition, a dentist can apply a sodium fluoride varnish 2 to 4 times per year.
People should avoid sugary or acidic foods and beverages and any irritating foods that are dry, spicy, or excessively hot or cold. People should especially avoid sugar near bedtime.
Drugs are the most common cause, but some diseases (most commonly Sjögren syndrome or HIV infection) and radiation therapy can also cause dry mouth.
Saliva flow can be increased by chewing gum that contains xylitol or sucking on sugarless candy, by taking certain drugs, and by using artificial saliva replacement.
Because people with dry mouth are at high risk of tooth decay, meticulous oral hygiene, additional preventive measures at home (including daily use of over-the-counter fluoride rinses or dentist-prescribed fluoride toothpaste), and dentist-applied fluoride are essential.