Dry Mouth

Learn about the causes and treatment of this common problem

Dear Doctor,
I am a dental hygienist and I am seeing more of my older patients with mouth dryness, especially those on multiple medications. Could you please give an overview of the causes and treatment of dry mouth?

Dear Barbara,
I'm glad you've brought this up. It's a great example of how dental professionals can help improve quality of life and even be the first to detect underlying medical conditions.

Dry mouth or xerostomia (“xero” – dry; “stomia” – mouth), affects millions of people in the U.S. It is caused by an insufficient flow of saliva, the liquid secreted by the salivary glands, which are located inside the cheeks by the top back molars and in the floor of the mouth. When functioning normally, salivary glands secrete two to four pints of saliva per day.

In addition to its lubricating qualities, saliva helps maintain oral health in a variety of ways. For example, it has digestive enzymes that begin the breakdown of food; antimicrobial (germ-killing) properties and agents that keep harmful bacteria and fungi in check. So its absence is more than just a minor annoyance.

Of course, there are times when mouth dryness is perfectly normal; you will often experience dryness upon waking because saliva flow slows down at night. In the case of dehydration, it is a sign that you need fluids. Stress, smoking, coffee, alcohol, onions, and spices can also cause temporary mouth dryness (as well as bad breath). Chronic dry mouth however, creates ideal conditions for tooth decay. One of the major functions of saliva is to buffer or neutralize acids. Without this powerful protection, decay can increase quickly, especially exposed tooth-root surfaces — seen commonly in older individuals.

Drugs And Dry Mouth

Over-the-counter (OTC), and prescription drugs are often the culprits behind xerostomia, which is why I'm not surprised you're seeing this problem in your older patients. It's not that aging in and of itself causes dry mouth, but older people tend to take more medicines. According to the Surgeon General, there are more than 500 medications that cause this side effect. Antihistamines (used to treat allergies), diuretics (drain excess fluid accumulation associated with high blood pressure and heart failure), and antidepressants, are the three most commonly used types of medications that cause xerostomia.

Disease And Dry Mouth

People receiving head and neck radiation or chemotherapy often experience dry mouth. These treatments can inflame, damage, or destroy the salivary glands. The damage can be temporary or permanent. Certain systemic (general body) or autoimmune (“auto” – self; “immune” – resistance system) diseases, in which the body reacts against its own tissue, can also cause dry mouth. Chief among them is Sjögren's syndrome, which primarily affects postmenopausal women and is characterized by dryness of mucous membranes (of the mouth, eyes, and throat). Other diseases known to cause dry mouth are: diabetes, a disease affecting normal sugar metabolism; Parkinson's disease, a brain disorder marked by uncontrollable tremor; cystic fibrosis, an inherited disease that causes thick, sticky mucus buildup in the lungs and digestive tract; and AIDS (acquired immunodeficiency syndrome).

Persistent Dry Mouth

Persistent or chronic mouth dryness throughout the day over many days is a sign that something is wrong. The cure will depend on the underlying cause, so it's important to ask a lot of questions. Do your patients drink plenty of fluids throughout the day? What medications are they taking? Do they have any chronic diseases or conditions? Have they had a complete physical recently? Are there red or white sores inside the mouth, and evidence of tooth decay?

There are also tests that dentists can perform to stimulate and then measure saliva flow; some provide immediate results, others take 48 hours. A scintigraph (“scint” – spark; “graph” – measure) is a diagnostic test used in nuclear medicine to determine saliva flow by injecting small amounts of radioactive material into a vein, which is taken up by the salivary glands and secreted into the mouth. A salivary gland biopsy (tissue sample) can also be taken.

Remedies For Dry Mouth

If it turns out medication is causing mouth dryness and a substitute is not available, these individuals should be advised to take a few sips of water before swallowing the medicine and a full glass afterwards. They should drink plenty of non-caffeinated fluids throughout the day and avoid sugary and acidic foods or drinks. Running a cool-air humidifier at night is also a good idea.

There are a variety of OTC and prescription saliva stimulants, and saliva substitutes that can temporarily relieve the dryness. Your patients can ask their dentist for a recommendation. Consuming xylitol (a naural sugar substitute) four to five times a day for a total of 5-11 grams can help stimulate saliva and reduce the chance of getting tooth decay. Products that contain xylitol include various chewing gums, candies, jams, toothpaste, mouth rinses and nasal sprays.

Above all, please remind the people you see with this condition how important it is to keep up their oral hygiene routines and see the dentist regularly. They need to know how xerostomia relates to their overall health and what they must do to control it and prevent it from causing other problems.