Section 8. Mouth and Dental Disorders

Chapter 111. Salivary Gland Disorders

Topic: Salivary Gland Disorders

Salivary Gland Disorders

There are three major pairs of salivary glands in the mouth. The largest pair of salivary glands, called the parotid glands, lies just behind the angle of the jaw, below and in front of the ears. Two smaller pairs, the sublingual and submandibular glands, lie deep in the floor of the mouth. In addition to these major glands, many tiny salivary glands are distributed throughout the mouth. All of the glands produce saliva, which aids in breaking down food as part of the digestive process.

See the figure Locating the Major Salivary Glands.

Other than cancer (see Section 8, Chapter 113), two major types of disorders affect the salivary glands: one that results in salivary gland malfunction, whereby not enough saliva is produced, and one that results in salivary gland swelling. When the flow of saliva is insufficient or almost nonexistent, the mouth feels dry. This condition is called dry mouth (xerostomia).

Salivary Gland Malfunction

Certain diseases and disorders can cause the salivary glands to malfunction and thus decrease saliva production, including Parkinson's disease, depression, chronic pain, HIV infection, and Sjögren's syndrome. Some drugs can decrease saliva production as well, including certain antidepressants, antihistamines, antipsychotics, sedatives, methyldopa, and diuretics.

The salivary glands often malfunction after a person has had chemotherapy or head and neck radiation for the treatment of cancer. Dry mouth due to radiation is usually permanent, especially if the radiation dose is high; that due to chemotherapy is usually temporary.

However, not all cases of dry mouth are caused by salivary gland malfunction. Drinking too little liquid and breathing through the mouth can dry the mouth. Anxiety or stress can also result in a dry mouth. The mouth may also dry somewhat as a person ages, although this is probably due to the greater likelihood of taking a drug that causes dry mouth than to the aging process itself.

Because saliva offers considerable natural protection against tooth decay, an inadequate amount of saliva leads to more cavities--especially on the roots of teeth. Dry mouth, if severe, can also lead to difficulty speaking and swallowing.

In rare cases, the salivary glands produce too much saliva. Increased saliva production is usually very brief and occurs in response to eating certain foods, such as sour foods. Sometimes even thinking about eating these foods can increase saliva production.

Salivary Gland Swelling

Salivary gland swelling can occur when one of the ducts that carry saliva from the salivary gland to the mouth is blocked. Pain may occur, especially during eating.

The most common cause of blockage is a stone. A stone can form from salts contained in the saliva. Blockage makes saliva back up inside the duct, causing the salivary gland to swell. A blocked duct and gland filled with stagnant saliva may become infected with bacteria. A typical symptom of a blocked salivary duct is swelling that worsens just before mealtime or particularly when a person eats a pickle (a sour pickle's taste stimulates saliva flow, but if the duct is blocked, the saliva has no place to go and the gland swells).

Mumps, certain bacterial infections, and other diseases (such as AIDS, Sjögren's syndrome, diabetes mellitus, and sarcoidosis) may be accompanied by swelling of the major salivary glands. Swelling also can result from cancerous or noncancerous tumors in the salivary glands. Swelling resulting from a tumor is usually firmer than that caused by an infection. If the tumor is cancerous, the gland may feel stone-hard and may be fixed firmly to surrounding tissues (see Section 8, Chapter 113).

An injury to the lower lip--for instance, from accidental biting--may harm any of the minor salivary glands found there and block the flow of saliva. As a result, an affected gland may swell and form a small, soft lump (mucocele) that appears bluish. Over a few weeks, the lump usually disappears by itself.

Diagnosis and Treatment

There are no good quantitative tests to diagnose salivary gland malfunction. However, the salivary glands can be squeezed ("milked") and the ducts observed for saliva flow.

Swelling due to blockage of a salivary duct is diagnosed because of the relationship of pain to mealtimes. To diagnose other causes of swelling, a dentist or doctor may perform a biopsy to obtain a sample of salivary gland tissue and examine it under a microscope.

If a salivary duct is blocked by a stone, a dentist can sometimes push the stone out by pressing on both sides of the duct. If that fails, a fine-wire-like instrument can be used to pull the stone out. As a last resort, the stone can be removed surgically.

A mucocele that does not disappear on its own can be removed surgically if it becomes bothersome. Similarly, both noncancerous and cancerous salivary gland tumors can usually be removed surgically. Treatment of other causes of salivary gland swelling varies with the cause.

Any person who has a disorder or who is taking a drug that dries the mouth must follow meticulous oral hygiene (brushing, flossing, and fluoride rinses), avoid sugars, and undergo dental examinations, cleanings, and fluoride treatments every 3 to 4 months.

When no specific treatment is available, saliva substitutes are marginally helpful. One drug that does help some people is pilocarpine, but the drug is often ineffective if the salivary glands have been damaged by radiation.