Saliva, or spit, is made by the salivary glands and is very important for a healthy mouth. It moistens and breaks down food, washes away food particles from the teeth and gums, and helps people with swallowing. In addition, saliva contains minerals such as calcium and phosphate that help keep teeth strong and fight tooth decay.

Dry mouth, also called xerostomia (ZEER-oh-STOH-mee-ah), is the condition of not having enough saliva to keep the mouth wet. Dry mouth can happen to anyone occasionally—for example, when nervous or stressed. However, when dry mouth persists, it can make chewing, swallowing, and even talking difficult. Dry mouth also increases the risk for tooth decay or fungal infections in the mouth because saliva helps keep harmful germs in check.

Dry mouth is not a normal part of aging. If you think you have dry mouth, see your dentist or doctor to find out why your mouth is dry.

The Salivary Glands

Many small salivary glands are housed within the mucous membranes of the mouth and tongue. These minor exocrine glands are constantly secreting saliva, either directly into the oral cavity or indirectly through ducts, even while you sleep. In fact, an average of 1 to 1.5 liters of saliva is secreted each day. Usually just enough saliva is present to moisten the mouth and teeth. Secretion increases when you eat, because saliva is essential to moisten food and initiate the chemical breakdown of carbohydrates. Small amounts of saliva are also secreted by the labial glands in the lips. In addition, the buccal glands in the cheeks, palatal glands in the palate, and lingual glands in the tongue help ensure that all areas of the mouth are supplied with adequate saliva.

The Major Salivary Glands

Outside the oral mucosa are three pairs of major salivary glands, which secrete the majority of saliva into ducts that open into the mouth:

• The submandibular glands, which are in the floor of the mouth, secrete saliva into the mouth through the submandibular ducts.
• The sublingual glands, which lie below the tongue, use the lesser sublingual ducts to secrete saliva into the oral cavity.
• The parotid glands lie between the skin and the masseter muscle, near the ears. They secrete saliva into the mouth through the parotid duct, which is located near the second upper molar tooth (Figure).

Saliva

Saliva is essentially (98 to 99.5 percent) water. The remaining 4.5 percent is a complex mixture of ions, glycoproteins, enzymes, growth factors, and waste products. Perhaps the most important ingredient in saliva from the perspective of digestion is the enzyme salivary amylase, which initiates the breakdown of carbohydrates. Food does not spend enough time in the mouth to allow all the carbohydrates to break down, but salivary amylase continues acting until it is inactivated by stomach acids. Bicarbonate and phosphate ions function as chemical buffers, maintaining saliva at a pH between 6.35 and 6.85. Salivary mucus helps lubricate food, facilitating movement in the mouth, bolus formation, and swallowing. Saliva contains immunoglobulin A, which prevents microbes from penetrating the epithelium, and lysozyme, which makes saliva antimicrobial. Saliva also contains epidermal growth factor, which might have given rise to the adage “a mother’s kiss can heal a wound.”

Each of the major salivary glands secretes a unique formulation of saliva according to its cellular makeup. For example, the parotid glands secrete a watery solution that contains salivary amylase. The submandibular glands have cells similar to those of the parotid glands, as well as mucus-secreting cells. Therefore, saliva secreted by the submandibular glands also contains amylase but in a liquid thickened with mucus. The sublingual glands contain mostly mucous cells, and they secrete the thickest saliva with the least amount of salivary amylase.

Salivary glands The major salivary glands are located outside the oral mucosa and deliver saliva into the mouth through ducts.

HOMEOSTATIC IMBALANCES

The Parotid Glands: MumpsInfections of the nasal passages and pharynx can attack any salivary gland. The parotid glands are the usual site of infection with the virus that causes mumps (paramyxovirus). Mumps manifests by enlargement and inflammation of the parotid glands, causing a characteristic swelling between the ears and the jaw. Symptoms include fever and throat pain, which can be severe when swallowing acidic substances such as orange juice.

In about one-third of men who are past puberty, mumps also causes testicular inflammation, typically affecting only one testis and rarely resulting in sterility. With the increasing use and effectiveness of mumps vaccines, the incidence of mumps has decreased dramatically. According to the U.S. Centers for Disease Control and Prevention (CDC), the number of mumps cases dropped from more than 150,000 in 1968 to fewer than 1700 in 1993 to only 11 reported cases in 2011.

Regulation of Salivation

The autonomic nervous system regulates salivation (the secretion of saliva). In the absence of food, parasympathetic stimulation keeps saliva flowing at just the right level for comfort as you speak, swallow, sleep, and generally go about life. Over-salivation can occur, for example, if you are stimulated by the smell of food, but that food is not available for you to eat. Drooling is an extreme instance of the overproduction of saliva. During times of stress, such as before speaking in public, sympathetic stimulation takes over, reducing salivation and producing the symptom of dry mouth often associated with anxiety. When you are dehydrated, salivation is reduced, causing the mouth to feel dry and prompting you to take action to quench your thirst.

Salivation can be stimulated by the sight, smell, and taste of food. It can even be stimulated by thinking about food. You might notice whether reading about food and salivation right now has had any effect on your production of saliva.

How does the salivation process work while you are eating? Food contains chemicals that stimulate taste receptors on the tongue, which send impulses to the superior and inferior salivatory nuclei in the brain stem. These two nuclei then send back parasympathetic impulses through fibers in the glossopharyngeal and facial nerves, which stimulate salivation. Even after you swallow food, salivation is increased to cleanse the mouth and to water down and neutralize any irritating chemical remnants, such as that hot sauce in your burrito. Most saliva is swallowed along with food and is reabsorbed, so that fluid is not lost.

What is saliva?

Saliva, or spit, is made by your salivary glands. It helps keep you and your mouth healthy. For example:

• It moistens and breaks down the foods you eat, which makes it easier for you to chew and swallow.
• It washes away small food pieces from your teeth and gums, which helps fight against tooth decay.
• It contains minerals such as calcium and phosphate, which can also help fight tooth decay.
• It contains antibodies that can fight against infections of the mouth and throat. Antibodies are proteins that your immune systemmakes to fight foreign substances such as viruses and bacteria.

What is dry mouth?

Having dry mouth, also called xerostomia, means that you don't have enough saliva to keep your mouth wet. Everyone has a dry mouth once in a while, like when you are nervous or stressed. But if you have a dry mouth all or most of the time, it can be uncomfortable. It can make chewing, swallowing, and even talking difficult. It also raises your risk for tooth decay or infections in the mouth.

What causes dry mouth?

There are many possible causes of dry mouth, including:

• Side effects of certain medicines, such as some medicines for high blood pressure, depression, and bladder-control issues
• Diseases such as Sjogren's syndrome, HIV, salivary gland disorders, and diabetes
• Radiation therapy, which can damage your salivary glands if they are exposed to radiation during the treatment
• Chemotherapy, which can make your saliva thicker and cause your mouth to feel dry
• Nerve damage, when it involves the nerves that tell salivary glands to make saliva
• Breathing through your mouth
• Use of alcohol, tobacco, or other substances

What are the symptoms of dry mouth?

The symptoms of dry mouth may include:

• A sticky, dry feeling in your mouth
• Trouble chewing, swallowing, tasting, or speaking
• A burning feeling in your mouth
• A dry feeling in your throat
• Cracked lips
• A dry, rough tongue
• Mouth sores
• An infection in your mouth
• Bad breath

How is the cause of dry mouth diagnosed?

If you have dry mouth, it's important to find out the cause. To do that, your health care provider or dentist will review your medical history, examine your mouth, and ask about any medicines you take. They may also suggest blood tests or a test that measures how much saliva you produce.

What are the treatments for dry mouth?

Treatment for dry mouth depends on the cause. For example, if a medicine is causing dry mouth, your provider or dentist may suggest adjusting the dosage or switching medicines. In some cases, they might give you artificial saliva or a medicine to help your salivary glands work better.

There are also several things you can do to help relieve your symptoms:

• Drink plenty of water
• Avoid drinks with caffeine, which can dry out your mouth
• Chew sugarless gum or suck on sugarless hard candy to stimulate saliva flow
• Avoid spicy or salty foods because they can cause pain if your mouth is dry
• Avoid alcohol and tobacco
• Using a humidifier at night
• Use a mouthwash made for dry mouth

Since dry mouth can raise your risk of tooth decay, it's important to brush and floss your teeth regularly and see your dentist at least twice a year.

There are several possible causes of dry mouth:

• Side effects of some medicines. Hundreds of medicines can cause the salivary glands to make less saliva. For example, medicines for high blood pressure, depression, and bladder-control issues often cause dry mouth.
• Disease. Sjögren's syndrome, HIV/AIDS, and diabetes can all cause dry mouth.
• Radiation therapy. The salivary glands can be damaged if they are exposed to radiation during cancer treatment.
• Chemotherapy. Drugs used to treat cancer can make saliva thicker, causing the mouth to feel dry.
• Nerve damage. Injury to the head or neck can damage the nerves that tell salivary glands to make saliva.

Symptoms of dry mouth include:

• A sticky, dry feeling in the mouth
• Trouble chewing, swallowing, tasting, or speaking
• A burning feeling in the mouth
• A dry feeling in the throat
• Cracked lips
• A dry, rough tongue
• Mouth sores
• An infection in the mouth
• Bad breath

Your doctor or dentist will review your medical history and ask about any medications you take. He or she may also suggest blood tests or a test that measures how much saliva you produce.

Radiography of the SALIVARY GLANDS or ducts following injection of contrast medium.

Depending on the cause of your dry mouth, your health care provider can recommend appropriate treatment. For example, if medication is causing dry mouth, the doctor or dentist may advise changing medications or adjusting the dosages, or may prescribe a saliva substitute.

There are also self-care steps you can take to help ease dry mouth, such as drinking plenty of water, chewing sugarless gum, and avoiding tobacco and alcohol. Good oral care at home and regular dental check-ups will help keep your mouth healthy.

You can relieve dry mouth symptoms by:

• Sipping water or sugarless drinks often.
• Sipping water or a sugarless drink during meals. This will make chewing and swallowing easier. It may also improve the taste of food.
• Avoiding drinks with caffeine, such as coffee, tea, and some sodas. Caffeine can dry out the mouth.
• Chewing sugarless gum or sucking on sugarless hard candy to stimulate saliva flow; citrus, cinnamon or mint-flavored candies are good choices. Some sugarless chewing gums and candies contain xylitol and may help prevent cavities.
• Avoiding spicy or salty foods, which may cause pain in a dry mouth.
• Avoiding tobacco or alcohol. They dry out the mouth. If you are a current smoker, consider quitting.
• Using a humidifier at night.