What is xerostomia (dry mouth)?

Dry mouthThe technical name for a dry mouth is called xerostomia. Xerostomia is the subjective feeling of oral dryness, which may or may not be associated with a problem with the salivary glands.

Xerostomia is not a disease. It is a symptom of various medical conditions. Dry mouth is a common complaint among older adults, affecting approximately 20% of the elderly, and 10% of the total population.


What is the purpose of saliva?

Saliva has an abundance of roles in the mouth, and most people take for granted the important role it plays in lubricating the oral tissues, taste, speech, digestion, mastication, and swallowing. It is useful in the dilution and clearing of material from the mouth, and also acts to maintain the health of the mucosa inside the oral cavity. Another important function of saliva is to protect the teeth from tooth decay as it has antibacterial and buffering properties to minimise the harm from dental plaque.


What causes dry mouths?

There are 3 major salivary glands (submandibular, sublingual and parotid) and thousands of minor salivary glands throughout the mouth. All of these are stimulated by the autonomic nervous system. Stimulation by the nervous system causes saliva to be released into the mouth.  Saliva can be either watery, or of a thicker consistency depending on what type of stimulation occurs.

Causes of xerostomia include many common medications, Sjögren’s Syndrome, some cancer therapy, and other systemic problems.


Medications

Xerostomia most commonly occurs as a side effect of medications. When the site of the medication being used acts upon the autonomic nervous system, there is a possibility the individual will have a dry mouth. Drug types which have been related with xerostomia include antihistamines, antihypertensives, tricyclic antidepressants, and sedatives.

Consuming a greater number of medications (as is common in the elderly) results in a higher chance of having a dry mouth.

Recreational drugs such as marijuana and heroin may also cause temporary or permanent reduction in saliva flow depending on usage and other factors.


Sjögren’s syndrome

Sjögren’s syndrome, which occurs mostly in postmenopausal women, is an autoimmune disease that particularly involves the salivary and lacrimal glands. In this disease process, the person has impaired saliva flow rates.

Approximately 95% of people with Sjögren’s syndrome experience xerostomia. Dryness of the eye, nose, throat, skin and vagina are also common complaints.

‘Primary Sjögren’s syndrome’ is limited to the eyes and salivary glands whereas those with ‘secondary Sjögren’s syndrome’ also have another type of inflammatory disease such as rheumatoid arthritis or lupus erythematosus.


Cancer therapy

Medical therapies such as radiotherapy to the head and neck that includes the salivary glands as part of their treatment often result in a permanent dry mouth.

Small amounts of radiotherapy can merely result in inflammation and temporary loss of saliva flow, however high doses over a long period of time (as radiotherapy usually is) results in essentially fibrosis (scar tissue) of the saliva glands.


Systemic diseases

There are a large number of conditions that can affect salivary gland function and lead to complaints of dryness, including:

Other causes of poor saliva flow include:

  • dehydration due to low water intake, vomiting, diarrhoea or polyuria;
  • psychological causes, such as depression, anxiety, stress or fear;
  • Alzheimer’s disease or stroke that may alter the ability to perceive oral sensations;
  • activities such as hyperventilation, breathing through the mouth, smoking or drinking alcohol; and/or
  • trauma to the head and neck area can damage the nerves supplying sensation to the mouth and related structures.

 

 


Signs and symptoms of a dry mouth

Dry mouthClinical symptoms

A reduction of saliva may lead to the following symptoms:

  • complaints of a dry mouth;
  • oral burning or soreness or a sensation of loss of, or altered taste;
  • the need for frequent drinks to be taken whilst eating or talking;
  • difficulty in talking;
  • difficulty in swallowing dry foods;
  • recurrent salivary gland swellings/infections;
  • cracked lips at the corner of the mouth; and/or
  • generalised oral soreness and ulceration in those who wear dentures.


Clinical signs

The following clinical signs may be visible in a person who complains of a dry mouth and its associated symptoms:

  • swollen salivary glands;
  • absence of saliva inside the mouth;
  • dry, paper-thin ‘parchment’ appearance of oral mucosa or appearance of small amounts of frothy saliva in an otherwise dry mouth;
  • mucosal changes on the inner surface of cheek and tongue;
  • dry and cracked lips;
  • evidence of a fungal infection; and
  • development of new tooth decay, especially on unusual places.

Tooth decay and candidiasis, which is a type of fungal infection, are the most common complications in individuals with salivary gland hypofunction (under-functioning). As discussed above, saliva plays an important role in the prevention of tooth decay.

Oral candidiasis essentially occurs when there is a change in the oral environment, due to either systemic or local factors such as iron deficiency or dry mouth respectively.


Treatment for dry mouth

Management depends on the underlying cause of the xerostomia and the degree of salivary gland impairment. Where xerostomia is related to medication use, effective treatment of symptoms may be important to maintain compliance with the medication regime.

Treatment typically includes four areas:

  • increasing existing saliva flow;
  • replacing lost saliva flow;
  • control of tooth decay; and
  • specific measures such as treatment of infections.


Increasing saliva flow

Sugarless candies and lollies are beneficial for most people in encouraging saliva flow to relieve a dry mouth. A lot of sources recommend sipping water frequently and during meals to assist with swallowing food, however some people find this causes a drier sensation to the mouth as the water washes away any existing saliva in the mouth.

As humans, the smell of appetising food stimulates our salivary flow to increase automatically.  In general, the stronger the flavour enhancer, the more saliva is produced. Addition of flavour enhancers such as herbs, condiments and fruit extracts may make swallowing and eating more manageable to individuals complaining of their food tasting bland, papery, salty or otherwise unpleasant. Conversely, it is important to minimise substances which dry the mouth such as alcohol, tobacco and caffeine products (coffee, tea, some soft drinks).


Replacing lost saliva flow 

Artificial saliva is formulated to mimic natural saliva, but do not cause more saliva to be secreted into the mouth, rather it feels like someone else’s saliva in the mouth, and can be quite unpleasant for some people. In general, artificial salivas contain an agent to increase viscosity of saliva.

Anhydrous crystalline maltose (ACM) is being experimented with to stimulate saliva production and new studies showing the use of ACM in people with Sjogren’s syndrome have been positive. Other dry mouth products exist and it is prudent to check with the pharmacist or dentist to see if any given product is suitable.

All artificial saliva, and saliva stimulating medications are relatively expensive and a simple home remedy is to buy some oil, and routinely spray it into the mouth to provide relief, because oil is a better lubricant than water. It is important to find a remedy that works for each individual, and a simple home remedy may in fact be better than an expensive alternative. Using a humidifier at night may aid in the management of a dry mouth at night.


Controlling tooth decay

Tooth decay and fungal infections are the most common complications in an individual with poor saliva flow. Brush and floss thoroughly, and use fluoridated toothpaste twice a day to prevent tooth decay. Also ensure that dental checkups and scale and cleans are regularly completed.  People who develop fungal infections are treated with anti-fungal medications but increasing the moisture in the mouth helps significantly in avoiding this problem.


Key points

  • Xerostomia is the subjective feeling of oral dryness, which may or may not be associated with a problem with the salivary glands.
  • Causes of xerostomia include many common medications, Sjögren’s Syndrome, some cancer therapy, and other systemic problems.
  • A reduction of saliva may lead to the following symptoms: complaints of a dry mouth, the need for frequent drinks whilst eating or talking, difficulty in talking and swallowing dry foods etc.
  • Sip water frequently and during meals – to assist with swallowing food.
  • Use saliva substitutes and dry mouth products as necessary, and use those that are of benefit only.
  • Sugar free gum and sugar free lollies help stimulate saliva flow.
  • Consider using a humidifier at night.
  • Brush and floss thoroughly and make sure oral hygiene is excellent.
  • Have regular dental checkups and scale and cleans.

Kindly written by Dr Akhil Chandra BDSc. (Hons UWA)

Dentist, Whitfords Dental Centre and Editorial Advisory Board Member of the Virtual Dental Centre

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