Xerostomia, defined as a real or perceived lack of saliva, is a prevalent but under-recognised condition, particularly in the elderly, which the dental team may be the first to diagnose. This article describes the functions of saliva and discusses the causes, symptoms and management of xerostomia.

By Dr Paula K. Friedman

The increasing importance of recognising and addressing the “invisible disease” of xerostomia has featured in the literature [1, 2]. While not directly life-threatening (no one ever died of dry mouth), suffering from xerostomia can indeed create profound and negative signs and symptoms for the person experiencing the real or perceived lack of saliva.

It is useful to review the functions of saliva before discussing the ramifications of absence of saliva on the oral cavity and on quality of life. The following list provides a brief overview of the often under-recognised yet very important physiological functions of saliva.

Functions of saliva

• Forms a pellicle to act as a physical barrier to the invasion of microorganisms
• Acts a moisturising lubricant to prevent abrasive tooth wear and soft tissue trauma
• Provides potent antimicrobial effects which protect against bacteria, fungi and viruses in the mouth
• Creates a washing effect to help clear the oral cavity of microorganism and food debris, especially sugars/refined complex carbohydrates
• Supports a hydrating effect that moistens the mouth and aids in chewing and swallowing
• Promotes remineralisation of teeth and the retarding of demineralisation because it is a saturated solution of calcium and phosphate ions
• Develops a high buffering capacity, which protects the dentition against acids from both external and internal sources and aids in the control of the microorganisms that are responsible for dental decay and oral fungal infections

In our experience of working with the elderly population over the past 30 years, we have become increasingly aware of the prevalence of xerostomia as an under-recognized entity.  When we retract the buccal mucosa and/or the tongue and the mirror sticks to the tissue, that is usually an indication that the patient is experiencing dry mouth.  However, unless specifically asked, patients often do not report xerostomia as a problem.  Many medical history forms do not ask whether the patient has ever or is currently experiencing dry mouth. There are a number of conditions that may alert the dental team to the possibility of xerostomia. The causes of xerostomia will be reviewed in the next section.

Causes of xerostomia
While xerostomia may be attributed to a number of etiologic factors, primary among them is the large (and growing) number of medications, both prescribed and over-the-counter, that many elderly patients use every day. The use of multiple medications is referred to as “polypharmacy.” There are currently over 500 medications that can cause xerostomia. Among the categories of medications that have strong links to xerostomia are antihypertensives, anticholinergics, antidepressants, antihistamines and diuretics, as well as non-steroidal anti-inflammatory agents. In addition, patients often take more than one category of these drugs, and studies have shown that using three or more medications increases the probability of the patient experiencing xerostomia.

Other causes include systemic illnesses, such as diabetes, autoimmune diseases especially Sjögren’s syndrome, immunosuppressed status (transplants, AIDS, radiation therapy, chemotherapy) and alcoholic cirrhosis. Emotional issues such as anxiety, depression and stress may also lead to xerostomia, either directly or secondary to the medications prescribed for treatment. Hormonal alterations associated with pregnancy and menopause also have been associated with dry mouth. All of these conditions —polypharmacy, systemic illnesses, and emotional conditions — can contribute to the patient experiencing xerostomia. 

Sequellae
If a patient has xerostomia, what are some of the sequellae that dry mouth may cause?

• Difficulty with tasting, chewing, and swallowing
• Burning sensation in the mouth or tongue
• Esophageal dysfunction, including chronic esophagitis
• Nutritional compromises
• Higher frequency of intolerance to medications
• Increased incidence of glossitis, candidiasis, angular cheilitis, halitosis, bacterial sialadenitis
• Decreased resistance to loss of tooth structure due to attrition, abrasion, and erosion
• Loss of oral buffering capacity
• Increased susceptibility to mucosal injury
• Inability to wear removable prostheses
• Markedly increased susceptibility to dental caries, especially cervical caries

Clearly, each of the conditions listed above has significant implications for quality of life. Having difficulty speaking, tasting, chewing and swallowing affects most of the social interactions that patients, especially elderly patients, enjoy. In addition, patients report other quality of life issues that may not be as immediately apparent to the clinician: inability to whistle (one can’t whistle with a dry mouth), inability to sing (at home, in a community chorus group, or in a church choir, for example), difficulty smiling (mucosa sticks to patients’ teeth or prostheses), and inability to play brass or woodwind musical instruments. While one can certainly appreciate with a clinician’s expertise all the intraoral manifestations, it is impressive to realise how many joyful acts of life may be removed or diminished in a xerostomic patient’s life as a result of their dry mouth.

In a recently published article, Wiener et al conducted a study to evaluate the relationship between self-reported xerostomia and clinical measurement of hyposalivation [3]. Their results indicted that xerostomia is a subjective condition, with no relationship between hyposalivation and self-reported xerostomia, and modest but significant correlation between clinically assessed dry mouth and self-reported xerostomia.

Management of xerostomia
Most management of xerostomia is palliative, with treatment falling into topical management and systemic management. The increasing prevalence of dry mouth as a patient quality of life issue may easily be observed by entering “dry mouth spray” on a web browser and noting the number of manufacturers and products marketed for this use. Manufacturers respond to demand from the market-place, and by inference, there appears to be a growing number of xerostomia-alleviating products.

In general, topical approaches include efforts to keep oral tissues moist. Patients should be told to sip water or sugarless drinks frequently. Artificial saliva (available at most pharmacies), use of sugar-free gum or sweets to stimulate salivary flow, frequent sips of water, alcohol-free oral rinses/mouthwashes and restricted intake of caffeine, tobacco, alcohol and carbonated beverages (which contain drying agents) may help to improve the patient’s perception/experience of dry mouth. Patients should also be  aware that spicy or salty foods may cause pain or discomfort in a dry mouth. Many patients find that using artificial saliva, which comes in a small spray bottle that they can put on their bed-side cabinet, provides helpful relief during the night, when their symptoms may be exacerbated.  Because symptoms may appear worse at night, using a humidifier while sleeping may be helpful.

In patients who retain some salivary gland function, systemic management may be considered as an option. Acetylcholine analogues stimulate exocrine glands and therefore increase salivary output. However, other exocrine functions may also be increased and can cause the following side effects:  gastrointestinal upset; sweating; tachycardia; reflex bradycardia; increased pulmonary secretions and blurred vision (especially at night). Contraindications to use of systemic therapy include gall bladder disease, narrow-angle glaucoma, acute iritis, uncontrolled asthma, hypersensitivity to the drug and renal colic. The typical prescription of an acetylcholine analogue is pilocarpine, prescribed as 5 mg tablets, with 5-10 mg to be taken three times per day. The daily dose should not to exceed 30 mg.

As with all medications for the elderly, it is better to start with a low dose which may be slowly increased. A trial of one week is recommended initially, unless any adverse events occur. The treatment should be re-evaluated after one week.

Last, and certainly most importantly, regular dental checkups and routine cleaning and fluoride applications (fluoride varnish around the cervical areas, or prescription-strength fluoride gel) are critical if good oral health is to be maintained. Routine home-care, including gently brushing teeth at least twice a day, flossing daily, using a fluoride-containing toothpaste, as well as visiting the dentist at least every six months, are important for managing periodontal health and reducing caries risk.

References
1. Friedman PK, Isfeld D. Xerostomia: the “invisible” oral health condition. Todays FDA 2010; 22(1): 61-3.
2. Friedman PK, Isfeld D. Xerostomia: the “invisible” oral health condition. J Mass Dent Soc 2008; 57(3); 42-4.
3. Wiener RC, Wu B, Crout R, Wiener M, Plassman B, Kao E, McNeil D. Hyposalivation and xerostomia in dentate older adults. J Am Dent Assoc 2010; 141(3): 279-84.

The author
Paula K. Friedman, DDS, MSD, MPH
Professor and Associate Dean for Strategic Initiatives
Director, Geriatrics and Gerontology
Director, Geriatric Dentistry Fellowship Program
Boston University Goldman School of Dental Medicine
72 E. Concord St.,
B308
Boston, MA  02118, USA
e-mail: pkf@bu.edu