The Etiology of Xerostomia

Dental hygienists are uniquely positioned to detect xerostomia. Part of the dental hygiene process of care is to provide thorough intra- and extraoral examinations. They typically see their patients at least two times per year, putting them at the forefront of patients’ oral health care needs. Dental hygienists must be able to recognize the signs of xerostomia in order to educate patients of the potential causes and implications and provide recommendations for symptom relief.

While xerostomia is often associated with decreased salivary function, the condition is actually defined as the subjective complaint of dry mouth, regardless of the amount or composition of saliva.¹ To objectively determine whether salivary gland hypofunction (SGH), or hyposalivation, exists, the amount of salivary flow must be compared to the amounts of absorption and evaporation of saliva in the mouth.¹ Some studies use xerostomia and SGH interchangeably, while others create more defined parameters.² This factor, in addition to limited data, make it difficult to accurately determine the prevalence of xerostomia in the United States. The American Dental Association states that prevalence estimates range anywhere from 0.9% to 64.8%.³

SALIVARY FUNCTION

Saliva is secreted through the salivary glands, which are composed of different types of cells. The acinar cells and myoepithelial cells are most important in the secretion process. The acinar cells are responsible for whether the saliva is serous, mucous, or a mixture of the two, while the myoepithelial cells assist in secretion.⁴ Saliva is almost completely made up of water (99%). The remaining 1% is composed of multiple minerals, bicarbonate, immunoglobulins, proteins, enzymes, mucins, urea, and ammonia.⁴

Saliva serves an important role in maintaining oral and systemic health, as it initiates digestion.⁵ It plays a role in speaking, chewing, and swallowing. By reducing acidity, preventing demineralization, and initiating remineralization, saliva protects the tooth structure.^5,6 Saliva also maintains the integrity of the soft tissues—including the mucosa, gingiva, and tongue—and reduces the risk of infection.^5,6

Xerostomia can cause discomfort and more severe cases can result in sensitivity of the tissues, a burning sensation, or even ulcerations.^5,6 It may become difficult to speak and swallow, as the tongue can become dry, fissured, or atrophic.⁵ Saliva naturally bathes the teeth and aids in remineralization, and without it, plaque accumulation and subsequent gingival inflammation may increase. In addition, lack of saliva may raise the risk of tooth decay or erosion.^5,6 Extraorally, the lips may peel or become chapped, and angular cheilitis may occur.⁵

MEDICATION USAGE

One of the most common causes of xerostomia is medication use.² Chemicals present in medications can alter pathways in the nervous system that stimulate salivary gland secretion.⁷ More than 500 medications note xerostomia as a side effect, including anticholinergic, antihistamines, antihypertensive agents, opioids, antidepressants, antipsychotics, and skeletal muscle relaxants.⁵ These medications do not cause damage to the salivary glands, but rather lead to hyposalivation.⁵

The risk of xerostomia grows as the number of prescription medications taken at once increases. Polypharmacy refers to taking more than one medication at a time.⁸ Polypharmacy occurs when an individual has multiple medical conditions that require different medications for treatment.⁸ Between 2011 and 2014, the US Centers for Disease Control and Prevention (CDC) identified 48.9% of the US population as taking at least one or more prescription medications, 23.1% as taking at least three or more prescription medications, and 11.9% as taking five or more prescription medications.⁹ Polypharmacy is more common among older adults, as this population experiences more health problems.^8,10 Dental hygienists must be prepared to treat older adults, as the number of individuals age 65 and older continues to rise in the US.¹¹

Medications used to treat mental health disorders, particularly antidepressants, often carry xerostomia as a side effect. With high numbers of Americans experiencing mental health problems, dental hygienists should be well versed in the oral health effects of treatment. According to the National Institute of Mental Health, one in five Americans has a mental health illness.¹²

Antihistamines are another type of medication that can cause xerostomia. Available in both over-the-counter and prescription options, antihistamines reduce or block histamines, which are produced by the body in response to allergens.¹³ Patients taking antihistamines should be advised of the risk of xerostomia.

SYSTEMIC DISEASES

Several medical conditions can also cause xerostomia, such as diseases of the endocrine system, viral infections, bacterial infections, granulomatous diseases, and others.¹⁴ Diabetes, for example, is often accompanied by polyuria and dehydration, which may lead to dry mouth.¹⁴ Xerostomia has been documented in 14.62% of those with type 2 diabetes, as well as 38.5% of children and 53% of adolescents with type 1 diabetes.¹⁴ Xerostomia may also be an issue for patients with human immunodeficiency virus due to the proliferation of CD8 + cells and parotid gland enlargement.¹⁴

Perhaps the condition most directly associated with xerostomia is Sjögren syndrome. An autoimmune disorder that causes the body’s immune cells to attack the salivary glands, Sjögren syndrome can lead to dryness of several body tissues and organs, particularly the eyes and mouth. Approximately 4 million Americans have Sjögren syndrome, making it one of the most common autoimmune diseases in the US.¹⁵ The oral symptoms of Sjögren syndrome may cause the patient to visit his or her dentist before a physician, so dental hygienists need to be able to recognize the oral manifestations. Without saliva present, the colonization of bacteria and fungi is more likely. Oral candidiasis is one of the most common conditions seen in patients with Sjögren syndrome.¹⁶ Yan et al¹⁶ found that 87% of those with the syndrome did, in fact, have oral candidiasis. In addition to causing pain, the clinical signs of oral candidiasis include erythema of the mucosal surfaces; angular cheilitis; and variations of the tongue, such as erythema, fissuring, and loss of papillae on the dorsal surface.¹⁶ Patients with Sjögren syndrome are also at increased risk for caries, including those that involve the roots and incisal surfaces.¹⁷

Other autoimmune disorders that have been linked to xerostomia are rheumatoid arthritis, systemic lupus erythematosus, primary biliary cirrhosis, and scleroderma.¹⁴ Each of these conditions often coexists with Sjögren syndrome. Sjögren syndrome may also be related to thyroid diseases, hepatitis C, and Epstein-Barr virus. Patients with these health problems should be educated about xerostomia signs and symptoms.¹⁴

CANCER/RADIATION TREATMENT

According to the National Cancer Institute, cancers of the head and neck represent about 4% of all cancers in the US.¹⁸ A small portion of head and neck cancers are found in the salivary glands. Treatment often includes radiation therapy, which attacks the cancer cells with high energy radiation.¹⁹ Unfortunately, other cells in the region may also be harmed. Salivary glands are generally located in the direct line of radiation. This causes a change in the output of the saliva almost immediately. The first week to 10 days of radiation treatment is generally the worst, and the salivary flow could decrease by 50% to 60%.¹⁹ Subsequently, the salivary flow may continue to decrease another 10% for up to 3 months after radiation therapy ceases.¹⁹ The decreased amount of saliva is accompanied by changes in the salivary composition, both of which lead to an inability to buffer the acidity in the mouth. This chronic xerostomia affects approximately 80% of those receiving radiation therapy.

LIFESTYLE

Excessive alcohol use, smoking, and eating habits are all factors that may increase the risk of xerostomia. Alcohol consumption is a common social activity in the US, but overuse can have significant health consequences. According to the National Institute on Alcohol Abuse and Alcoholism, 15.1 million adults have an alcohol use disorder, which is defined as the inability to stop using alcohol despite its negative consequences.²⁰ Consuming large amounts of alcohol in a short time, such as binge drinking, can change the composition of the saliva as well as decrease the amount that is made and secreted by the salivary glands thus leading to xerostomia.²⁰ Chronic alcoholism can lead to xerostomia by causing cell death of the acinar cells that aid in the composition and secretion of the saliva.²¹

While most are aware of the potential cancerous and respiratory effects of smoking, negative oral health effects are often taken less seriously. Dyasanoor and Saddu²² found that smoking leads to reduced salivary flow as well as xerostomia. Results demonstrated that while 37% of smokers reported symptoms of xerostomia, 43% exhibited signs of hyposalivation.²² Interestingly, in nonsmokers, 13% reported symptoms of xerostomia while only 8% showed signs of hyposalivation.²² This not only proves a higher presence of xerostomia in smokers, but it also illustrates the difference in perceptions of how smokers vs nonsmokers regard their health.

EATING DISORDERS

Another less common consideration is the effect of eating disorders. Bulimia nervosa is a psychological disorder that is classified by binge eating with inappropriate methods of weight loss to compensate for binge-eating episodes. These methods include vomiting, improper use of laxatives and diuretics, and excessive exercise, all of which can lead to dehydration and xerostomia. Furthermore, those with bulimia may be taking antidepressants, which can lead to xerostomia.²³ The World Health Organization estimates the prevalence of bulimia to be only 1%, with 12 new cases per 100,000 each year.²³ While the prevalence might seem low, statistics do not include unreported cases. Dental hygienists should be able to recognize oral signs of bulimia.²³

MANAGEMENT

Patient education is key to effectively addressing xerostomia.⁵ Patients with medical conditions or on drug regimens that may decrease salivary flow should be informed of their increased risk for xerostomia, as well as provided with effective ways to prevent or mitigate it. Social histories should also be considered and patients who disclose alcohol or tobacco use should be informed of the associated oral risks and provided with referrals for treatment and resources for cessation. Dental hygienists can also provide nutritional counseling and should inform patients of how certain foods and drinks (such as those with a high-sugar content, high acidity, or caffeine) can be harmful in the presence of xerostomia.²⁴ Patients should be educated on the increased risk of decay, inflammation, and ulcers, as well as difficulty in physiological functions like chewing and swallowing.⁵

When xerostomia exists, or has the potential to exist, in-office treatments are beneficial. Fluoride varnishes, sealant placement, and more frequent recare appointments can address the increased risk for caries.⁵ At-home recommendations may include more frequent brushing, increased use of interdental aids, prescription fluoride toothpastes, and fluoride mouthrinses. Oral health care products with arginine bicarbonate and calcium carbonate may support a neutral pH and healthy enamel.²⁵ The use of products with amorphous calcium phosphate (ACP), casein phosphopeptide-ACP, calcium sodium phosphosilicate, and tricalcium phosphate can help patients with xerostomia reduce their caries risk.²⁶

For patients in pain, palliative measures may be necessary. While most provide only temporary relief, sucking on ice cubes, lozenges, and chewing sugar-free gum with xylitol may be helpful.⁵ Mouthrinses, toothpastes, and sprays noted as artificial saliva also can provide some comfort for patients.⁵ Oral health care products with a neutral pH and those containing carboxymethylcellulose or those with natural ingredients can alleviate symptoms.²⁶ Other remedies to recommend may include drinking water frequently including while eating, and sleeping with a humidifier.²⁴

Beyond the clinical considerations, dental hygienists should engage in interprofessional collaboration, consulting with patients’ medical providers if necessary. If the patient is experiencing xerostomia, but has no known medical or social causes, a physical exam and blood test may be useful to see if an underlying systemic condition exists.⁵ If the patient is taking multiple medications that are worsening the severity of xerostomia, his or her physician should be contacted to see if an alternative treatment or lifestyle change would help to decrease the use of medications.⁵ For patients with medical conditions, such as Sjögren syndrome, the use of sialogogues, or drugs that stimulate the secretion of saliva maybe be appropriate.²⁴

CONCLUSION

The exact prevalence of xerostomia may be difficult to define, but the supporting evidence linked to its occurrence is plentiful. In a world where medical conditions and treatments are constantly emerging, dental hygienists and health care providers must be able to bridge the gap between the literature and appropriate patient recommendations. Dental hygienists play an important role in increasing awareness regarding the causes of xerostomia, its impact on the oral cavity, and management strategies.

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From Dimensions of Dental Hygiene. July/August 2019;17(7):50–53.