Xerostomia: Mechanisms and Therapeutic Approaches

What is xerostomia?

Xerostomia, commonly referred to as dry mouth, is a clinical condition characterized by a reduction in salivary flow or an alteration in saliva composition that leads to persistent oral dryness. Saliva plays a critical role in maintaining oral and systemic health by lubricating oral tissues, facilitating chewing and swallowing, initiating digestion, buffering acids, and protecting teeth and mucosa against microbial damage.

Xerostomia may be transient, such as during dehydration, stress, or anxiety, or it may become chronic when salivary gland function is persistently impaired. While aging is frequently associated with dry mouth, xerostomia is not a normal consequence of aging itself but rather reflects cumulative medication use, systemic disease, or glandular dysfunction.

When prolonged, xerostomia significantly affects oral health, nutritional status, speech, taste perception, and overall quality of life.

Physiological role of saliva

Saliva is produced primarily by the parotid, submandibular, and sublingual glands and contains water, electrolytes, enzymes, mucins, antimicrobial peptides, and immunoglobulins. Its functions include:

• Mechanical cleansing of food debris

• Neutralization of acids produced by oral bacteria

• Antimicrobial defense

• Lubrication of oral and pharyngeal tissues

• Facilitation of taste and swallowing

• Protection of tooth enamel and mucosal integrity

A reduction in salivary flow disrupts these protective mechanisms and predisposes individuals to oral disease.

Clinical manifestations of dry mouth

Patients with xerostomia may experience persistent or fluctuating symptoms, including:

• Dryness or sticky sensation in the mouth

• Thick, stringy saliva

• Halitosis

• Difficulty chewing, swallowing, or speaking

• Dry or sore throat

• Hoarseness

• Grooved or fissured tongue

• Altered or diminished taste perception

• Difficulty wearing dentures

• Increased adherence of food or lipstick to teeth

Because saliva supports digestion and taste, xerostomia may reduce appetite and enjoyment of food, contributing to unintended weight loss or poor nutrition.

Etiological factors

Xerostomia results from impaired salivary gland secretion or altered neural regulation of saliva production. The most common causes include:

Medication-related causes

Hundreds of medications can reduce salivary flow, particularly:

• Antidepressants and antipsychotics

• Antihypertensives

• Anxiolytics

• Antihistamines and decongestants

• Muscle relaxants

• Opioid and non-opioid analgesics

Polypharmacy substantially increases xerostomia risk, especially in older adults.

Cancer-related therapies

• Chemotherapy may temporarily alter saliva quantity and composition

• Radiation therapy to the head and neck can cause permanent salivary gland damage, depending on dose and field

Systemic diseases

Dry mouth may occur in association with:

• Diabetes mellitus

• Stroke

• Neurodegenerative disorders such as Alzheimer’s disease

• Autoimmune conditions, particularly Sjögren syndrome

• HIV infection

• Oral fungal infections

Neurological and mechanical factors

• Nerve injury or surgery involving the head and neck

• Chronic mouth breathing or snoring

Lifestyle and substance-related factors

• Tobacco use

• Alcohol consumption

• Recreational drug use, particularly methamphetamines and cannabis

• Diets high in sugar or acidic foods

Risk factors

Individuals at increased risk of xerostomia include those who:

• Take multiple medications with anticholinergic or sympathomimetic effects

• Undergo cancer therapy

• Have autoimmune or metabolic disease

• Use tobacco, alcohol, or recreational drugs

• Consume diets rich in sugar or acidic substances

Complications of chronic xerostomia

Insufficient saliva leads to progressive oral and systemic complications:

• Accelerated dental plaque accumulation

• Increased risk of dental caries and periodontal disease

• Oral mucosal ulcerations

• Angular cheilitis and cracked lips

• Oral candidiasis (thrush)

• Difficulty chewing and swallowing, leading to malnutrition

• Impaired speech and social discomfort

Untreated xerostomia can therefore significantly impair both physical health and psychosocial well-being.

Diagnostic evaluation

Diagnosis is based on clinical history and physical examination, focusing on symptom duration, medication use, systemic disease, and oral findings. In selected cases, additional investigations may include:

• Measurement of unstimulated and stimulated salivary flow

• Blood tests to assess autoimmune or metabolic disorders

• Imaging or biopsy of salivary glands when structural disease is suspected

Management and treatment strategies

Treatment of xerostomia is directed at the underlying cause when possible. Management strategies may include:

• Adjustment or substitution of xerogenic medications

• Optimization of systemic disease control

• Use of saliva substitutes or stimulants

• Behavioral measures such as frequent hydration and sugar-free chewing gum

• Rigorous oral hygiene and regular dental follow-up

In autoimmune or radiation-induced xerostomia, long-term symptom management and prevention of complications are central goals of care.

Scientific references

1. Turner MD, Ship JA. Dry mouth and its effects on the oral health of elderly people. Journal of the American Dental Association. 2007;138(Suppl):15S–20S.

2. Villa A, Abati S. Risk factors and symptoms associated with xerostomia: a cross-sectional study. Australian Dental Journal. 2011;56(3):290–295.

3. Jensen SB, Pedersen AM, Vissink A, et al. A systematic review of salivary gland hypofunction and xerostomia induced by cancer therapies. Supportive Care in Cancer. 2010;18(8):1039–1060.

4. Fox RI. Sjögren’s syndrome. The Lancet. 2005;366(9482):321–331.

5. Guggenheimer J, Moore PA. Xerostomia: etiology, recognition and treatment. Journal of the American Dental Association. 2003;134(1):61–69.