Dry mouth at night

Introduction

Dry mouth at night, also known as nocturnal xerostomia, is a common condition that affects many individuals. It can lead to discomfort, difficulty sleeping, and potential oral health complications. Understanding the causes, clinical features, and management strategies is essential for improving patient quality of life.

Anatomy and Physiology of Salivary Glands

Major Salivary Glands

The major salivary glands are responsible for producing the majority of saliva in the oral cavity:

• Parotid glands: Located near the ears, they secrete serous, watery saliva.
• Submandibular glands: Found beneath the lower jaw, they produce a mixture of serous and mucous saliva.
• Sublingual glands: Situated under the tongue, these glands primarily secrete mucous saliva.

Minor Salivary Glands

Minor salivary glands are scattered throughout the oral mucosa and contribute to continuous lubrication:

• Present in the lips, cheeks, palate, and tongue
• Help maintain mucosal moisture and assist in speech and swallowing

Saliva Production and Regulation

Saliva production is regulated by the autonomic nervous system and serves multiple functions in oral health:

• Parasympathetic stimulation increases watery saliva production
• Sympathetic stimulation increases mucous-rich saliva
• Saliva aids in digestion, protects oral tissues, and lubricates the mouth for speech and swallowing

Causes of Dry Mouth at Night

Physiological Causes

• Normal Reduction of Saliva During Sleep: Saliva production naturally decreases at night, leading to mild dryness in the mouth.
• Mouth Breathing During Sleep: Breathing through the mouth instead of the nose can exacerbate dryness and irritation of oral tissues.

Medications

• Antihypertensives, which may reduce saliva flow
• Antidepressants, particularly tricyclics and SSRIs
• Antihistamines, commonly used for allergies
• Diuretics that increase fluid loss and contribute to dehydration

Systemic Diseases

• Diabetes mellitus, causing reduced salivary gland function and dehydration
• Sjögren’s syndrome, an autoimmune disease affecting salivary glands
• Rheumatoid arthritis, which can be associated with secondary Sjögren’s syndrome
• Chronic kidney disease, leading to fluid imbalance and xerostomia

Oral and Lifestyle Factors

• Dehydration due to insufficient fluid intake
• Smoking and alcohol consumption, both of which reduce saliva production
• Caffeine intake before bedtime, which may contribute to dryness
• Obstructive sleep apnea, leading to mouth breathing and dry oral tissues

Clinical Presentation

Symptoms

• Dryness and stickiness in the mouth, especially upon waking
• Difficulty swallowing, speaking, or tasting
• Throat irritation or hoarseness
• Bad breath due to reduced saliva-mediated cleansing

Physical Examination Findings

• Dry, cracked, or reddened oral mucosa
• Thick, frothy, or absent saliva
• Increased dental caries, gingivitis, or oral infections

Diagnostic Evaluation

Medical History

• Comprehensive medication review to identify xerogenic drugs
• History of systemic diseases such as diabetes or autoimmune disorders
• Assessment of sleep and breathing patterns, including mouth breathing or snoring

Laboratory Tests

• Blood glucose levels to assess for diabetes mellitus
• Autoantibody panels for Sjögren’s syndrome, including anti-Ro/SSA and anti-La/SSB
• Renal and liver function tests if systemic disease is suspected

Special Tests

• Sialometry to measure saliva flow rate and quantify xerostomia
• Imaging of salivary glands using ultrasound or MRI to detect structural abnormalities
• Sleep study for evaluation of obstructive sleep apnea if mouth breathing is prominent

Treatment and Management

Conservative Measures

• Hydration and increased water intake throughout the day and before bed
• Use of saliva substitutes, oral gels, or mouth rinses to maintain moisture
• Humidifier use in the bedroom to reduce nighttime dryness
• Proper oral hygiene, including regular brushing, flossing, and dental checkups

Medication Adjustments

• Review and modification of medications that contribute to dry mouth
• Use of sialogogues such as pilocarpine or cevimeline to stimulate saliva production

Treatment of Underlying Conditions

• Optimizing blood glucose control in diabetes
• Management of autoimmune diseases such as Sjögren’s syndrome
• Treatment of sleep apnea using CPAP or oral appliances to reduce mouth breathing

Complications

• Dental Caries and Enamel Erosion: Reduced saliva leads to decreased natural protection of teeth, increasing the risk of cavities and enamel wear.
• Oral Infections: Higher susceptibility to candidiasis, gingivitis, and other infections due to impaired antimicrobial function of saliva.
• Difficulty with Speech and Swallowing: Persistent dryness can interfere with articulation and the ability to chew and swallow food comfortably.
• Sleep Disruption and Fatigue: Discomfort from dry mouth may cause frequent awakenings, leading to daytime fatigue and decreased quality of life.

Prevention and Patient Education

• Maintaining Hydration: Encouraging adequate fluid intake throughout the day, particularly before bedtime.
• Proper Oral Care Routines: Regular brushing, flossing, and dental visits to minimize risk of dental disease.
• Avoiding Alcohol, Caffeine, and Tobacco at Night: Reduces xerostomia and improves oral mucosal health.
• Regular Dental Checkups: Early identification and management of dental caries, oral infections, and mucosal changes.

References

1. Ship JA, Fox PC. Salivary gland disorders. In: Fehrenbach MJ, Herring SW, editors. Illustrated Anatomy of the Head and Neck. 6th ed. St. Louis: Elsevier; 2018. p. 235-251.
2. Fauci AS, Kasper DL, Hauser SL, et al. Harrison’s Principles of Internal Medicine. 20th ed. New York: McGraw-Hill; 2018.
3. Turner MD, Ship JA. Dry mouth and its management. Dent Clin North Am. 2017;61(3):451-468.
4. Fox RI. Sjögren’s syndrome. Lancet. 2005;366(9482):321-331.
5. Villa A, Connell CL, Abati S. Diagnosis and management of xerostomia and hyposalivation. Ther Clin Risk Manag. 2014;10:45-51.
6. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. 9th ed. Philadelphia: Wolters Kluwer; 2021.
7. Turner MD, Ship JA. Dry mouth: evaluation and management. Med Clin North Am. 2015;99(6):1167-1184.
8. Ghezzi EM, Ship JA. Nighttime dry mouth: causes and treatment. J Am Dent Assoc. 2003;134(6):732-738.
9. Fox PC, van der Ven PF, Sonies BC, Weiffenbach JM, Baum BJ. Xerostomia: evaluation of a symptom of diverse etiologies. J Am Dent Assoc. 1985;110(4):519-524.
10. Claudia L, et al. Management of nocturnal xerostomia in adults. Oral Dis. 2019;25(7):1724-1735.