This condition can result in discomfort, interfere with speech and swallowing, make wearing dentures difficult, cause halitosis, and impair oral hygiene by causing a decrease in oral pH and an increase in bacterial growth. Long-standing xerostomia can result in severe tooth decay and oral candidiasis. Xerostomia is a common complaint among older adults, affecting about 20% of them.
Stimulation of the oral mucosa signals the salivatory nuclei in the medulla, triggering an efferent response. The efferent nerve impulses release acetylcholine at salivary gland nerve terminals, activating muscarinic receptors (M3), which increase saliva production and flow. Medullary signals responsible for salivation may also be modulated by cortical inputs from other stimuli (eg, taste, smell, anxiety).
Xerostomia is usually caused by the following:
Drugs are the most common cause (see table Some Causes of Xerostomia); about 400 prescription drugs and many over-the-counter (OTC) drugs cause decreased salivation. The most common include the following:
Some Causes of Xerostomia
The rise of illicit methamphetamine use has resulted in an increasing incidence of meth mouth, which is severe tooth decay and periodontal inflammation caused by methamphetamine-induced xerostomia. The damage is exacerbated by the bruxing and clenching caused by the drug along with elevated intake of sugary beverages and poor oral hygiene while under the influence of the drug. This combination causes very rapid destruction of teeth.
Tobacco use usually causes a decrease of saliva.
History of present illness should include acuity of onset, temporal patterns (eg, constant vs intermittent, presence only on awakening), provoking factors, including situational or psychogenic factors (eg, whether xerostomia occurs only during periods of psychologic stress or certain activities), assessment of fluid status (eg, fluid intake habits, recurrent vomiting or diarrhea), and sleeping habits. A history of use of recreational drugs should be taken.
Review of systems should seek symptoms of causative disorders, including dry eyes, dry skin, rashes, and joint pain (Sjögren syndrome).
Past medical history should inquire about conditions associated with xerostomia, including Sjögren syndrome, history of radiation treatment, head and neck trauma, and a diagnosis of or risk factors for HIV infection. Drug profiles should be reviewed for potential offending drugs (see table Some Causes of Xerostomia).
Physical examination is focused on the oral cavity, specifically any apparent dryness (eg, whether the mucosa is dry, sticky, or moist; whether saliva is foamy, thick, stringy, or normal in appearance), the presence of any lesions caused by Candida albicans, and the condition of the teeth.
The presence and severity of xerostomia can be assessed in several ways. For example, a tongue blade can be held against the buccal mucosa for 10 seconds. If the tongue blade falls off immediately when released, salivary flow is considered normal. The more difficulty encountered removing the tongue blade, the more severe the xerostomia. In women, the lipstick sign, where lipstick adheres to the front teeth, may be a useful indicator of xerostomia.
If there appears to be dryness, the submandibular, sublingual, and parotid glands should be palpated while observing the ductal openings for saliva flow. The openings are at the base of the tongue anteriorly for the submandibular and sublingual glands and on the middle of the inside of the cheek for the parotid glands. Drying the duct openings with a gauze square before palpation aids observation. If a graduated container is available, the patient can expectorate once to empty the mouth and then expectorate all saliva into the container. Normal production is 0.3 to 0.4 mL/min. Significant xerostomia is 0.1 mL/min.
Dental caries may be observed at the margins of restorations or in unusual places (eg, at the gum line, incisal edges, or cusp tips of the teeth).
A common manifestation of C. albicans infection is areas of erythema and atrophy (eg, loss of papillae on the dorsum of the tongue). Less common is the better-known white, cheesy curd that bleeds when wiped off.
Xerostomia is diagnosed by symptoms, appearance, and absence of salivary flow when massaging the salivary glands.
No further assessment is required when xerostomia occurs after initiation of a new drug and stops after cessation of that drug or when symptoms appear within several weeks of irradiation of the head and neck. Xerostomia that occurs with abrupt onset after head and neck trauma may be caused by nerve damage.
Concomitant presence of dry eyes, dry skin, rash, or joint pain, particularly in a female patient, suggests a diagnosis of Sjögren syndrome. Severe tooth discoloration and decay, out of proportion to expected findings, may be indicative of illicit drug use, particularly methamphetamines. Xerostomia that occurs only during nighttime or that is noted only on awakening may be indicative of excessive mouth breathing in a dry environment.
For patients in whom the presence of xerostomia is unclear, sialometry can be conducted by placing collection devices over the major duct orifices and then stimulating salivary production with citric acid or by chewing paraffin. Normal parotid flow is 0.4 to 1.5 mL/min/gland. Flow monitoring can also help determine response to therapy.
The cause of xerostomia is often apparent, but if the etiology is unclear and systemic disease is considered possible, further assessment should be pursued with biopsy of a minor salivary gland (for detection of Sjögren syndrome, sarcoidosis, amyloidosis, tuberculosis, or cancer) and HIV testing. The lower lip is a convenient site for biopsy.
When possible, the cause of xerostomia should be addressed and treated.
For patients with drug-related xerostomia whose therapy cannot be changed to another drug, drug schedules should be modified to achieve maximum drug effect during the day because nighttime xerostomia is more likely to cause caries. Custom-fitted acrylic night guards carrying fluoride gel may also help limit caries in these patients. For all drugs, easy-to-take formulations, such as liquids, should be considered, and sublingual dosage forms should be avoided. The mouth and throat should be lubricated with water before swallowing capsules and tablets or before using sublingual nitroglycerin. Patients should avoid decongestants and antihistamines.
Patients using continuous positive airway pressure for obstructive sleep apnea may benefit from using the humidifier function of the device. Patients using oral appliance therapy may benefit from a room humidifier.
Symptomatic treatment consists of measures that do the following:
Drugs that augment saliva production include cevimeline and pilocarpine, both cholinergic agonists. Cevimeline (30 mg orally 3 times a day) has less M2 (cardiac) receptor activity than pilocarpine and a longer half-life. The main adverse effect is nausea. Pilocarpine (5 mg orally 3 times a day) may be given after ophthalmologic and cardiorespiratory contraindications are excluded; adverse effects include sweating, flushing, and polyuria.
Sipping sugarless fluids frequently, chewing xylitol-containing gum, and using an over-the-counter saliva substitute containing carboxymethylcellulose, hydroxyethylcellulose, or glycerin may help. Petroleum jelly can be applied to the lips and under dentures to relieve drying, cracking, soreness, and mucosal trauma. A cold-air humidifier may aid mouth breathers who typically have their worst symptoms at night.
Meticulous oral hygiene is essential. Patients should brush and floss regularly (including just before bedtime) and use fluoride rinses or gels daily; using newer toothpastes with added calcium and phosphates also may help avoid rampant caries. An increased frequency of preventive dental visits with plaque removal is advised. The most effective way to prevent caries is to sleep with individually fitted carriers containing 1.1% sodium fluoride or 0.4% stannous fluoride. In addition, a dentist can apply a 5% sodium fluoride varnish 2 to 4 times a year.
Patients should avoid sugary or acidic foods and beverages and any irritating foods that are dry, spicy, astringent, or excessively hot or cold. It is particularly important to avoid ingesting sugar near bedtime.
Drugs are the most common cause, but systemic diseases (most commonly Sjögren syndrome or HIV) and radiation therapy also can cause xerostomia.
Symptomatic treatment includes increasing existing saliva flow with stimulants or drugs, and artificial saliva replacement; xylitol-containing gum and sugarless candy may be useful.
Patients with xerostomia are at high risk of tooth decay; meticulous oral hygiene, additional preventive measures in home care, and professionally applied fluorides are essential.