Dry mouth is a common but distressing problem associated with a range of local and systemic factors and may be either transient or permanent in nature. In dentate patients, xerostomia can cause rapidly progressive caries, erosion and periodontal disease and in the edentate, candida infection is a common problem. Both eating and speech can become uncomfortable. Management is aimed at relieving the symptoms and reducing the risk from the major dental diseases.

Xerostomia or dry mouth is a problem for many patients and can vary in severity from a minor irritation to a very distressing clinical problem. It is not a disease entity, but a clinical manifestation of salivary gland dysfunction. The condition presents as dryness often accompanied by a burning sens­ation in the oral mucosa; eating and sometimes speech is difficult and the sensation of taste is reduced. The mucosa is often pale and atrophic with a dry or 'sticky' feel. The tongue may be infl­amed and show atrophy of the papillae together with fissuring and cracking. Xerostomia is rarely a direct cause of infection however, once the condition is established the oral mucosa, especially that of the tongue, may become prone to Candida albicans infection.

Aetiology

A convenient way of classifying the causes of xerostomia is as temporary or permanent.

Temporary Causes:

Psychological

Anxiety and depression are well recog­nized as causes of reduced salivary flow, as many students become aware at examination times! However, these psychological problems are often treated with drugs, which may be salivary inhibitors.

Duct Calculi

A blockage of the duct of a major salivary gland, commonly the submandibular, can produce dryness on the affected side, together with pain and swel­ling in the gland, especially on stimula­tion. If untreated the obstruction may lead to progressive fibrosis of the gland and permanent xerostomia.

Sialoadenitis

Inflammation of the salivary glands can cause reduced secretion. Acute infections include mumps and post-operative paro­titis, while chronic conditions include swellings related to nutritional deficiency and hypersensitivity to iodine. However, many cases of intermittent swelling of the salivary glands are idiopathic and are described as “chronic nonspecific sialoadenitis” and may be associated with duct calculi.

Drug Therapy

A wide variety of drugs may cause xerostomia. Anticholinergic and sympathomimetic agents may be implicated and this group includes tri-cyclic antidepressants, bronchodilators and antihistamines. Diuresis produced by drugs or alcohol can result in dehydration and xerostomia. In most cases function reco­vers after the drug is withdrawn. Zyban, a newly introduced drug to aid smoking cessation can cause xerostomia and since the demand for the drug is likely to be high, its use may become a common aetiological factor.

Permanent Causes:

Salivary Gland Aplasia

Congenital absence of one or more of the major salivary glands is a rare but recog­nized condition of unknown aetiology.

Sjogrens Syndrome

This combination of dry mouth, dry eyes, and often rheumatoid arthritis, mainly affects women over 40 years of age and is often accompanied by a mild fever. About half of the pati­ents with this syndrome also present with, or go on to develop, swellings of the major salivary glands, which display similar histology to Mikulicz's disease.

Other Systemic Disorders

Xerostomia is associated with diabetes mellitus, probably as a consequence of polyurea, as well as Parkinson's disease, cystic fibrosis and sarcoidosis. It has been reported in cases of vitamin A, ribofla­vin and nicotinic acid deficiencies and anaemia.

Radiotherapy

One of the most dramatic and distressing causes of xerostomia is therapeutic radiography for head and neck tumors. The effect on the glands of the irradiated side is often rapid and profound. Post-radiation glandular atrophy is partly due to a reduction in the vascularity of the gland and partly to the direct effect of the x-rays on the highly specialized and sensitive secretary epithelial cells. While recovery of function can occur after several months, in many cases a permanent xerostomia develops. Radiation does not appear to damage the teeth or periodontal tissues directly, the effect on the dentition resulting solely from the reduction in salivary flow.

Surgical desalivation

Surgery or physical trauma to the salivary glands duct may result in damage to the gland, duct, blood or nerve supply and impair secretion.

History and Examination

It is important to establish whether the dry­ness is continual or intermittent, whether it is accompanied by pain or swelling, if unilateral or bilateral and whether there is any relevant history of anxiety, stress or depression, a systemic disorder, irra­diation, trauma, surgery or medication. The patient's occupation, diet and domestic situation are often relevant.

Unilateral dryness with pain or discomfort and swelling in the aff­ected gland on stimulation is often an indication of a duct calculus. Sjogren's syndrome commonly produces bilateral swelling, often constant and accompanied by the other symptoms of the syndrome, and in many cases lymph node enlargement. A punch biopsy of labial glands and by serological tests may be needed to confirm the diagnosis. As well as looking for evidence of enlargement of salivary glands and lymph nodes and unilateral dryness, the palpation of the floor of the mouth for evidence of sub­-mandibular duct calculi and examination of the major duct openings, as inflam­mation or swelling of the orifice may indicate the presence of a distally placed calculus. These are often revealed by simple radiography, as in Figure 1.

It is easy to obtain an indication of basal blow rate by asking the patient to expectorate into a 25 ml glass measuring cylinder for 3 min, first without stimulation and then while chewing paraffin wax or sorbitol chewing gum. Flow rates for healthy adults of less than 0.2 ml/min at rest and less than 0.5 ml/min when stimulated should be regarded as low.

While the more dramatic forms of xerostomia are not common, a more typical case of non-specific xerostomia is a post-meno­pausal woman, living alone with few family or other social contacts, surviving on a low income and a marginally inade­quate diet, and wearing old ill-fitting dentures. The combination of atrophy of the oral mucosa due to hormonal changes and a mild chronic candidosis and reduced salivary flow due to age and depression for which she might have medication, together with a mar­ginal iron deficiency anaemia, is suffi­cient to produce a degree of discomfort which a cursory oral examination will not reveal.

Management

The basic principles of management are:

• Eliminate or address any aetiological factors – drugs, calculi and emotional problems. The patient’s repeat prescription list is often a useful source of information and it may be wise to consult the GP.

• Promote salivary stimulation – sugar-free chewing gum is effective and convenient. Sucking of boiled sweets of the lemon drop type is often a well-received suggestion, but only for full denture wearers!

• Give artificial saliva if needed. These can be found in the Dental Practitioners Formulary, but may be of limited value. Animal mucin, usually porcine, is found in some formulations and some patients may not wish to use them. Frequent sipping of iced water may be more helpful.

• The relief that can be given to many sufferers is limited. However, patience and consideration, esp­ecially towards the elderly, is as important as clinical intervention.

• Regular review to monitor the condition of teeth, gingivae and mucosa and to give support and reinforcement of preventive measures.

Preventive measures:

Apart from measures to alleviate the symptoms, it is essential to institute an appropriate preventive regime for dentate patients to reduce the risks of caries, erosion and periodontal disease –

• Oral hygiene instruction must be given to establish effective plaque control with minimal trauma. Where the mouth is sore, a soft toothbrush, changed frequently may be needed and it may be helpful to try different brands of fluoride toothpaste. A pre-brushing mouthrinse may be of value in some cases.

• Carefully planned dietary advice to reduce the intake of both sugar-sweetened and acidic (erosive) foods and drinks is essential. A 3-day diary is often a useful exercise in helping to reduce risk factors. Patients should be encouraged to increase total fluid intake by drinking more water and milk and to avoid carbonated drinks, fruit juice and squash and glucose drinks.

• Topical fluoride therapy is essential to reduce the risk from caries. All dentate patients with xerostomia should use a full strength fluoride toothpaste containing 1000 - 1500 ppm F twice daily. A daily fluoride mouthrinse (0.05% NaF, equivalent to 250 ppm F) is an effective and useful additional therapy. This should not be used immediately before or after toothbrushing or mealtimes. Where compliance is likely poor, a fluoride gel application every 3 or 4 months may be more effective. A chorhexidine mouthrinse may be helpful as a plaque suppressant for short-term use after radiotherapy.

Further Reading

Mason DK, Chisholm DM. Salivary Glands in Health and Disease. Toronto: WB Saunders, 1975.

Lavelle CLB. Applied Oral Physiology 2nd edn. London: Wright, 1988

Levine RS. Saliva: 3. Xerostomia - aetiology and management. Dental Update, June, 1989.