Article
Specialist referral may be indicated if the Practitioner feels:
Saliva is essential to oral health. The most obvious and important function of saliva is in eating, for taste and to lubricate food, as well as protecting the mucosa and teeth (Table 1). The water, mucins and proline-rich glycoproteins lubricate food and help swallowing. Importantly, saliva is essential for normal taste perception. Saliva is protective via the washing action, via various antimicrobial components such as mucin, histatins, lysozyme and lactoferrin, and via specific antibodies to a range of micro-organisms that the host has encountered.
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Salivary gland secretion from the major (parotid, submandibular and sublingual) and minor glands (multiple mucous glands scattered throughout the mouth – especially the lips and soft palate), is mainly under neural control, under the influence of the autonomic nervous system, although various hormones may also modulate its composition. In general, parasympathetic stimulation increases salivation, while sympathetic stimulation produces more viscous saliva and therefore appears to depress salivation.
Thus, in acute anxiety, when there is sympathetic stimulation, the mouth feels dry. The mouth is also dry if the parasympathetic system is inhibited by, for example, various drugs. Anything that damages the glands, or reduces body fluids, can also reduce salivation.
Dry mouth (xerostomia)
Dry mouth (xerostomia) is a complaint that is the most common salivary problem and is the subjective sense of dryness which may be due to:
Patients who have chronically decreased salivary flow (hyposalivation) suffer from lack of oral lubrication, affecting many functions, and they may complain of dryness (xerostomia), and can develop dental caries and other infections (candidosis, or acute bacterial sialadenitis) as a consequence of the reduced defences.
Causes
There are physiological causes of hyposalivation. Thus a dry mouth is common during periods of anxiety, due to sympathetic activity; mouthbreathers may also have a dry mouth and advancing age is associated with dry mouth, probably because of a reduction of salivary acini, with a fall in salivary secretory reserve.
Very rarely, salivary glands may be absent at birth – so-called salivary gland aplasia or agenesis.
Most salivary gland dysfunction is acquired (Table 2).
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In most older people complaining of xerostomia, the cause is usually due to medication or disease. Indeed, the main causes of dry mouth are iatrogenic, particularly drug use. There is usually a fairly close temporal relationship between starting the drug treatment or increasing the dose, and experiencing the dry mouth. However, the cause for which the drug is being taken may also be important. For example, patients with anxiety or depressive conditions may complain of dry mouth even in the absence of drug therapy (or evidence of reduced salivary flow).
Drugs recognized as causes of reduced salivation include mainly those with anticholinergic, or sympathomimetic, or diuretic activity. These include those cited in Table 3.
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Irradiation for malignant tumours in the head and neck region, such as oral cancer, can produce profound xerostomia. Other sources of irradiation, such as radioactive iodine (131I) used for treating thyroid disease, may also damage the salivary glands, which take up the radioactive iodine.
Dehydration, as in diabetes mellitus, chronic renal failure, hyperparathyroidism or any fever and diabetes insipidus is an occasional cause of xerostomia.
Diseases of salivary glands can also cause salivary dysfunction. These are mainly Sjögren's syndrome (a multisystem condition discussed below); sarcoidosis; HIV disease; liver diseases; and cystic fibrosis (mucoviscidosis) (Figure 1).
Finally, it is important to recognize also that some patients complaining of a dry mouth have no evidence of a reduced salivary flow or a salivary disorder (ie they have xerostomia but not hyposalivation), and in these there may be a psychogenic reason for the complaint.
Clinical features
The patient with hyposalivation may have difficulty in:
Patients may also complain of unpleasant taste or loss of sense of taste, or halitosis.
The patient with hyposalivation may complain of a dry mouth or these sequelae alone, or also complain of dryness of the eyes and other mucosae (nasal, laryngeal, genital). Those with eye complaints have blurring, light intolerance, burning, itching or grittiness, and sometimes an inability to cry.
Systemic features (such as joint pains) may be suggestive of Sjögren's syndrome.
Examination may reveal that the lips adhere one to another, and an examining dental mirror may stick to the mucosa because of the reduced lubrication. Lipstick or food debris may be seen sticking to the teeth or soft tissues, and the usual pooling of saliva in the floor of the mouth may be absent. Thin lines of frothy saliva may form along lines of contact of the oral soft tissues, on the tongue, or in the vestibule. Saliva may not be expressible from the parotid ducts. The tongue is dry (Figure 2) and may become characteristically lobulated and usually red, with partial or complete depapillation (Figure 3).
Complications of hyposalivation can include:
Hyposalivation may explain why patients, who are apparently complying with dietary advice, have uncontrollable recurrent caries.
Diagnosis
Hyposalivation is a clinical diagnosis which can be made by the practitioner predominantly on the basis of the history and examination.
It can be helpful to document salivary function by salivary function studies, such as salivary flow rates (sialometry). Collection of whole saliva (oral fluid) is currently the routine technique for sialometry used by many clinicians, despite the fact that it is rather inaccurate and non-specific. It is usually carried out by allowing the patient to sit quietly and dribble into a measuring container over 15 minutes; in a normal person, such an unstimulated whole saliva flow rate exceeds 1.5 ml/15 min (0.1 ml/min).
Keypoints: dry mouth
Diagnosis is clinical but investigations may be indicated, including:
The Specialist may be needed to:
Investigations that may be indicated to exclude systemic disease, particularly to exclude:
Commonly used investigations may thus include:
It is important to remember, as stated above that, in some patients complaining of a dry mouth, no evidence of a reduced salivary flow or a salivary disorder can be found. There may then be a psychogenic reason for the complaint.
Management (see below)
Sjögren's syndrome
Sjögren's syndrome (SS) is an uncommon condition found in association with dry mouth and dry eyes. The other key features of SS are evidence of an auto-immune reaction, shown usually by serum auto-antibodies and sometimes confirmed by demonstrating mononuclear cell infiltrates in a labial salivary gland biopsy. Sjögren's syndrome can affect any age, but the onset is most common in middle age or older. The majority of patients are women with a female:male ratio of 9:1
Aetiopathogenesis
Sjögren's syndrome is an auto-immune disease affecting mainly exocrine glands like the salivary glands, lacrimal glands and pancreas. There may be a viral aetiology and a genetic predisposition.
The most common type of SS is secondary Sjögren's syndrome (SS-2), which comprises dry eyes and dry mouth and a connective tissue or auto-immune disease, most commonly rheumatoid arthritis (RA). Other connective tissue disorders may be associated, eg systemic lupus erythematosus and scleroderma (Table 4). However, SS can appear by itself, and in the absence of a connective tissue disease is often termed sicca syndrome, usually referred to as primary Sjögren's syndrome (SS-1). Nevertheless, both forms are chronic and can affect not only the salivary glands, but also extraglandular tissues. Chronic B lymphocyte stimulation can occasionally lead to B cell neoplasms, such as lymphoma.
| SS-1 | SS-2 | |
|---|---|---|
| Dry mouth | Yes | Yes |
| Dry eyes | Yes | Yes |
| Connective tissue disease | No | Yes |
| Extraglandular problems | More common | Less common |
Sjögren's syndrome is often characterized by a raised erythrocyte sedimentation rate (ESR) and several auto-antibodies – particularly antinuclear factor (ANF) and rheumatoid factor (RF), and more specific antinuclear antibodies known as SS-A (Ro) and SS-B (La).
Clinical features
Sjögren's syndrome presents mainly with eye complaints which include sensations of grittiness, soreness, itching, dryness, blurred vision or light intolerance. The eyes may be red with inflammation of the conjunctivae and soft crusts at the angles (keratoconjunctivitis sicca). The lacrimal glands may swell.
Oral complaints (often the presenting feature) including:
However, SS is a more generalized disorder which involves not only the exocrine salivary and lacrimal glands, but can have a range of other complications, summarized in Figure 7.
Diagnosis
Diagnosis is made from the history and clinical features, and may be confirmed by auto-antibody studies and sometimes by other investigations, such as ultrasound (Figures 8 and 9), sialometry and labial salivary gland biopsy. In Specialist units various international criteria (American/European consensus diagnostic criteria) are used to confirm the diagnosis.
Management of hyposalivation
There is no specific treatment yet for SS, but the hyposalivation can be managed, and dental preventive care is essential. The dental team have an important role to play in this.
Any underlying cause of xerostomia should, if possible, be rectified; for example, xerostomia-producing drugs may be changed for an alternative, and causes such as diabetes should be treated.
Patients should be educated into efforts to avoid factors that may increase dryness, and to keep the mouth moist (Table 5).
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Salivary substitutes or mouth-wetting agents may help symptomatically; various are available including:
| UK trade names | Offered as | Contains fluoride | Main constituents | Comments |
|---|---|---|---|---|
| AS Saliva Orthana | Spray or lozenge | +/- | Mucin Xylitol | Spray contains ?fluoride but is unsuitable if there are religious objections to porcine mucin |
| Biotene Oralbalance | Gel | - | Glycerate polymer base, |
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| BioXtra | Gel | - | Colostrum, |
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| Luborant | Spray | + | Carboxymethylcellulose | |
| Glandosane | Spray | - | Carboxymethylcellulose | ‘Glandosane’ has a low pH and therefore is best avoided in patients with a natural dentition |
| Saliveze | ||||
| Xerotin | ||||
| Salinum | Liquid | - | Linseed and phosphate buffer |
As patients with objective xerostomia are at increased risk of developing caries, it is important that they take a non-cariogenic diet and maintain a high standard of oral hygiene. The regular use of topical fluoride agents and ACP (amorphous calcium phosphate) form important components of long-term care.
Salivation may be stimulated by using diabetic sweets or chewing gums (containing sorbitol or xylitol, not sucrose). Cholinergic drugs that stimulate salivation (sialogogues), such as pilocarpine or cevimeline, should be used only by a Specialist. Oral complications should be prevented and treated.
Keypoints for patients: dry mouth
Useful websites:
http://www.bssa.uk.net/
http://www.nidcr.nih.gov/AtoZ/LetterS/SjogrenSyndrome/
http://sjsworld.org/
http://www.nidcr.nih.gov/OralHealth/Topics/DryMouth/
Sialorrhoea (hypersalivation; ptyalism)
Infants frequently drool but this is normal. The complaint of sialorrhoea (excess salivation) is uncommon and may be true salivary hypersecretion: usually caused by physiological factors such as menstruation or early pregnancy, local factors such as teething or oral inflammatory lesions, food or medications (those with cholinergic activity such as pilocarpine, tetrabenazine, clozapine), or bynasogastric intubation. In some cases, apparent hypersalivation is caused not by excess saliva production but by an inability to swallow a normal amount of saliva (False sialorrhoea) caused by neuromuscular dysfunction (eg in Parkinson's disease, cerebral palsy, or learning disability) or by pharyngeal or oesophageal obstruction, such as by a neoplasm.
Treatment is of the underlying cause if possible and then the use of behavioural approaches or antisialogogues. Occasionally, surgery to redirect the salivary gland ducts into the oropharynx may be helpful.