Saliva has a significant role in the maintenance of oral health. It is estimated that an average individual produces between 750–1500 mL per day.
The functions of saliva include lubrication, taste mediation, digestion and re-mineralization of teeth. Saliva also has an important antimicrobialrole. Qualitative and quantitative changes to saliva an have a significant impact on the patient’s quality of life. The most common patient complaint is xerostomia, which may present symptomatically as difficulties in chewing, speaking and the wearing of dentures. Often the patient will report that they frequently need to sip water during the day, especially during meals. They may also have a reduced taste sensation or persistent metallic, bitter or salty taste(dysgeusia). The clinical signs of xerostomia can include red (erythematous) oral mucosa which is dry and may be ulcerated often secondary totrauma. Rampant dental caries including extensive restoration experience and frequent episodes of oral candidosis are also common clinical observations. Radiographically will often show extensive cervical and interproximal caries.
AETIOLOGY
The most common causes for xerostomia would be secondary to poly-pharmacy, as seen in patients prescribed antidepressants or antihypertensives. Other causes include auto-immune related disorders (Sjogren’s syndrome); metabolic disorders such as diabetes, anorexia nervosa or bulimia; anxiety disorders; iatrogenic causes (radiotherapy, chemotherapy) and rarer conditions such as developmental disordersa (salivary gland aplasia).
TREATMENT
Treatment options for xerostomia vary based on the aetiology and whether any saliva is able to be stimulated from any/all of the major salivary glands. If no saliva flow is detected then there is a reduced effectiveness of treatment options currently available. Some of the treatments available essentially include:
- Non-cariogenic sialogogues e.g. sugar free chewing gum stimulates saliva flow in those patients able to produce any saliva
- Hydration (8-10 glasses of water daily) which should not be over-looked as an important factor in managing a xerostomic patient. This also includes the frequent use of a spray bottle containing water during the day, especially when the patient is walking/doing manual related chores.
- Replacement (saliva substitutes) which is a mucin or methoxy-cellulose based product, used before meals and before bed.
- Dietary modifications including avoidance of foods with a low pH (e.g. citrus fruits), caffeine, spicy foods, alcohol, and salty foods
- Psychiatric and behavioral counseling for coping strategies and reduction of behavioral and lifestyle factors associated with the condition
- Pharmacological option such as Pilocarpine 5mg three times a day before meals and before bed in patients that have some saliva producing capacity. This medication is contra-indicated in patients with acute glaucoma, cardiovascular or respiratory disorders such as asthma.
The use of a SLS free toothpaste such as the Biotene' toothpaste is ideal because it contains fluoride but without the detergent component (SLS) which increases the permeability of the oral mucosal surface. The avoidance of alcohol based oral rinses which have a dehydrating effect on the oral tissues is critical. Discussion with the patients' medical practitioner as to the feasibility of changing a medication to a less xerostomic producing drug, such as changing from a diuretic drug to an Angiotensin Converting Enzyme (ACE) inhibitor is of value. It may be possible to have the offending drug dosage reduced or to alter the time of administration of the drug so that a xerostomic producing drug may be able to be taken in the morning. This would avoid the enhanced xerostomic effect due to the circadian rhythm of saliva flow reducing at night compared to during the day.
Future Directions of Managing a Xerostomic patient
Most attention thus far has been directed to relief of dryness symptoms and management of any oral problems that arise. This is accomplished with oral rinses, gels, saliva replacement products and localized stimulation of salivation.
At present however there are no curative therapies or treatments capable of preventing further salivary dysfunction in chronic conditions. More recent research has been looking at ways we may be able improve the management of our xerostomic patients.
Some of these novel approaches include:
Gene Therapy Gene transfer refers to the delivery of a selected segment of DNA (a gene or transgene) into target tissues such as via an rhinovirus model. This theoretically would permit correction or restoration of function in a damaged major saliva gland or further, introduction of a gene of interest (such as those associated with the production of insulin) produce a functional protein which could then systemically be used in the treatment of diabetes. The saliva glands offer some unique advantages for gene therapy. The glands are easily accessible via the ducts of the major glands to permit delivery of gene(s) retrograde. In addition, the glands are well encapsulated which means that little of the retrograde gene distillate would reach the systemic circulation. This is important when considering viral vectors. This concept of therapy is not science fiction, as there are mice, rats, mini-pigs and rhesus monkey models that have been successful.
Sparing saliva glands in cancer therapy In the United States, the drug Amifostine which was discovered in the 1950's scavenges free radicals, which makes it particularly useful in sparing normal tissue (such as a saliva gland) in a patient undergoing radiotherapy. The drug can be administered intravenously or subcutaneously 15 minutes before radiation dose is given. The most common side-effect is nausea. Improved salivary substitutes Research is also being undertaken into genetically engineered artificial saliva and further development of a specific cholinergic agonist that stimulates only salivary glands and not sweat glands.