Salivary enhancement therapies

When salivary output is reduced chronically to a significant extent, there is a marked increase in dental caries. As the role of saliva in protection of the oral hard tissue is well recognized, there have long been efforts to enhance salivary function in conditions with associated secretory hypofunction. The rationale is that by stimulating salivary output, caries and other oral complications will be reduced or eliminated. The most widely used method for increasing salivary function is a combination of masticatory and gustatory stimulation. A large number of systemic agents have also been proposed as secretagogues, but only a few have shown consistent salivary enhancing properties in well-designed, controlled trials. Pilocarpine has been shown to improve symptoms of oral dryness and to increase salivary output in patients with Sjögren's syndrome and postradiation xerostomia. Recently, cevimeline has shown significant salivary enhancement in Sjögren's syndrome. Pilocarpine and cevimeline have a similar mechanism of action, side effect profile and duration of activity. No secretagogues have been linked directly in clinical trials to either caries prevention or a reduction in the existing caries rate of salivary dysfunction patients. Improved secretagogues are needed, with fewer side effects, increased duration of activity and greater potency. Future research directions include gene therapeutic approaches to direct salivary growth and differentiation or modify remaining tissues to promote secretion, creation of a biocompatible artificial salivary gland and salivary transplantation. With improved secretagogues, the effects of conditions that result in reduced salivary function and increased caries will be ameliorated.