Symptoms of salivary gland hypofunction resulting in hyposalivation
Apart from an increased susceptibility to caries, other oral and systemic disturbances may also be associated with hyposalivation (Box 7).
Hyposalivation, or reduced SSR, is not synonymous with xerostomia, which is a symptom reflecting the end result of the process of inflow of pure saliva, evaporation, adsorption to the oral mucosa, and outflow of saliva. Of the saliva that enters the mouth, as much as 0.20 to 0.25 mL/min may evaporate, causing a sensation of dryness, especially in mouth breathers. Smokers may also experience dryness. A study on dental health status related to smoking habits found that, although smokers had higher mean values for stimulated SSR than did nonsmokers, significantly more
smokers reported symptoms of dry mouth (Axelsson et al, 1998).
Experiments by Dawes (1987) showed that subjects experienced a feeling of dry mouth when their normal SSR was temporarily reduced by 50% (eg, a reduction in stimulated SSR from 2 to 1 mL/min or in unstimulated SSR from 0.4 to 0.2 mL/min).
Even healthy individuals with "normal" salivary flow rates can experience symptoms of dry mouth: Studies have reported that 20% of 30 year olds and 50% of 55 year olds are so discomforted by dry mouth that they resort to salivary stimulation or rinsing.
The sensation of dryness is usually attributable to hypofunction of the minor salivary glands, which produce a mucin-rich, high-viscosity secretion, rather than to hypofunction of the major glands. Because there is little, if any, relationship between subjective complaints of xerostomia and actual quantitative salivary flow, it is important to measure the SSR in each individual patient. The data in Table 13 show that proper individual diagnosis is almost impossible, although on a population level these numbers are relatively reliable. To assess susceptibility to caries or carious
activity, the SSR should be monitored regularly in individual patients and not assessed as "normal" or "abnormal" on the basis of just one measurement.
A very low SSR, particularly for unstimulated saliva, results in clinical changes in the oral cavity (Box 8). The most conspicuous feature of salivary gland hypofunction is dryness of the lining oral tissues. The oral mucosa may appear thin and pale, lose its glossy sheen, and feel dry: a tongue blade or mirror drawn across the surface may adhere. Such dry, thin mucosa can also be diagnosed by optical measurements with infrared light (Fig 92) or by mechanical friction measurements (Fig 93).
Other clinical changes are increases in dental caries; oral infections, especially
candidiasis; fissuring and lobulation of the dorsum of the tongue and occasionally the
lips; angular cheilosis (Figs 94 and 95); and occasional swelling of the salivary
glands. Milking of the salivary glands may not yield any saliva. New carious lesions
are common, and develop rapidly¾within weeks or months rather than years¾and
often at atypical sites: the mandibular anterior teeth, at the cervical margins of recent
restorations (Fig 96), and on the incisal edges.
Candidiasis may appear as smooth red patches or as a diffuse area of intense redness
(the erythematous or atrophic form); as white-to-ecru, removable plaques (the
pseudomembranous form or thrush); or as white plaques that cannot be removed by
scraping (the hyperplastic form). These lesions often appear on the dorsum of the
tongue and the palate. The presence of Candida on the mucosal surfaces and in the
saliva can readily be determined by a simple dip-slide test.
Patients with xerostomia may also have a wide variety of nonoral clinical signs (see
also Box 7). Ocular changes include xerophthalmia, keratoconjunctivitis, decreased
lacrimation, and the accumulation of viscous secretions in the conjunctival sac.
Involvement of the exocrine glands may lead to pharyngitis and laryngitis, persistent
hoarseness, a dry cough, and difficulty with speech. Nasal dryness may induce scab
formation, epistaxis, and loss of olfactory acuity. A decrease in the production of
saliva, as well as in secretions from the gastrointestinal tract, may lead to reflux
esophagitis, heartburn, and constipation.
