ReviewSalivary hypofunction: An update on aetiology, diagnosis and therapeutics
Introduction
Saliva is of paramount importance for the maintenance of oral and general homeostasis. It displays a crucial role in the digestive function, taste, cleaning, hydratation of the oral mucosa, and protection of the teeth, due to buffering and remineralization properties. Besides, saliva controls the composition of the oral microflora due to antibacterial, antifungal and antiviral properties, protecting the body from deleterious extrinsic influences. Saliva is composed of more than 99% water along with electrolytes; the protein components include immunoglobulins, digestive enzymes such as amylase and lipase, and antibacterial and antifungal enzymes, as well as mucins.1, 2, 3, 4 Salivary secretion is controlled by the autonomous nervous system, mainly by parasympathetic nerve signals. About 90% of saliva is produced by the major salivary glands and the daily volume varies from 0.5 to 1.0 L.4, 5, 6 When at rest, 65% of saliva is produced by the submandibular glands, which produce saliva rich in mucin, which supplies lubrification for the mucosa. Under stimulation, the parotids account for 50% of salivary volume.4, 5, 7
Nederfors8 suggests that salivary dysfunctions can be divided into three aspects: xerostomia, as subjective alteration; hyposalivation, as objective reduction of salivary flow and alterations in salivary composition. In early stages, hyposalivation is characterized by decreased salivary volume, besides saliva is thick and dispersed. The oral mucosa becomes dry and atrophic, and the patients can gradually show dysgeusia, dysphagia and dysarthria, as well as risk of developing ulcerations, caries, gingivitis, periodontitis, candidosis, and bacterial sialadenitis, among others.9, 10 Those changes cause important harm to the oral homeostasis and to the quality of life.
Considering the abovementioned, the present study is an updated approach of the main risk factors associated to salivary dysfunctions, such as drugs, systemic diseases, radiation and ageing. The diagnostic methods and therapeutic measures, including regenerative therapies and the use of stem cells to restore salivary function are also discussed. A Medline/PubMed/search was conducted using the terms xerostomia, hyposalivation, dry mouth and salivary hypofunction in combination with aetiology, drugs, systemic disorders, diagnosis, management, and treatment. Articles published in the English language were selected and reviewed. Suitable references from these articles were also reviewed.
Section snippets
Diagnosis of salivary dysfunctions
The diagnosis of salivary dysfunctions can be obtained by means of subjective and objective methods. These methods can be classified into questionnaires or interviews, secretion tests, mucosal surface tests, qualitative analyses, functional analyses and glandular morphology analyses11 (Table 1).
Subjective methods are used to determine the intensity and cause of xerostomia.12 A number of questionnaires have been utilized, and there is not a consensus on the best form of grading xerostomia,
Drugs
Several drugs are able of inducing hyposalivation and xerostomia, but they rarely cause irreversible damage to the salivary glands. In Table 2 were listed classes of drugs with potential to cause salivary dysfunction. Unfortunately few studies have examined salivary flow, much of the data, being based on a subjective complaint of dry mouth. Besides, little data about the effects of many supposed xerostomia-inducing drugs on salivation are available. Although the exact mechanisms whereby some
Therapeutic options
The therapeutic approach of salivary dysfunctions depends basically on residual glandular function and is aimed at the alleviation of symptoms and prevention and correction of eventual sequelae, as well as at the treatment of associated systemic diseases. The treatment of hyposalivation and xerostomia can be classified as (1) preventive, (2) symptomatic, (3) topical and systemic stimulants, (4) disease-modifying agents, and (5) regenerative.81, 150
Conclusions
Salivary dysfunctions are common, have a negative impact on the quality of life, and can be caused by a number of local and systemic conditions. In the present study we described subjective methods, as well as objective methods for determining alterations in salivary secretion. In addition to this, we addressed the possible etiologic factors and established treatments in the literature, as well as new therapeutic strategies still under investigation. Clinicians must be aware of the signs and
Funding
There is no funding source to state in this research.
Competing interest
There is no conflict of interest in this research.
Ethical approval
Not applicable.
References (200)
- et al.
Health benefits of saliva: a review
J Dent
(2005) - et al.
Xerostomia: a day and night difference
Radiother Oncol
(2012) - et al.
Clinical assessment of oral dryness: development of a scoring system related to salivary flow and mucosal wetness
Oral Surg Oral Med Oral Pathol Oral Radiol
(2012) - et al.
Development of a Visual Analogue Scale questionnaire for subjective assessment of salivary dysfunction
Oral Surg Oral Med Oral Pathol Oral Radiol Endod
(2001) - et al.
Lip biopsy for the diagnosis of Sjögren's syndrome: beware of the punch
Int J Oral Maxillofac Surg
(2014) - et al.
Imaging the major salivary glands
Br J Oral Maxillofac Surg
(2011) - et al.
Modified schirmer test – a screening tool for xerostomia among subjects on antidepressants
Arch Oral Biol
(2014) - et al.
The spirometric efficacy of once-daily dosing with tiotropium in stable COPD: a 13-week multicenter trial
Chest
(2000) - et al.
Activation of alpha(2)-adrenoceptors in the lateral hypothalamus reduces pilocarpine-induced salivation in rats
Neurosci Lett
(2009) - et al.
Calcium antagonists cause dry mouth by inhibiting resting saliva secretion
Life Sci
(2007)