Periodontal diseases, dental caries, oro-facial pain and oral cancer are main global oral health burdens.1 In recent years, saliva has been recognized as a promising diagnostic fluid both in clinical and research settings. The diagnosis of oral diseases at an early stage improves prognosis.2 Diagnosing and monitoring the progression of oral diseases by using non-invasive, point-of-care technologies would improve therapeutic outcomes and patients’ quality of life.

Saliva acts as a medium to dissolve solids and it facilitates the digestion of starch, chewing, and bolus formation. It has a lubricating and cleansing effect on teeth and other oral tissues, it promotes the mineralization of teeth, and has antibacterial, antiviral, and antifungal properties.3 Saliva consists mainly of water (99%) and a variety of electrolytes and proteins (1%), e.g., ions, enzymes, protein complexes, and other organic molecules and bio-chemical agents.4

Saliva may be considered either as gland-specific or as whole saliva. Gland-specific saliva is secreted by the parotid, submandibular, sublingual, and minor salivary glands.5,6 Whole saliva is a mixture of secretions from the salivary glands and constituents of non-salivary origin such as gingival crevicular fluid, blood and blood derivatives, desquamated epithelial cells and other cellular components, nasal and bronchial secretions, microorganisms, microbial enzymes, and many extrinsic substances (e.g., food debris, toothpaste and mouthwash components).

Saliva in mouth

Changes in the concentration of enzymes or other components of saliva can be used as biomarkers or diagnostic indicators for oral and systemic diseases.7 Gland-specific saliva can be used to diagnose pathoses specific to one of the major salivary glands. Biomarkers in whole saliva may be used to diagnose or to identify patients at risk of several oral and systemic conditions, e.g., dental caries, periodontal diseases, hereditary disorders, autoimmune diseases, malignancies, certain infectious disease, and to monitor drug and hormone levels.