The power of saliva: Antimicrobial and beyond

Abstract

The oral cavity is a major portal of entry for pathogens that may lead to changes in the normal microflora The homeostasis of the oral cavity is maintained by saliva, an extracellular fluid produced by salivary glands and secreted in the mouth through openings called salivary ducts There are three pairs of large salivary glands and hundreds of small (minor) glands; the main glands are the parotid (located in front of and just below each ear), the submandibular (located below the jaw), and the sublingual glands (located under the tongue) (Fig Human saliva is 99% water, and it is estimated that a healthy person produces 600 mL per day; however, during sleep, the amount drops to nearly 0 Saliva fulfills key functions in the mouth, including maintenance of oral hygiene, lubrication, chewing, and swallowing of food (Fig 2). Additionally, saliva contains several important enzymes such as amylase, lysozyme, and lipase, and therefore, the process of digestion starts the moment food enters the mouth Importantly, saliva is crucial for defense against microbial species, as it is rich in antimicrobial compounds such as hydrogen peroxide, lactoferrin, and lysozymes Consequently-in addition to affecting taste, chewing, and swallowing-disruptions in saliva secretion increase the frequency of oral conditions such as oral candidiasis, gum disease, and tooth decay (caries), as well as respiratory tract infections Xerostomia (a subjective feeling of oral dryness) and salivary hypofunction (a clinically objective decrease in saliva production) are the most commonly reported side effects of medications; however, HIV-AIDS and autoimmune disorders can also lead to salivary dysfunction Additionally, although infrequent, stones (sialoliths) in the gland ducts may obstruct the flow of saliva, and infections or tumors in the salivary glands may also impact salivary function. Importantly, individuals with all these conditions tend to be highly predisposed to oral candidiasis, likely due to compromised salivary antimicrobial effectors Therefore, it has become evident that saliva amasses an infinite wealth of beneficial protective and healing properties, particularly in its defense against microbial inhabitants of the oral cavity, commensals and pathogens alike.