Saliva is a complex fluid that contains a diverse array of molecules, including urea, ammonia, uric acid, glucose, cholesterol, fatty acid, triglycerides, neutral lipid, glycolipid, amino acid, steroid hormones, mucin, amylase, lectin, glycoprotein, lysozyme, peroxidase, and lactoferrin. Saliva also has high concentrations of various electrolytes, such as Na + , Cl -, Ca 2+ , K + , HCO 3-, H2PO4 -, F -, I -, and Mg 2+, which are derived from the serum. Moreover, saliva contains over 700 microorganisms that are related to both oral and systemic diseases. The composition of saliva makes it a valuable tool for diagnosis and monitoring of various medical conditions.