Saliva is the external environment of teeth, which plays the role of buffering, washing, antibacterial and bacteriostatic. A large amount of thin saliva is beneficial to cleaning the tooth surface, reducing the accumulation of bacteria and food residues, and also helping to dilute acidic products. A small amount of thick saliva is easy to stay and promote the formation of dental plaque and stick to the teeth. Reduced saliva secretion or breathing and sleeping at night will also promote the formation of dental plaque. At the same time, the nature and composition of saliva also affect the buffering capacity and the living conditions of bacteria.
Saliva is a digestive juice, mostly water, and also contains mucin and amylase. Saliva can not only moisten the mouth, soften food and facilitate swallowing; Amylase can promote the decomposition of starch into maltose and enhance digestion; Saliva can also remove food residues and foreign bodies in the mouth and keep the mouth clean. In addition, saliva also contains lysozyme, which has bactericidal effect. Mucin can protect gastric mucosa and increase its antiseptic effect. So, avoid spitting casually.
Saliva is colorless and tasteless, with a pH of 6.6 to 7. 1. The daily secretion of normal people is about 1.0 to 1.5 liters (the daily saliva secretion of herbivores such as cattle and sheep is as high as 65438+ 0/3 of their body weight). Human saliva moisture accounts for 80%; Organic substances mainly include mucin, mucopolysaccharide, salivary amylase, lysozyme, immunoglobulin (IgA, IgG, IgM), blood group substances (A, B, H), urea, uric acid and free amino acids. Inorganic substances include Na+, K+, Ca2+, Cl-, HCO3- and some gas molecules.