There are many reasons for the coloration of teeth and yellowing. Generally speaking, there are two types, endogenous and exogenous:
Exogenous coloration is due to the presence of a variety of bacteria on the surface of teeth, which secrete many viscous substances on the surface of teeth, tea scale, smoke stains in daily diet, and certain minerals in drinking water and minerals in people's saliva. Adsorption on these sticky substances forms plaques and tartars that gradually yellow or blacken the teeth.
Endogenous staining occurs during tooth development. For example, if tetracycline is deposited in the dentine, the teeth become yellow, brown, or dark gray, known as tetracycline teeth; if the drinking water contains too much fluorine, it may also be Lead to dental fluorosis, tooth surface was white chalk, tan patches; if the nerves of the teeth after necrosis, hemoglobin and bacterial decomposition products can also make the teeth black.