There are many reasons for tooth coloring and yellowing, which can be broadly divided into two aspects: endogenous and exogenous. Exogenous coloring is due to there are many kinds of bacteria, tooth surface they secrete many sticky substance, the tea scale, YanZi diet and drinking water for some minerals adsorption on these sticky substance, gradually make teeth become yellow or black. Endogenous colouring is formed in the process of tooth development, such as tetracycline deposition in the dentine, which makes the teeth yellow, brown or dark grey, called tetracycline teeth; If there is too much fluoride in drinking water, it can also cause fluorosis, white chalk and brown patches on the teeth. If the tooth nerve necrosis is combined with the bacterial decomposition product, it can also make the teeth black. For exogenous tinted teeth, coffee, tea, smoking and red wine are the main culprits.
