Daily brushing, teeth or yellowing may be caused by smoking, enamel wear, improper brushing posture, endogenous tooth coloring and other factors. 1. Smoking: cigarettes contain tobacco, tar and other harmful substances, combustion inhaled into the mouth, these substances will form pigmentation on the surface of the teeth, after a long time will form a stable stains, that is, smoke stains, generally through the brushing of the teeth can not be brushed off. 2. Enamel wear: with age, the enamel on the surface of the teeth will usually be gradually worn down, and the yellow dentin will be gradually exposed, in which case, even if you brush every day, your teeth will not become white. 3. Improper brushing posture: If you take the incorrect brushing posture every day, resulting in cleaning is not in place, usually can not be very good to remove the yellow material on the teeth. 4. Endogenous tooth coloring: such as tetracycline teeth, dental fluorosis, etc. may lead to tooth coloring. It is recommended that you do not smoke, brush your teeth correctly, and if enamel wear occurs, it should be repaired in time to avoid adverse consequences.