I clean my teeth (or scaling) through a dentist everyone half a year, why are my teeth still yellow or gray?
Scaling and cleaning of tooth can only get rid of plague and prevent cavities, it can not prevent the discoloration of the enamel. Common discolorations include aging, nerve degeneration , consumption of stained substances (coffee, tea, red wine, tobacco, colas), consumption of tetracycline (antibiotics) during tooth formation, or excessive fluoride can all cause tooth discoloration.