These dyschromia appear over time, they are due to colouring agents present in food, tobacco, etc.
External origin, it affects only the tooth surface
The main advantage of whitening with a dentist lies in the control of the treatment and the safety of the dosages chosen. Indeed, the active oxidizing substance must be properly adapted to the patient.
Either the dentist will give you a personalized kit to do the treatment yourself at home, or he will be responsible for the application of hydrogen peroxide activated either by heat or by light.
In the office, the application is done with a brush, except that the lips are spread by an oral protector, so that the product stays on the teeth, and that your gums are protected. The treatment will be spread over 2 or 3 sessions of one hour.