The first thing you need to do is to clean your teeth, then take protective measures, and finally apply the material to lighten your teeth. 1. Clean teeth: cold light teeth whitening first ultrasonic cleaning, the teeth above the removal of dirt, if there is gingivitis, periodontitis, it is necessary to anti-inflammatory good before cold light whitening, so as to avoid cold light materials to stimulate periodontal tissue. 2. Do a good job of protective measures: give the patient to wear good protective glasses, teeth with rubber barriers, is conducive to moisture and avoid chemical substances to stimulate the gums. 3. Apply materials as well as light on the teeth: apply desensitizer and acid etching agent on the surface of the teeth, and then rinse and dry them before using the cold light whitening instrument to light on them. Generally need to light 2~3 times, each time about 30 seconds, to achieve the whiteness of the patient needs. After the cold light whitening teeth must pay attention to dental hygiene, try not to eat some pigmented food, so as not to stain the teeth. Specifically, you should go to an authoritative hospital for consultation, and a professional doctor will operate and guide the treatment.