Your dentist will place a rubber guard or protective gel on your gums to protect them from irritation. Then, the dentist will put peroxide gel into a custom-molded tray and place the tray on your teeth. Your dentist will put a rubber shield over your gums, apply a bleaching gel to your teeth and place you under a laser or a bright light for 30 minutes of less. The light activates the chemical in the gel and whitens your teeth more quickly than bleaching alone. Dentists usually recommend that you place a whitening product on your teeth while you are at home, so make sure that you follow your dentist's instructions to get the best results. Dental whitening treatments are expensive, but they can last up to 3 years.

TL;DR in Chinese:
到牙医诊所漂白牙齿。 用激光美白牙齿。 在家跟进治疗。