Hot sale teeth whitening pen Treatment range:1. For the teeth affected exogenously, such as the teeth affected by coffee, sauce, tea etc 2. For mildly tetracycline affected teeth.3. For genetic yellow teeth.4. For unknown reason yellow or black teeth.Training:When you buy our products, you should be after trained to use the product for the treatment. We have user manual, Video online service to teach you how to use the machine.