I searched for the most reputable oral cavity on Meituan, searched for some comparison pictures of whitening teeth, and then found ruitai Jiabao Oral cavity. My friend and I joined a group to whiten teeth. I have yellow teeth, and my friend is tetracycline teeth. We both turned white at the same time, about an hour. The doctor showed me the mirror, and I found that my teeth turned white obviously. My friend may have tetracycline teeth, and his teeth are much whiter than before, but it is my honor to accept my advice. Thank you. Wish you a happy life!