Review (5/5): Follow the instructions as written.
The whiting effect was good after 4 applications and has stayed white even though I drink coffee(4cups) every morning. It’s important to dry your teeth well before brushing the solution on your teeth, wait 30 seconds and don’t drink anything for at least one half hour. It has not been painful at all! I intend to keep using it. I don’t think it colors porcelain crowns, but those stay white on their own. I haven’t had white teeth for years. I keep smiling to see the positive effects!