Before you bleach

A first-timer should always consult her dentist before trying any tooth whitener, even an over-the-counter product, because not all teeth react to whitening the same way. Some types of dental work (like caps, crowns, and veneers) don't take to lightening because peroxide can't penetrate them. Stains caused by antibiotics, like tetracycline, are also tricky, because they can occur in the layers inside the tooth, which brighteners can't reach. Your dentist will be able to advise you about the best method for you.