Aside from being vain about my skin, I also am conscious about my teeth. I believe I have a very nice smile but what's a great smile if you have stained and yellow teeth? So my mom bought these Crest white strips from eBay and I tried it. The strips are designed as sticker strips for the upper and lower teeth. I followed the instrustions and placed them on my teeth for 30 minutes. The stips are transparent plastic films with gel-like dots that adhere to your teeth. Although I did not feel any pain, it was a bit uncomfortable because the taste is not that desirable and I was a bit salivating. However, after 30 minutes, when I removed the strips, my teeth definitely looked whiter. The strips are designed to be used for a week so you would have really whiter teeth after that but I guess for me, it was that effective that I noticed the difference. I don't have dark stains though so I guess it would vary from person to person depending on the degree of whiteness that you want to achieve.