Starts brighter, then gets whiter
Got these for my husband.  He has perfectly aligned teeth (naturally) and has never had a cavity.  However, we were starting to call his teeth his "pearly yellows."  I guess he drinks too much espresso.<br /><br />Anyhow, we bought the classic strips because of the lower level of peroxide - he is sensitive to stronger amounts (it makes his gums hurt).  Within the first 2 days we saw his teeth starting to look brighter, but not really whiter.  It wasn't until around the 5th day that we could say, "wow" - this stuff is really working.  He didn't even need the full 2 weeks - his teeth are quite white now.  He uses the remaining strips once per week to maintain the whiteness.
Rating: 5 stars