Crest Whitestrips really do work, and there arent any "nasty side effects" or whatever you said about store bought stuff. Honestly i get commments almost every single day about how white my teeth are. I have sensitive teeth, so i dont even use them like it says to (the directions say use them twice a day for 30 minutes for 7 days in a row), i just use one every now and then like maybe once or twice a week and they are STILL ridiculously white. plus i drink coffee and pop allll the time. honestly there's nothing better, plus now they are only like $25 and one kit lasts me for months since i just use them every now and then. if your teeth are pretty stained you might want to follow the directions on the box to get the best effect. your teeth might be sensitive or ache a little after you've done it for a few days, but its normal...and it will stop. small price to pay for super white teeth!