I wanted to mention this to anyone lazy like me who just glimpses at the box and thinks “24 treatments-about a month’s worth”. For no good reason, Crest lists 24 because they are counting each strip (top and bottom) individually, so there are only 10 normal treatments in this box (and 2 1-hour). If you use them daily, as directed, you will be done in a week and a half. I feel dumb for not reading it further but also feel it is a bit misleading by Crest and do not see why they would list them like that except to make it sound like there are more.
Other than that, my doctor recommended at-home treatment because my teeth are sensitive. About 20 minutes in, I do get pain jolts but have been able to get past them.
After using the entire box, though, I have not noticed a difference in my teeth’s whiteness. I took before and after pictures in the same spot while holding a Bridget napkin up by my mouth to be able to better compare but they look the same. The only difference I see is that my fingernails grow pretty quickly.