i’m currently doing this to my teeth. i’ve done them before (but a different type) about 2 years ago and i’m really craving bright white teeth.
i wish i had taken a photo before to compare to when i finish. the main problem with them is that, as you see your teeth every day, others tend to notice the improvement more than you do. i think they’ve got much whiter, but as i’m only 3 days in i’ll have to finish the course and see.
i’d definitely recommend them! read the reviews available online first, but as they’re only about £20 on ebay they’re definitely worth a go in my opinion.