I got my braces removed many years ago, 6 or 7 to be exact, and I was sent home with a take home whitening kit that used a carbamide peroxide gel, around 22% I believe. I was instructed to put a small amount in each depression of a retainer I have and use overnight, maybe 2 or 3 nights in a row. Well it worked fine, with some sensitivity of course, and i wanted to use it again. I realize that it expires after about 2 years at the max, but i went ahead and used it again as directed for 3 nights. The kit had 2 syringes, and one was still unused. I should have just used that, but instead finished off an old half empty one w/ no results. Heres my question.... Is there any danger of damaging my enamel with this expired product? This is not an easy answer I know but i would appreciate it... I used the unopened syringe and started seeing results around the edges and ridges of my molars, areas of pure white.... after only 3 hours so I think the unopened syringe may still have something left in it.... Of course I dont want to do permanent damage to my teeth because i am too lazy or cheap to buy a new whitening kit so, I took it out and came down to the computer for some answers. Just wondering if anyone knew the dangers, if any. Thank you.