The active ingredient for all good tooth whiteners is carbamide peroxide. The safest strength for effectiveness is usually between 12-20+%; seems like 16% is the most popular for the 'professional' kits from the dentist for a couple hundred. There's also some 'in the office' laser whitening thats pretty expnsive. You can get the 'professional' kits in the 'net for around $50. The peroxide can cause tooth sensitivity (my teeth usu. ache a little fo a couple days after a few treatments) and may irritate your gums if you get too much on them. The kit is works very well from my experience, and the product stores for a while for a 'freshen up' every 6 mos - 1 yr or so..
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