Thanks for your help. I didn't notice the replies until now :(
Carbamide peroxide is effective and safe for vital bleaching. However, in order to achieve therapeutic effect, adequate contact time is essential.
Ive only tried 2 different kinds of teeth whitening the crest white strips and the all white system. The crest white strips didnt do much and they were kinda a hassle. But the all white system worked really good for me, I recommend it to everyone. I did the 30% because my teeth are not really sensitive. Anyways hope this helps, oh and you can get them for dirt cheap on http://www.dentist.net