A couple years ago I fell and broke front tooth. Nothing to serious I guess because a dentist just put some kind of something there and the tooth looks real. I don't know what it is they used and the doctor can't be found. I really need to do some whitening on my teeth but will it work on what the dentist used for my tooth? I don't want white teeth with half a yellow one!

Moniava,
There is not a whitening system around that will change the colour of existing fillings or crowns. The ideal would be to whiten your teeth to the shade you want then get the filling replaced to match. This will mean some regular maintenance on your part to keep your own teeth matching the colour of the newly restored tooth.
Good luck.