You can download a picture with teeth with braces, Open that picture and altar the size of it if you need, then open your picture on the same page to where you can see both of them at the same time.
You can either
1) create a new layer on the picture you got with the braces on it, Delete the original layer, use the magic wand tool to select pieces of the photo you don't need, like the teeth its on and unnecessary stuff. Then crop everything else out except the braces. Then Move the braces from that picure frame, to the frame with you in it, move it where you need to, and Mess with it a little to where it fits or whatever else.
ORRR
2) You can use the stamp tool, (sounds easier but its a lot messier and wont look as good than the other way.) Contact me or use the tutorial or help at the top and search for "Stamp Tool"
