Follow the link to the dentalvision newsletter written by Dennis Braunston. He has a lot of good tips and suggested camera setting to get great photos.
I was recently giving a photography course at Dr. Ernie Casares, San Diego, California. When we were finished he showed me a very cool gadget called a MicroLux TransIlluminator. He puts its condensed LED light behind the patients tooth. It turns the tooth from opaque to translucent, revealing cracks, craze lines and fissures.