Dino-Lite has a complete line of USB digital cameras with magnification turning them into digital microscopes. Follow the link to see how they work and some sample images.
This product is already being used by forensic examiners (I’ve seen it on CSI) and dermatologists. However it has great application in a dental office or dental lab. They even offer a dental adaptor that attaches the camera to a dental mirror. It looks like it was designed by a non dentist and would be awkward but never the less there it is.
The best part is the price. The basic models start at $150 and go up to $400. Compare that to $2000 loupes or $20,000 chairside microscopes.