I am a dentist and do a lot of intra-oral photography and lecture on the topic.
The canon 60mm is a great lens fast and sharp. You must understand depth of field. Pugwash did a great review recently. You need to use this lens at high f stops stopped down for 1:1 photograph. The canon 60 is great at f 16 22 32.
what camera are you putting the lens on film or digital. With digital with the sensor factor the 60mm is perfect and I use it in the office with my digital camera. With film the 100mm macro would be the better choice because of working distance.
vivitar makes a very good inexpensive 100mm macro under $200. I have one in the office that works great. this could be a low cost ooption.