The only drawbacks...1) everything took at least twice as long as a real dentist would have taken and...2) there were a couple of occasions when the student told me that that was the first time he/she had done what was about to be done to me.On one occasion I could feel the student's hands shaking inside my mouth! Good thing an instructor was looking over his shoulder at the time! ;-)
There are free clinics associated with almost every major medical school where students practice under vey close supervision. It is a great answer to indigent care and usually the medicine is first rate because there is an experienced attending literally standing over the should of the medical clerk.