Try to find a clinic or something. I shadowed about 10 hours at private practice. Both dentists would answer questions, but were more interested in not making their patients feel like guinea pigs for a pre-dent kid (i understand, us being in the middle of a college town which sends more kids to dental school than any other school in the country).
I found a clinic that would let me shadow there for the summer. After watching a few procedures I jumped right in and learned how to assist the assistants. I would wipe down laboratories after each patient, run instruments in the ultasonic cleaner and then in the autoclave, prepare the rooms with instruments for the next procedure, run xrays films,... I learned so much that way. I ended up coming every day 8-12 and racked up 130 hrs pretty quick. The doctor would stop in the middle of the procedure and have me come over to his view so I could see something pretty cool.
The point is, don't make shadowing a service the doctor will do for you. When you talk to him make sure he knows u want to be an asset to the office and will make their jobs easier. Do nice things for the office every once in a while like donuts, or a muffins or fruit. I expect an awesome LOR from the dentist.
