hi,
i simply walked into a dental office one day and told the receptionist my story (my background...interest in dentistry...interest in observing at their office). she was incredibly understanding and welcoming. so i sent her my resume and she set up an appt with the dentist. from there on, i have been going to the office once a week to observe. 😀
so all you have to do is walk in a ask...doesn't hurt to try. you're bound to find an understanding dentist! good luck!
-wasabi007