I think that it depends on what you have in your background experience. There are plenty of people who have only shadowed for 20 hours, and I doubt an interviewer would ask something like...what is the difference in technique of seating an upper vs. a lower impression tray. But if you been working as an RDA for 6 years, you probably better know a little more.
In the course of conversation, you may get questions about dentistry that you don't know, but just tell them you haven't learned that stuff yet. But if you write down that you volunteered as a sterilization tech for 12 months at a dental office and the person says "ultrasonic" and you go..."what's an ultrasonic?" then you might have problems.