A few questions you will want to include:
1. What expanded duties did you do at Dr. X's office?
2. What brands and kinds of cements and bonding materials are you familiar with?
3. Per OSHA regulations, how do you sterilize instruments?
4. Explain how you handle a patient who shows signs of being afraid.
Keep in mind that until you see a new hire in action you really won't know what kind of employee you have.