I was asked this question. Just tell them why you are interested in dentistry. You've had experiance in the medical field...and I assume you've had some in dentistry...why do you like one over the other. Thats all. None of the questions interviewers ask are meant to trip you up, nor do you have to be eloquent in your answer. Can you hold a conversation easily, thats all they want to know. Just let it flow baby!