I think that the interviewer honstly thought you did a good job. If he/she didn't, nothing needed to be said. You're probably fine as long as you were honest and your ideas were thoughtful.
At one of my interviews, the interviewer didn't say anything that I could remember. At the same school but with a different interviewer, the interviewer said something to the effect of "There will be some doctors who will try to talk you out of medicine but don't let them convince you. After all, you don't know what medicine was like 20 years ago. All you can do is learn to operate within the system as it stands today. I think you're passionate and you know some things about the delivery system." I thought that was a little wierd since I never said that I had doubts. We did spend a lot of time talking about problems with health delivery, though. We shook hands and I left. Another one at a different school was really nice and caught me off guard. While we were shaking hands he said, "I hope you keep us in mind when you get your acceptances." I was really surprised cause I honestly didn't know whether I'd be getting any acceptances so I said, "Oh, I don't know about that." What I meant was I didn't know that I'd even have 1 acceptance but then I worried that he might take it as "I don't know whether I'd consider your school." It all worked out fine, though.