Very good question!
I agree with Ms. Carole. Having been a professor, I preferred being addressed as Professor. I would extend it to any of your university teachers. If they are teaching the class, they are the professor. Of course, if they earned a doctorate, Dr is more appropriate but I don't think to many teachers would be offended being called professor.
However, I always told my students to call me Jeff. I am very informal in class as long as the respect is there.
I also agree with Ms. Carole about using Ms.