jpn,
PBL stands for problem-based learning, and it's a different style of teaching dental material. Right now only three schools in the US utilize fully-integrated PBL curricula: Harvard, Indiana (where I am), and USC. Without getting into too many grimy details, our PBL sessions are useful from both knowledgeability and professionalism angles. If you want to know more, give me a PM and I'd be happy to tell you all I can about it.