The trilogy of episodes with Dr. Nate Lawson comes to its conclusion.   We'd like to think this one is more "Return of the King" than "Spider-Man 3"  but we'll let you be the judge of that. In this episode Dr. Lawson waxes poetic on bioactivity.  What is it?  If these bioactive ions are released and no one is around to see them, did it really even happen? We discuss Activa, Glass Ionomers, pulp caps and liners, and much much more.