I agree with gavin, don't write anything about dentistry. You are writing to a bunch of dentists who already know about the profession, I doubt if they really care what your take on the profession is.
This is your chance to let the committee know that you are more than just a DAT score and GPA. Let them know your motivation for dentistry, dental experience, and how you came to your decision to pursue dentistry. You may also want to discuss any past work and leadership experiences.
Good luck!
Class of 2008, Creighton