To quote BU's head of admissions, "There isn't one" (boy did i feel like a chump when i got that response to my question during the interview)
DMD = Doctor of Medical Dentistry (i think) and is primarily used by eastern schools...
DDS - Doctor of Dental Surgeory and is used by everyone else - however I think the general public recognizes DDS as the dental postscript to a name, but most people don't really pay attention anyway (case and point, my mother thought the "DO" after her OB/GYN's name meant that she had more specialized training than the MD's in the clinic, not that she was a different kind of doctor - case and point: your patients won't notice your degree, unless they're medical education gurus)