I think there are no difference, but historically The first Dental School in the world which was The Baltimore College of Dental Surgery, awarded the DDS, because back then dentistry was integrated in Medicince, to be more precise Suergery, and as we all know Dentistry is a form of Surgery, and even in forign countries a degree of BDS is awarded, because of the foucous on Surgical Aspect of Dentistry, but as many said DMD came because of intergration of Medical School and Dental School currucuillum in the pre-clinical years, but this is not always the case, but even those school that awarded DMD use to call their degree DDS, It also has to do with the states law regarding titling dentist, it is funny to know that one of the Dentist I worked with had his DMD from Pittsburg but when he came to Virginia to practice, the Virginia Board wrote a DDS on his liscnce
Khalid