Is there any difference between studying dentistry and dental surgery ?

No: Dds or dmd are the professional designations for doctors of dental surgery or dental medicine. Oral surgery is a recognized specialty within dentistry that requires additional training.

Synonymous: The terms are synonymous. The dental degree: dds means doctor of dental surgery. As opposed to oral surgeon, which is a dental specialty.

Same: The degrees are the same today : dds and dmd. The older is doctor of dental surgery. Oral surgery is a specialth within dentistry which requires a residency after dental school. This may be 4-6 years in duration, and may also earn you an md.

Yes There Is: Becoming a dentist requires eight years of college: four years of undergraduate work (Bachelor's degree) and then four years of post-graduate work (Doctorate degree in dentistry). If you want to become an oral surgeon, then it requires an additional four to five years of post-doctoral training (at least).

Degrees: Dentists hold either a DDS or DM D degree, and they a synonymous. An Oral and Maxillofacial Surgeon has an additional 4-5 years of residency training. It's like the difference between a Primary Care Physician and a specialty like Orthopedic Surgery, OBGyn, Urology, etc.