I am not sure about US DDS programs however I have a relative who graduated from dentistry in UBC, Vancouver Canada.
If this person completes his/her BDS then he/she can apply to a Canadian school and earn the DMD degree (Doctor of Dental Medicine) in 2 years.
However the catch is that you pay alot more than Canadian students.
I think around 25-30,000 per year. However it is only for the last two years. Look into the following program at UBC. http://www.dentistry.ubc.ca/academic_programs/iddcp/default.asp
It seems to me that dentistry will really pick up in India with the way things are going there. Please make sure you dont jump on the immigration bandwagon just because it is perceived to be the right/best thing.
Migrating is not the only path for your future... look into going into private practice in India as well.