Let me try to understand you better, you have a dental degree from out of USA right? Well there are many dental schools in the USA that accept international dentists in their 2-3 year USA programs. This is a MUCH easier path for you to obtain your DDS/DMD from USA..... well I shouldn't say "easy", its extremely competitive as you can imagine
What you are asking for is the typical 4-year DDS programs that WE (undergrad students) try to get into. This is would be a lengthy process for you because you have to go back to college (in USA) and take your pre-reqs (general biology, general chemistry, organic chemistry, physics, english composition, and maybe Biochemistry and microbiology) AND THEN take the DAT test. They are going to treat you just like a typical pre-dental student. This could take you anywhere from 2-3 years and many schools require at least 90 credit hours in college, thats almost the equivalent of a bachelors degree............ And to answer your question, for this process, they want to know the undergrad GPA (meaning USA undergrad GPA). So if you haven't taken any courses in the USA, your GPA is nothing