If you go overseas, you need to do your schooling over if you intend to practice in the US--it's not like med school. Some schools have advance placement for international dentists so you can finish dental school in the US in 3 years, but most schools require that you do all 4 years (UOP excepted). Long story short, assuming your dental school overseas is 2 to 3 years, expect to spend 5 to 7 years after completing your BS before you're actually a dentist in the states.