Assuming that you are talking about the same 2 programs that I am thinking of,
yea, i know several people that have done it. there are 2, 1 for dent and 1 for med. called bio-dent and bio-med. you basically take the same classes as dent and med students. if you do well, you are almost guarenteed a spot in the next years class. Also, I think that if you get A's in the classes, they count them towards the next year (first year of dent or med school).
also, they only take very few into these programs. like 4 or 5 per year. So its just as competitive as dent or med school