I'd have to say a large under-served population. The distribution of dentists isn't equal... There may be areas where there are 2 dentists on a single block, but in Kansas there are on ave. 1250 patients per dentist and there are like 6 counties w/o any dentist at all!
Also I think since general dentists usually provide mainly preventative care, alot of people who don't have dental insurance or money to spend don't see a dentist on a regular basis. Its ok to wait to see a dr. until you're sick, but if you wait to see a dentist until you're in pain it's gonna cost you a lot more!! Educating the public on the importance of preventative care is important!!