How many more years of college do you need after becoming a dental hygienist to become a dentist?

I am in a dental hygiene program because the closest dental school (for d.m.d.'s) is over 2 hours away and I have a family (small son). I really want to become an actual dentist in the future as we don't have very many dentists in my area, and as a person who has had teeth problems, I have very strong feelings to this profession. I was just unsure of how many more years after completion of the dental hygiene studies it would take to go onto be a dentist. I did not know whether any of the hours from this course would transfer to the dental program or whether you go from scratch with the whole 4years of dental school.

How many more years of college do you need after becoming a dental hygienist to become a dentist?
4 years depending on what credits they give you for your subjects already done as a hygienist.