I'd say it depends on the interest rate your money is getting. You could definitely use the $8500 or so in subsidized loans and keep $8500 of your money working for you each year through dental school. If you have money earning interest at a greater rate than 7.9%, you might consider taking out the unsubsidized loans as well.
It gets complicated though depending on how much money you have to pay for tuition. You can always calculate what interest you need on your money to outpace the interest accrued on a year's worth of unsubsidized financial aid. If you can get that interest rate, go for it.