BYU looked at medical school in the late 1960's and early 70's and opted to go with a law school. First, the cost is staggering to maintain. The Church had already divested itself of the hospital system it built. Second, the government regulations on certain procedures would not be in keeping with Church beliefs. Third, their was a consensus that the state of Utah could not support two medical schools at the time.

As far as a Dental school I think it would just be cost.