None of us are the admissions comittee (may be a few here 😉). But let me give you my 1 cent.
Find the professor that is going to be able to highly recommend you to the dental school. It is not going to make that much of a difference whether it comes from a general biology teacher or upper division biology. In fact, if you call a different school, they might say "Are you kidding? We would much rather have an upper division biology professor recommend you than a teacher you had 3 years ago!"
General Course Professor + really good recommendation = 👍👍👍
Upper Div. professor + really good recommendation = 👍👍👍
Both my professors were upper division and I got in 😀
Just my 1cent😎