I completely understand your situation. I was in the same place 2 years ago. I did a 2-year masters and for me it was the best choice I ever made. I only had 1 semester of graduate credit on my transcript when I applied though and was rejected to 8 of the schools I applied to, silent at 2 schools, interviewed at 1, and was accepted at 1.
If you get a 4.0 in a masters, which I know is totally do-able cause I did it and we have about the same undergrad gpa's, then I bet a dental school would look past your pharmacology grade.
Plus I would tell dental schools in your supplemental application essays about what happened in your pharmacology class. Just put a positive spin on things. Don't say "I had the worst professor ever" but just be honest. If your girlfriend broke up with you, a family member died, you just didn't understand the professor's teaching style, or even if you just hated the class then write about it in your essays but in a positive light. You could say "I took pharmacology and at the time I hated the class. I received an F and it genuinely affected me. I learned X, Y, Z from this experience and am now a better student because of it. In my masters (or post-bacc) I did A, B, C differently and was much more successful and am so much more confident in myself because of it."
People are accepted to dental schools with lower gpa's and DAT scores every year. Check out the ADEA dental school book for more information. There are people accepted with a 2.1 or a 15 on the DAT every year. Don't give up if it's something you really want.