Several schools have master's programs that you can finish in one year. The ones I am aware of are geared towards med students who need to raise their gpa and become stronger applicants. But since the first year med and dental classes are the same (physio, immuno, histo, etc) these programs can work for you as well.
BU Med schools had one (masters in medical sciences), Tulane has one (i believe master's in pharmacology), Georgetown has one in physiology, and Creighton has one.
I did the one at BU. It was fun living in Boston for a year, but it was expensive. I got to take a lot of first year dent/med school classes and I think it helped me with the application process and I will have a stronger foundation for first few years of dent school, so hopefully it will be easier and I will do better on the boards.
Good luck.