If you're applying next year, then hopefully the next year of coursework can boost your GPA to a 3.5. That'll 1. Be a competitive GPA and 2. Show ADCOMs that you've successfully changed your study habits and can handle a science-heavy course load.
To better your application, I'd continue volunteering since a lot of dental schools like to see community service. Then, study hard for the DAT to aim for 20+. If you get your GPA up, continue volunteering, and score well on the DAT, I think you'll be a competitive applicant (without needing to do a postbacc) with a great story to tell.