Well, I might as well re-hash what everybody else has said, along with my own spin on it:
You aren't going to get in this year with those grades and DAT score. You need to significantly raise your GPA (or at least have an amazing upward trend -- the 2.5 wouldn't be bad if you've had several semesters of 3.7+ work). Your DAT scores are below average for the vast majority of schools, and average for just a handful. I believe your low GPA won't allow you to be competitive at that handful of schools.
Having said that, I *do* believe you have what it takes to make it in dentistry from a purely emotional standpoint. Volunteering, research, clinical experience, etc. show that you have a winners' heart and a heart that desires to enter the profession. The only problem is that those items won't gather you interviews. If you were to obtain interviews, then those items would be a huge plus to your application (and no doubt, your abilities in those areas would overshadow those of many other applicants).
Take a year to study and prepare yourself. Prepare heartily for the DAT, and do heavy research on which schools to apply to. The researching of schools will be key to your gaining acceptances. Also plan on applying very early in the application cycle, as this will boost your odds of interviews. Have your LORs and fees in order, and be prepared to enter the app. process next year.
Good luck with your plans, and remember that in the end the decision is yours. The opinions offered here (mine included!) are valuable, yet none of us knows your entire situation or your complete motivations.
And above all, know that your performance on the DAT does not say anything conclusive about who you are, how well you are suited to practice dentistry, or anything about your self worth. Just as people can have great days, they may also have bad days. If you feel that you were having a great day when you took the exam, perhaps a re-evaluation of study habits is in order. But foremost, don't put yourself down -- you'll need the strength in order to be a successful applicant, whenever you decide it is right for you to apply.