I think you have a great chance of getting in. Not a lot of applicants have the hands-on experience that you do. And you are correct when you say that working will bring down your GPA. However, knowing that you want to continue on in dentistry because you have physically seen what is like in an office is more than a lot of people that simply "shadow" because you are actually a part of the staff and you know what the business is like, and how to treat patients.
For everything you lack in (like GPA) you just need to bring them up elsewhere. So if you have DAT scores higher than your science grades then it shows that you have learned the material, and you understood it well enough to take a standardized test.
However, some schools DO look at numbers a lot, and others look at experience. I would try to take UPPER LEVEL classes and do well in them (rather than re-take lower level ones) during the year before you apply.
If it makes you feel better, I know people with overall GPA's of 3.0's that have gotten into great dental schools because they simply had the passion for dentistry and the experience that would show the school that they would make a great dentist.
Also, don't listen to people that tell you that you won't get in. They are not on admissions boards, and half of them haven't gotten in anywhere themselves.