Generally, retaking the DAT will help improve your chances. BUT getting a lower score the second time around WILL hurt you. I would only recommend retaking the exam it if you have the time and the motivation to do better. The DAT is a standardized test and as a result it is the best definition of what kind of applicant you are. A strong DAT score carries significant merit vs. GPA which varies across colleges.
Ultimately, the general rule is, if you can improve anything before the next application season, do it. The more you improve your application the better off you will be. Based on responses by admissions officers, applying with the same application used the previous year will almost always result in an identical response from the schools. Give them something to show how you’ve grown.
Now that your application is mostly completed, this time around be sure to APPLY EARLY. Applying as early as possible to June 1st has a tremendous effect on your chances of getting in. For example, those who applied early on SDN with a 3.3 have been getting interview opportunities. Since admissions is rolling, as people are awarded an interview, fewer spots remain for the following batches of applicants and interviewers.
Last but not least, DON’T give up hope! You can always become a dentist, it just depends on determined you are to become a dentist. It is common for people to continue towards a Masters Degree or even a PhD and apply for dental school. The point is that it is never too late to get into dental school.