I do also think that you should re-take.
First, lots of schools have cut-off minimum and they are like 17 or below (depending on schools but 13 will definitely be below cut-off), which means that some schools will not even look at you just because of that score.
AA of 18 is not too bad, although it is still below average of matriculated students (accepted and starting dental school), but some schools might have problems with your DAT score not being in accord with your GPA.
It would help us if you can give us more detail on your DAT scores (different sections) and also where you went to school for undergrad. Especially if you went to not well-known schools and have 4.0 sGPA and have 18 AA, then some schools might think that reason why your GPA is high is because the school was easy.
Even if you do get invited for interview, when they are making the final decision, your DAT can be an issue during their discussion. If you're an applicant for this year then DAT re-take would be too late, but if you're applying for next year, I would say re-take in order to make sure that you have good chance of getting in.
also, it sounds like you were just using Kaplan, do some searches on DAT forum and find right materials to study.
If you are capable of making 4.0 in all your science courses, I am pretty sure you can do much better on DAT.