Dont do DH unless you want to do it instead of dentistry. I've heard that doing really well in a MS program can help. You can most likely improve on a 19 DAT with some work too.
I guarantee you will get better chances if you....
1. Retake DAT and improve your scores. At least AA 20~21, TS 20~22 and PAT 19 or above.
2. Work or volunteer at places where you can show your "commitment to service"
3. Take your "TIME" and work on your personal statement. (------ This is really important. Don't make a boring story, but include your uniqueness
relating to dentistry. Do not ever write it as a college application essay.
My stats last year were AA18, TS18 and PAT 20. This year, I retook and scored AA 22, TS 22 and PAT 26. My GPA was 3.5 overall and 3.7 sci. I didn't do any master or special program. Graduated from well known college with bio degree. I also completely rewrote my personal statement.
Last year, I was only invited to two interviews and got into only one dental school. However, because of these two changes, I was invited to 10 interviews and got into multiple schools out of 15 dental schools I applied. Rejected from two schools as well. If you need help later, please pm me.
Good luck!