As Mr. Restriction Endonuclease says, can't hurt, might help. 😀
You can play it with this angle: If the interviewer asks you why you want to go to dental school and all that, you can say that you have had a lot of exposure to the profession since your immediate relative is a graduate of this esteemed institution, so you are familiar with the profession and would love to be a part of it for the rest of your life, yadda yadda...
This was part of the spiel I gave to NYU when I interviewed for Fall 2000 admission (my sister graduated NYUCD '00, and an uncle NYUCD '86). And yep I was accepted that year. 😉