Dental,
This is a good question. I'm sure a lot of us on this forum will have various thoughts and opinions to share about this topic. I will share with you mine!
From my exposure to current dental students who are interested in specializing or who already have been placed in a specialty training position, all have done some research while they were in dental school. They've all told me that you pretty much need all of the following to be competitive (all specialties in general):
1) Good grades (GPA) => top 5% of your class
2) Good board scores => >90 percentile
3) Research experience
4) Strong clinical training in the particular specialty that you want to pursue (EX: Oral Surgery, you have better extracted teeth like crazy during your Pre-doctorial dental education)
Now, here comes the gray, debatable area. About graduating from certain school that will increase your chances of getting into a specialty training spot....I would say "yes" that may help you a bit, if you have all of the criteria mentioned above (obviously you're competitive enough), but if you lack in GPA or board scores, I really don't think that just the fact you graduated from Columbia or UPenn and you know people (connections) that you'll land a specialty training position while competing with another applicant who has strong everything and is obviously competent from Howard!
I guess what I'm trying to say is, if you want to specialize, just make sure you do everything to increase your chances of getting accepted.
Now if you say two applicants are applying for the same specialty position and they both have the same credentials, one from UPenn and one from Nova, and the specialty director is a UPenn alumni, then obviously the UPenn applicant has an advantage. Again, it all goes back to "increase your credentials as much as you can as a Pre-doctorial dental student"! That means, more research, more procedures, more ECs!
It's not which school you graduated from, but what have you done at "YOUR" school prior to your graduation!? Just my opinion! 😎