So I hate to be the guy to tell you there's no Santa but orthodontics is considered the most competitive (right there with oral surgery) dental specialty. I'm not sure of the analysis of DAT and GPA scores with respect to this specialty program but I do know you will need to be in the top 5-10% of your graduating dental class.
There's a pretty nasty statistic in that ~50% of dental school applicants have aspirations for orthodontics. In fact, one student once told me a story where on the first day of dental school, a professor asked all the students how many of them wanted to become an orthodontist. About 60% of the class raised their hands. Unfortunately the numbers don't add up and when dental school is over, you will be competing against 100 other students for a program with 2-4 seats available. It's cut throat and not only will you need to be the best of undergrads to get into dental school.. you are going to have to find a way to be the best of the best. Not saying this isn't possible, it will just take a lot of work.
Personally, I would advise to never tell anyone you want to do orthodontics during your application to dental school. Furthermore, I wouldn't apply to dental school if this is all you want. Just knowing the competitiveness of this specialty, you should be happy being a general dentist and be pleasantly surprised if you are accepted into an orthodontics program. If a dental school catches wind that you only want to be an orthodontist, you just put up a wall with them. In addition to all these reasons, you have no idea what you want to do until you get into dental school. I've talked with many dental students about specialties and the majority of them have agreed that it takes a coupe years of dental school to really know what you want to do.
I'm not saying don't specialize. In fact, I would recommend that everyone start dental school with the intentions of specializing, as just to keep your scores competitive enough so that if one day you do want to do something like this, that door isn't completely shut.
I'm not trying to discourage you but just know what you're up against and know that there are plenty of situations where you may want to keep your "orthodontist card" hidden.