Odds of Getting In
If you're thinking there are many spots for orthodontists at accredited schools, think again. UCLA, for example only has eight openings in their program. USC accepts six. Wow. Better be at the top of your game.
However, there are plenty of programs out there. If you study, work hard, and are good at it, there's plenty of demand for orthodontists. Think of all those teeth that need to be straightened.
It's a competitive field once you graduate and transition to the workplace. Coming from a school with a good reputation and good placement program will get you started much faster in paying back your student loans. You may want to network in dental school and team up with your friends who are dentists and be their resident orthodontist. Teamwork and getting along with others will certainly help you get in.