how do people on pass/fail systems get chosen for specializing?
That's where the reputation of the school plays a major role. Honestly, the hardest part about Harvard Dental is getting in, just like it is with any other great institution. Because there are only 35 students at Harvard, they can afford to have a pass/fail system where everyone that graduates has a great shot at doing what they want to do. People who want to go into certain specializations would do what's generally required: research in that area, networking with professionals, etc.