You sound a lot like I felt when I was a 4th-year dental student. I didn't know what I wanted to specialize in, but I was pretty sure I wanted to specialize. I decided to work in PP for a year or two to hone my interests, see what appealed to me in a non-school environment. I went from school to a Associateship position doing general dentistry on mostly kids. I originally thought I wanted to do endo, maybe OMFS, didn't really consider ortho because our DDS program skimmed over it. Once in practice I realized what I liked and didn't like about practicing, and I realized I wanted to do ortho and would really not like doing endo or OMFS.
I really think my Associateship helped me get into the program I did for ortho on the first try. Many faculty noticed me because I went out of private practice back to school (which was unusual for ortho), they knew my dedication to the specialty because I was giving up 150K per year in current income to go back to school, they knew I had based my decision on 2 years of real-world experience in private practice and I truly knew what I wanted in a career, and they loved that I had experience seeing patients (especially kids and teens) because they felt it would make me a better resident to the ortho patients.
My dental school stats were good, but not ortho good, so I really think the experience made the difference. During the interview process I spoke with some other interviewees who said there are ortho programs that prefer applicants with private practice experience (hospital-based programs), whereas the university programs look at stats more. I didn't know that before I applied, so I didn't apply to any hospital-based programs, but luckily a university appreciated my experience and I was accepted.
If I could change anything I did before applying, it would be to get research experience in dental school. Many programs didn't like that I didn't have research, even if I did have 2 years of PP experience. And the thought of trying to do research once in private practice was really challenging.