The number of canals you do in school will not factor into getting into endo. If you look at the applications for all the programs, not one will ask how many canals/teeth you have done. There are many things that factor into getting into endo, but those things will have very different weights at different programs. Some programs only want 4.0 students that were at the top of the class, other programs place more weight on experience. The faculty at your school will know what schools look for what, and can guide you on where to apply based on your strengths. Endo overall does have a lot more residents with post-grad experience compared to other specialties, which makes sense for endo. For OS and ortho, your career is so different from general dentistry, experience really doesn't matter, but for endo it does as endodontists need to know if a tooth is restorable or not, etc. But on the other hand, if you have good grades, board scores, and class rank, you can easily get in right out of school. Some people will need a GPR/AEGD/private practice experience to make up for slightly lower grades/class rank.