To give my perspective on your origninal question, I would say for oral surgery it's going to depend entirely on the program. (if you come somewhere like Michigan where they pride themselves way too much on research, than having it on your app is going to be a big plus. I am sure there are many OS programs out there which are more clinical and a lot less academic, and if I were you, that's where I'd apply.
For ortho, as others have said, you're going to have to get an MS, meaning, you'll have to do research during your program, so already having a foundation in it would be beneficial for ortho, but clearly not req'd.
For endo, as a previous poster said, research isn't critical, but it's all going to depend on philosophy of the program. For example, in Michigan, U of M would be all over that research experience, but Detroit Mercy would more than likely put less emphasis on it and more on rank, NBDE I, externships, etc. Endo is very tough to get into right out of school. You may need a GPR/AEGD or a year or 2 out in the real world as an associate.
Best of luck in whichever route you choose.