Bucktooth:
Several points of clarification:
"IF" I were to be interested in Plastic Surgery fellowship, I would have to complete a OMS/MD residency which is 6 years
If this were to be the case, then I would have to complete the 3rd & 4th years of allopathic medical education (medical school rotations), which leads to the MD degree.
These two years of medical schools are usually completed within the 6 years of OMS/MD residency. An OMS residency will be a MD by the time when (s)he is a PGY-4.
But before all of that, an OMS resident (PGY-1) must take the USMLE and pass it to enter PGY-2, which is medical education 3rd year curriculum.
Samples of a 6-year OMS/MD residencies:
http://www.mayo.edu/mms/md-oms-clinical.html
http://cpmcnet.columbia.edu/dept/dental/OMS/OMS_Res2.html
http://www.tambcd.edu/oralsurgery/postdoc/postdoc.html
http://www.mgh.harvard.edu/oralsurgery/residency/residency.htm
http://www.pbhs.com/omsnet/block/dept/resi/index.html
Now, with all that said, it should become clear to you that USMLE Step II should not be any problems now because an OMS/MD resident have had the proper medical school training to pass the exam.
Now, applying to Plastic Surgery residency and/or fellowship, I'm sure it is VERY competitive. But if I do well on Step I, I believe that itself is significant/suffice enough to be a competitive applicant for a spot since that is one of the most considered factor in the matching process. Afterall, all medical students (including myself if I were to be in a 6-year OMS/MD residency) are compared based on the USMLE Step I scores.
Now, if I opt to do ONLY a 4-year OMS residency which does not lead to a MD degree, then I am obvioulsy not qualified to even apply to a Plastic surgery fellowship because I don't have a MD degree. Also, in this case, I wouldn't need to take the USMLE Step I, II and III because again there's no MD curriculum or degree involved in this OMS route.
So, to sum up:
1) you don't need to take the USMLE Step I, II or III, if you are only doing the 4-year OMS residency
2) you are not qualified to apply for an AMA Plastic Surgery fellowship without a MD degree
3) I strongly believe that the competitiveness of matching into a Plastic Surgery residency/fellowship is largely based on the USMLE Step I scores (weighs more than Step II and III).
4) I believe doing Plastic Surgery with my knowledge in Dentistry is a very attractive option, but I'm not EVEN close being there yet. I hardly know if I'll even match into an OMS/MD residency yet? All too early to tell or even plan. I'm not even finished with my 2nd year, for god sakes!
Only thing I'm positive at this point is that my grades are up there, my class rank is pretty good, I have a 90 on NBDE Part 1 and I'm offered an OMS externship at LSUHSC which offers the OMS/MD 6-year residency. All other things are only fun to talk about and cool to dream. Perhaps one day, they all will come true, but for now, I've got to eat my lunch and go back to class at 1 PM.
Hope things are more clear now.