Ok guys.... FWIW. I participated heavily in the admissions process at my 4 year OMS program and this is how I perceive the the situation. It may be slightly different at the 6 year programs.
It's a sales job pure and simple. Used to be 2 pronged. Now may be 3 pronged. There is nothing wrong with this. It's what makes the world go round.
First prong.........get the interview. You know what this entails, it's all over this forum: best grades and test scores you can muster, class rank, LOR's, etc. GPR or 1 year OMFS fellowship if you don't. If you think you can do better on an exam and have the time and money then do it. (if I was pre-screening your app for interviews I would think to myself....this SOB really wants this, let's interview him and see how he carries himself.)
Second prong..... the interview. If you get the interview you can get into the program. It's all you here. We are looking to see if you are a grown-up. Personal appearance and grooming. How you answer questions, how you anticipate questions, eye contact, delivery. What you do and say when you don't know the answer to a question. (talk to current residents if possible - get some idea of the questions.) Questions that you ask when prompted can be equally important. Figure this out ahead of time but don't sound too rehearsed or canned. Better to formulate a question based on some information presented during the interview. Shows that you pay attention and process rapidly. Practice interviewing yourself or have someone else do it. Be serious about it.) Do not interrupt. Turn off your cell phone. Think about it. You're the interviewer. Who do you want? The kid with the really good academic record who has the personality of a squid or the kid who has slightly less academic prowess but whose enthusiasm you like and whose desire is almost palpable (but well-controlled and poised during the interview)
Third prong........medical school interview. I did this on my own and not as part of the OMFS program so I can't speak to specific programs. My guess is that there are similarities. Try to figure out ahead of time what the med school is looking for in their admissions process and give it to them. My best guess these days would be along the lines of "I am seriously considering a career in academia and the completion of both degrees will enable me to better pursue that goal as most of the academic positions today are calling for both degrees and I think in the future it will be a requirement." (doesn't really matter if this really happens or not) or "medical school curriculum will enable me to have a better understanding of the whole patient and therefore provide better overall treatment." Be humble. They don't necessarily know what it takes to get all the pre-requisites that you did in order to secure the interview. Let them know that you would be honored to be offered a spot at their med school and would work very hard to ensure that their decision was a wise one.
Lastly, apply to 4 year programs as well. You will be every bit as good an oral surgeon and if you really have that desire to get a medical degree, the opportunity to do so will likely be greater at the completion of a hospital based residency with a fistful of recommendations from all the M.D. heads of the various departments that you have befriended during your 4 years.
Awe, they'd do no such thing...give it a shot. But please be so kind as to match your first round so I wouldn't have to compete with you the year after. 
