I personally have never heard of, met, and/or know of one. The DO/OMFS track was once brought up to the Nova OMFS program director by the University administration, but that idea got shot down in a heart beat. For those of you don't know, Nova Southeastern University has an Osteopathic medical school offering a degree in Doctor of Osteopathics (DO).
Since Nova OMFS residents and Nova DO medical students rotate in many of the same hospitals, the idea of a 6-year DO/OMFS residency seem natural. Further, at our DO medical school here, the DO students are able to earn their DMD dental degree (a joint-degree program) [details of the DMD-DO joint degree program is unknown at this time]. hypothetically, we may very well have a DO med student do a joint DMD degree program and later apply and match into an OMFS residency (viola, a DO/OMFS in the making). Will we see something like a DO/OMFS in the future? Probably, but not anytime soon!
Two ways to have a DO/OMFS:
1) a DO student earning the DMD degree and then apply and match into an OMFS residency
2) a 6-year double degree DO/OMFS residency (which is non-existent at this point in time)
Option #1 is more realistic and likely than option #2
{odds and ends: currently only Nova Southeastern University (NSU) and A.T. Still University of Health Sciences (ATSU) has both a dental and a DO medical school with NSU being the only one with an OMFS residency (4-year) currently between the two. If any DO/OMFS residencies will arise in the future, then these two schools may be the pioneer of that unique training track.}