OMFS is a specialty of dentistry (albeit one with a lot of surgical overlap. It's not uncommon to see an OMFS resident rotating on a gen surg service for a time). You get DDS or DMD and do either a 4 year residency or an integrated 6 year OMFS residency with four years OMFS + 2 years of med school to earn the MD. As a non-dentist, I have no idea what the true advantages of this are, but there are discussions in the appropriate fora if you go looking.
Ortho is open to MDs and DOs. There are some AOA ortho residencies. Either way it is a five year residency after medical school. Otolaryngology (and it is all just semantics whether it's called Otolaryngology, Otorhinolaryngology, ENT, Oto. & head and neck surgery [Oto-HNS], or Oto and Facial Plastics-the 5 year residency is to get boarded in Oto.). It too is a five year residency. Most ortho and ENT residencies have gone away from doing a gen surg PGY1 followed by PGY2-5 in the specialty and now have a PGY1 that is predominantly specialty focused. This is at least true, to my knowledge, in the allo world; I'm less sure in the osteo world but you can look it up. Very few ENTs did a gen surg + ENT residency, unless they just figured out late in their training that they wanted to do ENT and not gen surg. ENT is not a fellowship, it is its own primary specialty.