The answer depends on the exact kind of oral surgery, and on who performs it. Usually, Medicare Part Bdoesn't cover oral surgery. That's because Medicare considers most work performed by an oral surgeon to be "dental" rather than "medical." But Medicare Part B can cover oral surgery in a few instances. If the treatment involves not teeth but a problem with tissue inside the mouth, or with the bones of the mouth and jaw, Medicare might cover it.
The key to whether Medicare will pay is whether physicians (M.D.s) as well as dentists and non-M.D. oral surgeons also perform the same kind of treatment. If so, the surgery might be considered "medical" care covered by Medicare Part B even if performed by a non-M.D. oral surgeon. Also, the oral surgeon who performs the operation must participate in Medicare -- not all oral surgeons do.
If you are in the process of scheduling oral surgery, ask the oral surgeon's office whether they participate in Medicare and if so, to request in advance that Medicare cover the procedure. It may take some written documentation by the oral surgeon's office, which could take some time. If the oral surgeon's office receives approval from Medicare, you will know ahead of time that the surgery will be covered. If the oral surgeon does not participate in Medicare but the surgery is of the type Medicare might cover, consider asking for a referral to a different oral surgeon who does Medicare-covered work.