I feel your pain, Murphy. I had 29 teeth extracted at once, as a result of rampant radiation caries that was medically necessary, but was not covered by Medicare being it was after radiation treatment, and not in preparation for radiation or was during surgery to remove neoplastic disease.
Here is somewhat dated detailed information that may help you with an appeal or reimbursement is, "Extending Medicare Coverage for Preventive and other Services." In it, there are 5 conditions that are covered, one being Head and Neck Cancer, which is explained in more detail.
What is covered are extractions of teeth prior to radiation, oral examination if extractions are to performed.
What is not covered is an oral exam if no extractions are to be performed prior to radiation, preventive care to reduce risk of radiation caries (fluoride trays, supplemental topical fluoride, treatment for radiation caries).
https://www.ncbi.nlm.nih.gov/books/NBK225261/Here is a more recent report on covered oral care, although less detailed:
http://www.medicareadvocacy.org/med...is-coverable-under-current-medicare-law/Good luck