Although I didn't have Medicare when I first had radiation, and had two teeth extracted, it is to my understanding that Medicare covers extractions if it is needed to have done in order to have cancer treatment, and is not usually covered after treatment, when it is then considered cosmetic.

The 20% sounds like what Medicare A, B, doesn't cover, unless you have secondary insurance or a Medicare supplemental plan. Medicaid, if one can qualify, apparently covers dental, and some are able to get dual coverage with Medicare and Medicaid.

Also, the usual wait time for a tooth extraction is usually 21 days, depending on healing, before starting radiation treatment, although some doctors believe two weeks is enough, and in event of anything sooner, prophylactic antibiotics, as a precaution, may be needed in thinking that effects of radiation don't start until 10-14 days after starting, and healing should be complete, but chemo effects start a few days after infusion. One may need dental clearance, I did, before starting radiation treatment after extractions.

Good luck with everything.