Same thing happened to Kris's teeth. They just fell apart. Broke off at the gum line. It took 18 months before he got any treatment. He has had them all root canalled now by the hospital dentist. That's not the end though, one of them has again broken. He uses a high fluoride toothpaste that we get from a specialist dentist practice in town. He has a water pik.
I don't know. His teeth were always terrible and crumbly. He was at the dentist at least every 4 months for running repairs before cancer . Maybe some are more prone to this decay come what may after radiation .
Hope the Greenlane clinic can help.
Tammy

Caregiver/advocate to Husband Kris age 59@ diagnosis
DX Dec '10 SCC BOT T4aN2bM0 HPV+ve.Cisplatin x3 35 IMRT.
PET 6/11 clear.
R) level 2-4 neck dissection 8/1/11 to remove residual node - necrotic with NED
Feb '12 Ca back.. 3/8/12 total glossectomy/laryngectomy/bilat neck dissection/partial pharyngectomy etc. clear margins. All nodes negative for disease. PEG in.
March 2017 - 5 years disease free. Woohoo!