So you are saying you did not have your teeth removed, used fluoride and so far so good?
Usually only bad teeth are removed prior to radiotherapy.
Occasionally the bone where the teeth are seated will die, particularly the lower jaw or mandible. This is known as osteoradionecrosis. Then teeth issues begin and eventually have to be addressed because the roots of the teeth are sitting in dead bone and the tooth no longer can survive. This is not common but can happen and is repairable with some difficult surgery. On the bright side the recovery is much quicker than that of the actual cancer treatment previous.
Someday (soon) I may post a discussion about my mandible resection.