Anita, the lack of saliva and the chemistry changes in the remaining saliva seem to make it easier for thrush to develop. Watch the sugar and starches when eating because it is food for thrush organisms. Brushing right away after eating seems to help keeping it at bay too.

Mark, 21 Year survivor, SCC right tonsil, 3 nodes positive, one with extra-capsular spread. I never asked what stage (would have scared me anyway) Right side tonsillectomy, radical neck dissection right side, maximum radiation to both sides, no chemo, no PEG, age 40 when diagnosed.