Hi there ,
I too had trismus , was given a therabyte to use as part of a study trial . Once treatment began I could only use it for the first 3 weeks felt to ill between week 3 and 6. Did try as often as I could once the treatment had finished and found it really did help . Seem to have a psychological problem with it now ( that's just me thought) it reminds me of bad times and when I was ill and very sickly so I've not used it for 5 months but I do daily stretches several times throughout the day . I can fit 3 fingers in my mouth and the dentist says there are no issues. My teeth don't seem to be have been affected but realise what's good today may not be tomorrow and vice versa! I continue to brush them religiously after eating anything and use Duraphat toothpaste on prescription twice a day with a natural toothpaste in between. Still have issues with a sore tongue but no where near as bad as it was. I've learnt from here that it can be up to 2 years after radiotherapy before healing is complete . Keep on with the stretches .... Worth the hassle!