The simplest solution for keeping trismus at bay is to use wooden tongue depressors from the drug store each day. While your mouth is opening normally (usually before treatment) stack a batch of these between your front teeth. I could hold 15. Then, every day through treatment, and for a couple of months afterwards, keep trying to put that number there. The stretching begins when you can't manage the original number, and you really have to stretch the muscle to do it, holding them in your mouth for at least 10 minutes after each (painful) stretch. If you do this, at the end of it all you should be able to keep your ability to open normally. I ended up at the finish line only able to put 12 in despite all the work, but there are people here who can only open their mouths 1/2 inch at the end of treatment..... and that is a serious problem.

When the muscle gets radiated scar tissue forms in it making the elasticity disappear. (scar tissue is not elastic). The trick is to keep micro tearing the scar tissue to prevent it from become intractable.

All this may be tough for some, since they just don't want to eat, do the exercises, or anything during treatment more than be sick and sleep. While all that is understandable given the inevitable depression that many of us go through, treatment is an active participation process to have the best end result. Participation in knowledge acquisition, asking the right questions, asking for/getting the right treatments and pain meds, and even simple jaw exercises and proper diet and hydration. It all takes effort and work, in addition to what the docs are doing.