Hi Vicky,

Your father is probably suffering from Trismus. A side effect of the radiation. Please do a search on the message baord and especially the main site for "trismus". There is a lot of information in both places.

I went to a physical therapist (until my insurance ran out) that is a specialtist in working with TMJ. The treatment was similar.
People are supposed to be able to put 3 fingers in their mouth. I am only able to get one in, at my best in therpy I was able to do 2. There is also a Therabyte devise (listed on this site) that is helpful. I have just started using it and can tell a bit of improvement (thanks, Rosie)
With more to come I'm sure.

Hopefully your Dad can get help to work on those jaw muscles.

Take care,
Dinah