Even though i have pls/umn i can relate to your jaw issues.
Since it spread to bulbar region about 5-6yrs ago i have had many problems.
My jaw on right side tends to spasm,jaw will go stiff then slam shut suddenly........more distressing but can be painful if you catch your tongue.
A year ago i had a spasm during the night that resulted in a cracked lower molar on right side,was in pain with jaw spasms for months and doped up on meds.
I went to dentist about tooth and they did quite alot of xray scans of jaw,said tmj area looked good and it was to do with spasms .......i said i did find i had pain around tmj area but they said it was reffered pain.
My gp has said i could have botox injections but they can cause long term complications.
Also get spasms and weakness in lower facial muscles and have difficulty eating,i have to keep stopping as it can be painful and tiring.
Wattif,i totally understand....it was a big blow when i started with the bulbar issues.