When they inject deep in the jaw for work like root canals in the back. They ended up sticking the needle right in the nerve/tendon area that moves your jaw causing inflammation. They had trouble getting my lower numb so they kept injecting and injecting and injecting.
Once injured/inflammed, I think the muscle reacts by locking up to prevent further damage.
My ordeal went on for about 3 months. I couldn't talk back to the better half all that time, so life was peaceful....
