Reason For Discomfort In Opening The Mouth Along With Teeth Pain?

Hello, helping a friend. He has never smoked. Has diabetes (often very high 200-450), AIDS patient, liver damage-I think maybe 8% working-he is supposed to take lactulose to help clean (system?) rarely does-often his ammonia level is very, very high that has caused mental issues sometimes, many medications...I think thats all. My concern/question is: he is now unable to open his mouth fully to even eat. Has lost 20-30lbs in the last two months. He tries to open and It seems as if his mouth/jaws just look up and he has to try to force mouth open, can take up 20-40 seconds. Also constant teeth grinding that causes major headaches. Which way do I start in trying to help him. We checked medications and this problem is not listed as a side effect of any of his meds.