Where exactly is the pain located? What type of pain (throbbing, sharp, etc.)? Does anything seem to aggrivate the pain?
Do you ever hear him grind his teeth at night? Does anything else make you think he might be clenching/grinding?

Minor point: TMJ is just the joint, TMD is a problem with the joint. When you see your doctor, you can impress him with the correct term ;)

I think teeth grinding is a symptom of having parasites. The NHP is here to do on this forum. I'd venture a guess that chiropractic could be of some temporary help until the parsites were getting gone. What's the MD going to do about it that really solves anything?

TMJ is usually caused by the anterior rotation of the Atlas on the side of TMJ pain. The Transverse process of the Atlas is rather long and when it gets stuck rotated to one side or the other it will interfer with the normal movement of the mandible causing the TMJ joint to get inflamed. Ouch!!!

Quite easy to fix with a good upper cervical adjustment.

Parasites cause clenching of the teeth by the ammonia they secrete constantly stimulating the adrenals. It's like being on speed all the time. Tightens you up to include clenching the teeth.

Doc