My brother is having pain in his back teeth what should he do?

EDIT: Before these visits he went to a free clinic which did some work on his teeth, but did not fix his pain apparently at which point he got some dental insurance and then went to a dentist. However, the payments are not cheap even then.

He has gone to orthodontist, and has been twice to the dentist. At this point they did a cleaning and told my brother (so he told me) that he needed a filling. Then the second visit, for the filling, they said he didn’t need a filling, but instead he had a cracked tooth.

He has been complaining that his two teeth in lower jaw towards back hurt. At this point they recommended him to endodontic and said he might need a root canal. Guess the next visit is anyones guess at this rate…..But he also really doesn’t have the money.

My guess was he might be grinding his teeth. Any ideas?