When I'm assuming they had a vet checked the teeth multiple times? Did they just do a visual check and if so did they use a scope to check the molars? Also were x-rays taken? You can't really see the molars without at least a endoscope, ideally a camera one so they can get a better look after, and it's impossible to see the roots at all without an x-ray.
If it is malo, then teeth trimming is really only buying time, there is no cure or way to correct it (short of removing all their teeth, but that is not advised, it risks breaking the jaw and/or killing them), so long as the roots haven't started growing yet you can take the chin in for regular teeth trimming, but that's about it. If the chin recovers quickly and goes back to being a normal chin after the teeth trimming then you can get lucky and not need trimming again for several months. If they don't go back to chewing on things though you may need more frequent trimmings since they wont wear down their teeth if they aren't chewing on things. Once they get to the point of needing trimmings frequently, like every few weeks and aren't recovering to being a normal active chin after trimmings it's time to think about quality of life. Also if the roots start to grow personally I think it's best to just let them go before they are in too much pain. The top teeth roots will grow up into the skull and puncture the eyes and brain, and the bottom ones grow down into the jaw, breaking the jaw.
However there are some other possibilities other then malo. Like a tooth spur or spurs, which can be helped if the teeth to some extent, by providing a variety of hay, different hay is chewed differently so it can help wear the teeth more evenly since spurs are caused by uneven wear. To be clear before a certain someone tells me I'm wrong, I have no scientific proof that it works other then people having chins with tooth spurs switching to a variety of hay after having the spurs trimmed and they haven't come back. Maybe it was the trimming maybe it was switching to a variety of hay. Another possibility is an abscess or sore in the mouth causing pain when they try to eat or chew on things, which can be helped with meds. It could also be over grown molars from lack of chewing, that have curled over the tongue trapping it, sometime simply trimming the teeth so they line up again is enough to correct the issue so they can chew again. It could also be broken or rotten tooth or teeth, removing the problem tooth or teeth can help, but removing teeth does set a chin up for malo eventually. Since their teeth aren't in sockets they will move and become misaligned over time. Also the opposite tooth from the one extracted will need to be trimmed every so often since it wont have the other tooth to wear against anymore.