We imported 10 tigrinnus last year, and one of them came in with a smashed, upturned mouth, obviously from impacting on the walls of the box. We were heartbroken for the fish, it looked pretty painful, as the upper jaw was totally pointing straight up
We tried a few minor things to get it to snap down, but couldn't get this very active skittish fish to settle enough to work on him/her. Finally we decided to let nature take it's course. We weren't sure that it would be able to eat enough to sustain itself.
The fish still has a slightly turned up mouth, easily distinguished from the rest of the cats, but it's no longer in any doubt that this fish will survive. After about 8 months with us, he's fine.