I hope your cage mate is doing okay today.
My vet visit had mixed results. Nothing in his mouth appeared so serious that he would stop eating completely, in her opinion. She said it's not often that a 13-14 year old chinchilla just gets a major dental disease all of the sudden. No issues with the roots of the teeth growing the wrong way.
However, the 5 weeks of not grinding his teeth down might have caused his incisors to overgrow a bit. It's possible the original irritation healed up but then we transitioned into the side effect of the critical care only diet. There was also another point on a molar.
She did find some moderate misalignment of teeth but we knew that before. What's new info to me is she said the distance between the lower sets of teeth and the tongue was not wide enough. Trimming was required. That could be the problem. It wasn't advanced where the tongue was lacerated, etc.
So, we just need to get through the recovery and see what happens.