while i agree with most of what lweck as said, the one thing that i must say is that while malo is not a "curable" disease there are things that can help slow the growth of roots. and trimming/filing teeth is a necessary part of maintaining oral health in a rodent.
by that i mean, if they have points on their teeth they need to be filed, otherwise they can get an abrasion in their mouth which can get infected. also filing/trimming will often stop the drooling.
if your chin is eating pellets and hay and gnawing on wood those things file the teeth naturally, which is why a normal chinchilla does not require dental vet visit.
and not every case is the same. my chin was diagnosed over 2 years ago. honestly i dont think it is genetics.....i think it was environmental. basically i blame myself. i was not educated when i got him over 6 years ago....feed him raisins and whole peanuts and didnt give him wood every single day. Now all my chins get pellets, the best hay, and 1 shredded wheat a day. they get an organic herbal mix that contains only herbs, flowers, & a pinch of oats, crushed rose hips (vitamin c). and i prepare my own wood and they all get at least 1 stick per day and all have wood shelves they can gnaw on.
so it is not always genetics that you are fighting, sometimes it is making up for mistakes you or someone else made.
but at the end of the day........the most important thing is to do what is right for your situation and your pet.
Krysten--the worst person in the world would not have spent all the time & money you have spent on your chin. you are doing what you think is best for your situation. good luck i hope penelope is back on the right tract and is feeling better real soon.