What sources would you like? There are little to no actual studies done on chinchillas but there are plenty on other rodents. There are no documented cases of root elongation that ends well for any animal. I know many people who have done every treatment under the sun including the calcium and sunlight bulbs only to find the same results (no cure or help). Speaking from personal experience (work in the veterinary field) I see people trim, file, pull teeth and try alternative treatments and it changes nothing. So Im not suggesting euthinasia lightly. I know from many many many malo cases that the animals suffer. It really is the kindest thing to do even though it sounds heartless it is a very loving act.
The 'malo' chins with happy endings are often misdiagnosis. A true malo case is irreversible and at best manageable for a limited time. Malo comes in a few froms. Misalignment where the teeth dont line up properly. This leads to spurs which can cause ulcers in the mouth and is very painful. The chin will need dentals (to file down the teeth) every 2-4 months for its whole life, plus meds which is costly and hard on the chin. Another form is root over growth. There is no treatment or management for this form. I personally spoke with Cornell zoologists who told me that there is NO option besides euthanasia for this type of malo. There are also lazy chewers who only chew on one side causing the other side to not wear at all. This also requires routine dentals to treat.
Look up the biology on chinchillas. Their teeth sit in a grove on the jaw, not in sockets like other animals. This means if one is removed the others will migrate since there is nothing to hold them in place causing misalignment in the teeth. It just makes a bad thing worse. The opposing tooth should have also been extracted (now that the tooth has nothing to wear on, it will overgrow in a matter of weeks).
Why was the tooth loose? Were the gums infected? Was there damage to the tooth? At this point you need to be realistic. You are buying time and really need to consider the quality of life. I know you keep hearing euth but would you like to live with migraines and constant discomfort? Meds are only going to dull that, not eliminate it. Speaking from personal experience, when i had a cavity in my wisdom tooth, pain killers didnt do a dang thing. So I cant imagine what a tooth growing into your brain must feel like. You can always repeat the xrays and stage the growth if you feel the need but i truly think that keeping a chin alive based on long shot hopes is selfish