Since chinchilla teeth are being formed throughout life, anything can influence "bad behavior" of the teeth. Metabolic disease, vitamin or mineral imbalances, trauma, poor chewing habits, inflammation from periodintal disease, infection of the tooth pockets, genetics, being domesticated. All these influences have to be considered and addressed in chinchillas. The physiology of continuously growing teeth requires that the teeth are worn at the natural rate in order for the teeth to function properly and not overgrow-since chinchillas are domesticated we are not able to replicate the natural diet and it is not possible for normal tooth wear rates to be achieved the diets we feed, consentrated ration-pellets and hay, so the effect of lack of tooth wear is a major problem, add genetic issues and there you are.
When you add genetics-a chin whose teeth grow more rapidly that normal, and the chin is on a consentrated ration I:E: pellets and hay, this results in elongation of the teeth above the gum, this holds the mouth open at rest, with this increased contact of the teeth surfaces and the constant contact of the teeth surfaces, this condition will stop the eruption of the teeth above the surface and kick start the eruption of the teeth below the surface-elongation of the roots. As long as chinchillas are domesticated and the natural diet is not replicated and you have these chinchillas who have the issue with fast growing teeth, you will have elongation. People switch the term elongation and malocclusion back and forth like they are the same, they are not, they are two very different conditions.
