Chinchillas are born with white teeth. Their teeth change color as they grow, sometime between 6 and 12 weeks, from what I have seen. An adult chin who has white teeth is not getting enough calcium. Too little calcium can lead to a condition called hypocalcemia, which can cause seizures. It is important to check their teeth to make sure they are the proper color. Mine range from a medium yellow to a deep caramel-orangey color. I have also seen the sides of the teeth turn a little white. When I see this I usually give a little calcium supplement, like half of a Tums with calcium tablet. I'm probably being a little overly cautious, but better safe than sorry.