All (or at least most) members of order Rodentia (rodents) have incisors that grow rapidly, and they must constantly chew roughage to keep their teeth worn to a functional length. At some time in this GH's life it must have had a diet lacking the essential roughage. Once the teeth are grown beyond a position where they can be employed in chewing, they will just keep on growing out unchecked. Thus the "saber-toothed" GH! In this case, one tooth evidently received just enough wear to keep it worn back, while the other tooth did not. Quite unusual, I would guess. Both incisors growing out is a severe threat to the survival of the animal, because it cannot chew most foods properly for efficient digestion, or requires much longer to chew the same amount of food and thus suffers prolonged exposure to predation.
