The normal bite of a rabbits teeth has the upper incisors overlapping the bottom ones. Malocclusion can also be known as buck or wolf teeth. This is where the bottom incisors overlap the top ones and cause the teeth to grow curved and if not clipped or burred down will grow into the rabbits cheeks or roof of the mouth.
This can be a hereditary fault in the genes and the rabbit can be born with it. Even if parents show normal teeth if they have a recessive genetic gene then there is a 25% chance of their offspring being born with the defect. Malocclusion can also result from injury by biting and pulling on the hutch or rabbit cage mesh wire.
Most rabbit breeders cull stock with malocclusion, but pet shop breeders may not resulting in the recessive gene being passed onto their offspring and so the problem grows.