Rabbits, guinea pigs require mostly hay-based diet

Rabbits and guinea pigs differ from most other mammals in that their teeth grow throughout their life.

Their diet of fibrous plant material requires lots of chewing, which causes wear and tear on the teeth, but, because they're constantly growing, the teeth are not ground down too far, nor do they grow too long.

With the constant growing and reduced use, the teeth eventually become much longer than normal, a condition called dental malocclusion. "This affects their ability to eat properly and, in severe cases, can prevent the pet [from] properly closing the mouth, resulting in discomfort, pain and, if severe, starvation."

The clearest sign of dental malocclusion is overgrown teeth. To check for this, Gething says, hold the pet rabbit or guinea pig gently and lift the lip - if the front teeth look long and spindly and, in some cases, are bent or not properly meeting up, the teeth are overgrown. "Quite often, they will have wet lips and chin from saliva staining and drooling, and there may be a bad smell from the mouth."

Once the pet cannot eat properly, there may be noticeable weight loss and lethargy, and, Gething says, in severe cases, the teeth can press back into the gums and jaw, resulting in swelling and facial pain, and sometimes a watery eye discharge.

Dental malocclusion is painful and it affects a pet's quality of life, but it can be easily prevented.