Lots of our friends have guinea pigs and they make wonderful, low maintenance pets that can be very rewarding, particularly for young children. It is important to know that guinea pigs have continually growing and erupting teeth. Generally speaking, this is rarely a problem for your pet, if it is fed a high quality mixed diet that allows them to gnaw, chew, and wear down their teeth while eating.
Guinea pigs have two top and two bottom incisor teeth. These are usually around 1-1.5 cm long. If your guinea pig is healthy and eating properly these teeth should be relatively even and meet each other in the middle of the mouth. This means your pig is naturally wearing down it's teeth at the appropriate rate.
Sometimes things happen to cause teeth to break. This could be for a number of reasons, including your pig chewing on wire or it's cage, or maybe beacuse it has taken a fall and chipped one or two on the way down. It is extremely important to check your guinea pigs teeth regularly for injury as uneven teeth can cause discomfort, pain, and eating problems, leading to a form of guinea pig 'anorexia'.
Guinea pigs also have a row of back teeth that are called 'cheek teeth'. These are usually quite far back and difficult to inspect. A vet will possibly flush the mouth out with water before using a depressor or dilator to properly assess the teeth.
Occassionally, guinea pigs will refuse to eat altogether and this could be because it is experiencing some dental pain. It is essential to get your guinea pig to a veterinarian to have them filed to an even plane again. Guinea pigs need a low calorie, high fibre diet and should be fed high quality hay and lots of fresh, clean grass every day.