Q: I would like to know about the different ways a tooth can grow in the wrong place on a horse. I know that a tooth can push out of the side of the head or inside the roof of the mouth, but can a tooth ever grow out of the front of the head close to the eye? —Mary O’Connor, via e-mail
A: Strictly speaking, dental tissue, if it develops in an abnormal place, can appear anywhere in the body. If a tooth or toothlike structure appears in an area very far from its intended location, it’s usually part of a tumor. A teratoma is a benign tumor that contains different types of tissue, from bone to dental tissue or even hair. It’s rare, but it can occur anywhere anatomically. The more common type of structure, to which you are probably referring, is a “dentigerous cyst,” sometimes known as an “ear tooth.” This is a sac or cystlike structure that contains dental tissue, sometimes discrete teeth that typically appear near the ear as a chronic draining tract, sometimes with associated swelling. While these usually occur very near the ear, sometimes they can emerge in other areas, nearer to the eye. They must be completely excised to obtain a cure. If any of the structure’s lining remains, it will not heal.
Injuries as a young horse or aberrations in embryonic development can lead to malpositioned teeth that can erupt as you describe, next to existing teeth, closer to the palate, or even out toward the cheek but usually still within the mouth.