Veterinarians and researchers have only recently described a dental disorder called equine odontoclastic tooth resorption and hypercementosis (EOTRH) that affects older horses’ incisors and canines. Because this disease comes on slowly and insidiously, many owners and their vets don’t pick up on it until it’s in its late—and painful—stages. So Padraic Dixon, MVB, PhD, Dipl. EVDC(Equine), FRCVS, chair of equine surgery at The University of Edinburgh’s Easter Bush Veterinary Centre, in Midlothian, U.K., described how to recognize EOTRH at the 2018 British Equine Veterinary Association Congress, held Sept. 12-15 in Birmingham, U.K.

What Is It?

Characterized by resorption of the tooth’s hard, calcified tissues (cementum, dentin, and enamel) and, initially, EOTRH is similar a common dental resorption disorder seen in cats and sometimes in humans. Resorption occurs when odontoclasts—the cells responsible for resorbing the roots of deciduous (baby) teeth during eruption of permanent teeth—become overactive and unregulated (somewhat similar to osteoporosis in older people, said Dixon).

“The horse’s own cells destroy the teeth,” he said. “Odontoclasts can remove or destroy the three tissues (enamel, cementum, dentin) and even the pulp.”

To compensate for this resorption, the horse’s body usually responds by laying down more cementum on the outside of affected teeth, he said. What the horse ends up with are very thick teeth that are damaged at their center.

Dixon estimated that EOTRH occurs in about 5% of horses over the age of 15.


Diagnosis and Treatment

It can take years for affected teeth develop extensive hypercementosis; the early signs are much subtler.

“If you have any lesion affecting multiple incisors in adult horses, think EOTRH,” said Dixon.

He said suspicious owners can perform a “carrot test”—asking the horse to bite down on a carrot with various incisors to gauge whether those teeth are painful. These horses might also lose weight, be reluctant to graze, and have bitting issues.

To accurately diagnose EOTRH, however, the veterinarian must take intraoral radiographs, which Dixon said are easy to evaluate due to the disease’s destructive and, later, proliferative nature.

“Currently, there is no known treatment for EOTRH-affected teeth, and loose, fractured, or painful teeth should be extracted using sedation and local anesthesia,” he said.


It the horse’s teeth are still stable and pain-free, though, they do not need to be extracted just yet. It’s once the tooth starts to break down that teeth are vulnerable to periodontal disease, fracture, and infection.

“These lesions can cause great pain that can be a serious welfare problem for affected animals,” said Dixon.

After extracting affected teeth, the surrounding incisors might ultimately become loose. Thus, he said if the veterinarian is extracting more than four incisors in a row, it might be worth surgically extracting all six incisors at once. While this might sound and look drastic, “it can give horses a new lease on life,” Dixon said.