Q: My horse has just been diagnosed with equine odontoclastic tooth resorption and hypercementosis (EOTRH). I understand it is a rare disease of older horses, with no cure. The treatment is to remove all the affected teeth. I am looking for information on this disease, since, as you can understand, I am a bit upset about the fact that my horse will most likely lose all his incisors. He’s only 19 and still a very active and fit dressage horse.
A: We wrote about equine odontoclastic tooth resorption and hypercementosis (EOTRH) in a Case Report (“A Mouthful of Trouble,” EQUUS 378) that ran in March 2009, and since then, we have seen an increased number of cases and have gathered more information on long-term follow-up of the affected horses. Before getting on to describing the disease here, we are happy to relay the good news first: After a few weeks of healing time, your horse will most likely be much more comfortable, and there’s no reason he shouldn’t continue to remain active and fit for years to come.
EOTRH, which was first identified in 2004, is characterized by the dissolving (resorption) and/or overgrowth (hypercementosis) of the cementum, which is the bonelike tissue that covers the surface of the equine tooth and lines the deep cup on the biting surface (infundibulum). Some of the bone around the tooth sockets may also be destroyed (lysis). The disease primarily affects the incisors and canine teeth, and it usually begins in the corner teeth and moves inward. The lower teeth may be more severely affected than the upper ones.
The cause of EOTRH is still not fully understood. But it is believed that, as horses age, the increasing angulation of the incisors puts pressure on the periodontal ligament that holds them in place. The resulting chronic inflammation in the gums seems to affect the structure of the teeth in some way.
Early on, there may be no visible signs. Then redness, swelling and recession may develop in the gums over the affected tooth or teeth. As the disease progresses, gingival ulcerations, heavy plaque and fistulae (draining tracts) with purulent discharge may be observed. Eventually, the teeth may loosen in their sockets or even fracture. Some teeth may take on a bulbous, roughened, cauliflower-like appearance.
As the disease develops, horses may show pain while grazing or eating carrots or apples, they may become head shy or start refusing the bit, and they may resent manipulation or tapping of their incisors.
EOTRH is diagnosed by observing the external signs of infection and by radiology to look for the destruction and/or overgrowth of bony tissue below the gum line. The disease is progressive, meaning that once it is under way, the effects cannot be reversed. The only treatment is to extract the loose, painful and fragile teeth. A veterinarian may opt to remove only one or two teeth at a time, using regional and local anesthesia in the standing horse. In severe cases, however, the horse may need to have all of his incisors extracted at once, which is best done under general anesthesia.
After the surgery, the extraction sites need to be flushed twice daily with a disinfectant solution until complete healing occurs in three to five weeks. Oral nonsteroidal anti-inflammatory drugs (NSAIDs) may be prescribed for the first week or so, but most horses experience immediate relief after the extraction of the painful teeth, and their appetites improve right away. It’s also best not to ride with a bit until the extraction sites are healed.
Horses generally cope quite well without their incisors. They quickly learn to use their tongue and gums to pick up their feed and even crop grass. Still, it’s a good idea to modify their diets to include softer pelleted senior feeds. Another common effect is that the horse’s tongue is more likely to protrude when he’s relaxed.
Patty Latham, DVM
Jim Latham, Jr., DVM
Mill Creek Veterinary Service
Fort Collins, Colorado