As if horses weren't prone to enough injuries and health issues, a new dental disease surfaced in 2004. It's literally a mouthful: equine odontoclastic tooth resorption and hypercementosis (EOTRH). And because it's so recently identified, Ann Pearson, MS, DVM, and her colleagues at Reata Equine Veterinary Group, in Tucson, Ariz., conducted a study to identify risk factors and create more awareness among veterinarians. She presented her results at the 2013 American Association of Equine Practitioners convention, held Dec. 7-11 in Nashville, Tenn.

EOTRH is a very painful disease primarily affecting horses' incisors and canine teeth, Pearson explained. "In our experience, the teeth appear bulbous, irregular, and discolored," she said. "Gingival receding is often seen along with shifting of incisor positioning."

In previous reports, veterinarians have noted that the disease tends to appear in horses older than 15 and more commonly in Thoroughbreds and Warmbloods than in other breeds.

Treatment for EOTRH includes removing the affected teeth, a potentially painful procedure for the horse and a difficult one for the veterinarian that requires continuous follow-up evaluations to ensure the mouth remains balanced, Pearson said.

EOTRH primarily affects horses' incisors and canine teeth.

Photo: Courtesy Dr. Ann Pearson

In their study, Pearson and her colleagues analyzed Reata Equine medical records on more than 13,000 veterinary calls for any reason from 2000 to 2012. These horses ranged in age from 1 to 40 (average age 9.3) years; represented more than 70 breeds (nearly a third were Quarter Horses, with another fifth being Arabians); and were a mix of mares (35%), geldings (45%), and stallions (20%).

Pearson determined whether these horses exhibited any of her hypothesized EOTRH risk factors:

  • Excessive dental work;
  • Periodontal disease;
  • A low-mastication diet (or one that doesn't require much chewing), including a lack of pasture and/or an alfalfa-only diet;
  • Endocrine disorders such as pituitary pars intermediary dysfunction (PPID, or Cushing's disease) and equine metabolic syndrome (EMS);
  • Laminitis;
  • Clinical behavioral signs of frequent involvement with water (e.g., playing, standing by water tanks, etc.);
  • Excessive salivation or foaming of the mouth;
  • Breed;
  • Sex; and
  • Age.

Of the 3,461 horses evaluated, Pearson found that 696 had an endocrine-related disorder, 577 had laminitis, 269 had excessive dentistry, 135 had EMS, 79 consumed alfalfa-exclusive diets, 59 had PPID, 40 exhibited behavioral signs of EOTRH (e.g., mouthing water buckets), and 39 had periodontal disease.

Pearson then sent follow-up surveys to owners of horses diagnosed as having EOTRH. She said the survey results combined with the horses' histories validated the statistical results for the risk factors. She focused in on what she considered four main risks:

  1. Excessive dentistry "Horses with excessive dentistry were five times more likely to have EOTRH," she said. "Dr. Carsten Staszyk (DrMedVed) in 2010 hypothesized that mechanical stress within the periodontal ligament may be the initiating factor."
  2. Periodontal disease/lack of grazing Pearson said horses with prior periodontal disease were also five times more likely to develop EOTRH, possibly due to lack of blood supply to the gums as well as a lack of saliva bathing. "We are hypothesizing that a lack of grazing time will not allow the horse to have his head down in proper position to allow the saliva to have the full effect of bathing the incisors and removing stagnant feed," she explained.
  3. A primarily alfalfa hay diet Horses fed alfalfa, which requires little mastication (chewing), without grazing on pasture are twice as likely to have EOTRH, Pearson said. "The lack of chewing time and difference in elevation of the head will decrease the amount, time, and path of bathing the teeth and gums with saliva," she said.
  4. Endocrine disease and laminitis Pearson said horses with EMS or PPID were 2.3 and 2 times, respectively, more likely to develop EOTRH. "The hormonal effects of cortisol (associated with PPID) may weaken the periodontal ligaments, and the high levels of glucose and insulin in the blood may affect essential components of the cementum (tissue that covers much of the visible portion of the tooth) and periodontal ligament adversely, thereby increasing the risk of periodontal disease," she explained. Laminitis alone was not found to be a significant risk factor for EOTRH.

Other notable findings Pearson described included that Arabians appear at greater risk of developing EOTRH than other breeds, based on her study results, and that mares and geldings are less prone to the condition than stallions. Age, however, was not a significant predictor of EOTRH.

"This is perhaps somewhat surprising but tells us that it is not maturation in and of itself that puts a horse at risk of EOTRH," she said. "Rather, it is the other risk factors that attend to aging."

In conclusion, she said, a combination of several factors might put a horse at risk for developing EOTRH. Owners should work together with their veterinarians to provide a detailed history of the horse and help prevent the disease.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.

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