Disease Du Jour: EOTRH  – EquiManagement

Mild cases of EOTRH
A case of mild equine tooth resorption and cementum hyperplasia (EOTRH). | Courtesy of Garden State Equine Dental Clinic

In this episode, Amelie McAndrews, DVM, DAVDC-Eq, of Garden State Equine Dental Clinic joins us to talk about equine tooth resorption and cementum hyperplasia (EOTRH). She discusses the prevalence of the disease and describes common clinical symptoms, treatment options, and more.

What is EOTRH?

McAndrews describes EOTRH as “a painful and progressive condition in middle-aged to older horses.” Although it primarily affects the incisors and canines, there are some reports that the cheek teeth are also affected.

“Tooth resorption begins at the periphery of the tooth, usually at the root or crown, and then progresses towards the pulp,” explains McAndrews. When tooth resorption occurs, inflammatory cells cause fibrosis of the gums and periodontal ligament. Horses also experience alveolar osteolysis and distortion of the vascular channels around the teeth. The tooth is resorbed by odontoblast cells and cementum hyperplasia ensues.

“The way I explain this to owners is that the tooth begins to resorb or essentially dissolve, and then the body tries to repair these defects by depositing cementum, which is tooth resorption,” McAndrews said. The problem is, cementum is deposited where it shouldn't be, and it's more brittle than the tooth tissue it replaces.

“It kind of becomes a self-perpetuating process, the teeth become more and more resorbable, they deposit cementum, and cementum has different properties than the dental tissue it replaces, and that's how the disease process progresses,” she says.

The horse then develops periodontal disease and osteomyelitis around the affected teeth. McAndrews noted that this disease process is different from tooth resorption in cats and humans.

How common is dental resorption in horses?

Moderate EOTRH cases
Moderate cases of EOTRH. | Courtesy of Garden State Equine Dental Clinic

In a recent study of horses 5 years and older, radiographic examination revealed a very high incidence of tooth resorption, McAndrews said. “They found that 88 percent of the horses and 49 percent of the teeth had radiographic evidence of tooth resorption,” she said.

Additionally, studies have shown that 20% of horses and 7.6% of teeth have cementum hyperplasia, and nearly 16% of incisors in asymptomatic horses have undergone tooth resorption severe enough to require extraction. Age is associated with an increased rate of tooth resorption, which is higher in the angular incisors of horses over 15 years of age.

While these percentages are alarmingly high, the tricky part is determining when tooth resorption reaches pathological levels and causes pain in horses, McAndrews said.

What causes EOTRH?

Researchers still don't know the cause of EOTRH, but they have a few theories. McAndrews said the most popular theory is that biomechanical stress on the teeth may cause the condition. Horses' incisors begin to shorten between 13 and 15 years of age, resulting in a reduction in surface area for periodontal ligament attachment. Due to the smaller surface area, certain parts of the tooth experience greater concentrated stress, resulting in the release of cytokines. These cytokines release fragmented cells, which trigger tooth resorption.

Once teeth begin to resorb, horses can develop periodontal disease. This leads to another theory: A bacterial infection may cause EOTRH.

Others speculate that iatrogenic dental procedures such as excessive flotation may cause the condition. In another recent study, researchers looked at trace minerals in cementum hyperplasia.

“Unfortunately, we don't know the length of it,” McAndrews said. “If we don't know what's causing it, it's harder to stop the progression of the disease because we don't know what exactly we're stopping other than tooth resorption and cementum hyperplasia.”

Clinical symptoms of EOTRH

EOTRH takes many years to develop, and veterinarians often don't diagnose it until the horse is in the later stages of the disease, when it begins to affect the crowns of the teeth, McAndrews said. Even if a horse has significant radiographic changes, clinical signs can be subtle, making it difficult to link radiographic changes to pain, she said.

Common clinical signs include gingivitis, periodontitis, small pits in dental calculus, and a bulbous appearance of the incisors due to cementum hyperplasia. If the disease progresses far enough, fractures, loose teeth, and periodontal pockets may develop. Horses may be sensitive to the speculum and not comply with oral examinations. They may experience weight loss, vomiting, bad breath, and biting problems. Some horses will rub their front teeth against the wall. Others are largely asymptomatic, perhaps because they have learned to tolerate the gradual onset of discomfort.

Diagnosing EOTRH

Radiographs of horses with EOTRH
Radiographs of a moderate EOTRH case (left) and a severe case (right). | Courtesy of Garden State Equine Dental Clinic

EOTRH requires radiological diagnosis guided by clinical examination. You'll see on X-rays follicular bone loss accompanied by ligamentous widening or compressive osteitis,” McAndrews said. “That can lead to periapical abscesses. They may get osteomyelitis, and you'll see the tooth Fracture and, of course, tooth resorption.

McAndrews says grading tooth resorption can be helpful to owners. Grade 1 involves cementum and a small amount of enamel; Grade 2 involves dentin; Grade 3 is when the tooth is resorbed into the pulp, which is the stage at which veterinarians typically recommend tooth extraction; Grade 4 is when the tooth has lost structural integrity; Grade 5 is when only the tooth remains Case.

Treating EOTRH

Severe cases of EOTRH
Severe cases of EOTRH require tooth extraction. | Courtesy of Garden State Equine Dental Clinic

McAndrews said veterinarians have tried a variety of treatments for EOTRH, from brushing to steroids to antibacterial medications to splinting the teeth. These are unsuccessful for long-term management. Because veterinarians still don't know what causes the disease, nor do they know how to stop its progression. This makes tooth extraction the most effective option.

“It's a really tricky thing from a customer communications perspective, especially if the owner isn't expecting it,” McAndrews said. “I try to put myself in the owners’ shoes and validate all of their concerns.”

McAndrews reviews radiographs with owners, showing normal and abnormal conditions, which is helpful for visual learners. She sometimes has clients talk to other horse owners whose horses have undergone the calming procedure. She never forces a decision on the owners and listens to all their questions.

When it comes to tooth extraction procedures, McAndrews says it's important to remove all front teeth, especially because it's difficult to correlate radiographic changes with pain to know which teeth are most painful. She also said veterinarians must be prepared to remove the entire tooth even if it fractures, which is likely to happen if the tooth has undergone extensive resorption. “If you leave some teeth in, they will continue to be sore and develop drainage channels and develop more cementum growth,” she explains.

McAndrews further noted that the veterinarian should be skilled in performing nerve blocks and be prepared to take post-extraction X-rays. Many of these extractions can be carried out on the farm by a GP, but some cases may be easier to treat in a clinic.

McAndrews said the extraction site will look bad for a while after the surgery, but will eventually heal well. “Any complications associated with the surgery are primarily related to the effects of the need to sedate the horse,” she said.

McAndrews points to a recent study by Bo Rainbow, DVM, who sent a survey to owners of horses who had had this procedure. Owners report improvements in their horses' body condition, hay fall, eating speed, general behavior, resistance to bridles and head shaking. Overall, owners say their horses seem happier and have improved quality and longevity. More than 90% of respondents stated that they would perform the procedure again and would perform the procedure on another horse in the future.

“I think this really shows how much we can improve the lives of horses by solving these very painful dental problems,” McAndrews said. “When you remove that source of pain, they often gain a new lease of life. It can be a very, very beneficial process.

About Dr. Amelie McAndrews

Amelie McAndrews, DVM, DAVDC-Eq, is a Board Certified Equine Dentist™ and Diplomate of the American College of Veterinary Dentistry. With only a handful of Board Certified Equine Dentists™, she is the only practicing equine dental specialist in the mid-Atlantic region and eastern Pennsylvania. In addition to owning the Garden State Equine Veterinary Dental Clinic, she is a clinical assistant at Penn State's New Bolton Center where she manages the referral dental cases.

Originally from Connecticut, McAndrews completed a residency and then worked in general equine clinics in New Jersey for five years. During her time as a general practitioner, her interest and caseload became increasingly focused on equine dentistry. She has found that her patients’ quality of life can be significantly improved by addressing issues identified during a comprehensive dental exam. Garden State Equine Veterinary Dentistry was established in 2015 with the goal of helping more horses improve their oral health. She uses minimally invasive techniques to improve the outcomes of equine oral surgeries.

McAndrews regularly presents dental disease to equine veterinarians and teaches equine dentistry to veterinarians and veterinary students. She is a graduate of the American Pony Club and enjoys teaching horse management skills to local pony club members and educating horse owners on equine dentistry.

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