Equine Odontoclastic Tooth Resorption and Hypercementosis (EOTRH)

By: Dr Shannon Lee, BVSc MACVSc MICEVO, Equine Dental Vets

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image courtesy of Advanced Equine Dentistry

As well as being quite a mouthful, Equine Odontoclastic Tooth Resorption and Hypercementosis (better known as EOTRH) is a form of periodontal disease causing the destruction of dental tissues that lead to weakness, tooth fracture, pain and infection. 

Back in 2007, Dr Shannon Lee from Advanced Equine Dentistry diagnosed the first cases in Australia. Here, he explains about what is a common, yet poorly understood, progressive disease that, at present, has no cure and requires expert treatment and management from your Equine Dental Vet.

In dentistry, tooth resorption is the breakdown or destruction, and subsequent loss, of the structures of a tooth that is caused by living body cells attacking part of the tooth.

EOTRH is the equine version of a disease that shares similarities with diseases found in cats and humans. It’s a disease that veterinarians worldwide are becoming more aware of, with the first cases in Australia diagnosed by Dr Shannon Lee back in 2007.

Unfortunately, it is quite a common disease and there is currently no cure, although treatment to manage the condition and allow horses to continue on in successful, pain-free competitive careers does exist.

In a recent research study into the disease conducted in Germany, researchers used dental X-rays to examine the area around the horse’s teeth, under the gum. From this, they discovered that all the horses in the study aged 15 and over were severely affected by EOTRH. Research like this continues around the world into this unusual disease.

What is EOTRH?

At some point in the lives of many horses, and for reasons we still do not fully understand, something triggers a response from their immune system to begin breaking down some of the tissues within and around their teeth.

Typically, it is the front (incisors) and canine teeth that are affected, and the disease causes both the breaking down of tissue (called odontoclastic tooth resorption) and the laying down of new tissue in response to the inflammation (called hypercementosis)

The result for these horses is the progressive and often rapid loss of major parts of the tooth structure (mainly the structures below the gum line) and the development of tooth weakness leading to tooth fracture, pain and infection.

The science

In 2008, Dr Carsten Staszyk and his team of researchers were some of the first anatomists to really take a close look at EOTRH.

At the time, Dr Staszyk’s team proposed the theory that the disease was linked to stress on the periodontal

ligament caused during mastication (chewing) in the horse - a theory that has since been largely discounted, due to the common occurrence of the disease in canine teeth, which undergo no such stress.

Nevertheless, the information gained in that study by looking at sectioned teeth at a microscopic level really did provide answers about the cells involved and the process that shows how the disease progresses.

Talking about cell types it is probably necessary to go a step back and explain that in the normal, healthy mouth there are both odontoblasts and odontoclasts. Odontoblasts are cells responsible for the production of certain dental tissues (dentine), while odontoclasts are cells responsible for the destruction of certain dental tissues.

It is when these odontoclasts are ‘switched-on’ at an inappropriate time (by a method researchers don’t yet understand) that we see the destruction of parts of the teeth.

The body’s reaction to the tooth resoprtion is to switch-on other cells called cementoblasts to produce a tissue called cementum (see image on Page 13).

Cementum is a tissue that links the outside of the tooth with the periodontal ligament (the ligament attaching the tooth to the rest of the body). By switching-on these cells, the body is trying to keep hold of the EOTRH-affected teeth. Unfortunately, the strategy does not work. It does, however, often result in the production of a lot of cementum (or hypercementosis) and this causes some of the characteristic changes seen in both the teeth and the jaw of many EOTRH-affected horses. (See image of horse’s teeth on Page 13).

New information about EOTRH is emerging all the time as scientists piece together more of this jigsaw puzzle through research. Currently, it is thought most horses are not seen as having signs of EOTRH until around the age of 15, but the results of future research may challenge this.

There are several different types of EOTRH that have been identified and described - being mainly categorised depending of the degree of resorption versus the amount of hypercementosis.

Typically, what an owner or a veterinarian might see first are signs of periodontal disease, such as gingivitis (or inflammation of the gums), changes to the bones surrounding the horse’s front teeth with thickening, loss of bone density leading to tooth mobility, small abscesses in the gum in the form of small pustules, holes in the teeth near the gumline or a tendency to break teeth.

What do I do if I’m concerned my horse might have EOTRH?

Firstly remember treatment is available, and so, it’s important not to panic. Diagnosis of EOTRH can be confirmed by your Equine Dental Vet and will be based on both a physical examination of the teeth and dental X-rays.

If your horse does have EOTRH, the treatment and/or management recommended for the affected teeth will be extraction, and will occur when the disease has progressed to the point that it is necessary to remove these teeth to prevent pain and infection.

Will my horse cope after extraction of affected teeth?

The simple answer is yes. EOTRH-affected horses are in a great deal of pain (even though they often show little outward signs of a problem) and will be trying as much as possible not to put pressure on the affected teeth, which will affect their feed intake and behaviour.

Horses are grazers and use both their front teeth and their lips to pick up food. They do not use their front teeth to chew. This means that horses affected by EOTRH who have had incisor teeth or canine teeth removed cope very well.

It is important to understand that, as most of the disease occurs within the teeth and under the gum line, X-rays are a vital tool to both assess the level of damage and make decisions about which teeth need to be removed. Only your Equine Dental Vet has the necessary knowledge and training to be able to help you with this disease or refer you to an expert veterinary consultant.

Looking forward

At present, we are able to help these horses by relieving pain, as well as providing information to their owners to help them understand the disease. Perhaps in the future, it may be possible to better understand what triggers the disease in the first place and this will undoubtedly be the key step necessary to search for a cure.

As we provide better care for our growing population of ageing horses, more and more people are going to find themselves affected by this disease, so a greater awareness of EOTRH amongst horse owners will ultimately lead them to find the help they need earlier.

Although the diseases that affect other species, such as the disease affecting cats (Feline Oral Resorption Lesions), also still have no cure and are dealt with in a very similar method to EOTRH.

What can I do to prevent EOTRH in my horse?

Unfortunately, because the disease has no cure and the cause is not fully understood at present, the best and only prevention available is to make sure each horse has regularly scheduled examinations by your Equine Dental Vet.

A list of Equine Dental Veterinarians can be found by visiting www.equinedentalvets.com.

Be aware that some people may offer advice about prevention or treatment and point you towards documents that are not up-to-date. If in doubt, ask your vet to refer you to a specialist consultant.

Currently, there is no known prevention for EOTRH.

About the Author: Dr Shannon Lee is a Consultant Veterinarian in Equine Dentistry. Dr Lee has established himself as one of the leading experts in this field worldwide. He spends a significant amount of time lecturing and teaching veterinarians both in Australia and overseas, whilst still finding the time to examine, treat and help around 3,000 horses each year in his dedicated equine dental practice.

Dr Lee is a subject examiner for the Australasian College of Veterinary Scientists in Equine Dentistry and provides a referral dental surgical service to many veterinary practices across both Australia and New Zealand. Further information can be found at: www.advancedequinedentistry.com.au. 

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