EOTRH in Horses: Symptoms, Causes, and Treatment

Equine Odontoclastic Tooth Resorption and Hypercementosis (EOTRH) is a progressive dental disease affecting older horses, leading to pain and difficulty eating. The condition involves the gradual breakdown of tooth structure, often going unnoticed until significant discomfort or visible changes occur. Early detection is essential for maintaining a horse’s quality of life.

Recognizing warning signs and understanding treatment options can help manage the disease effectively.

Primary Dental Changes

EOTRH primarily affects the incisors and, in some cases, the canine teeth of older horses, leading to structural deterioration. The disease manifests through two concurrent processes: resorption and hypercementosis. Resorption involves the breakdown of the tooth’s internal and external structure, where odontoclasts erode the dentin and enamel, weakening the tooth and increasing susceptibility to fractures and infections. Hypercementosis, a compensatory response, results in excessive cementum deposition around affected teeth, causing bulbous, thickened roots. This abnormal accumulation can fuse teeth to surrounding bone, exacerbating discomfort and functional impairment.

As the disease progresses, these structural changes alter the dental arcade. Affected incisors may develop uneven wear patterns and excessive tartar buildup due to reduced self-cleaning. The gumline often recedes, exposing roots and creating pockets where bacterial infections thrive. In severe cases, teeth loosen or fracture, causing significant pain and difficulty grasping and chewing food. Horses may avoid biting hard treats like carrots or apples due to increased sensitivity.

Microscopic examination of extracted teeth from affected horses reveals extensive dentin porosity and inflammatory infiltrates in surrounding periodontal tissues. Histopathological studies indicate an irregular resorptive process, where some areas degrade rapidly while others remain intact, making early detection challenging. Radiographic imaging often shows lytic lesions within tooth roots, confirming the extent of resorption.

Clinical Indicators

Early signs of EOTRH often go unnoticed, as horses may not exhibit obvious discomfort until the disease has progressed significantly. Subtle behavioral changes can provide the first clues. Horses may show reluctance to accept treats requiring biting, increased sensitivity when handled around the muzzle, or a preference for softer feeds. These minor shifts often precede more apparent clinical signs.

As the disease advances, visible changes in the incisors become more pronounced. Affected teeth may appear discolored, with a reddish-brown hue due to inflammation and vascular compromise. The gum tissue around the incisors often becomes swollen, receded, or inflamed, sometimes with draining tracts exuding pus. These fistulous tracts indicate bacterial invasion into deeper periodontal structures, contributing to chronic infection and pain. Horses with severe EOTRH may exhibit excessive salivation, aversion to bit pressure, or headshaking behaviors.

Pain-related symptoms extend beyond feeding and handling difficulties. Some horses develop a dull expression or reluctance to engage in normal activities, reflecting chronic discomfort. Weight loss can occur when pain significantly impacts feed intake. In severe cases, horses may compulsively rub their muzzle against solid objects in an attempt to relieve discomfort, further damaging tissues. These behavioral and physical signs help veterinarians assess potential EOTRH cases.

Possible Contributing Factors

The exact causes of EOTRH remain unclear, but several factors appear to influence its development. Age is a consistent risk factor, with the condition predominantly affecting horses over 15. As horses age, natural changes in dental structure occur, including decreased vascular supply to periodontal tissues and alterations in cementum composition. These changes may reduce the teeth’s ability to repair minor damage, increasing susceptibility to resorption and abnormal cementum deposition.

Dietary influences may also play a role. Horses consuming high-sugar diets or limited forage may experience altered oral pH, contributing to chronic inflammation around the incisors. Acidic conditions can weaken dental structures in other species, raising questions about similar effects in horses. Additionally, horses relying heavily on processed feeds may experience reduced natural incisor wear, leading to imbalances in occlusal forces that strain the periodontal ligament and surrounding bone.

Environmental conditions and management practices further complicate the picture. Horses in regions with high soil fluoride levels may experience increased mineral deposition in dental tissues, potentially exacerbating hypercementosis. Repetitive bit pressure or excessive cribbing behavior might accelerate structural breakdown. While no single environmental factor has been definitively linked to EOTRH, the cumulative effect of these variables likely contributes to disease progression in predisposed horses.

Diagnostic Imaging Methods

Detecting EOTRH in its early stages requires advanced imaging, as external examination alone often fails to reveal the full extent of the disease. Radiography is the primary diagnostic tool, providing a detailed view of internal tooth structures and surrounding bone. Dental radiographs typically show lytic lesions in the roots, characterized by areas of decreased radiodensity where resorption has occurred. Hypercementosis appears as irregular, bulbous thickening along the root surface, highlighting the contrast between eroded and overgrown areas. These radiographic patterns help assess disease severity and determine whether extraction is necessary.

In some cases, computed tomography (CT) offers a more precise evaluation, particularly when radiographs yield inconclusive results. CT scans provide cross-sectional imaging with higher resolution, allowing for a three-dimensional reconstruction of the affected teeth and surrounding bone. This method is particularly useful for identifying early-stage changes or evaluating cementum overgrowth. While CT imaging is less common due to cost and accessibility, it has proven valuable in research settings and specialized equine dental practices.

Treatment Methods

Managing EOTRH prioritizes pain relief and long-term oral health. Since the disease is progressive and irreversible, treatment focuses on alleviating discomfort and preventing complications. In mild cases, conservative management may include pain control, anti-inflammatory medications, and specialized dental care to slow progression. Non-steroidal anti-inflammatory drugs (NSAIDs) such as phenylbutazone or firocoxib help reduce pain and inflammation. Regular dental maintenance, including professional cleanings and plaque removal, may minimize bacterial load and slow deterioration.

For advanced cases, tooth extraction is the most effective intervention. Severely compromised incisors cause continuous pain and infection, making removal the best option for restoring comfort. Horses adapt well to the loss of multiple incisors, often showing immediate improvement in appetite and demeanor post-extraction. The procedure is typically performed under sedation with local anesthesia, using specialized dental elevators to minimize trauma. Post-operative care includes pain management, antibiotics if infection is present, and dietary modifications to support healing. Many horses resume normal eating behavior within days, demonstrating that incisors are not essential for effective forage consumption.