Equine Odontoclastic Tooth Resorption and Hypercementosis (EOTRH) is a progressive and painful dental condition primarily affecting the incisor teeth of middle-aged and older horses. This disorder involves the gradual, destructive breakdown of tooth structure and an abnormal, excessive reaction from the body to stabilize the weakening teeth. EOTRH has only recently been properly identified and named, leading to increased recognition of its prevalence. The condition is characterized by a combination of two distinct pathological processes that cause discomfort and compromise the dental health of affected equines.
What Equine Odontoclastic Tooth Resorption and Hypercementosis Is
EOTRH is named for the two primary cellular changes occurring within the affected teeth: resorption and hypercementosis. Resorption involves the destruction of tooth material (cementum and dentin) carried out by specialized cells called odontoclasts. This process forms resorptive lesions that dissolve the tooth structure, often starting at the root surface.
Hypercementosis is the body’s attempt to stabilize the deteriorating tooth by depositing excessive, irregular cementum, the hard tissue covering the tooth root. This abnormal proliferation causes a noticeable, bulbous enlargement of the tooth roots, visible on X-rays and sometimes externally as swelling around the gumline. While resorption can occur independently, hypercementosis is typically a secondary reaction to the destruction of the tooth structure.
EOTRH most commonly affects the permanent incisors (front teeth), though canine teeth can also be involved. The definitive cause remains unknown but is considered multifactorial. Hypotheses include chronic mechanical stress on the periodontal ligament, immune-mediated responses, and the involvement of certain oral bacteria, which may trigger the destructive and proliferative cellular processes.
The disease is progressive and is most frequently observed in horses over 15 years of age, though cases have been reported in horses as young as ten. Since the underlying etiology is not fully understood, there is currently no known method to prevent the condition. The internal pathology involves the breakdown of cementum and dentin, often accompanied by inflammation and endodontic disease within the tooth pulp cavity.
Recognizing Observable Symptoms
Clinical signs of EOTRH can be subtle in the early stages, as horses often hide signs of oral pain until the condition is advanced. Owners may first notice behavioral indicators of discomfort, such as reluctance to bite into hard treats or sensitivity when being bridled or when the muzzle area is touched.
Painful teeth can lead to changes in grazing behavior, causing difficulty ripping grass or entirely avoiding grazing. Other common behavioral signs include head shaking, increased irritability, or a general change in demeanor due to chronic pain. Horses may also exhibit signs of discomfort while eating, such as drooling or a decreased appetite, which can lead to weight loss.
Physical changes visible upon oral examination include inflammation of the gums surrounding the incisors, known as gingivitis. In more severe cases, small red dots (petechiae) or ulcers may appear on the gums just above the affected teeth.
As the disease progresses, the gums may recede (gingival recession), exposing more of the tooth root. Pus or small draining tracts (fistulas) may be visible along the gumline, indicating an infection. The affected teeth can become loose or fractured due to internal structural breakdown, and the excessive cementum buildup may cause a bulbous swelling around the tooth roots.
Professional Diagnosis and Management
A definitive diagnosis of EOTRH requires more than a physical examination because the most significant changes occur beneath the gumline. The veterinarian performs a thorough oral examination, often under standing sedation, to inspect the incisors and gums for signs of inflammation, recession, and swelling. Intraoral radiography (dental X-rays) is the mandatory next step to accurately assess internal damage and confirm the diagnosis.
X-ray images provide a clear view of the tooth roots and surrounding bone, revealing the characteristic lesions of EOTRH. Radiographic findings include resorptive lesions (areas of decreased density) and excessive cementum deposits resulting in bulbous root enlargement. Radiographic staging determines the severity of the condition and which teeth require intervention.
The only effective management for moderate to severe EOTRH is the extraction, or surgical removal, of the affected teeth. Medications and rinses offer only temporary relief and do not address the progressive pathology. Extraction eliminates the source of chronic pain and infection, leading to a marked improvement in the horse’s quality of life.
The procedure is typically performed with the horse standing, utilizing heavy sedation and local nerve blocks. Following extraction, horses are usually prescribed non-steroidal anti-inflammatory drugs for pain management and antibiotics to prevent infection. Horses generally recover quickly, often eating a soft diet within a day and feeling significantly better within a week. Horses manage remarkably well without incisors, quickly learning to use their lips and tongue to prehend food and graze effectively.