Bit & Bridle

Equine Tooth Resorption (EOTRH)

Other Names

  • EOTRH
  • Equine odontoclastic tooth resorption and hypercementosis
  • Incisor resorption in horses

What is Equine Tooth Resorption (EOTRH)?

Equine Odontoclastic Tooth Resorption and Hypercementosis (EOTRH) is a progressive, painful dental disease primarily affecting the incisors and canine teeth of older horses. The condition is characterised by two simultaneous processes: odontoclastic resorption — the pathological breakdown and destruction of dental hard tissue (cementum, dentine, and enamel) — and hypercementosis — the irregular, abnormal deposition of new cementum around the affected tooth roots as a reparative response. These opposing processes result in teeth that are structurally compromised, painful, and often affected by secondary infection.

EOTRH is believed to be significantly under-diagnosed, partly because horses are stoic and may not display obvious signs of dental pain until the disease is well advanced, and partly because the condition requires specific radiographic investigation to confirm. It predominantly affects horses over 15 years of age, and prevalence increases markedly with advancing age.

Causes

The precise aetiology of EOTRH remains incompletely understood. Current thinking suggests a multifactorial origin:

  • Chronic mechanical loading: The incisors bear considerable occlusal forces, and it is hypothesised that chronic loading triggers an inflammatory response in the periodontal tissues over time.
  • Periodontal disease: Bacterial infection and inflammation of the periodontal ligament may initiate or perpetuate the resorptive process.
  • Endocrine factors: Some studies have explored links with pituitary pars intermedia dysfunction (PPID/equine Cushing’s disease), which is also prevalent in older horses.
  • Age-related degeneration: Cumulative wear and biochemical changes in ageing dental tissues likely play a role.

Genetics and breed predisposition may also contribute — some lines appear more susceptible than others.

Symptoms and Signs

Many horses with EOTRH show subtle signs that owners may initially attribute to behavioural changes or general ageing:

  • Reluctance to bite into hard feed such as apples or carrots
  • Dropping food (quidding) or slow eating
  • Preference for softer feeds
  • Resentment of the bit, head shaking, or ridden behaviour changes
  • Swelling, thickening, or lumpy appearance of the gum tissue at the base of incisors
  • Bad breath (halitosis) from secondary bacterial infection
  • Visible loosening or abnormal spacing of incisor teeth
  • Drooling or excessive salivation
  • Weight loss in advanced cases where eating is significantly impaired

Diagnosis

  • Clinical examination: Visual and manual inspection of the incisor arcade and canine teeth. Signs of gingival swelling, fistulae (sinuses draining pus), tooth mobility, or irregular tooth surfaces should prompt further investigation.
  • Dental radiography: The definitive diagnostic tool. Periapical radiographs of the incisors reveal the characteristic changes of EOTRH — resorptive lesions within the tooth root, irregular cementum deposition, and widening of the periodontal ligament space. Radiography is essential to grade severity and guide treatment decisions.
  • Oral endoscopy: Can provide additional information on crown surfaces and gingival pocketing.

Treatment

EOTRH is progressive and has no medical cure. Treatment options range from palliative management to surgical extraction:

  • Dental extraction: The only truly effective treatment for significantly affected teeth. Extraction of painful, resorbing incisors typically results in marked and rapid improvement in comfort and eating behaviour. Many owners report that affected horses appear considerably brighter and more comfortable following incisor removal than anticipated.
  • Horses can eat without incisors: Horses that have had incisors removed can still graze, though pasture access (especially very short grass) may be somewhat limited. Most adapt well to eating hay, soaked hay, and soft feeds.
  • Pain management: NSAIDs provide temporary relief but do not halt disease progression; they are used as a bridge to extraction or for horses where extraction is not possible.
  • Dental hygiene: Gentle cleaning and appropriate supportive dental care can slow secondary infection in early-to-moderate cases.

Referral to an equine dental veterinarian with radiographic capability is strongly advised for suspected EOTRH cases. The British Equine Veterinary Association (BEVA) maintains a register of qualified equine dental practitioners.

Prevention

There is currently no proven method to prevent EOTRH. However:

  • Annual dental examinations for all horses over 15 years, specifically including visual assessment of the incisor arcade and palpation for gingival changes.
  • Dental radiography of the incisors in horses showing any behavioural or feeding changes, even if the changes seem subtle.
  • Early detection allows intervention before extensive resorption and secondary infection develop.

Prognosis

EOTRH is progressive and incurable, but the prognosis for quality of life following appropriate treatment is good. Horses that undergo extraction of severely affected teeth typically recover well and show significant improvement in comfort within days to weeks. Delayed treatment allows ongoing pain and secondary infection, which can compromise overall health and welfare.

When to Call the Vet

Arrange a dental check if your older horse:

  • Is showing reluctance to eat hard feed or taking unusually long to eat
  • Has lumpy or abnormal-looking gum tissue around the incisors
  • Shows resistance to bitting or unexplained behavioural changes
  • Has visible tooth loosening or abnormal incisor spacing
  • Has bad breath that doesn’t improve with regular feed management

Frequently Asked Questions

Can horses live comfortably without their front teeth?

Yes — most horses adapt remarkably well to incisor removal. They can still eat hay, haylage, and a variety of feeds, though very short pasture grazing may be more challenging. The relief from chronic pain is typically so significant that the horses are clearly happier and more comfortable than before surgery.

At what age does EOTRH typically develop?

EOTRH is predominantly a disease of horses over 15 years, with prevalence increasing significantly in horses over 20. It is rarely seen in younger horses, though early radiographic changes can occasionally be detected in horses as young as 12–13 years.

Is EOTRH related to equine Cushing’s disease?

A possible association has been suggested in the literature, since both conditions predominantly affect older horses. However, the relationship has not been definitively established, and EOTRH occurs in horses without PPID. Horses with both conditions should be managed for each disease separately.

How quickly does EOTRH progress?

Progression is variable. Some horses remain stable with mild changes for several years, while others deteriorate more rapidly. Regular radiographic monitoring (every 12–18 months in known cases) helps assess the rate of progression and informs the decision about timing of extraction.