Radiographic Evaluation of Equine Odontoclastic Tooth Resorption and Hypercementosis (EOTRH) in Horses Living Under Natural Conditions in Iceland

Outside of Iceland, the Icelandic horse is prone to the development of Equine Odontoclastic Tooth Resorption and Hypercementosis (EOTRH). The aim of this study was to determine the radiographic prevalence and clinical signs of EOTRH in elderly horses (≥15 years) in Iceland. The rostral oral cavity of 170 horses (aged 15-30 years) was examined clinically. In addition, husbandry and nutritional management history was recorded by use of a questionnaire. Radiographs (2-4 views) of 188 horses were evaluated, findings were categorized by numerical staging of the condition and collated with clinical and anamnestic findings. 45.7% of the horses showed no radiographic changes. 26.6% of the horses were suspicious for EOTRH. In 26.6% of horses mild radiographic stages of EOTRH were seen, while in 1.1% of horses the signs were classified as moderate. Severe manifestation was not present in this sample of horses. Radiographic findings were strongly age-dependent (<i>P</i> < .001). No horse showed EOTRH-associated clinical signs of fistulae, bulbous enlargement of the roots or tooth mobility. The radiographic findings were likely caused by age-related processes. In Iceland, 82.4% of the examined horses spent 9-12 months of the year grazing on pasture. Radiographic, clinical and anamnestic findings were compared with selected findings in a population of Icelandic horses in Germany. Horses in Iceland had 7.8 times less risk of developing EOTRH compared to Icelandic horses in Germany. The remarkably low prevalence of clinical and radiographic EOTRH-like changes in horses in Iceland is likely to be related to their natural living environment.