Characterisation of equine odontoclastic tooth resorption and hypercementosis: A comparative study using microCT and radiography in age-matched controls.

Background: Equine odontoclastic tooth resorption and hypercementosis (EOTRH) is a painful disorder primarily affecting the incisor teeth of horses over 15 years of age. Clinical signs of the disease include prehension problems, halitosis and in severe cases weight loss. The disease predominately affects the reserve crown and presents as a loss of dental tissue and excessive build-up of cementum.

Objectives: To determine the radiographic scores of horses with EOTRH and age-matched controls and to increase understanding of EOTRH using microCT to compare teeth from horses with EOTRH and age-matched controls.

Study Design: In vivo and ex vivo studies.

Methods: This study used radiography (in vivo) and microcomputed tomography (microCT) (ex vivo) to help understand and help characterise the imaging changes that occur in EOTRH. For radiography, 87 patients were assessed using a radiographic scoring system for EOTRH. The microCT study was undertaken on 20 extracted cadaver incisor teeth which were scanned and segmented to measure the different dental tissues. These were assessed using a descriptive analysis (surface roughening, tooth resorption, root blunting and pulp cavity).

Results: Radiographic scoring demonstrated that 03s were more severely affected than 01s in EOTRH. Total radiographic score and age had a weak positive correlation. Following microCT, we identified that EOTRH teeth had a lower pulp and enamel volume and therefore significantly higher pulp and enamel ratios relative to the whole tooth volume, compared with control teeth. Cementum and dentine volumes were more variable in EOTRH teeth. Thus, their ratios relative to the whole tooth volume were not different to control teeth.

Main Limitations: The number of horses was relatively small.

Conclusions: Results suggest differing degrees of tooth resorption and hypercementosis, in different affected teeth potentially indicating multiple phenotypes of the disease. We provide further evidence of the presence of subclinical EOTRH imaging changes in some teeth.