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 mastication problems, halitosis and weight loss. The disease predominately affects the reserve crown and presents as a loss of dental tissue and excessive build-up of cementum. Objectives: Determine the radiographic scores of horses with EOTRH and age-matched controls. Increase understanding of EOTRH using microCT to compare teeth from horses with EOTRH and age matched controls. Methods: This study used radiography ( in vivo) and microcomputed tomography (microCT) ( ex vivo) to help understand and characterise EOTRH. For radiography, 87 patients were assessed using a radiographic scoring system for EOTRH. The microCT study was undertaken on 20 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, pulp cavity). Study design: In vivo and ex vivo studies. 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 ratios relative to the whole tooth volume, compared to 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, potentially indicating multiple phenotypes of the disease.

Background Equine dental diseases significantly impact on a horse’s overall health, performance, and quality of life. They can result in secondary infections and digestive disturbances, potentially leading to colic. A recently described disease affecting the incisors of horses is equine odontoclastic tooth resorption and hypercementosis (EOTRH). Understanding EOTRH is crucial for early diagnosis, effective management, and prevention of its severe consequences. Objectives To determine proteomic differences in incisor cementum in horses with and without clinical EOTRH. Study Design Comparative and observational clinical study. Methods Teeth were extracted and cementum was isolated using a diamond wire. Proteins were extracted using an optimised sequential workflow, and trypsin digested for mass spectrometry. Protein identification and label-free quantification was undertaken. Results In total 1149 unique proteins were detected in cementum across all samples. We identified four proteins exclusively in EOTRH affected cementum. EOTRH samples showed a higher heterogeneity than healthy samples. In total 54 proteins were increased in EOTRH, and 64 proteins were reduced (adjusted p-value < 0.05). Inflammatory proteins, such as cathepsin G (p = 0.004), neutrophil elastase (p = 0.003), bactericidal permeability-increasing protein (p = 0.002), azurocidin (p = 0.003) and lactotransferrin (p = 0.002) were all increased in EOTRH. Pathway analysis revealed that antimicrobial peptides (Z score 2.65, p = 1.93E-09) and neutrophil degranulation (Z-score 1.89, p = 1.7E-04) were commonly up-regulated canonical pathways. Main limitations The sample size was limited. Conclusion EOTRH leads to biochemical changes within the cementum proteome, which are important in explaining the physiological changes occurring in disease. Differentially abundant proteins may represent promising biomarkers for earlier disease detection and establishment of a cell-based model could provide further insight into the role these proteins play in hypercementosis.