Application of the horse grimace scale in horses with dental disease: Preliminary findings
Authors: A. Sidwell, Marco Duz, Bradley Hill, S. Freeman, S. L. Hole
Journal: The Veterinary Record
Summary
# Application of the Horse Grimace Scale in Horses with Dental Disease Dental disease remains under-diagnosed in equine practice, partly because practitioners lack objective tools to quantify oral discomfort; this preliminary work by Sidwell and colleagues examined whether the horse grimace scale (HGS)—a validated facial expression pain metric—could reliably assess pain from dental pathology in a cohort of 12 affected horses. Using blinded observer assessment of lateral photographs, the researchers scored dental pain using both the HGS and a numerical rating scale (NRS), finding that interobserver reliability was notably poor for both tools (ICC = 0.27 for HGS and ICC = 0.36 for NRS), though equine odontoclastic tooth resorption and hypercementosis (EOTRH) and periodontal disease consistently generated the highest pain scores across observers. These findings suggest that pain scales developed for acute conditions lack sensitivity to the chronic, possibly more subtle facial changes associated with dental disease, pointing toward a critical gap in equine pain assessment methodology. Whilst the work supports existing clinical impressions that EOTRH and periodontal disease cause observable discomfort, practitioners should recognise that current facial expression-based tools cannot reliably differentiate pain severity in dental cases, highlighting the need for a dental-specific ethogram to improve diagnostic accuracy and pain recognition in the clinic.
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Practical Takeaways
- •Current facial expression-based pain scales are not reliable for assessing dental pain in your horses—clinicians should not rely on these tools alone for dental pain evaluation
- •EOTRH and periodontal disease appear to cause more noticeable pain responses than other dental conditions, so heightened vigilance for these specific conditions is warranted
- •Improved assessment methods for dental pain are needed; until these are developed, combine multiple clinical signs and owner observations rather than relying on any single pain metric
Key Findings
- •Horse grimace scale and numerical rating scale showed poor interobserver reliability (ICC = 0.27 and 0.36 respectively) for assessing dental pain in horses
- •EOTRH and periodontal disease produced the highest mean pain scores, suggesting these conditions cause more obvious pain signs than other dental disorders
- •Acute pain assessment tools are unreliable for evaluating chronic dental pain in horses
- •A dental-specific ethogram is needed to accurately identify and quantify dental pain in horses