Assessment of Skin and Mucosa at the Equine Oral Commissures to Assess Pathology from Bit Wear: The Oral Commissure Assessment Protocol (OCA) for Analysis and Categorisation of Oral Commissures

SIMPLE SUMMARY: The goal was to implement a protocol to categorize and record pathological findings at the lip commissures. First, the precise anatomical location was defined; second, pigmentation was classified as natural or potentially pathological; and third, pathological lesions were characterized. Associations between the horse’s history and the observed findings were sought. A convenience sample of 206 horses presented for routine dental prophylaxis were sedated; the mouth was held open with a gag, and photographs were taken of the oral commissures and adjacent areas of the lips. The horses were divided in two groups: horses that had never been bitted and horses currently or previously bitted. The owners completed a questionnaire describing the horse’s name, identification number, breed, age, sex, colour, training level, and discipline. The photographs were analysed in a systematic manner, and a score chart was developed to standardize the reporting of lesions. Potentially pathological pigment changes occurred more frequently in horses with a higher level of training (p = 0.04) and light-coloured horses (p = 0.0004), but were not associated with current bit use or the discipline that the horse participated in (p = 0.20). Scars were more frequent in horses competing at a higher level. Only two horses had contusions/erosions, five had ulcers and none showed bleeding; these numbers were too low for statistical analysis. ABSTRACT: This study addresses the presence and location of natural pigmentation, potentially pathological changes in pigment, interruptions of the natural lining (scars), roughness, and erosions/contusion (bruising) in and around the corners of the lips of 206 horses presented to a veterinarian for routine preventative dental treatment. After sedation, photographs were taken and later evaluated for the presence of lesions. During the photographic analysis, the Oral Commissure Assessment (OCA) protocol was developed to map precisely the areas of skin and mucosa around the corners of the lips, and the presence of lesions was recorded for each area. Potentially pathological pigment changes occurred more frequently in horses with a higher level of training (p = 0.04) and in light-coloured horses (p = 0.0004), but there was no association with the current use of a bit or the discipline that the horse participated in (p = 0.20). Scars occurred more frequently in horses competing at a higher level. Only two horses had contusions or erosions, five had ulcers, and none showed bleeding; these numbers were too low for statistical analysis. Using the OCA protocol provides a detailed method for categorizing and recording lesions in and around the corners of the lips, including natural vs. potential and/or definite pathological character.