Peripheral caries is common in British horses, primarily affecting the caudal cheek teeth. There was limited evidence of an association between feeding and PC. The association between PC and concurrent dental disorders indicates that these should be addressed in affected horses.

Summary Several different theories on the aetiology of dental caries have been proposed, but it is generally accepted that it is primarily caused by acidogenic microorganisms converting fermentable carbohydrates to acids. There is still some discussion on whether caries is caused by specific microorganisms or a nonspecific mix of different microorganisms and on whether caries is a classical infection or is caused by dysregulation of the normal oral bacteria (dysbiosis). Two types of dental caries are recognised in horses, i.e. peripheral dental caries and infundibular dental caries, with peripheral caries appearing to be increasingly recognised. Little is known about the prevalence and severity of peripheral dental caries in the general equine population, or the risk factors and microorganisms involved in its aetiopathogenesis. Limited pathological studies have shown 2 types of cemental destruction in equine peripheral caries, and indicate that gross dental examination underestimates the severity of equine peripheral caries.

Summary Background Although, peripheral caries (PC) affects almost half of UK horses, no comprehensive microbiological study has been performed on this disorder. As a high proportion of oral bacteria cannot be conventionally cultured, molecular microbiological techniques such as Next Generation Sequencing are required to examine the complex oral bacteria community. Objectives To identify the microbiota involved in equine PC, including comparing microbiota at the more commonly and severely affected three caudal cheek teeth with the less commonly affected three rostral cheek teeth. Study design and Methods Equine dental plaque samples were collected from the palatal aspects of cheek teeth of 63 horses. DNA was isolated and amplified using PCR, targeting the V4 region of the 16S rRNA gene and Next Generation Sequencing of these gene amplicons was performed. The acquired data were processed and analysed using Mothur and R. Results Streptococcus species was the genus most commonly associated with equine PC, whereas Gemella species was the genus most associated with the control group. In a further analysis where the rostral and caudal cheek teeth were compared with each other and with the control group. Veillonella species was the most commonly associated genus with PC of the rostral cheek teeth, Streptococcus species was the most associated genus with the caudal cheek teeth, and Corynebacterium with the control group. Main limitations Some bacteria can have multiple heterogeneous copies of the 16S rRNA gene, which can affect the estimation of their relative abundance. Conclusions Similar to caries studies in other species, acidogenic and aciduric microorganisms including Streptococcus species were found to be associated with equine peripheral caries.