Equine Peripheral Caries Research Articles

Recent advances in the treatment and prevention of equine peripheral caries.

Equine peripheral caries is a common condition characterized by demineralization and degradation of the clinical crown of equine cheek teeth. The condition can cause significant pain and morbidity, particularly in severe cases. Recent studies indicate that the condition is driven by environmental conditions within the mouth, as only the clinical crown of the tooth is affected (the reserve crown below the gingival margin remains unaffected). It is hypothesized that peripheral caries is driven by changes in oral pH, with risk factors for the condition including the intake of high-sugar feeds (oaten hay and feeding moderate levels of concentrate feed) and access to drinking water with an acidic pH. However, other identified risk factors include breed (Thoroughbred), limited pasture access, and concurrent dental or periodontal disease. Further studies have been able to show that affected teeth can recover from the condition if the inciting cause is removed and the unaffected reserve crown is allowed to replace the damaged clinical crown. Improvements in the condition can be observed within a few months. Signs of inactive (recovering) caries include a darker color and a smooth, hard, and reflective surface, and there is a new layer of unaffected cementum at the gingival margin, indicating that the newly erupted tooth is unaffected. Peripheral caries is a common and often overlooked condition in horses, which can often be treated with simple changes to equine management.

Retrospective case review investigating the effect of replacing oaten hay with a non‐cereal hay on equine peripheral caries in 42 cases

Equine peripheral caries can cause significant morbidity and can have considerable welfare implications. Recent research suggests that diets with high water soluble carbohydrate (WSC) content are associated with high risk of peripheral caries. Previous work has indicated that the condition may be treatable if the inciting cause is removed and the damaged tooth allowed to erupt out, being replaced by the unaffected tooth previously under the gingival margin. To see whether the peripheral caries process can be ceased if oaten hay (typically high WSC) is removed from the diet and replaced with a non-cereal hay (typically lower WSC). Retrospective blinded longitudinal study. Forty-two cases with peripheral caries that were on oaten hay were asked if they would change the hay type from oaten hay to a non-cereal hay or straw (meadow, Rhodes hay, lucerne hay or barley straw). Photographs were taken at the time and then again at subsequent visits. The photographs were anonymised, randomised and scored by six equine veterinary dentists using the Jackson et al. 'Peripheral Caries Grading System' grading scale. At follow-up, 69.0% of cases were marked as inactive, compared with 47.6% of cases at baseline (OR: 2.45, 95%CI: 1.12-5.36, P=.02). Significantly lower grades of peripheral caries were observed in the gingival, middle and occlusive third of the molars (triadan 9-11's) at follow-up compared with baseline. However, significant improvements were not observed in the premolars (triadan 6-8's). This is a review of clinical records, not a prospective study. As such, other changes in the diet and management were not recorded, and there was no control group. Recommending clients change their horse's diet from oaten hay (high WSC) to a typically lower WSC hay was associated with significant improvements in equine peripheral caries located in the molars.

A Randomized Controlled Trial Assessing the Effects of Feeding High Water Soluble Carbohydrate (WSC) Oaten Hay Versus Low WSC Oaten Hay on Equine Peripheral Dental Caries

Equine peripheral caries (PC) can cause significant dental pathology and appears to be increasing in prevalence and recognition in many areas [1, 2]. Previous studies have identified risk factors for the condition including the feeding of oaten hay [3]. It was hypothesized that this may be due to the higher water soluble carbohydrate (WSC) or “sugar” content of the hay. A randomized control trial involving 30 horses on three properties was completed. The horses were randomly assigned to two groups: high WSC (H-WSC) or low WSC (L-WSC) oaten hay and were then sedated and intraoral photographs and endoscopy were performed for baseline levels. They were maintained on this assigned hay source for three months when they were again sedated, examined, and photographs and endoscopic videos recorded. Horses with significant PC were then changed to meadow hay (previously shown to be lower risk for PC [3]) for seven months and re-examined to assess for recovery. Images and videos were anonymized and graded for PC, and the PC grades of the teeth before and after intervention were compared using a Fisher exact test. Thirteen horses fed L-WSC hay and 15 fed H-WSC hay completed the study. Of horses fed the H-WSC oaten hay, 60% deteriorated and of horses on L-WSC oaten hay, 53.8% improved in PC grade over the trial, however, the difference was not statistically significant (P = .274). All three horses available for recheck after changing to meadow hay improved.

A new equine peripheral caries grading system: Are the caries likely active or inactive?

Equine peripheral caries can be a significant welfare issue in affected horses. Recent work has shown that complete reversal of the condition may be possible if the primary risk factor can be identified and corrected. Determining whether caries are active (deteriorating) or inactive (improving) is of vital importance when formulating a management and treatment plan. A new grading system is proposed that looks at whether caries are likely active or inactive to assist clinicians deciding whether intervention is required. To examine the reliability of an alternative grading method for equine peripheral caries. Online survey of veterinary surgeons. Reviewers (n=22) graded images of peripheral caries using three methods: the traditional grading system, a new research grading system and a new clinical grading system. Percentage agreement and Fleiss' kappa were used to examine the participant's agreement of the severity of caries. All percentage agreements and Fleiss' kappa values were significantly greater than zero (P<.001). The Fleiss' kappa for the new methods were higher (ranging from 0.48 to 0.58), but not significantly different from the traditional method (0.40). There was a high level of consistency in the assessment of caries as either active or inactive with both grading systems reporting over 80% agreement. Feedback on the grading systems was positive with over 90% of reviewers saying they were likely to use the system. The use of photographs provided some difficulties with image quality and judging whether the dentin was affected without an occlusal image. The new grading system produced a consistent estimate of caries severity and provided high levels of agreement on whether the caries were likely 'active' or 'inactive'. This is likely to be very useful clinically to assist practitioners to determine whether intervention is required.

A histological and ultrastructural study of equine peripheral caries.

Peripheral caries (PC) has recently been shown to affect over half of UK and Australian horses. To examine affected cheek teeth histologically and ultrastructurally, to assess the possible route(s) of carious infection into the dental tissues and to further describe the pathological changes in affected teeth. Descriptive pathological study. Four control and 16 cheek teeth with different grades of PC were examined grossly, histologically and by electron microscopy. Cariogenic bacteria from plaque entered peripheral cementum perpendicular to the sides of teeth alongside Sharpey's fibres or vascular channels or more horizontally alongside exposed intrinsic fibres and cemental growth lines. Subsequent intra-cemental bacterial spread created different patterns of caries including vertical and horizontal flake-like patterns; deep, large flask-shaped or smaller superficial ellipsoid-shaped lytic lesions. Cemental caries progressed to affect enamel, dentine and even pulp. Gross examination underestimated the degree of caries observed on histological evaluation. No dental histories were available; all teeth were examined on a single occasion. Equine PC causes different patterns of cemental lesions that appear dependent on the route of cariogenic bacterial invasion. Progression of caries can lead to pulpitis and tooth loss. Gross examination can underestimate the true extent of caries.

A microbiome analysis of equine peripheral dental caries using next generation sequencing.

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. 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. 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. 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. Some bacteria can have multiple heterogeneous copies of the 16S rRNA gene, which can affect the estimation of their relative abundance. Similar to caries studies in other species, acidogenic and aciduric microorganisms including Streptococcus species were found to be associated with equine peripheral caries.

Prevalence and analysis of equine periodontal disease, diastemata and peripheral caries in a first-opinion horse population in the UK

Equine dental disease remains a widespread affliction in domestic horses, with the potential to cause significant welfare problems. This retrospective study aimed to increase understanding of this aspect of equine health by examining dental records of 932 horses, taken from a 1-year period of first-opinion practice in south-western England and southern Wales. Three grossly-identifiable dental diseases were analysed: equine periodontal disease, diastemata and peripheral caries.The prevalence of active periodontal disease, diastemata and peripheral caries were 13.9%, 8.7% and 8.2%, respectively. Periodontal disease was more common in the mandibular than maxillary arcades (P<0.001) and in the premolar (06–08) than molar (09–11) cheek teeth (P<0.001). Diastemata were also observed more frequently in the mandibular than the maxillary arcades (P<0.001) and in premolar than molar cheek teeth (P<0.001). Peripheral caries were significantly more common in molar than premolar cheek teeth (P<0.001). A positive association was demonstrated between periodontal disease and diastemata (Exp(B)=4.22; P<0.001). Increasing age was a significant risk factor for periodontal disease (P<0.001) and diastemata (P<0.001). Sex was not conclusively established as a risk factor for any dental disease.

Equine peripheral dental caries: An epidemiological survey assessing prevalence and possible risk factors in Western Australian horses.

Peripheral dental caries is defined as macroscopic destruction of the calcified dental tissues and can cause considerable dental pathology and pain. It appears to occur at a high prevalence in Western Australian horses. At present, risk factors for the condition are poorly understood, making treatment and prevention difficult. To assess the prevalence of and potential risk factors for peripheral caries in Western Australian horses. Cross-sectional, epidemiological study. A survey of 500 Western Australian horses was administered in two sections. The first section was completed by the owner and referred to the horse's signalment, diet and husbandry conditions. The second section was completed by veterinarians and focused on the horse's oral health. A multivariable logistic regression model was used to assess risk factors associated with peripheral caries. Peripheral caries was present in 58.8% (95% confidence interval [CI] 54.5-63.1%) of surveyed horses. Breed was significantly associated with peripheral caries, with Warmbloods (odds ratio [OR] 0.44, 95% CI 0.24-0.82; P = 0.009) and Western breeds (OR 0.38, 95% CI 0.19-0.78; P = 0.008) being less likely to have peripheral caries than Thoroughbreds. Dietary risk factors included oaten hay (OR 2.90, 95% CI 1.87-4.53; P<0.001). A meadow hay-based diet was protective (OR 0.47, 95% CI 0.27-0.80; P = 0.005). Horses with access to quality pasture all year were less likely to have peripheral caries than horses without access to grazing (OR 0.31, 95% CI 0.15-0.66; P = 0.002), as were horses on groundwater compared with horses on rainwater (OR 3.35, 95% CI 1.65-6.78; P = 0.001), drinking water (OR 2.03, 95% CI 1.14-3.62; P = 0.016) or dam water (OR 3.53, 95% CI 1.08-11.53; P = 0.037). Peripheral caries was positively correlated with periodontal disease (OR 4.53, 95% CI 2.91-7.06; P<0.001) and feed packing (feed present between the teeth without significant periodontal pocketing) (OR 1.94, 95% CI 1.32-2.85; P = 0.001). Not every owner of eligible horses seen during the study period agreed to participate. An epidemiological study is unable to show causality. Western Australian horses have a high prevalence of peripheral caries. Management factors that may help to prevent or reduce peripheral caries include more access to quality pasture, use of groundwater, feeding on meadow hay and avoidance of oaten hay.

An epidemiological survey on the prevalence of equine peripheral dental caries in the United Kingdom and possible risk factors for its development.

Equine peripheral caries (PC) is an increasingly recognised disorder that causes premature wear of teeth and dental fractures and thus has major welfare implications. Little information is available on its prevalence or severity in UK horses and there are no proven associations with any risk factors. To document the prevalence of PC over a wide area of the UK, assess its intraoral distribution and severity in affected horses and examine for potential risk factors for its development. Cross sectional study. Experienced personnel were recruited for a UK wide dental survey on their patients during dental examinations. Established guidelines were used for grading PC. Frequency of PC occurrence was compared between teeth and dental arcades using McNemar's tests. Potential risk factors for PC were screened using univariable logistic regression prior to building a multivariable model. A total of 706 horses were examined by 25 participants, showing a 51.7% prevalence of PC (365/706). Some regional differences in prevalence were found. The PC primarily affected the cheek teeth with the 12 caudal being significantly more commonly affected than the 12 rostral cheek teeth. Most of the hypothesised risk factors including age, breed, sex, time at pasture and feeding of silage (haylage) were unproven. A limited association with moderate levels of concentrate feeding was observed. The presence of concurrent dental abnormalities were significantly associated with the likelihood of having PC. Not all regions in UK were included and there may be inconsistencies between examiners. 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.

Equine peripheral and infundibular dental caries: A review and proposals for their investigation

SummarySeveral 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.