Treatment of equine cheek teeth by mechanical widening of diastemata in 60 horses (2000-2006)

REASON FOR PERFORMING STUDY: Cheek teeth (CT) diastemata are a significant cause of painful dental disease in horses and limited factual information is available on the treatment of this disorder. OBJECTIVE: To assess the response to mechanical widening in the treatment of diastema. METHOD: Details of the presenting signs and treatment of cases of CT diastema by widening were recorded and the response to treatment of these cases assessed by re-examinations and by obtaining follow-up information from owners. RESULTS: Sixty horses of various breeds, median age 9 years, with clinically significant CT diastemata were classified as having primary (inadequate rostro-caudal CT compression: n = 29) and secondary (to other dental abnormalities: n = 31) diastemata. Quidding was present in 82% of cases, weight loss in 35%, halitosis in 17% and bitting disorders in 12%; 85% of the identified CT diastemata involved mandibular CT and 15% maxillary CT, with caudal CT more commonly affected. Of 273 identified diastemata in the 60 horses, 207 were deemed to have significantly associated periodontal food pocketing and were widened to 4.5-5.5 mm diameter on their occlusal surface using a mechanical burr. The 29 horses with primary diastemata received a median of 1.3 treatments each and at 10 months following their last treatment 72% showed complete remission of signs and 28% showed good improvement. The 31 horses with secondary diastemata received a median of 2.2 treatments each and, at mean 9 months following their last treatment, 48% showed full improvement, 42% good improvement, 6% slight improvement and 3% no improvement. Inappropriate areas of the clinical crown were removed from 4 CT without causing pulpar exposure; one case was reported to have a transient oral infection post treatment and another developed an apical infection in a treated tooth that was unrelated to the diastema widening. CONCLUSION: Diastema widening is an effective treatment of periodontal pocketing in CT diastemata. POTENTIAL RELEVANCE: The described treatment of CT diastema widening by trained personnel is an effective and safe treatment, but repeated treatments are often necessary, especially with secondary diastemata.     

An anatomical study to evaluate the risk of pulpar exposure during mechanical widening of equine cheek teeth diastemata and 'bit seating'

Reasons for performing study: Cheek teeth (CT) diastemata are a major equine dental disorder that can be treated by mechanically widening the diastemata. There is limited anatomical knowledge of the spatial relationships of the individual pulps to the adjacent interproximal surfaces; on the risks of exposing the 6th pulp horn when performing the clinically unproven ‘bit seating’ procedure on Triadan 06s. Objectives: To describe the anatomical relationships between the occlusal and interproximal surfaces of CT and the adjacent pulp horns; and between the 6th pulp horn and the occlusal and rostral surfaces of Triadan 06s. Methods: The CT from 30 skulls of horses subjected to euthanasia for non‐dental reasons were sectioned to expose the rostrally and caudally situated pulp horns to allow the anatomical relationships between the pulp horns and the occlusal and interproximal aspects of the CT to be assessed. Results: Pulp horns were mean ± s.d. of 5.74 ± 1.45 (range 1.3–10.8 mm) from the nearest interproximal surface, with 5.3% of pulp horns being <3.5 mm from the interproximal surface. In contrast to expectations, pulps tended to became closer to the interproximal surface (and also to the occlusal surface) with increasing age. Teeth with physiologically tall clinical crowns, and also those in the Triadan 09 position had pulps that were closer to the interproximal surfaces than the remaining CT. The more caudally situated pulp horns, i.e. in particular, the 4th maxillary and 5th mandibular pulp horns were closer to the interproximal surfaces than the remaining pulp horns and these pulp horns also had the thinnest sub‐occlusal secondary dentine. Pulps that were close to the interproximal surface were also found to be close to the occlusal surface of the CT. Conclusions and potential relevance: While diastema widening is theoretically safe between the majority of CT, a small proportion of pulp horns are only 1.3 mm from an interproximal surface and others lie just 1.6 mm beneath the occlusal surface, and such pulps are at risk of pulpar exposure and to thermal injury during this procedure. The risk of pulpar exposure increases when dental tissue is removed from the caudal aspects of CT.     

Treatment of maxillary cheek teeth apical infection caused by patent infundibula in six horses (2007–2013)

Six young horses presented with clinical signs of maxillary cheek teeth apical infection (bilateral in 2 horses) that included the presence of rostral maxillary swellings with discharging sinus tracts and were unexpectedly found to have no evidence of endodontic infection in 7 affected teeth. The apical infection of these teeth was attributed to infundibular dysplasia that allowed inoculation of the periapical tissue with contaminated oral contents. Treatment was by debridement and obturation of affected infundibula from their occlusal aspect using techniques normally used for endodontic therapy. Five out of 6 cases showed resolution of clinical signs over a mean follow‐up period of 19 months (range 6–48 months). These cases demonstrate that patency of the infundibular apex is a potential cause of cheek teeth apical infection in young horses, which can be successfully treated by debridement and subsequent infundibular restoration.     

A study of the thickness of cheek teeth subocclusal secondary dentine in horses of different ages

Reasons for performing study: There is limited knowledge on the thickness of subocclusal secondary dentine in equine cheek teeth (CT). Hypotheses: Subocclusal secondary dentine is of consistent thickness above different pulp horns in individual horses and its thickness increases with age. Methods: 408 permanent CT were extracted post mortem from 17 horses aged 4–30 years, with no history of dental disease. The CT were sectioned longitudinally in the medio‐lateral (bucco‐palatal/lingual) plane through each pulp horn, and the thickness of the secondary dentine overlying each pulp horn was measured directly. Results: The subocclusal thickness of secondary dentine above the pulp horns of CT varied from a mean thickness (above all pulp horns) of 12.8 mm (range 5–33 mm) in a 4‐year‐old to 7.5 mm (range 2–24 mm) in a 16‐year‐old horse. There was wide variation in the depth of subocclusal secondary dentine above different pulp horns, even within the same CT. In contrast to expectations, occlusal secondary dentine thickness did not increase with age. There were no significant differences in occlusal secondary dentine thickness between rostral and caudal, or medial and lateral aspects of the CT, or between contralateral CT. Mandibular CT had significantly thicker subocclusal secondary dentine than maxillary CT. Pink coloured secondary dentine was sometimes found 1–3 mm occlusal to the pulp horn in sectioned CT and this was likely caused by artefactual blood staining from the underlying pulp during sectioning. Conclusions: The thickness of subocclusal secondary dentine varies greatly between individual pulp horns, teeth and individual horses and can be as low as 2 mm over individual pulp horns. Potential relevance: Due to the great variation in the thickness of subocclusal secondary dentine between horses, and even between pulp horns in individual CT, there is a risk of exposure or thermal damage to pulp and thus of apical infection, even with modest therapeutic reductions of CT occlusal overgrowths. In the light of these findings, great care should be taken when reducing equine CT overgrowths and larger dental overgrowths should be reduced in stages.     

Treatment of oromaxillary fistulae in nine standing horses (2002–2006)

Reasons for performing study: There is minimal published information on equine oromaxillary fistulae that are unrelated to cheek teeth (CT) repulsion or on the conservative treatment of these atypical fistulae. Objectives: To report equine oromaxillary fistulae unrelated to CT extraction and describe their management in standing horses. Methods: Case details of oromaxillary fistulae of atypical aetiology occurring at 2 referral centres between 2002–2006, including their treatment and response to treatment were examined. Results: Nine cases of oromaxillary fistula were recorded, mainly in aged horses (median 22 years). Fistulae were associated with CT diastemata in 7 cases, fractured CT in one and a central defect in a worn CT in another. After removing food and exudate from the sinuses, 6 cases were treated successfully by filling the diastema or dental defect with polymethylmethacrylate (PMMA). Following dental extraction, the other 3 cases were treated successfully by use of PMMA alveolar packing. Conclusion: Older horses can spontaneously develop oromaxillary fistulae, usually secondary to CT diastemata. In the absence of apical infection, this disorder can usually be treated successfully in standing horses by treating the sinusitis and sealing the oral aspect of the diastema with PMMA. Potential relevance: Older horses with sinusitis should be assessed for the presence of CT diastemata and oromaxillary fistulae. If detected, these disorders can be treated successfully in the standing horse.     

Investigation of the sensitivity and specificity of radiological signs for diagnosis of periapical infection of equine cheek teeth

Reasons for performing study: Radiography is commonly used for the diagnosis of equine cheek teeth (CT) infection but, to our knowledge, no study to date has evaluated the relative values of individual specific radiographic signs when making a diagnosis. Objectives: To investigate the sensitivity and specificity of individual radiographic signs identified from the literature for the diagnosis of CT apical infection using a retrospective case‐control study. Methods: Cropped radiographs taken using computed radiography of 41 apically infected CT and 41 control CT were independently blindly evaluated by 3 clinicians for the presence of 12 predetermined radiographic signs associated with CT apical infection. A final diagnosis of either noninfected or infected was made. Sensitivity and specificity were calculated for the presence or absence of each radiographic sign for each clinician. Uni‐ and multivariable conditional logistic regression were used to determine strength of association of the 12 radiographic signs with apical infection. Results: Median sensitivity and specificity for the diagnosis of CT apical infection were 76 and 90%, respectively. Periapical sclerosis, clubbing of one or 2 roots, degree of clubbing and periapical halo formation had the highest sensitivities (73–90%), with moderate specificity (61–63%). Multivariable conditional logistic regression revealed that severity of periapical sclerosis and extensive periapical halo were strongly associated with CT apical infection. Conclusions: The presence of periapical sclerosis and formation of a periapical halo were strongly associated with CT apical infection. Computed radiography appears to have a higher sensitivity but similar specificity to previously published results using film radiography to detect CT apical infection. Potential relevance: These findings may aid practitioners when interpreting radiographs of equine CT as to the relative significance of their findings.     

Description of a technique for orthograde endodontic treatment of equine cheek teeth with apical infections

An orthograde endodontic method, similar to that used in human dentistry, is described for use on endodontically diseased permanent cheek teeth in horses. The technique has been adapted to meet the anatomical and physiological differences between hypsodont and brachyodont teeth and is performed in sedated horses. The techniques of debriding the pulp cavity and use of dental materials which fulfil the requirements for equine teeth are presented here. The results of this technique appear to be promising but have yet to be evaluated in a peer‐reviewed study. By using orthograde endodontic therapy on sedated horses it is now possible to save endodontically diseased permanent cheek teeth.     

Pathological studies of cheek teeth apical infections in the horse: 4. Aetiopathological findings in 41 apically infected mandibular cheek teeth

Examination of 41 extracted, apically infected mandibular cheek teeth (CT) without obvious causes of infection included radiography, computerised axial tomography and decalcified and undecalcified histology. In CT with recent infections, some pulps remained viable, with proliferative soft and calcified tissue changes confined to the apex. With more advanced CT infections, occlusal pulpar exposure was sometimes present (in 34% of the 41 CT), some infected pulp chambers were filled with necrotic pulp or food, and extensive destructive or proliferative changes were present in the calcified apical tissues.No physical route of infection to the apex was found in 24 CT (59%) that consequently were believed to have anachoretic infections. Fractures involving pulps, including fissure fractures between the clinical crown and infected pulps, were found in eight (20%) CT. Some CT had vertical, full length periodontal destruction between the infected apex and the gingival margin that were believed to be the route of infection in four (19%) CT and dysplastic changes were believed to have caused one (2%) infections.     

Pathological studies of cheek teeth apical infections in the horse: 5. Aetiopathological findings in 57 apically infected maxillary cheek teeth and histological and ultrastructural findings

Examination of 57 apically infected maxillary cheek teeth (CT) showed one or more viable pulps and minimal apical calcified tissue changes present in recently infected CT. With chronic infections, pulps were necrotic or absent, pulp horns were filled with food if occlusal pulpar exposure was present, and gross caries of dentine was occasionally present. With chronic infections, the apical changes varied from gross destructive changes in some teeth, to extensive proliferative calcified apical changes in others. Infundibular caries was believed to cause apical infection in just 16% of infected (maxillary) CT, anachoretic infection in 51%, periodontal spread in 12%, fractures and fissures in 9%, dysplasia in 5% and miscellaneous or undiagnosed causes in 7%.Histology showed viable pulp and absence of circumpulpar dentinal changes in some recently infected CT, but chronically infected teeth had loss of predentine and progressive destruction of the circumpulpar secondary, and even primary dentine, with bacteria identified within the dentinal tubules surrounding infected pulps. Tertiary dentine deposition was rarely detected. Scanning and transmission electron microscopy confirmed these histological findings and showed extensive destructive changes, especially to the dentinal architecture surrounding the pulp chambers of some infected teeth.     

An acute outbreak of equine dysautonomia (equine grass sickness) in a group of eight Przewalski's horses (Equus ferus [caballus] przewalskii)

Equine grass sickness (EGS) is a neurodegenerative disease affecting grazing equids of which a single case of the chronic clinical presentation has previously been reported in a Przewalski's horse (Equus ferus [caballus] przewalskii). A group of 8 Przewalski's horses were moved to a new enclosure, recently vacated by a group of 4 Eastern kiang (Equus kiang holdereri) that showed no evidence of disease. After 23 days the first Przewalski's horse showed clinical signs of acute EGS including flank sweating, belly kicking, rapid loss of body condition, cessation of faecal passage, nasogastric reflux and mouthing water. It was subjected to euthanasia within 48 h due to lack of therapeutic response. Within 24 h of this first case developing clinical signs, a further 5 Przewalski's horses showed similar clinical signs of acute EGS and were subjected to euthanasia. Post mortem examinations confirmed acute EGS, with all animals demonstrating typical chromatolysis, cytoplasmic hypereosinophilia, cellular swelling, vacuolation, pyknosis and loss of nuclei in approximately 90% of neurones in the cranial cervical and cranial mesenteric ganglia and myenteric and submucosal plexi of the ileum. Two Przewalski's horses within the group showed no clinical signs of disease. No single pathogen was identified as the causal agent, but the epidemiological pattern of the outbreak was typical for that previously reported for acute EGS in domestic equids. All affected animals and the 2 surviving Przewalski's horses had low antibody titres to Clostridium botulinum type C. This is the first report of acute EGS in a herd of Przewalski's horses.     

Review of two viral agents of economic importance to the equine industry (equine herpesvirus-1, and equine arteritis virus)

Equine herpesvirus type-1 (EHV-1) and equine arteritis virus (EAV) are infectious agents that cause serious health risks to horse populations and are disbursed worldwide, which can lead to significant financial losses. In addition to being responsible for abortion and neonatal death, these viruses are associated with respiratory illness. Although previous research and reviews have been written on these viruses, both viruses still affect horse populations around the world and the vaccines currently available are not completely protective, especially against EHV-1 and equine herpes myeloencephalopathy (EHM). Moreover, EAV is considered a threat to the $102 billion equine industry in the United States. As a result, these viruses represent a huge threat to the horse industry and efforts geared towards preventing the outbreak of the disease are strongly encouraged. For this reason, updates about these viruses are necessary and require more and more discussion on the nature and characteristics of these viruses to know how to overcome them. Prevention and control of abortion and neonatal foal death caused by each of the two viruses depend on appropriate management strategies coupled with prophylactic vaccination. This review presents the latest detailed information on EHV-1 and EAV from several aspects such as transmission, clinical signs, pathogenesis, latest developments on the treatment of the diseases, vaccination, and finally challenges and future perspectives. The information presented herein will be useful in understanding EHV-1 and EAV and formulating policies that can help to limit the spread of these viruses within horse populations.     

Clinical findings and progression of 10 cases of equine ulcerative keratomycosis (2004–2007)

Ulcerative keratomycosis is a serious sight‐threatening disease of horses and the veterinary literature is replete with cases of poor visual outcome following this condition. During a 3 year period, 10 horses were treated for confirmed keratomycosis at the Veterinary Teaching Hospital (VTH) of the University of Cordoba (Spain). Ulcerative keratomycosis accounted for an average of 8.62% of the total equine ophthalmic admissions during this time and an average of 33.3% of horses were diagnosed with infectious keratitis. Fungi were diagnosed using cytology (n = 4) and/or culture (n = 8) and histopathology (n = 1). Aspergillus sp. was the most commonly isolated fungus. Medical therapy alone or combined medical and surgical treatment was utilised for therapy depending on the clinical condition. Miconazole 1% was the most common topical antifungal therapy employed. Median duration of treatment was 73.12 days. Records were evaluated to determine visual outcome and globe survival.