N. du Toit

Anatomical studies of maxillary cheek teeth infundibula in clinically normal horses

REASONS FOR PERFORMING STUDY Although clinical disorders of equine maxillary cheek teeth (CT) infundibula are common, anatomical knowledge of these structures is poor. HYPOTHESIS Anatomical examinations of sectioned CT infundibula will better define their shapes and sizes and allow identification of infundibular cemental variations and changes. MATERIAL AND METHODS Cheek teeth were extracted post mortem from 33 horses, aged 3-30 years, without a clinical history of dental disease. The CT were sectioned longitudinally in the bucco-palatal plane through the widest aspects of both infundibula. The infundibular surfaces were then assessed morphologically, including by measurements of areas of cemental variations and changes. Specimens from selected teeth were examined histologically. RESULTS Infundibular length and infundibular surface area, and infundibular length as a proportion of dental crown length progressively decreased with age, e.g. infundibular length was up to 89 mm after eruption to 2 mm in one older horse. Triadan 06 and 09 positions had significantly shorter CT and therefore infundibula, than the other 4 Triadan positions. Only 11.7% of infundibula were filled completely with normal appearing cementum, 8.2% of infundibula (especially the 09 position) had complete cemental caries; 22.6% of infundibula had areas with cemental hypoplasia and the remaining 57.5% of infundibulae had a variety of other cemental appearances, including the presence of central defects, localised occlusal caries and cemental discolourations. Histology showed the presence of an apical blood supply to infundibular cement in younger horses. CONCLUSIONS Anatomical variations of CT infundibular cement are very common and some changes, such as areas of localised cemental hypoplasia, may predispose to the development of infundibular caries. POTENTIAL RELEVANCE This more complete description and quantification of CT infundibular anatomy should allow more rational assessment and treatment of equine CT infundibular disorders.

Donkey dental anatomy. Part 1: Gross and computed axial tomography examinations

Post-mortem examination of 19 donkey skulls showed that donkeys have a greater degree of anisognathia (27% width difference between upper and lower jaws) compared to horses (23%). Teeth (n=108) were collected from 14 skulls and examined grossly and by computed axial tomography (CAT). A greater degree of peripheral enamel infolding was found in mandibular cheek teeth (CT) compared to maxillary CT (P<0.001). A significant increase in peripheral cementum from the apical region to the clinical crown was demonstrated in all CT (P<0.0001). All donkey CT had at least five pulp cavities with six pulp cavities present in the 06s and 11s. A new endodontic numbering system for equid CT has been proposed. A greater occlusal depth of secondary dentine (mm) was present in older donkeys (>16 years) than in the younger (<15 years) donkeys studied. Based on gross and CAT examinations, donkey dental anatomy was shown to be largely similar to that described in horses.

Clinical dental examinations of 357 donkeys in the UK. Part 1: Prevalence of dental disorders

REASONS FOR PERFORMING STUDY Dental disorders have a high prevalence in older donkeys and horses, but the nature and pathogenesis of many of these disorders have yet to be established. OBJECTIVES The identification and determination of the prevalence of important dental disorders in different age groups in a large single population of donkeys, to establish a better understanding of the nature and pathogenesis of these disorders. METHODS A prospective cross-sectional study was performed on the donkey population at The Donkey Sanctuary with detailed oral examinations of 357 donkeys within 7 different age groups (age range 2-53 years) recorded. RESULTS The prevalence of dental disease in all donkeys was 73%, increasing in prevalence from 28% in the youngest to 98% in the oldest age group. There was an increase in prevalence of commonly recognised dental disorders with increasing age, such as: diastemata (3.8% in youngest to 86% in oldest group); missing teeth (0-56%); overgrown teeth (15-86%); worn teeth (8-84%); displaced teeth (0-38%); and periodontal disease (0-28%). CONCLUSIONS There was a significant increase in the prevalence of dental disorders with increasing age with the largest significant increase for most dental disorders occurring in the 15-20 year age group. POTENTIAL SIGNIFICANCE: Most dental disorders significantly increase in prevalence in the 15-20 year age group and, therefore, prophylactic geriatric dental treatment in donkeys should be commenced from age 15 years.

Post mortem survey of dental disorders in 349 donkeys from an aged population (2005-2006). Part 1. Prevalence of specific dental disorders

REASON FOR PERFORMING STUDY Donkey dental disorders are being recognised with increased frequency worldwide and have important welfare implications; however, no detailed investigations of dental disorders in donkeys appear to have been published. OBJECTIVES To determine the prevalence of specified dental disorders in donkeys by performing a prospective post mortem study on donkeys that were subjected to euthanasia or died for other reasons at the Donkey Sanctuary, UK. METHODS Post mortem examinations were performed on 349 donkeys over an 18 month period, 2005-2006. The presence and extent of specified dental disorders were recorded and these data analysed to determine their prevalence and common locations. RESULTS A high prevalence (93%) of disorders was noted in the population with a median age of 31 years. In particular, cheek teeth diastemata (85% prevalence) were very common, often associated with advanced periodontal disease. Other disorders observed included missing teeth (in 55.6% of donkeys), displaced teeth (43%), worn teeth (34%), local overgrowths (15%), focal sharp overgrowths (3%) and dental-related soft tissue injuries (8%). CONCLUSIONS AND POTENTIAL RELEVANCE Aged donkeys have a high prevalence of significant dental disease, especially cheek teeth diastemata. These findings highlight the importance of routine dental examinations and prophylactic dental treatments to improve the dental health and welfare of donkeys.

Clinical dental examinations of 357 donkeys in the UK. Part 2: Epidemiological studies on the potential relationships between different dental disorders, and between dental disease and systemic disorders

REASONS FOR PERFORMING STUDY Dental disease has been shown to be a risk factor for weight loss and colic in horses. No extensive clinical studies in donkeys have investigated the potential relationship between different dental disorders, or between dental disease and systemic disorders. OBJECTIVES To determine possible associations between dental disease and body condition score, weight loss, the need for supplemental feeding and prevalence of colic in donkeys of all ages, and to gain a better understanding of the pathogenesis of dental disease by the determination of associations between different dental disorders. METHODS A prospective cross-sectional analysis of clinical dental examinations of 357 donkeys in The Donkey Sanctuary, Sidmouth was performed. Other epidemiological factors such as estimated age group, body condition score, weight loss, medical history and supplemental feeding were also recorded, and multiple regression analyses were performed to determine possible associations. RESULTS Donkeys from older age groups were more likely to have dental disease, poor body condition score and suffered previous colic episodes. The presence of dental disease was also significantly associated with weight loss, colic, low body condition score and the need for supplemental feeding. The presence of diastemata, periodontal disease, wave mouth, smooth mouth and step mouth are frequently associated with the presence of other dental disorders. CONCLUSIONS In addition to oral-related pain, dental disease can cause significant systemic disorders and so has increased welfare implications in donkeys. Some dental disorders promote the development of other types of dental abnormalities and thus increase the severity of dental disease in individual animals. POTENTIAL SIGNIFICANCE: Effective treatment of dental disorders slows down the progression of dental disease and decreases the risk of developing some medical disorders such as colic and weight loss that are associated with dental disease.

Donkey dental anatomy. Part 2: Histological and scanning electron microscopic examinations

Ten normal cheek teeth (CT) were extracted at post mortem from donkeys that died or were euthanased for humane reasons. Decalcified histology was performed on three sections (sub-occlusal, mid-tooth and pre-apical) of each tooth, and undecalcified histology undertaken on sub-occlusal sections of the same teeth. The normal histological anatomy of primary, regular and irregular secondary dentine was found to be similar to that of the horse, with no tertiary dentine present. Undecalcified histology demonstrated the normal enamel histology, including the presence of enamel spindles. Scanning electron microscopy was performed on mid-tooth sections of five maxillary CT, five mandibular CT and two incisors. The ultrastructural anatomy of primary and secondary dentine, and equine enamel types-1, -2 and -3 (as described in horses) were identified in donkey teeth. Histological and ultrastructural donkey dental anatomy was found to be very similar to equine dental anatomy with only a few quantitative differences observed.

Morphological study of tracheal shape in donkeys with and without tracheal obstruction.

REASON FOR PERFORMING STUDY There is limited information on the gross tracheal morphology of donkeys with or without tracheal abnormalities. OBJECTIVES To: 1) examine the morphology of tracheas of donkeys with and without clinical and/or post mortem evidence of tracheal obstruction; 2) record the cross-sectional dimensions and shapes of tracheal rings at fixed sites; and 3) document prevalence, sites and characteristics of detected tracheal abnormalities. METHODS The tracheas of 75, predominantly aged (median age 30 years, range 7-48 years) donkeys that died or were subjected to euthanasia on humane grounds were examined. Five had severe dyspnoea due to tracheal obstruction (with intercurrent lung disease in 3), while 7 had post mortem evidence of severe tracheal airway obstruction. Every 5th tracheal ring was dissected free and the inner and outer vertical and transverse dimensions and cross sectional areas were measured. Each dissected ring was photographed and the shape of the trachea was classified as normal or, in one of 6 abnormal grades, according to the type and degree of structural abnormality present. RESULTS The tracheas had a mean of 43 (range 34-50) tracheal rings that tended to be more oval in shape in the distal cervical region. Only 31.2% of rings examined had a circular to oval shape. Dorso-ventral flattening was present in 0.9% of tracheal rings, dorsal ligament separation in 24.4%, slight cartilage deformity in 26.0%, moderate cartilage deformity in 10.4%, marked cartilage deformity in 1.9% and miscellaneous other abnormalities in 4.9% of tracheal rings. The 12 donkeys with ante or post mortem evidence of tracheal obstruction had significantly increased tracheal abnormality grade in comparison to the remaining donkeys. CONCLUSIONS AND POTENTIAL RELEVANCE Structural tracheal abnormalities are present in most old donkeys, but generally do not cause clinical problems in these sedentary animals unless intercurrent pulmonary disease is present.