dentistry

Post mortem survey of dental disorders in 349 donkeys from an aged population (2005-2006). Part 2: epidemiological studies

Reason for study

Dental disorders have recently been recognised as having major clinical and welfare implications in donkeys. However, no investigation appears to have examined the association of dental disorders with managemental factors and any intercurrent illness.

Objectives

To determine the association of dental disorders observed in a post mortem study with age group, body condition score, time since last dental treatment, feeding and the illness that necessitated euthanasia or caused death.

Methods

A prospective study documented the type and prevalence of dental disorders in 349 mainly aged donkeys (median estimated age of 31 years) that were subjected to euthanasia over an 18 month period in 2005-2006. The estimated age, body condition score, supplemental feed status, time since last dental treatment and nature of the intercurrent disease that necessitated euthanasia or caused death were also recorded. Multivariable analysis was performed to examine associations of these factors with specific dental disorders and between specific dental disorders.

Results

There was a high prevalence (93.4%) of significant dental disease. Age group was significantly associated with the presence of dental disorders and an older age range was a high risk factor for the presence of cheek teeth (CT) diastemata. There was a significant association between the presence of CT diastemata and the concurrent presence of displaced, missing and worn CT. There was also a significant association between the presence of diastemata and colic.

Conclusions and potential relevance

Aged donkeys have a high prevalence of dental disorders especially of CT diastemata. Dental disorders and, in particular, the presence of CT diastemata were significantly associated with colic. Routine, prophylactic dental treatments should be performed, especially in aged donkeys.

Volume
40
Issue
3
Start page
209
End page
213
Publication date
Country

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

Reason for 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.

Volume
40
Issue
3
Start page
204
End page
208
Publication date
Country

Polyodontia in donkeys

Polyodontia is defined as the presence of teeth in excess of the normal dental formula. In equids, supernumerary teeth are uncommon but, when present, are usually located mainly in the caudal aspects of the cheek teeth rows (distomolars), also being found adjacent to normal cheek teeth or even in an ectopic location. It is believed that this disorder is a result of an inappropriate differentiation of dental germinal tissue during gestational development, with external trauma also acting as an initiating factor, when teeth germs are affected. The presence of these abnormal teeth can lead to axial displacement, dental overgrowths, dental-related soft tissue damage, diastemata formation, periodontal disease and development of secondary sinusitis. A large prospective, cross-sectional study was performed in 800 donkeys, with the aim to investigate the prevalence and aetiopathogenesis of clinically diagnosed oral and dental disorders. Polyodontia was recorded in 2.25% of the donkeys, presenting 36 supernumerary teeth, with 2.80% being incisors and 97.20% cheek teeth, with prevalence increasing with age. The caudal aspects of the maxillary cheek teeth rows were the most common locations for supernumerary teeth development (distomolars). The mandible was far less commonly affected than the maxilla. Although polyodontia is uncommon in donkeys, it should be considered in the differential diagnosis of dental disease. A methodical oral examination and a complete radiographic survey of the entire dental arcades are crucial for a correct early diagnosis and treatment plan implementation. The increasing prevalence of fully erupted supernumerary teeth recorded in older groups suggested a late onset eruption process, and therefore, in donkeys undergoing regular dental prophylaxis, the presence of previously unnoticed supernumerary teeth should always be sought.

Volume
25
Issue
7
Start page
363
End page
367
Publication date
Country

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.

Volume
176
Issue
3
Start page
345
End page
353
Publication date
Country

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.

Volume
176
Issue
3
Start page
338
End page
344
Publication date
Country

Dimensions of diastemata and associated periodontal food pockets in donkey cheek teeth

Equine cheek teeth (CT) diastemata often cause deep periodontal food pocketing and are therefore regarded as a painful dental disorder of equidae. However there appears to be no information available on the size or shape of these diastemata. This post mortem study examined 16 donkey skulls (mean age = 32-years) containing 45 CT diastemata to define the anatomical shape and dimensions of these diastemata, and of the associated periodontal food pockets that occur with this disorder. Diastemata were found to more commonly involve mandibular (56.0%) compared with maxillary CT (44.0%), and 71.0% of these diastemata had adjacent intercurrent dental disorders that may have predisposed donkeys to the diastemata. The median widths of all diastemata were 2.0-mm at the occlusal surface and 3.1-mm at the gingival margin, with no diferences in widths between the lateral or medial aspects of diastemata. Diastemata were defined as open (60.00%) or valve (40.00%) based on their gross appearance. This classification was confirmed to be accurate by measurements that showed valve diastemata to have an occlusal to gingival width ratio of 0.4, in contrast to open diastemata where this ratio was 1.07. Food was impacted in 89.0% of diastemata, but all diastemata had adjacent periodontal disease. Periodontal food pocketing was present adjacent to 76.0% of diastemata, more commonly on the lateral aspect (73.0% prevalence; mean pocket depth = 4.1-mm) than the medial aspect (47.0% prevalence; mean pocket depth = 2.4-mm). The depth of periodontal pockets of diastemata was not associated with the height of the erupted crowns of adjacent CT.

Volume
26
Issue
1
Publication date
Country

Comparison of the microhardness of enamel, primary and regular secondary dentine of the incisors of donkeys and horses

The microhardness of the enamel, primary dentine and regular secondary dentine of seven donkey and six horse incisors was determined with a Knoop indenter at the subocclusal and mid-tooth level. The mean microhardnesses of the donkey incisor enamel, primary dentine and secondary dentine were 264·6 63·00 and 53·6 Knoop Hardness Number, respectively. There was no significant difference between the microhardness of the enamel and primary dentine on the incisors of the donkeys and horses, but the microhardness of the regular secondary dentine of the donkeys' incisors at the mid-tooth level was slightly but significantly less than that of the horses. There was also a difference in the microhardness of the secondary dentine between the subocclusal and mid-tooth levels in both donkey and horse incisors.

Because most donkeys live well beyond 30 years of age (Crane 1997), it has been proposed that their teeth may be harder than the teeth of horses, wear more slowly, and thus remain functional for longer (Misk and Seilem 1999). There have been studies of dental microhardness in human beings (Craig and Peyton 1958, Collys and others 1992), sheep (Suckling 1979), cattle (Attin and others 1997) and horses (Muylle and others 1999b). In horses, there are differences between breeds in the rate of dental wear caused by attrition (Muylle and others 1997, 1998) and in the microhardness of enamel and secondary dentine (Muylle and others 1999b), which could account for these differences. It is proposed that there may be a similar difference between the microhardness of the teeth of donkeys and horses that may contribute to the less rapid attrition of donkey teeth.

The aim of this study was to compare the microhardness of the enamel and primary and secondary dentine of the incisor teeth of donkeys and horses, to determine whether there was a significant difference between them.

Volume
162
Issue
9
Start page
272
End page
275
Publication date

Common dental disorders in the donkey

Normal dental anatomy and the range of dental disorders found in donkeys are largely similar to those described in horses. Recent studies have shown dental disease to have a high prevalence in donkeys. Some dental disorders, such as diastemata, displaced teeth and wave mouth can have serious clinical consequences by causing oral pain and weight loss and even predispose to colic. Many of these signs can be prevented by regular dental treatment that can slow down or even prevent the progression of these disorders.

Publication date

Colic in the donkey

The donkey is a unique species of equine, with certain specific variations and adaptations that differ from its cousin the horse. The donkey is used by humans as a pack and draft animal in areas of the world where its ability to cope with low‐quality fiber and harsh conditions have excluded the horse. This chapter highlights the differences in anatomy and particularly physiology that have enabled the donkey to fulfill these roles. One of the consequences of being equipped to survive in areas of food scarcity is the tendency to deposit adipose if conditions are reversed. This fact, combined with insulin resistance, leads donkeys rapidly to become metabolically compromised and develop hyperlipemia as a response to stress and sudden reduction in appetite. The consequence is that many donkeys with colic must also be treated for hyperlipemia, which may have a higher mortality rate than the primary condition. Pain behaviors in the donkey may be more subtle than those in the horse and therapeutically there are differences in drug metabolism between donkeys and horses. This chapter summarizes the types of colic that occur in the donkey in relation to anatomic location and as a consequence of management and environmental factors.

Chapter number
38
Start page
471
End page
487

Anatomical, pathological and clinical study of donkey teeth

Eighty normal cheek teeth and 26 normal incisors extracted from 14 donkeys (median age 19 years) at post mortem were anatomically examined including grossly and by computerised axial tomography (CAT) imaging. Decalcified histology was performed on 54 sections from 18 teeth (8 donkeys), undeclacified histology on 16 sections from 7 donkeys and scanning electron microscopy on 10 sections from 10 teeth (3 donkeys). The dental formulae and tooth number was found to be the same as in horses with a higher prevalence (17 %) of canine teeth in female donkeys. A decrease in tooth length, pulp horn length and pulp horn width with age was illustrated, as was an increase in occlusal secondary dentine depth with age, although not all these age changes were statistically significant. Normal histological and ultrastructural features of donkey teeth were identified and found to be similar to equine findings. Enamel was found to be thicker buccally in both maxillary and mandibular cheek teeth. Quantitative measurements of transverse dentine thickness around pulp cavities, dentinal tubule diameters and densities, and enamel prism diameters were made. Left lower incisors (301) were extracted from 7 donkeys and 6 horses for micro-hardness determination of enamel, primary and secondary dentine using a Knoop Hardness indenter. No significant difference between donkey and horse incisor microhardness was demonstrated.

Examination of 19 donkey skulls at post mortem examination showed donkeys to have a higher degree of anisognathia (27%) compared to horses (23%). Post mortem dental examination of 349 donkeys (median age 31) demonstrated a high prevalence of dental disease (93%) and in particular cheek teeth diastemata (85%). Furthermore, age was associated with increasing prevalence of dental disease and diastemata. Diastemata were also associated with the presence of other dental disorders and with colic-related death in affected donkeys. Quantitative measurements of 45 diastemata from 16 donkeys showed no difference in the medial and lateral width of diastemata but periodontal pockets were deeper laterally. The definition of valve and open diastemata were confirmed. Pulp exposure, dental caries and periodontal disease were examined in detail (54 skulls) at post mortem. A total of 19 teeth were extracted for further detailed examination as performed in normal anatomy.

Clinical dental examinations were performed on 357 donkeys in the U.K. that were selected for age distribution, and the prevalence of dental disease in different age groups was found to increase from 28% in the youngest group (age 0-10 years) to 98% in the oldest group (age > 35 years). An increased prevalence of most dental disorders with age was demonstrated as was an association between dental disease and weight loss, poor body condition score, supplemental feeding and previous episodes of colic. Clinical dental examination of 203 working donkeys in Mexico showed similar types of dental disorders as found in the U.K. study, with dental disease present in 62%, of which 18% required urgent dental treatment. There was a significant association between age groups and dental disease, and age groups and body condition score, but there was no association between dental disease and body condition score. However, body condition score was not associated with supplemental feeding or faecal egg counts either.

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