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1.
A H Andrews 《Research in veterinary science》1975,19(3):322-326
Radiographs were taken of both the right and left sets of maxillary teeth in 23 Friesian cattle of known age. The stage of development of each permanent tooth was ascertained and the degree of root resorption in the deciduous premolars was noted. All stages in individuals were later than for those of the mandibular cheek teeth except in the case of the first permanent premolar. As with mandibular cheek tooth development stages of formation occurred within certain age limits. 相似文献
2.
A H Andrews 《The Veterinary record》1975,97(13):244-248
The mandibles of 78 Hereford cross Friesian steers all showing a full complement of temporary teeth were examined both visually and by radiography to determine whether it was possible to differentiate their various ages. All but one animal were slaughtered at the same weight (1020 lb-464 kg) and their ages at slaughter ranged from 1 year 3 months to 1 year 9 months. Differences were found between the mean ages for stages of resorption of the first temporary incisor roots, stages of first permanent incisor root formation and stages of second incisor crown formation, as determined by radiographic inspection. The results indicated that the age of a group of animals could be defined, but the age range within each development stage meant that it was not possible to define the age of individual cattle. 相似文献
3.
A. H. Andrews 《The Veterinary quarterly》2013,33(1):9-18
Summary The development of the mandibular cheek teeth was examined, both visually and by radiograph, in a group of 76 Hereford cross Friesian steers, of which all but one were slaughtered at the same weight ‐ 464 kg (1020 lb). The age of the youngest animal was 1 year 0.3 months whereas the slaughter ages of the others ranged from I year 3 months to I year 8 months. The first molar was fully erupted and crown and root formation complete in all but the youngest steer. In the other five cheek teeth there were one or more siginificant differences between the mean ages of tooth development stages as assessed by radiograph. Cattle of 1 year 3 months could not be absolutely distinguished from those of 1 year 8 months by intra‐oral second molar eruption. Examination of stages of development seen radiographically gave a maximum age range of 4 months before differentiation. In this study, development bf the first two molars was in advance of the three permanent premolars and in these latter teeth the second premolar was the most developed. 相似文献
4.
J L Shupe P V Christofferson A E Olson E S Allred R L Hurst 《American journal of veterinary research》1987,48(10):1498-1503
Teeth from cattle, sheep, and horses that ingested various fluoride intakes and teeth from field studies of these species plus deer, elk, and bison were examined for abnormalities. Approximately 99,000 animals in 322 herds were examined for fluorosis. From field studies, 988 cattle of various ages and with different degrees of dental fluorosis were slaughtered and necropsied. The severity of fluoride-induced mottling, hypoplasia, and abnormal abrasion of paired permanent incisor teeth was correlated with abrasion of premolar and molar (cheek) teeth that form and mineralize at approximately the same age. Severe irregular wear of cheek teeth impaired mastication and resulted in poor utilization of feed and unthriftiness. Excessive amounts of fluoride during tooth formation and mineralization induce characteristic dental changes. Offspring from the fluoride-affected animals did not have discernible fluoride-induced lesions in the deciduous teeth. 相似文献
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Observations on a sizeable collection of purebred canine fetuses of known age has afforded the opportunity to report baseline data on the timing of tooth germ development in the dog. The chronology of development of the deciduous dentition has been studied in a collection of 172 embryos and fetuses from purebred Beagles of known gestation. Microscopic examination of serial sections, enlarged reconstructions from serial sections and alizarin-stained clearings were used to visualize stages of development. These observations establish that the dental lamina is initiated at 25 days gestation and that calcification begins at 42 days in the deciduous teeth. 相似文献
7.
Reasons for performing study: There are few published data to support the ages of emergence of permanent dentition widely reported in horses. Objectives: To clarify the chronology and sequence of permanent premolar (PM) tooth emergence in Thoroughbred racehorses. Methods: A prospective study was undertaken in which records were kept of deciduous PM ‘cap’ extractions performed during routine dental examinations in Thoroughbred racehorses. Mixed effects multiple regression analysis was used to relate the observed ages, measured in days, for PM ‘cap’ extractions simultaneously with different predictive variables. Care was taken to account for clustering of multiple observed outcomes within individual horses. Results: A total of 508 deciduous premolar ‘caps’ were removed from 207 horses, mean ages at removal from PM2, PM3 and PM4 were 35.1, 37.7 and 45.1 months, respectively. Age at which deciduous ‘cap’ removal occurred was associated significantly with tooth row, upper or lower jaw and gender of the horse concerned. There was a significant trend for later ‘cap’ extraction age with more caudal teeth, teeth in the upper jaw and female gender. Conclusions: Age at removal of deciduous premolar ‘caps’ in this population differed considerably from the ages of emergence of permanent dentition reported widely in equine publications. The results provide the first evidence of sexual dimorphism in the eruption of the permanent premolar dentition in horses. These findings strongly support a model of cheek tooth eruption in the horse in which chronology and sequence of emergence are more complex than previously thought, but which is consistent with understanding of tooth eruption in species that have been studied in greater detail. Potential relevance: Abnormalities of cheek tooth eruption are thought to be a factor in the pathogenesis of a variety of dental conditions, and a thorough understanding of the process of eruption is fundamental to the development of rational strategies for prevention and treatment. 相似文献
8.
Thurley DC 《New Zealand veterinary journal》1984,32(3):25-29
The teeth and various supporting and ancillary tissues were examined post mortem from two flocks of sheep, one of which had previously shown high deciduous incisor wear. Sheep were killed in groups selected on clinical signs at equivalent ages from birth to 116 weeks of age. At the end of this time the lengths of clinical crowns of the remaining deciduous incisor teeth in the high wear flock were not measurable, whereas the other flock had up to 5.5 mm in visible crown. Using the cingulum as a marker, measurements were made from extracted teeth of the attrition of the crown and size of the root. The tooth root did not grow substantially longer after the 13th week of the sheep;s life. Wear facets were just visible in some sheep at six weeks. More rapid wear occurred three times in the high wear flock. The first of these was relatively small and occurred between the 13th and 27th week of age in I1 and I2. The second was larger and occurred between the 38th and 57th week of age in the winter/spring period. A third period of wear, which was not measured from the cingulum, because this structure had by then been worn away, was seen in the remaining deciduous teeth between the ages of 91 and 110 weeks of age, i.e., during the second winter and spring. In the low wear flock the first of these periods of wear did not occur, the second was of shorter duration and smaller size, and the third equivocal. Eruption of the teeth after the 6th week was principally passive. There was no difference in the degree of wear of the molar teeth from the two flocks. Histological examination showed that the wear was compensated for by the deposition of reparative dentine in the pulp cavity. This usually gave the appearance of an ordered process. However, when wear was excessively rapid, a different, less orderly form of reparative dentine was laid down. In a few cases the reparative process was not fast enough, and a connection developed between the mouth and the pulp causing pulpitis. There was no histological evidence that the supportive tissues of the teeth, or the upper dental pad, contributed to the excessive wear. 相似文献
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10.
In three donkeys the postnatal development of the teeth was studied at close intervals up to two years of age in one case and up to 5½ years in the other two cases. The findings were checked against the teeth in fÜrther 27 donkeys of known ages and two donkeys of estimated ages. The incisors were studied primarily by inspection and palpation, but also radiographically; whilst the cheekteeth were examined mainly radiographically.
The teeth of the donkey are narrower than those of the horse, and their replacement occurs about 3 months later than in the horse. 相似文献
The teeth of the donkey are narrower than those of the horse, and their replacement occurs about 3 months later than in the horse. 相似文献
11.
D C Thurley 《Research in veterinary science》1985,39(2):127-138
The development of permanent incisor teeth of sheep was followed from the age of six weeks to 116 weeks. The teeth were observed through the bud, cap and bell stages, and the development of enamel and dentine. At the same time that amelogenesis started, the papillary layer developed from the intermediate layer and the outer dental epithelium began to form the cell rests of Malassez. The ameloblasts went through secretory, transitional and maturational phases, and in due course disappeared, after which cementum was laid down over the enamel surface. Initially the connective tissue of the follicle surrounding the growing tooth was very loose, but was replaced from the crown end as the tooth developed, by more dense connective tissue. Around the time of eruption, melanocytes were found on the lingual surface of the coronal end of the follicle. The root was formed under the influence of Hertwig's epithelium, and the cell rests of Malassez appeared to continue to develop from the outer enamel epithelium. Odontoblasts, which arose from the pulp connective tissue, were initially cuboidal but became fusiform as the tooth matured. At the time of eruption, amelogenesis was almost complete and cementum covered the majority of the tooth surface. The cell rests and melanocytes of the tootth follicle appeared to migrate with the tooth as it erupted. The deciduous tooth was resorbed from the lingual surface. The junctional epithelium of the erupted permanent tooth may have arisen from the cell rests, remnants of the dental lamina or gingival epithelium, depending on the presence or absence of inflammation. 相似文献
12.
Nemec A Pavlica Z Stiblar-Martincic D Petelin M Erzen D Crossley D 《Journal of veterinary dentistry》2007,24(4):212-223
The purpose of this investigation was to evaluate the pulp of dog teeth affected by advanced periodontal disease. Histological examination was done on demineralized teeth extracted during clinical treatment of mature, client owned small and medium-size breed dogs with either good periodontal health or with advanced naturally occurring periodontal disease. Routinely stained sections from 5 clinically normal teeth and 22 teeth with advanced periodontitis from dogs between 5 and 12-years of age were examined using light microscopy. The pulp cavities of most teeth were narrow with low cellularity and some fibrosis of the pulp. Findings specific to periodontally affected teeth included acute and chronic pulpitis, vascular congestion, and pulp necrosis. A glomus body was identified in the pulp of one tooth and areas of poorly mineralized cementum were seen in both normal and diseased teeth. Age related changes in dog teeth appear similar to those reported for man and the rat. In addition to age related changes, the pulp of dog teeth with advanced periodontal disease were frequently inflamed or necrotic. This may reflect the advanced periodontitis affecting these teeth or a mechanical effect related to excessive tooth mobility. Further study is required to determine the etiology and significance of these findings and to investigate pulp status in less severely diseased teeth. 相似文献
13.
H Isogai E Isogai H Okamoto H Shirakawa F Nakamura T Matsumoto T Watanabe H Miura Y Aoi W Kagota 《Nippon juigaku zasshi. The Japanese journal of veterinary science》1989,51(6):1151-1162
The prevalence of dental disorders in dogs was studied by applying index systems for human with some modifications. A total of 251 mongrel dogs including 143 stray dogs kept in the Animal Protection Offices in Tokyo and Hokkaido and 108 pet dogs visiting veterinary clinicians in Chiba Prefecture and Hokkaido were used. Periodontitis was prevalent among these dogs regardless of their sources and its incidence was increased with age. The lesion was more severe and more frequent in the premolar and molar regions than in the maxillary and mandibular incisor regions. Missing of teeth was observed at a high and increasing incidence with age. The tooth most commonly lost was the first premolar, followed by the other premolars and molars, where severe periodontitis was frequently found. Calculus was seen on many teeth, and aging agravated its prevalence and severity. Dental caries was observed in stray dogs, but neither to a serious degree nor at a significant level. These findings emphasize the necessity of dental hygiene, proper dental care and continuous periodical survey for dogs. 相似文献
14.
A. S. Davies 《Anatomia, histologia, embryologia》1990,19(3):269-275
Postnatal development of the teeth of German Landrace and Göttingen Miniature pigs was studied by measuring the areas of each tooth visible on lateral radiographs of the mandibles. It was concluded that the appearance of the teeth at each stage, and the relation of their growth to that of the rest of the masticatory apparatus, relates mainly to postnatal changes in the relative location of the jaw pivot. 相似文献
15.
The objective of this study was to examine the spatial arrangement of the fiber apparatus of the equine periodontium which is supposed to meet two contrary requirements: (1) to attach the tooth firmly and elastically to the alveolar bone; and, to be appropriately remodeled and reconstructed in order to facilitate the prolonged eruption of the tooth. Specimens of periodontal ligament were obtained from the buccal and lingual/palatal aspects of the first molars from the maxilla and mandible of 12 horses. The animals were assigned to three age groups. Histological sections were prepared from three specific horizontal levels of the periodontal ligament and examined with conventional and polarized-light microscopy. At the gingival level, collagen fascicles (diameter > 200 microm) were densely packed. Their spatial alignment was the same in all age groups. The architecture of the collagen fiber apparatus differed at the middle and apical levels in the three age groups. There was a clear distinction between fibers, bundles, and fascicles. Bundling of collagen fibers, density of the fiber arrangement, and collagen fascicles with an alveolo-cemental orientation increased with age. The collagen fiber apparatus of the equine periodontal ligament is highly adaptive, responding continuously to the dynamic changes in the periodontal environment. Site-specific arrangements and age-dependent structural variations are assumed to maintain tooth support as the reserve crown gradually decreases in length with progressive dental attrition. Most of the age-dependent changes to the periodontal ligament in teeth examined in this study occurred at the apical level. The apical region of young teeth had no periodontal attachment, while the roots of older teeth were firmly attached to the alveolus. When evaluating periodontal ligament development, the individual tooth's 'dental age' should be considered rather than the animal's age to account for individual tooth eruption times. 相似文献
16.
Wasike CB Indetie D Pitchford WS Ojango JM Kahi AK 《Tropical animal health and production》2007,39(7):493-505
Data consisting of 18 884 weight records collected from 1273 Boran cattle from birth to 24 months of age were used to estimate covariance functions and genetic parameters for growth of Boran cattle using random regression (RR) models under a situation of small herd size and inconsistent recording. The RR model fitted quadratic Legendre polynomials of age at recording for additive genetic and permanent environmental effects. Genetic variance increased from birth, reaching an asymptotic value at 455 days and was maximum at 525 days of age after which it gradually dropped. Permanent environmental variance increased throughout the trajectory. Estimates of temporary environmental variance were heterogeneous across ages. Direct heritability and permanent environmental variance as a proportion of phenotypic variance fluctuated greatly during the early ages but later stabilized at intermediate to later ages; the estimates ranged from 0.11 to 0.33 and from 0.18 to 0.83, respectively. Genetic correlation estimates were positive, ranging from 0.10 to unity. The estimates declined with increasing in lag between the age points. Phenotypic correlation pattern was erratic between early ages, negatively low (-0.02) between the extreme data points and moderate to highly positive (>0.50) between intermediate and later points, with prominent spikes along the diagonal. It is concluded that RR models have potential for modelling growth of Boran cattle, notwithstanding conditions of small herd sizes and inconsistent recording. 相似文献
17.
试验旨在构建新疆褐牛不同生长阶段体尺体重性状的遗传参数估计模型,估计新疆褐牛生长发育性状的遗传参数,为新疆褐牛育种目标性状的确定和综合选择指数的制定提供理论依据。以1983－2017年收集的4个新疆褐牛核心育种场81头公牛后代的2 504条新疆褐牛体尺体重数据为研究材料,以初生及6、12和18月龄阶段的体重、体高、体斜长和胸围性状为研究对象,通过DMU软件构建多性状动物模型,以场、出生年份、出生季节和性别为固定效应,以加性效应和母体效应为随机效应,估计各性状的遗传力和遗传相关。结果显示,新疆褐牛初生至18月龄阶段体重遗传力估计值为0.22~0.61,体高遗传力估计值为0.43~0.46,体斜长遗传力估计值为0.29~0.52,胸围遗传力估计值为0.35~0.61。相同和不同生长阶段新疆褐牛各体尺体重性状间均呈现正的遗传相关和表型相关,其中相同生长阶段各体尺体重性状间的遗传相关系数为0.11~0.92,表型相关系数为0.05~0.92;不同生长阶段各体尺体重性状间的遗传相关系数为0.08~0.92,表型相关系数为0.01~0.72。18月龄与其他各生长阶段间体尺体重性状的遗传相关系数较高,且均属于中高遗传力性状。因此,在制定新疆褐牛综合选择指数时,应重点考虑18月龄阶段的体尺体重性状,从而进一步提升新疆褐牛生长发育性状的遗传进展。 相似文献
18.
The study describes crown and root formation of the permanent mandibular cheek teeth of fallow deer from a gestational age of 22–23 weeks up to a post‐natal age of 33 months. Tooth development was recorded using a scoring scheme based on morphological criteria ranging from crypt formation to completion of root growth. The morphological appearance of the enamel surface during three different stages (secretory‐stage enamel, maturation‐stage enamel and mature enamel) was described, and the approximate age at termination of the secretory stage of amelogenesis in the deciduous and permanent mandibular cheek teeth was determined. The data enable an age estimation of fallow deer up to 3 years of age and provide a basis for assessing the timing of stress episodes that affect tooth crown formation. This information is useful for the management of the species as well as in bioarchaeological and bioindication studies. 相似文献
19.
Lewis JR Okuda A Shofer FS Pachtinger G Harvey CE Reiter AM 《Journal of veterinary dentistry》2008,25(2):86-95
Abnormal extrusion of canine teeth is often noted in middle-aged and geriatric domestic cats. The same age group of cats also is commonly affected by tooth resorption (TR). This study explored the relationship between these two phenomena of unknown etiology. Using digital radiography, the distance between the alveolar margin (AM) and cementoenamel junction (CEJ), referred to as the AM-CEJ distance, was measured in clinically and radiographically healthy maxillary canine teeth of 24 TR-affected and 29 TR-free cats. The mean AM-CEJ distance of maxillary canine teeth of cats with and cats without TR was 2.68-mm and 2.22-mm, respectively. An analysis of covariance adjusting for age revealed a significant correlation (p = 0.02) between tooth extrusion and TR. Extrusion of the maxillary canine teeth became clinically apparent when an AM-CEJ distance of 2.5-mm or greater was evident in the absence of horizontal or vertical alveolar bone loss. Based on this criterion, 15 of 24 cats with TR (63.0 %) exhibited extrusion of maxillary canine teeth, compared to 9 of 29 cats without TR (31.0 %). Four extruded and five non-extruded maxillary canine teeth were evaluated histologically. Cementum of extruded teeth was significantly thicker compared to that of non-extruded teeth. Four of 4 canine teeth with extrusion (100 %) showed histological evidence of resorption, compared to 1 of 5 canine teeth without extrusion (20.0 %). These results suggest that tooth extrusion is linked to or may be caused by similar factors responsible for the development of TR. 相似文献