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ExperimentaL Oral Medicine
Published in Samuel Dreizen, Barnet M. Levy, Handbook of Experimental Stomatology, 2020
Samuel Dreizen, Barnet M. Levy
Dental changes in the experimental animals were strikingly similar to those described in human material. Microscopically, there were abnormal formation or secretion of enamel-like substances subjacent to and within the cell cytoplasm, vacuolization of ameloblasts, complete cystic destruction of ameloblasts, and cessation of enamel formation, resulting in notchlike defects. Lesions were found in both incisors and molars. Dentinal changes were represented by wide prominent incremental lines reflecting long periods of arrested development. In many instances, the odontoblastic layer in the root portions of the teeth was absent. Subjacent pulp contained large irregular masses of pink-staining osteoid tissue in which tubules were frequently present. Many of the odontoblasts showed marked cystic changes.
Odontogenic Epithelium and its Residues
Published in Roger M. Browne, Investigative Pathology of the Odontogenic Cysts, 2019
Ameloblasts are known to undergo cytological modulations57,58 during their life-cycle. Changes in patterns of the secretory products of the ameloblasts, the amelogenin and enamelin matrix proteins, are seen through the secretory and maturation zones of the ameloblasts59–61 (Figure 2).
Bone, Muscle, and Tooth
Published in Pritam S. Sahota, James A. Popp, Jerry F. Hardisty, Chirukandath Gopinath, Page R. Bouchard, Toxicologic Pathology, 2018
John L. Vahle, Joel R. Leininger, Philip H. Long, D. Greg Hall, Heinrich Ernst
Figure 17.4a shows the structure of a fully developed rat incisor on an H&E slide. Ameloblasts, the cells that produce enamel, consist of a single row of columnar epithelial cells at the outer area of the tooth section. External to the ameloblasts is a layer of stratified epithelium, which is the remainder of the embryonic dental organ. Internal to the ameloblasts is enamel, but it may appear as a clear space in decalcified tooth sections; it is often lost during decalcification. The periodontal ligament, a connective tissue area well supplied with blood vessels and nerves, lies just external to the cementum-covered dentin. The periodontal ligament also contains the cells responsible for formation of cementum, the avascular bone-like material that helps anchor the tooth in its socket (alveolus). Cementum is present only on the concave/lingual aspect of rodent incisors.
Enamel multidien biological timing and body size variability among individuals of Chinese Han and Tibetan origins
Published in Annals of Human Biology, 2021
Hakan Karaaslan, Jeffrey Seckinger, Amel Almabrok, Bin Hu, Hui Dong, Dengsheng Xia, Tsering Dekyi, Russell T. Hogg, Jian Zhou, Timothy G. Bromage
Enamel, the outermost layer of the crown of a tooth, is formed by ameloblast cells in two consecutive stages – secretion and maturation – that are regulated by different genes and hormones (Simmer et al. 2010). Despite the fact that ameloblasts secrete a mineralisable matrix in a variety of functionally important patterns, they form enamel incrementally. So-called enamel rods develop perpendicular to the secretory pole of the cell, whereas the incremental growth lines – daily cross-striations and long period striae of Retzius – are observed as mineralising fronts perpendicular to the rods (Boyde 1964). These histological structures concealed beneath the intact tooth surface, which can be seen in Figures 1–3 by light microscopy, have a long history of observation and inquiry (Havers 1691; Retzius 1837; Andresen 1898; Schour and Poncher 1937; Boyde 1964; Dean 1987). Experimental studies have confirmed the daily secretion rhythm represented by enamel cross striations (Okada 1943; Bromage 1991), and more recently the 24-h rhythm in ameloblast molecular clock function has been demonstrated (Athanassiou-Papaefthymiou et al. 2011; Zheng et al. 2011; Lacruz et al. 2012; Zheng et al. 2013).
Dental stem cells in tooth regeneration and repair in the future
Published in Expert Opinion on Biological Therapy, 2018
Christian Morsczeck, Torsten E. Reichert
These tissues have specific functions for tooth development [11,14]. The human enamel organ, for example, contains dental epithelial stem cells [17]. These epithelial stem cells are precursor cells for ameloblasts which produce the enamel of the tooth crown. Unfortunately, the human enamel organ with all dental epithelial stem cells is lost after tooth eruption. So, unfortunately, the genuine progenitor cells for ameloblasts are not available, for example, for the (re-)generation of the dental enamel and for whole tooth engineering. Whole tooth engineering has been already achieved in mice with early tooth germ cells from the dental epithelium and the dental mesoderm [5]. Interestingly, recently, Xu et al. isolated undifferentiated dental epithelial cells from the human dental follicle of impacted third molar tooth, but in very small amounts [18]. However, further investigations are required to characterize human dental epithelial stem cells from the dental follicle or from the Hertwig’s epithelial rest of Malassez, which are epithelial cells of the mature periodontal ligament (PDL) [19].
Crown heights in the permanent teeth of 47,XXY males and 47,XXX females
Published in Acta Odontologica Scandinavica, 2022
Raija Pentinpuro, Raija Lähdesmäki, Paula Pesonen, Lassi Alvesalo
Interactions, gradients and spatial field effects of multiple genetic, epigenetic and environmental factors influence the development of individual teeth and tooth type [11]. Each tooth passes through a series of well-defined developmental stages [12] in which the enamel knots regulate the morphology and determine the sites of the tooth cusps. At the bell stage the mesenchymal odontoblasts differentiate first to form dentine, followed by the epithelial ameloblasts, which form enamel. All the permanent tooth crowns apart from those of the third permanent molars will reach their final size and shape between the ages of 3.3 and 7.4 years [13] and acquire their roots in certain phases by 15 years [14]. The X and Y chromosomes affect the crown sizes, root lengths and morphology of the teeth [15–30] usually resulting in larger mesiodistal and labiolingual crown dimensions in the deciduous and permanent teeth of 47,XYY males and the permanent teeth of 47,XXY males than those of male population controls [31,32], while in 47,XXX females the maximum mesiodistal diameters of the tooth crowns of the permanent incisors, excluding canines, are likewise greater than those of population control females [33]. Individuals with one extra sex chromosome, such as 47,XYY and 47,XXY males, have been reported to have longer tooth roots than the male population [34,35] and 47,XXX females to have longer tooth roots than the female population [36]. Previous results have shown increased numbers of taurodont mandibular molars in 47,XXY males and 47,XXX females [23,24,27–29,37] and an increased frequency of two-rooted mandibular premolars in 45.X and 45,X/46,XX females [17,29,30].