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Experimental Stomatology
Published in Samuel Dreizen, Barnet M. Levy, Handbook of Experimental Stomatology, 2020
Samuel Dreizen, Barnet M. Levy
Microscopic changes were present in the ameloblasts, odontoblasts, and enamel organ. There were focal areas of degeneration in the ameloblastic layer, atrophy and complete disappearance of the lingual odontoblasts, and enlargement and hyperplasia of the labial odontoblasts. The lingual dentin was resorbed and eventually lost, permitting embryonic pulp cells to grow unrestrained into the surrounding soft tissue and form tumor masses.
Oral cavity
Published in Paul Ong, Rachel Skittrall, Gastrointestinal Nursing, 2017
The cap stage commences around week 10 gestation. The epithelial tissue continues to grow into the underlying mesenchyme and takes on the appearance of a cap. The structure is now called the enamel organ. It contains a group of star-shaped cells and aminoglycans called the stellate reticulum. These attract water and swell inside the enamel organ. The enamel organ, as the name suggests, is responsible for the production of enamel that covers the external surface of the tooth.
Preclinical characterization of bemarituzumab, an anti-FGFR2b antibody for the treatment of cancer
Published in mAbs, 2021
Hong Xiang, Abigael G. Chan, Ago Ahene, David I. Bellovin, Rong Deng, Amy W. Hsu, Ursula Jeffry, Servando Palencia, Janine Powers, James Zanghi, Helen Collins
Bemarituzumab administered to rats resulted in treatment-related findings at all dose levels with a clear dose relationship: most of the effects were more pronounced for animals given doses of 5 mg/kg and 100 mg/kg. The most prominent findings were incisor abnormalities (missing incisors, malocclusion, and discolored white teeth) that were accompanied by body weight loss and lack of weight gain caused by the decreased food intake due to the incisor deformation. Histopathologically, dysgenesis of the incisor was observed and the oral tissue demonstrated increases of ulceration and inflammatory cell infiltrates, most likely caused by the teeth malformation. Dysgenesis of the upper incisor teeth were characterized by primary and secondary changes. Primary changes included the complete loss of the enamel organ (replacement of the enamel organ by a thick zone of dense connective tissue resembling periodontal membrane) and disorganization of the pulp cavity and associated odontoblast and dentin layers. Primary changes were regularly accompanied by changes interpreted to be secondary to incisor malformation. These included remodeling of the tooth alveolus, increased thickness of the periosteum, scalloping of bone at the alveolar margin, formation of new woven bone at the alveolar margin, and the extension of new bone into the alveolar space and/or malformed tooth. The changes in teeth were consistent with the observation that FGFR2b signaling controls regeneration of rodent incisors, which is a rodent-specific phenomenon.18–20
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].
Dental stem cells for tooth regeneration: how far have we come and where next?
Published in Expert Opinion on Biological Therapy, 2023
At the beginning of tooth development in the first (mandibular) arch of an embryo the tooth germ consists of two tissues: the dental mesoderm, which originates from neural crest cells, and the dental ectoderm, which is part of the surface ectoderm [3,4]. These two types of cells are the origin of the tooth germ and make up the entire tooth [5]. However, during development these two dental cell types become three tissues, one derived from the ectoderm – enamel organ – and two from the mesoderm – dental papilla and dental follicle (dental sac) [6,7]. While the enamel organ is the source of ameloblasts and is heavily involved in tooth crown morphology, some dental epithelial cells become Hertwig’s epithelial root sheath cells involved in tooth root development [8]. The dental mesodermal tissues deliver stem cells for the development of the tooth root and the dental pulp/dentin complex [9]. Interestingly, both dental mesodermal tissues can be harvested from impacted wisdom teeth and their stem cells isolated and used for different applications [10]. In contrast, the enamel organ and most dental ectodermal cells are lost beforehand. Only epithelial rests of Malassez can be obtained for example from impacted wisdom teeth, but a significant number of dental ectodermal progenitor cells cannot be isolated from this source [11,12]. Moreover, these cells are not the genuine progenitors for ameloblasts and it remains nuclear whether they can be used as ectodermal tooth germ cells in whole tooth regeneration approaches, which is the most advanced goal in regenerative dentistry. This article first summarizes the state of the art in tooth engineering.