China
Africa
Explore chapters and articles related to this topic
Mesenchymal Stem Cells from Dental Tissues
Published in Vincenzo Guarino, Marco Antonio Alvarez-Pérez, Current Advances in Oral and Craniofacial Tissue Engineering, 2020
Febe Carolina Vázquez Vázquez, Jael Adrián Vergara-Lope Núñez, Juan José Montesinos, Patricia González-Alva
During tooth development, root formation begins with the apical proliferation of epithelial cells from the cervical loop. Then, proliferating epithelial cells give shape to the apical papilla, a soft tissue found at the apices of developing permanent teeth. The dental papilla contributes to tooth formation and is eventually converted into pulp tissue (Liu et al. 2015; Sonoyama et al. 2006).
The Cell Biology of Amelogenesis
Published in Colin Robinson, Jennifer Kirkham, Roger Shore, Dental Enamel, 2017
Ziedonis Skobe, Doris N. Stern, Kenneth S. Prostak
Amelogenesis is preceded by early events of tooth development divided into the initiation, morphogenetic, and cytodifferentiation phases.1 Teeth develop from a series of reciprocal interactions between oral epithelium and mesenchyme of the first branchial arch.2 The embryonic oral epithelium (or stomodeal ectoderm) is separated from the underlying connective tissue by a basal lamina. The first evidence of odontogenesis (the initiation phase) is the thickening of the oral epithelium, forming the primary epithelial band, which is the initial site of tooth specification.2 Increased mitotic rates in these epithelial thickenings results in a downgrowth of cells into the mesenchyme to form the dental lamina. The bud or terminus of the dental lamina gradually forms a cap-shaped epithelial structure, which surrounds condensed dental papilla mesenchyme at the sites around the arch where the teeth will form. At this stage of morphogenesis, the cap consists of an inner enamel epithelial (IEE) layer and an outer enamel epithelial (OEE) layer surrounded by a basal lamina.3'4,5 Cells of the stratum intermedium (SI) and stellate reticulum (SR) differentiate between the two layers. The edge of the cap, where the IEE and OEE meet, becomes the cervical loop, or proliferative epithelial region of the developing tooth.
Odontogenic Epithelium and its Residues
Published in Roger M. Browne, Investigative Pathology of the Odontogenic Cysts, 2019
During the later stages of crown formation, the development of the root begins. In the area of the cervical loop, the inner and outer enamel epithelium are continuous and with proliferation and downward growth of this bilaminar structure (Hertwig’s epithelial root sheath), the root is mapped out. This epithelial root sheath promotes the differentiation of root odontoblasts as well as being important in cementum formation. The inner epithelial layer of the root sheath is separated from the pulpal mesenchyme by a basement membrane that stains more strongly for fibronectin than the basement membrane on its enamel epithelial layer.62 Laminin and type IV collagen, however, appear to be more evenly distributed. Pulpal mesenchymal cells align themselves perpendicular to the inner basement membrane prior to differentiation into odontoblasts. A close relationship between the fibronectin and mesenchymal cell alignments along the inner basement membrane has been suggested.62,63 Thus, root and crown odontoblast differentiation appear to be similar processes although it has been reported64 that conversion of pre-dentin to dentin is faster in the root than crown analog of the mouse incisor. The inner cells of the epithelial root sheath do not differentiate into ameloblasts and after pre-dentin secretion, the basement membrane becomes discontinuous and these cells lose their cuboidal shape becoming progressively more flattened. The cells are thought to have a short secretory phase prior to fragmentation of the sheath65,70 giving rise to a matrix, which is thought to contribute to the intermediate cementum observed between dental cementum and Tomes’ granular layer in the tooth root. Similarities between intermediate cementum and the innermost, aprismatic layer of enamel have been reported,68,70 and it has been shown that the initial cementum exhibits immunoreactivity to enamel proteins,71,72 although this has not been confirmed.73 After tooth sheath fragmentation, the thin layer of matrix derived from it may be responsible for inducing cells of the dental follicle to differentiate into cementoblasts. Interestingly, cementum-like matrix has been observed on the enamel surface of teeth taken from 9-day-old mice in which the ameloblasts had been removed and the teeth re-inserted crown downwards into their bony crypts followed by transplantation in the subcutaneous tissue of hosts.74 The epithelial root sheath fragments persist in close proximity to the root surface as cell clusters in the periodontal ligament where they are known as the epithelial rests of Malassez.75
Cervicogenic dizziness alleviation after coblation discoplasty: a retrospective study
Published in Annals of Medicine, 2021
Liang-liang He, Ru-jing Lai, Jacqueline Leff, Rong Yuan, Jian-ning Yue, Jia-xiang Ni, Li-qiang Yang
Abnormal afferent inputs from the Ruffini corpuscles of the facet joints and the muscle spindles to the vestibulospinal nucleus in the degenerative cervical spine are considered as major pathological sources of CGD [9–11]. As the essential mechanoreceptive signal transport pathway in the cervico-vestibulo-cervical loop, cervical nerve root also possibly provokes CGD because of herniated cervical disc compression [5,12]. Besides, studies indicated that degenerative cervical discs have an abundant distribution of Ruffini corpuscles [13,14], which project abnormal proprioceptive inputs to C2–C8 of the dorsal root ganglion [15] and then reach the vestibulospinal nucleus [5]. (Figure 1) The contribution of degenerative cervical discs to CGD is further identified by desirable improvement following anterior cervical decompression and fusion [14,16,17].