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The sheath is also responsible for multiple or accessory roots (medial growth) and lateral or accessory canals in the root (break in epithelium). [3] It is controversial, but HERS may be involved in cementogenesis and the secreting of cementum, or that HERS-derived products might be related to enamel-related molecules, and that these proteins might initiate acellular cementum formation.
The sheath is irregularly fragmented in time and space as it promotes cementum deposition on the newly formed dentin. After this fragmentation, Hertwig's epithelial root sheath also participates in cementogenesis and formation of the periodontal ligament, giving rise to the epithelial rests of Malassez
It is thought that the central epithelial tissue of the cervical loop, the stellate reticulum, acts as a stem cell reservoir. In continuously growing teeth such as the rodent incisor the original structure of the cervical loop is maintained and no HERS forms. The stem cells provide the epithelial progeny to sustain the continuous growth.
Tooth development begins at week 6 in utero, in the oral epithelium. The process is divided into three stages: Initiation; Morphogenesis and; Histogenesis [2]; At the end of week 7 i.u., localised proliferations of cells in the dental laminae form round and oval swellings known as tooth buds, which will eventually develop into mesenchymal cells and surround the enamel organ.
For cementogenesis to begin, Hertwig epithelial root sheath (HERS) must fragment. HERS is a collar of epithelial cells derived from the apical prolongation of the enamel organ. Once the root sheath disintegrates, the newly formed surface of root dentin comes into contact with the undifferentiated cells of the dental sac (dental follicle).
The dental lamina is a band of epithelial tissue seen in histologic sections of a developing tooth. [1] [2] The dental lamina is first evidence of tooth development and begins (in humans) at the sixth week in utero or three weeks after the rupture of the buccopharyngeal membrane. It is formed when cells of the oral ectoderm proliferate faster ...
Root sheath may refer to any of these biological structures: Epithelial root sheath, a proliferation of epithelial cells located at the cervical loop of the enamel organ in a developing tooth; Root sheath (hair), at the base of a hair follicle Inner root sheath; Outer root sheath; Seed root sheath, root sheaths in the seeds of plants
In dentistry, the epithelial cell rests of Malassez (ERM) or epithelial rests of Malassez (pax epithelialis pediodontii) are part of the periodontal ligament cells around a tooth. They are discrete clusters of residual cells from Hertwig's epithelial root sheath (HERS) that didn't completely disappear.