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The Hertwig epithelial root sheath (HERS) or epithelial root sheath is a proliferation of epithelial cells located at the cervical loop of the enamel organ in a developing tooth. Hertwig epithelial root sheath initiates the formation of dentin in the root of a tooth by causing the differentiation of odontoblasts from the dental papilla.
During root formation the inner layers of epithelium disappear and only the basal layers are left creating Hertwig's epithelial root sheath (HERS). At this point it is usually referred to as HERS instead of the cervical loop to indicate the structural difference.
Radicular type: occupying most of the crown and root involving invagination of Hertwig's epithelial root sheath, lined with cementum. [20] Dens invaginatus has a clinical importance as teeth affected with dens invaginatus are predisposed to developing pulpal disease. The invagination allows entry of irritants into an area which is separated ...
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.
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
The inner root sheath (IRS) consists of: a delicate cuticle next the hair, composed of a single layer of imbricated scales with atrophied nuclei; Huxley's layer; Henle's layer; The term "trichilemmal" refers to the outer root sheath. [2] The IRS functions to mould, adhere, as well as participate in the keratinization of growing hair. [3]