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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.
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).
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.
Acellular cementum forms first. The cementoblasts differentiate from follicular cells, which can only reach the surface of the tooth's root once Hertwig's Epithelial Root Sheath (HERS) has begun to deteriorate. The cementoblasts secrete fine collagen fibrils along the root surface at right angles before migrating away from the tooth.
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.
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
The differentiation will extend down the slope of the dentine surface and reaches its limit, where the inner epithelium is fused with the outer enamel epithelium to form Hertwig's epithelial root sheath. Enamel mineral will increase daily (apposition growth) during the secretory stage of amelogenesis (enamel formation).
The most widely accepted theory suggests enamel pearls are formed from remnants of Hertwig’s epithelial root sheath (HERS), which adhere to the tooth surface after root development. [1] During normal tooth development, after dentin formation is initiated on the root surface, the root sheath disintegrates and moves away from the root allowing ...