HERTWIG’S EPITHELIAL ROOTH SHEATH

How a root is formed from hertwigs epithelial root sheath and functions of HER.

1. HERTWIG’S EPITHELIAL ROOTH SHEATH By SOFIA ALAM

2. DEFINITION HERS derives from the most apical extension of the enamel organ and consists of two cell layers, the inner and outer enamel epithelium.

3. BILAYERED Hertwig’s epithelial root sheath does not include stratum intermedium or stellate reticulum.

4. WHY IS THERE NO ENAMEL FORMATION IN HERS Absence of stellate reticulum. Cells of inner enamel epithelium remain short columnar and do not convert into tall columar ( ameloblasts ).

5. EPITHELIAL DIAPHRAGM The tip of the epithelial root sheath turns horizontally inwards; this turned in portion is known as epithelial diaphragm of root sheath

6. FORMATION OF HERS Hertwigs epithelial root sheath is formed when the coronal enamel and dentine reached future cemento -enamel junction.

7. INDUCTION OF DIFFERNTIATION Cells of hertwigs epithelial root sheath induce differentiation in radicular dental papillae cells that converts into odontoblasts . Odontoblasts subsequently differentiates into radicular dentine.

8. RESTS OF MALASSEZ After the first layer of radicular dentine has been laid down, the epithelial root sheath loses its structural continuity and its close relation to the surface of root. Its remnants persists as an epithelial network of strands near the external surface of root. The remnants are known as Rests of M alassez . These epithelial remnants are later found in periodontal ligament of erupted tooth.

9. ENAMEL PEARLS Also known as droplets of enamel. Fully functional cells that have the ability to form enamel. IF rest cells of malassez are still attached with dentine, then they become fully functional enamel producing cells called enamel pearls.

10. Determines the shape, size and number of roots. Plays a main character in differentiation of odontoblasts into radicular dentine. FUNCTIONS OF HERTWIGS EPITHELIAL ROOT SHEATH

11. Essential for the differentiation of dental follicle cells into periodontal structures. Rests of malassez play a fundamental role in root development, protect against root resorption .

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