Type of cementum coronal 2/3 of root:
1- acellular intrinsic fiber
2- acellular extrinsic fiber ****
c- Mixed
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Coronal cementum development:
Coronal cementum is formed in the cervical portion of the crown, its presence is restricted in localized areas of reduced epithelium of degenerate enamel. Enamel exposed as a result of epithelial degeneration provides a surface on which dental follicle cementoblasts are able to deposit cementum. Coronal cementum has no anchoring function. In histological sections this may appear as a cement "insula" on the cervical enamel surface or as a continuous cement "spur" with the root cementum and overlapping the cervical enamel. Most often, the coronal cementum is acellular and fibrillating.
Root cement development:
Root formation is dependent on the orderly growth of the Hertwig epithelial sheath, formed by the fusion of the inner and outer epithelia of the enamel organ, consisting of two rows of cubic or polyhedral cells.
Internal epithelial cells induce differentiation of connective tissue cells (dental papilla) into odontoblasts and as soon as the first layer of dentin is deposited the Hertwig sheath loses its continuity and its close relationship with the tooth surface, which ends. like the epithelial diaphragm. The latter further determines the formation of multiple roots.
As a product of root formation, Hertwig's epithelial sheath becomes punctured by ectomesenchymal cells of the dental follicle that traverse the sheath to reach the dentin surface.
These cells deposit a collagenous matrix, which widens the perforations of the sheath and gradually displaces the dentin surface.
Hertwig's epithelial sheath then breaks into a network of interconnected epithelial filaments located within the future periodontal ligament.
These epithelial remains are called Malassez cellular remains.
Prior to tooth eruption collagen adjacent to the dentin surface becomes remodeled into thin fibers perpendicular to the dentin surface, these thin fibers slowly mineralize on the outer surface of the dentin. The non-mineralized final part of the fibers diffuse into the future space of the periodontal ligament that later forms the main fibers of the periodontal ligament.
As the dental follicle (FD) becomes remodeled within the periodontal ligament, most of the collagen fibers that become embedded in the cementum originate from the periodontal ligament fibroblasts as extrinsic fibers. As the new cementum is deposited on the surface, the cementoblasts are displaced to the periodontal ligament, thus avoiding entrapment. Acellular fibrillar cementum, most commonly found in the cervical 2/3 of the root, is deposited below more slowly. Collagen fibers are dense and regularly bundled, often with adjacent collagen joining patterns in record.
When root surfaces undergo external resorption (gum cell-mediated resorption or periodontal ligament), damage may be limited in time and extent, often followed by a restorative phase, with a new cementum deposited on the previously resorbed surface. In the earlier repair phase, the reparative cementum is typically composed of cells, intrinsic cementum fibers.
Due to the lack of Sharpey fibers, this type of cementum does not contribute to teeth anchoring. A new anchor may be provided by extrinsic or mixed cementum fiber forming on the intrinsic fiber layer. Demineralization containing areas of repair cement often produces crack artifacts when the smear layer has not been removed (smear layer is when any instrument abrasions or cuts the dental structure, producing a layer of dentin sludge on the surface. This dentin sludge layer comprises organic components). and inorganic tissues of dental tissues, microorganisms, saliva etc. This layer is present in greater or lesser amount, depending on the type of instruments used).
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Coronal cementum development:
Coronal cementum is formed in the cervical portion of the crown, its presence is restricted in localized areas of reduced epithelium of degenerate enamel. Enamel exposed as a result of epithelial degeneration provides a surface on which dental follicle cementoblasts are able to deposit cementum. Coronal cementum has no anchoring function. In histological sections this may appear as a cement "insula" on the cervical enamel surface or as a continuous cement "spur" with the root cementum and overlapping the cervical enamel. Most often, the coronal cementum is acellular and fibrillating.
Root cement development:
Root formation is dependent on the orderly growth of the Hertwig epithelial sheath, formed by the fusion of the inner and outer epithelia of the enamel organ, consisting of two rows of cubic or polyhedral cells.
Internal epithelial cells induce differentiation of connective tissue cells (dental papilla) into odontoblasts and as soon as the first layer of dentin is deposited the Hertwig sheath loses its continuity and its close relationship with the tooth surface, which ends. like the epithelial diaphragm. The latter further determines the formation of multiple roots.
As a product of root formation, Hertwig's epithelial sheath becomes punctured by ectomesenchymal cells of the dental follicle that traverse the sheath to reach the dentin surface.
These cells deposit a collagenous matrix, which widens the perforations of the sheath and gradually displaces the dentin surface.
Hertwig's epithelial sheath then breaks into a network of interconnected epithelial filaments located within the future periodontal ligament.
These epithelial remains are called Malassez cellular remains.
Prior to tooth eruption collagen adjacent to the dentin surface becomes remodeled into thin fibers perpendicular to the dentin surface, these thin fibers slowly mineralize on the outer surface of the dentin. The non-mineralized final part of the fibers diffuse into the future space of the periodontal ligament that later forms the main fibers of the periodontal ligament.
As the dental follicle (FD) becomes remodeled within the periodontal ligament, most of the collagen fibers that become embedded in the cementum originate from the periodontal ligament fibroblasts as extrinsic fibers. As the new cementum is deposited on the surface, the cementoblasts are displaced to the periodontal ligament, thus avoiding entrapment. Acellular fibrillar cementum, most commonly found in the cervical 2/3 of the root, is deposited below more slowly. Collagen fibers are dense and regularly bundled, often with adjacent collagen joining patterns in record.
When root surfaces undergo external resorption (gum cell-mediated resorption or periodontal ligament), damage may be limited in time and extent, often followed by a restorative phase, with a new cementum deposited on the previously resorbed surface. In the earlier repair phase, the reparative cementum is typically composed of cells, intrinsic cementum fibers.
Due to the lack of Sharpey fibers, this type of cementum does not contribute to teeth anchoring. A new anchor may be provided by extrinsic or mixed cementum fiber forming on the intrinsic fiber layer. Demineralization containing areas of repair cement often produces crack artifacts when the smear layer has not been removed (smear layer is when any instrument abrasions or cuts the dental structure, producing a layer of dentin sludge on the surface. This dentin sludge layer comprises organic components). and inorganic tissues of dental tissues, microorganisms, saliva etc. This layer is present in greater or lesser amount, depending on the type of instruments used).
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