Dental Roots: Formation, Lengthening and Malformations of Roots| Stephy Publishers
SOJ Dental and Oral Disorder - (SOJDOD) | Stephy Publishers
Abstract
The Hertwig’s Epithelial Root Sheath (HERS) includes two layers: the Outer
Enamel Epithelial Root Sheath and the Inner Enamel Epithelium Epithelium (IEE
and OEE). They contribute both to the root formation. The inner columnar
epithelial cells (IEE) of the dental papilla are formed by cells located near
the dental papilla. They are at the origin of odontoblasts expressing FGF-4, -8
and -9 and at later stages BMP-2 and BMP7. The Outer Epithelial cells (OEE)
express SHH, Msx2, enamel matrix proteins, paxillin, and Pax-6. When the cells
of the HERS dissociate, intercellular spaces enlarge. Cells migrate from the
epithelial sac, and underwent phenotypic inter conversion into cementoblasts
and later cementocytes. The Hertwigs enamel epithelium contributes to cementum
formation. Epithelial rest of Malassez is remnants of the Hertwig’s root
sheath. They are implicated in cementogenesis. Root lengthening and dentin
thickening are involved in root elongation and dentin thickening to the
detriment of the pulp chamber that is gradually reduced in volume. Apexogenesis
and apexification contribute to root formation. Defects and abnormal root
formation implicate missing teeth(hypodontia), orteeth in excess (supernumary
teeth or hyperdontia) or mis-shapped structures. Genetic defects (Nfic, Ptc,
Dkk1, Osx, Smad4, and Wls) have been identified. Premature arrests of root
formation are due to apical infection, radiation, chemotherapy, as well as
genes alterations. Roots malformations include root dilacerations which are abnormal
curvature of the root and sharp bend of the crown or root axis. Taurodontism
and other misshaped root structures are also frequently seen in man. Two main
forms have been recognized: 1) the CLCN7 encoding a chloride channel, and 2)
the second related to a defective PLG gene (encoding plasminogen). Altogether,
theses defects contribute to major endodontic difficulties.
Keywords: Epithelial hertwig’s root
sheath, OEE, IEE, Cell rests of malassez, Apexogenesis apexification, Acellular
cement, Cellular cement, Taurodontism, Root dilacerations, Dental type I and
type III, Dysplasia, Hypophosphatasia
After the crown formation, the
roots are lengthening and extending below the cervical loop, where the enamel
organ fuse. The Epithelial Enamel Root Sheath (HERS) is reduced to a double
layer. Instead of the four layers of the enamel organ. The outer enamel
epithelium, and the inner enamel epithelium contribute efficiently to the root
formation.
Root Anatomy
The root formation is under the
controlof the Hertwig’s Epithelial Root Sheath (HERS). Mesenchymal cells of the
dental papilla differentiate into odontoblasts. It is a bilayer originated from
the apical region of the enamel organ. HERS is guiding root formation
determining the size, shape and number of tooth roots. HERS is a proliferation
of epithelial cells located at the cervical loop of the enamel organ. The
epithelial root sheath consists of confluent outer and inner epithelial strata,
in some cases enclosing a central layer similar to the stratum intermedium. C14
and PCNA are expressed in the HERS, as well as Insulin-like growth factor. In
most cases, HERS is essentially formed by two layers: the outer and inner
layers at the origin of roots(lengthening and thickening) and apex closure
(apexogenesis and apexification).
To read more #Dental #OralDisorder
https://www.stephypublishers.com/sojdod/fulltext/SOJDOD.MS.ID.000514.php
More #openaccessjournals
https://www.stephypublishers.com/
Abstract
The Hertwig’s Epithelial Root Sheath (HERS) includes two layers: the Outer
Enamel Epithelial Root Sheath and the Inner Enamel Epithelium Epithelium (IEE
and OEE). They contribute both to the root formation. The inner columnar
epithelial cells (IEE) of the dental papilla are formed by cells located near
the dental papilla. They are at the origin of odontoblasts expressing FGF-4, -8
and -9 and at later stages BMP-2 and BMP7. The Outer Epithelial cells (OEE)
express SHH, Msx2, enamel matrix proteins, paxillin, and Pax-6. When the cells
of the HERS dissociate, intercellular spaces enlarge. Cells migrate from the
epithelial sac, and underwent phenotypic inter conversion into cementoblasts
and later cementocytes. The Hertwigs enamel epithelium contributes to cementum
formation. Epithelial rest of Malassez is remnants of the Hertwig’s root
sheath. They are implicated in cementogenesis. Root lengthening and dentin
thickening are involved in root elongation and dentin thickening to the
detriment of the pulp chamber that is gradually reduced in volume. Apexogenesis
and apexification contribute to root formation. Defects and abnormal root
formation implicate missing teeth(hypodontia), orteeth in excess (supernumary
teeth or hyperdontia) or mis-shapped structures. Genetic defects (Nfic, Ptc,
Dkk1, Osx, Smad4, and Wls) have been identified. Premature arrests of root
formation are due to apical infection, radiation, chemotherapy, as well as
genes alterations. Roots malformations include root dilacerations which are abnormal
curvature of the root and sharp bend of the crown or root axis. Taurodontism
and other misshaped root structures are also frequently seen in man. Two main
forms have been recognized: 1) the CLCN7 encoding a chloride channel, and 2)
the second related to a defective PLG gene (encoding plasminogen). Altogether,
theses defects contribute to major endodontic difficulties.
Keywords: Epithelial hertwig’s root
sheath, OEE, IEE, Cell rests of malassez, Apexogenesis apexification, Acellular
cement, Cellular cement, Taurodontism, Root dilacerations, Dental type I and
type III, Dysplasia, Hypophosphatasia
After the crown formation, the
roots are lengthening and extending below the cervical loop, where the enamel
organ fuse. The Epithelial Enamel Root Sheath (HERS) is reduced to a double
layer. Instead of the four layers of the enamel organ. The outer enamel
epithelium, and the inner enamel epithelium contribute efficiently to the root
formation.
Root Anatomy
The root formation is under the
controlof the Hertwig’s Epithelial Root Sheath (HERS). Mesenchymal cells of the
dental papilla differentiate into odontoblasts. It is a bilayer originated from
the apical region of the enamel organ. HERS is guiding root formation
determining the size, shape and number of tooth roots. HERS is a proliferation
of epithelial cells located at the cervical loop of the enamel organ. The
epithelial root sheath consists of confluent outer and inner epithelial strata,
in some cases enclosing a central layer similar to the stratum intermedium. C14
and PCNA are expressed in the HERS, as well as Insulin-like growth factor. In
most cases, HERS is essentially formed by two layers: the outer and inner
layers at the origin of roots(lengthening and thickening) and apex closure
(apexogenesis and apexification).
To read more #Dental #OralDisorder
https://www.stephypublishers.com/sojdod/fulltext/SOJDOD.MS.ID.000514.php
More #openaccessjournals
https://www.stephypublishers.com/
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