Microscopic Differences in Cementum Structure and Mineral ...
4 Cementum
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Transcript of 4 Cementum
Acellular cementum (20-50 m)
Cellular cementum (150-200 m)
Physical Characteristics
2- Thickness
1-Color
Light yellowLighter in color than dentin
3- Permeability
Permeable from dentin and PDL sides.
Cellular C is more permeable than acellular C.
Chemical Composition
45-50 % Inorganic substances
50-55% Organic substances
Hydroxyapatite crystals
Collagen
protein
Polysaccharides
Trace elements
Cementum contains the greatest amount of fluoride in all mineralized tissues
Cementum Structure
Acellular cementum Cellular cementum
Cementoid layer
MalassezCementocytes
Acellular Cementum Thickness is 20-50 µ.
It is clear and structureless
Covers the coronal half of the root.
Incremental lines of Salter are parallel to the surface.
Sharpey’s fibers space can be seen in it .
Alternating layers of
a cellular and cellular cementum could be seen.
Cellular Cementum
Lacunae of cementocytes
Cementocytes
PDL side
Dentin side
CementocytesIncremental lines of Salter
Cementocyte And Osteocyte
Dentin side
PDL side
Lacuna
Canaliculi
Osteocyte
Cementocyte And Osteocyte
Periodontal ligament side
Dentin side
Lacuna
Canaliculi
Osteocyte
Cellular Cementum
Dentin side
PDL side
Viable superficial
cementocytes
Degenerated deep layer’s cementocytes
Incremental Lines Of Salter
They are hypermineralized area with less collagen fibers and more ground substance
In acellular C In cellular C
Intermediate CementumPremature
degeneration of epith. Root sheath of Hertwig ( after
odontoblasts differentiation and
before dentin formation)
It occur at apical 2/3 of premolars and molars roots and rare in incisors and deciduous teeth
Contains entrapped
epithelial cells
Cemento Dentinal Junction
CD
Smooth in permanent teeth Scalloped in deciduous teeth
30% cementum meets the enamel
in a sharp line
10% cementum and enamel doesn’t meet because of
delayed separation of epith root sheath of Hertwig (area of dentin not covered by C).
60% cementum overlaps E (afibrillar
cementum)
Cemento Enamel Junction
Afibrillar Cementum
The enamel at cervical area not covered by
reduced dental epithelium before
tooth eruption
The connective tissue of the dental sac lay down
cementum on the exposed enamel
Types Of Cementum
• 1- Acellular cementum
• 2- Cellular cementum
• 3- Intermediate cementum
• 4- Afibirllar cementum
Functions Of Cementum
1- Acts as a medium for attachment of collagen fibers of PDL (Sharpey’s fibers).
2- The continuous formation of cementum keeps the attachment apparatus intact.
Cementoid T
Cementoblast
3- Cementum deposition epically compensate for the attrition.
4- It is a major reparative tissue
( as in case of fracture or resorption of root)
Cementogenesis
• 1- Matrix formation • 2- Maturation
Collagen fiber type I
Ground substance
Hydroxy apatite crystals
1- Matrix formation
• Cementum is formed during root formation
Future C E J Epith. Diaph.
H E R
D
Cementoblasts
Cementoblast is a protein forming and secreting cell.
D
Cem
ento
bla
st
Large open face nucleus
R E R
Golgi apparatus
Mitochondria
Alkaline phosphatase
Secretory granules
Collagen fibers + ground substance.
Cementum
Cementoid layer
Cem
ento
bla
sts
Maturation occur layer by layer for the collagen fibers
Age Changes Of The Cementum
DD
Localised
1- Hypercementosis.
May affect one tooth or all teeth Hypercementosis
Hypercementosis hyperplasia
Hypercementosis hypertrophy
Increase number of Sharpey’s fibers
Decrease number of Sharpey’s fibers
Types Of Hypercementosis
2- Permeability
From periodontal
side, but remain at the
superficial recently formed
layers
From dentin side
remains at apical area
ONLY