the normal periodontium cementum alveolar bone
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The Normal PeriodontiumIII & IVCementum & Alveolar Bone
Periodontology 1
DENT 371
Dr. Hisham Al-Shorman
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Cementum
Thin layer of calcifiedtissue covers the roots of
teeth, in which embedded
collagen fibers attach the
teeth to the alveolar bone
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Development
Inner epithelial
root sheathIntermediate
Cementum1.
Intermediate Cementum:
Acellular
Very thin layer (10 nm)
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Development
Periodontal
Ligament
FibroblastsCellular-Acellular
Cementum
2. Cementoblasts
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Cementum
Varies in thickness
At apex (150-200 m)
Thin cervically (10-15 m)
Firmly adherent with root
dentine
Highly responsivemineralized tissue:
(maintenance of functional
position of tooth)
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Cementum Calcified avascular mesenchymal
tissue
Major component: type I collagen
(90%) ad type III (5%)
Types:
Acellular (primary)
Cellular (secondary) Source:
Extrinsic (Sharpeys fibers)
Intrinsic (cementum matrix)
Mixed
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Acellular Cementum
First cementum formed
Before tooth reaches
occlusion
Cervical 1/3rd - of root
Sharpeys fibers
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Acellular cementum
Root dentine
Fibers of Periodontal
Ligament
Cementum
EpithelialRests
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Acellular cementum
Most common pattern- adjacent to dentine
Structureless
Afibrillar cementum
Covers cervical enamel
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Cellular Cementum
Formed after toothreaches occlusion
More irregular
Less calcified
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Cellular cementum
Most common pattern Apical area
Inter-radicular areas Overlying acellular dentine
Cementocytes Inactive
In lacunae
Processes present in canaliculi
Processes connected via gap junctions
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Cellular cementum
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Cementum
Both types arearranged in lamellae
separated by
incremental lines
(rest periods)
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CEJ
Fail to meet Edge-to-edge Cementum overlaps
enamel
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Functions
Seal for the opendentinal tubules
Provides
attachment for the
PDL
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Physical Properties
Pale yellow
Softer than dentine
Permeability:
Varies with age and type of cementum
Decreases with age
Cellular is more permeable More permeable than dentine
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Cementicles
Calcified ovoid or round
nodule found in the PDL
Single or multiple nearthe cemental surface
Free in ligament;
attached or embedded in
cementum
Aging and at sites of
trauma
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Chemical Properties
Inorganic Organic Water
By weight 65% 23% 12%
By volume 45% 33% 22%
Hydroxyapatite crystals similar to those in bone
More concentration of trace elements (F) at surface
F levels higher in acellular
Collagenous organic matrix, primarily type I
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Resorption & Repair of
Cementum
Less susceptibility to resorption than bone
Localized resorption areas occur
Could be caused by microtrauma
May continue to root dentine
By multinucleated odontoclasts
Reversal line
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Alveolar Bone
Alveolar bone
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It is that portion of the maxilla and mandible that
forms and supports the tooth socket (alveoli)
AlveolarBone
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Alveolar Process
Alveolar bone proper
Cribriform plate, Bundle bone and Lamina dura
(radio)
Supporting bone
Compact cortical plates
Spongy or cancellous trabecular bone
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Alveolar Bone Forms with tooth eruption
Tooth-dependent structure
Consists of:
External plate of cortical bone
Alveolar bone proper (innersocket wall)
Cancellous bone
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Alveolar BoneStrucure - Cells:
Osteoblasts
Osteocytes
Osteoclasts (remodeling)
Composition:2/3 inorganic
1/3 organicmainly type I
collagen
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Anatomical Subdivisions
Interdental /
interproximal bone
Interradicular bone
Radicular bone
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Anatomical Subdivisions
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Alveolar Bone Remodeling The coupled function of both osteoblasts and
osteoclasts
Essential for: Normal function of teethadaptation
Repair
Resistance of force
Ca & P homeostasis (bone contains 90% of bodysCa)
Complex process regulated by hormonal and
local factors
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Development of Bony Crypt
The alveolar process develops during the
eruption of teeth
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Development of Bony Crypt
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Alveolar Process
No distinct boundary exists between the
body of the maxilla or mandible (basalbone) and the alveolar process
If teeth are lost the alveolar bonedisappears
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A section through the mandible after removal of
all teeth
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Radiographic appearance of the lamina dura. The
lamina dura is a radiopaque (whi te) l ine around the
roots of the teeth and the alveolar crest.
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Basal Bon e
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Fenestration & Dehiscence
Fenestration:
Loss of radicular bone,NOT including marginal
bone (window-like)
Dehiscence:Loss of radicular bone,
including marginal bone
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Cortical bone is composed of osteons =
Haversian systems
Microscopic Features
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Bone Cells
Osteoblasts: Bone-forming cells
Osteocytes
Osteoclasts: Bone-resorbing cells
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