The Normal Periodontium Cementum Alveolar Bone

7/28/2019 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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The Normal Periodontium Cementum Alveolar Bone

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