Dr.Jaffar Raza Syed | 1

Cementum

Cementum is calcified avascular mesenchymal tissue that forms the

outer covering of the anatomic root.

Cementum is a mineralised tissue overlying the root dentine. It does not

undergo physiological remodelling but is continuously deposited

throughout life. Cementum is classified into two types:

• Acellular.

• Cellular.

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Acellular cementum

Acellular cementum forms on root dentine during root formation and tooth

eruption. Fibres inserted from the periodontal ligament are mineralised within

the cementum and are known as Sharpey’s fibres and are abundant in acellular

cementum.

Cellular cementum

Cellular cementum lies over the acellular cementum. It contains cells called

cementocytes which lie in lacunae. The cellular cementum layer is thicker

in the apical region of the root where it is between 0.2 and 1 mm thick

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Types Of Collagen Are Present In Cementum

Type I – 90%, III, V, XII , XIV

Sources Of Collagen Fibres Of Cementum

(i) Fibroblasts which produce extrinsic sharpey’s fibers.

(ii) Cementoblasts which produce intrinsic fibres of the cementum

matrix.

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Biochemical composition of cementum.

(i) Inorganic: 40 - 50% – Hydroxyapatite

(ii) Organic: 50%

• Collagen: Type I, III, V, XII, XIV

• Non-collagenous: Fibronectin, bone sialoprotein,

osteopontin, osteocalcin, osteonectin, alkaline phosphatase

• Formative cells: Cementoblast

• Degradative cells: Cementoclast/Odontoclast

• Adhesion molecule: Cementum attachment protein

• Growth factor: Insulin like growth factor

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Classify cementum. Schroeder classified cementum as:

(i) Acellular afibrillar cementum (AAC):

It consists of only mineralized ground substance, which is a product of

cementoblasts. Cells, collagen extrinsic and intrinsic) fibres are absent.

It forms coronal cementum.

(ii) Acellular extrinsic fibre cementum (AEFC):

It consists of sharpey’s fibers and lacks cells, which is a product of

fibroblasts and cementoblasts. It is found in cervical third of the root.

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(iii) Cellular mixed stratified cementum (CMSC):

It consists of extrinsic and intrinsic fibers and cells which is a product of

fibroblasts and cementoblasts. It is found in apical third of roots and in

furcation areas.

(iii) Cellular intrinsic fibre cementum (CIFC):

It consists of cells and intrinsic fibres, lacking extrinsic collagen fibres,

which is a product of cementoblasts. It fills resorption lacunae.

(iv) Intermediate cementum:

It consists of cellular remnants of Hertwig’s sheath embedded in

calcified ground substance. It is present near cementodentinal

junction.

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Dr.Jaffar Raza Syed | 8

Thickness Of Cementum

In Coronal third — 16 - 60µm (Thickness of hair)

In Apical third — 150 - 200µm (Thickest)

Thicker in distal surfaces than mesial surfaces.

Normal variations in tooth morphology at CEJ.

• In about 60 - 65% — Cementum overlaps enamel.

• In about 30% — Edge to edge butt joint.

• In about 10% — Space present between cementum and enamel.