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005.cementum
1. 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.
2. Dr.Jaffar Raza Syed | 2
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
3. Dr.Jaffar Raza Syed | 3
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.
4. Dr.Jaffar Raza Syed | 4
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
5. Dr.Jaffar Raza Syed | 5
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.
6. Dr.Jaffar Raza Syed | 6
(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.
8. 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.
