Cementum

Dr. Muhammad Wasif Haq

What is Cementum?• Cementum is defined as “Calcified, avascular

mesenchymal tissue that forms the outer covering of the anatomic root.

• Two types depending upon embryological development and presence of cells:

(a) Aceullar (Primary) (b) Cellular (Secondary)• Provides attachment for Periodontal ligament

fibers to the tooth and protects dentine.

Composition of Cementum• 45%-50% Inorganic material and 50-55% Organic

portion.• Consists of: Matrix and collagen fibers.• Collagen Fibers derived from Fibroblasts

(Sharpey’s fibers/Extrinsic fibers) and Cementoblasts (Fibers in Cementum matrix/Intrinsic fibers)

• Ground substance and organic matrix (Cementoid) formed by Cementoblasts.

• Ground substance includes proteoglycans, glycoproteins and phosphoproteins.

Types of Cementum

Cementum

Acellular Cementum Cellular Cementum

Aceullular/Primary Cementum

• Location: From cervical margin to 2/3rd portion of root.

• First to be formed(hence primary) and covers half of the root.

• Devoid of cells (Hence aceullar)• Formation before tooth reaches the occlusal

plane.• Sharpey’s fibers support the tooth and are

completely mineralized except near C.D.J.; parially calcified.

Ceullular/Secondary Cementum

• Location: Apical 3rd region and inter-radicular region.

• Forms after tooth reaches the occlusal plane (hence secondary).

• Contains cells (hence the name cellular)• Sharpey’s fibers can be partially as well as

completely mineralized• Or• Can have central uncalcified core surrounded

by a calcified border.

Differences between type of Cementum

Primary Cementum Secondary Cementum

Location: Cervical margin to 2/3rd of root. Apical 3rd and inter-radicular region.

Formation: Forms before the tooth reaches occlusal plane.

Forms after tooth reaches occlusal plane.

Cells: No Cellular, contains cementocytes

Structure: Thin. Thick and irregular.

Calcification: More calcified Less calcified.

Incremental Lines• Cellular and aceullar cementum are separated by

lines that are parallel to the long axis of the root.• More mineralized than adjacent cementum.• They represent rest periods in cementum

formation and are more mineralized.

Schroeder Classification• Aceullar Afibrillar Cementum• Aceullar Extrinsic Fiber Cementum• Cellular Intrinsic Fiber Cementum• Cellular Mixed Stratified Cementum andIntermediate Cementum

Aceullar Types• Aceullar Afibrillar: Contains no cells, no fibers.

Only mineralized ground substance present.• Produced by Cementoblasts and found in

coronal cementum.• Aceullar Extrinsic Fiber: Contains Sharpey’s

fibers but no cells. • Produced by Fibroblasts and Cementoblasts.• Found commonly in cervical 3rd of roots but may

extend apically.

Ceullar Types• Cellular Intrinsic Fiber: Cells but no extrinsic fibers.• Produced by Cementoblasts and fills resorption

lacunae. • Cellular Mixed Stratified: Extrinsic and intrinsic

fibers (hence mixed) and has cells. • Co-product of Cementoblasts & Fibroblasts.• In apical 3rd of toot and in furcation.

• Experience is a hard teacher because she takes the test first and the lesson afterwards.

Cemento-Enamel Junction• Three types:

• OMG Rule:

• 60%-65% Overlapping of Enamel by Cementum

• 30% Cementum Meets Enamel edge to edge, butt joint.

• 10% Gap between Cementum and Enamel. • Clinical implication????????

Permeability & Thickness

• Young patients have more permeable Cementum.• Permeability diminshes with age.• Cementum deposition a continous process.• Thickest Cementum found in apical 3rd and

furcation areas ( Why???)• Cementum formation most rapid in apical regions;

compensation for tooth eruption & attrition.