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 and Intermediate 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.