Cementum in Periodontium

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Questions and Answers

What is the main function of cementum?

To protect the dentin from wear and tear

To provide attachment for the periodontal ligament (correct)

To provide a smooth surface for the enamel

To assist in the formation of the dental pulp

What is the composition of the inorganic substances in cementum?

Primarily enamel proteins

Mostly calcium phosphate in the form of hydroxyapatite crystals (correct)

Mostly collagen fibrils

Predominantly polysaccharides

What is the relationship between cementum and Sharpey's fibers?

Sharpey's fibers and cementum are separate structures with no connection

Sharpey's fibers are responsible for the formation of cementum

Sharpey's fibers are embedded within the cementum (correct)

Cementum is a component of Sharpey's fibers

Which of the following statements about cementum is TRUE?

Cementum is less permeable than enamel Signup and view all the answers

What is the significance of the high fluoride content in cementum?

It helps to prevent tooth decay Signup and view all the answers

What is the main difference between cellular and acellular cementum?

Cellular cementum is more permeable than acellular cementum Signup and view all the answers

What is the primary organic component of cementum?

Collagen fibrils Signup and view all the answers

Where does cementum begin and end?

At the cementoenamel junction (CEJ) and extends to the apex of the root Signup and view all the answers

What is the primary role of cementoblasts in the structure of cementum?

To line the root surface and secrete cementum Signup and view all the answers

Where are cementocytes located within the cementum matrix?

In lacunae Signup and view all the answers

What feature characterizes resting cementoblasts?

Reduction in cytologic features Signup and view all the answers

What type of cementum is typically found on the apical half of the root and contains cells?

Cellular cementum Signup and view all the answers

What distinguishes acellular cementum from cellular cementum?

Presence of cementoblasts on its outer surface Signup and view all the answers

What are Salter lines in the context of cementum?

Resting lines resulting from continuous deposition of cementum Signup and view all the answers

Which of the following types of fibers is present in intrinsic fibers cementum?

Intrinsic fibers characteristic of its matrix Signup and view all the answers

What is the characteristic feature of intermediate cementum?

Amorphous and not easily classified as dentin or cementum Signup and view all the answers

What is the primary feature of acellular cementum?

More calcified than cellular cementum Signup and view all the answers

Which statement accurately describes mixed fibers cementum?

Composed of both intrinsic and extrinsic fibers Signup and view all the answers

What occurs at the cementoenamel junction (CEJ) in most cases?

Cementum overlaps enamel Signup and view all the answers

Which type of fibers primarily compose acellular cementum?

Referred to as Sharpey's fibers Signup and view all the answers

What characterizes cellular cementum compared to acellular cementum?

Contains cementocytes within lacunae Signup and view all the answers

How does afibrillar cementum differ from other types of cementum?

It does not contain any fibers at all Signup and view all the answers

Which of the following statements about cellular cementum is true?

It is less calcified than acellular cementum Signup and view all the answers

What is the result of the retraction of the reduced enamel epithelium?

Development of afibrillar cementum on enamel surface Signup and view all the answers

What stage do cementoblasts enter after reaching full thickness?

Aquiescent stage Signup and view all the answers

What is hypercementosis?

Abnormal thickening of cementum Signup and view all the answers

Cementum deposition at the apices of teeth compensates for which condition?

Tooth loss occlusally by attrition Signup and view all the answers

What term describes the fusion of cementum to alveolar bone with obliteration of the periodontal ligament?

Ankylosis Signup and view all the answers

What do cementicles refer to?

Calcified nodules in the periodontal ligament Signup and view all the answers

How does aging affect the permeability of cementum?

It decreases gradually Signup and view all the answers

What is the role of cementum in the periodontal ligament?

Securing the binding of the tooth root to the alveolar bone Signup and view all the answers

What is the primary function of fibroblasts during cementogenesis?

Collagen fiber production Signup and view all the answers

What is the primary type of cementum deposited on the enamel surface by mesenchymal cells?

Afibrillar cementum Signup and view all the answers

In what percentage of teeth does cementum meet the cervical end of enamel in a knife edge-to-edge pattern?

30% Signup and view all the answers

What can occur in approximately 10% of teeth where cementum does not meet enamel?

Exposure of the underlying root dentin Signup and view all the answers

Which type of cells are responsible for cementogenesis?

Cementoblasts, Cementocytes, Fibroblasts Signup and view all the answers

What is the process that involves both matrix formation and mineralization in cementum development?

Cementogenesis Signup and view all the answers

How does the mineralization process in cementogenesis occur?

As the first layer of matrix is formed Signup and view all the answers

What characterizes the cementodentinal junction in deciduous teeth?

It shows a scalloped appearance sometimes Signup and view all the answers

The arrangement of mineral crystals in relation to collagen fibers during cementum formation is:

Parallel to the long axis of fibers Signup and view all the answers

Study Notes

Cementum

Part of the periodontium, which is the investing and supporting attachment system of the teeth
Consists of two soft tissues (gingiva and periodontal ligament) and two hard tissues (cementum and alveolar bone)
A calcified, hard connective tissue derived from ectomesenchyme of the dental follicle, forming the outer covering of the anatomic root
Begins at the cervical portion of the tooth at the cemento-enamel junction and continues to the apex
Avascular and non-innervated

Physical Characteristics

Color: Yellow, lighter than dentin but darker than enamel
Hardness: Lesser than dentin
Permeability: Permeable to inorganic ions and bacteria, which diminishes with age; cellular cementum is more permeable than acellular cementum
Thickness: Thinnest at the cemento-enamel junction (20-50μm) and gradually thicker apically, ranging from 150-200μm or more

Chemical Composition

45-50% inorganic substances (calcium phosphate in the form of hydroxyapatite crystals)
50-55% organic substances (collagen fibers embedded in a ground substance, polysaccharides, and proteins)
Contains the greatest amount of fluoride in mineralized tissues

Histological Structure of Cementum

Two forms of collagen: collagen fibrils and collagen bundles
Collagen fibrils constitute the main bulk of the organic material of cementum
Collagen bundles represent the embedded portion of the principal fibers of the periodontal ligament, known as Sharpey's fibers
Two types of cells functionally concerned with cementum: cementoblasts and cementocytes
Cementoblasts line the root surface and contain numerous mitochondria and a well-developed Golgi complex; they become entrapped in the cementum matrix and form cementocytes
Cementocytes are seen in lacunae in the cementum matrix and have numerous processes that may branch and anastomose with those of adjacent cementocytes

Types of Cementum

Based on cellular content:
- Cellular cementum: contains cells called cementocytes in lacunae, more frequently found on the apical half of the root
- Intermediate cementum: a thin, amorphous layer of hard tissue approximately 10 microns thick, intermediate between cementum and dentin
- Acellular cementum: doesn't contain cells, present on the cervical third or half of the root
Based on fibrillar content:
- Intrinsic fibers cementum: fibers derived from the synthetic and secretory activity of cementoblasts
- Extrinsic fibers cementum: fibers originate from the principal fibers of the periodontal ligament (Sharpey's fibers)
- Mixed fibers cementum: contains both intrinsic and extrinsic fibers
- Afibrillar cementum: lacks fibers, formed when the reduced enamel epithelium retracts from the cervical region of enamel, allowing mesenchymal cells to invade and differentiate into cementoblasts

Cementoenamel Junction (CEJ)

In approximately 60% of teeth, cementum overlaps the cervical end of enamel for a very narrow area at the CEJ
In 30% of teeth, cementum meets the cervical end of enamel in a knife-edge-to-edge pattern
In approximately 10% of teeth, cementum does not meet enamel, resulting in a zone of root dentin appearing devoid of cementum

Cementodentinal Junction

The dentin surface upon which cementum is deposited is relatively smooth in permanent teeth
The cementodentinal junction in deciduous teeth is sometimes scalloped

Cementogenesis

Takes place in two phases: matrix formation and mineralization
Three cell types responsible for cementogenesis: cementoblasts, cementocytes, and fibroblasts, all derived from ectomesenchymal cells
Growth of cementum is a rhythmic process, with new cementoid formed and old one calcified
Mineralization begins after forming the first layer of matrix, with mineral crystals deposited within and between collagen fibers

Clinical Considerations

Hypercementosis: abnormal thickening of cementum, may occur in one tooth or all teeth, in local areas of one root or generalized to the whole root
Cementum is more resistant to resorption from bone, making orthodontic therapy possible
Fusion of cementum to alveolar bone with obliteration of the periodontal ligament is termed ankylosis
Decrease in permeability of cementum with age
Cementicles: calcified oval or round nodules found in the periodontal ligament, single or multiple, near the cemental surface

Functions of Cementum

Furnishes a medium for the incorporation of the principal periodontal fibers, securing the binding of the tooth root to the alveolar bone
Serves as a reparative tissue in case of root fracture or resorption
Allows for functional adaptation of the tooth by cementum deposition at the apices, compensating for tooth loss occlusally by attrition
Protects dentin by blocking the dentinal tubules

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Description

This quiz covers the structure and function of cementum, a hard connective tissue in the periodontium that supports and attaches teeth. Learn about its composition, location, and characteristics.