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Cementum in Periodontium
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Cementum in Periodontium

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@IrresistibleTroll

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?

    <p>Cementum is less permeable than enamel</p> Signup and view all the answers

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

    <p>It helps to prevent tooth decay</p> Signup and view all the answers

    What is the main difference between cellular and acellular cementum?

    <p>Cellular cementum is more permeable than acellular cementum</p> Signup and view all the answers

    What is the primary organic component of cementum?

    <p>Collagen fibrils</p> Signup and view all the answers

    Where does cementum begin and end?

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

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

    <p>To line the root surface and secrete cementum</p> Signup and view all the answers

    Where are cementocytes located within the cementum matrix?

    <p>In lacunae</p> Signup and view all the answers

    What feature characterizes resting cementoblasts?

    <p>Reduction in cytologic features</p> Signup and view all the answers

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

    <p>Cellular cementum</p> Signup and view all the answers

    What distinguishes acellular cementum from cellular cementum?

    <p>Presence of cementoblasts on its outer surface</p> Signup and view all the answers

    What are Salter lines in the context of cementum?

    <p>Resting lines resulting from continuous deposition of cementum</p> Signup and view all the answers

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

    <p>Intrinsic fibers characteristic of its matrix</p> Signup and view all the answers

    What is the characteristic feature of intermediate cementum?

    <p>Amorphous and not easily classified as dentin or cementum</p> Signup and view all the answers

    What is the primary feature of acellular cementum?

    <p>More calcified than cellular cementum</p> Signup and view all the answers

    Which statement accurately describes mixed fibers cementum?

    <p>Composed of both intrinsic and extrinsic fibers</p> Signup and view all the answers

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

    <p>Cementum overlaps enamel</p> Signup and view all the answers

    Which type of fibers primarily compose acellular cementum?

    <p>Referred to as Sharpey's fibers</p> Signup and view all the answers

    What characterizes cellular cementum compared to acellular cementum?

    <p>Contains cementocytes within lacunae</p> Signup and view all the answers

    How does afibrillar cementum differ from other types of cementum?

    <p>It does not contain any fibers at all</p> Signup and view all the answers

    Which of the following statements about cellular cementum is true?

    <p>It is less calcified than acellular cementum</p> Signup and view all the answers

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

    <p>Development of afibrillar cementum on enamel surface</p> Signup and view all the answers

    What stage do cementoblasts enter after reaching full thickness?

    <p>Aquiescent stage</p> Signup and view all the answers

    What is hypercementosis?

    <p>Abnormal thickening of cementum</p> Signup and view all the answers

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

    <p>Tooth loss occlusally by attrition</p> Signup and view all the answers

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

    <p>Ankylosis</p> Signup and view all the answers

    What do cementicles refer to?

    <p>Calcified nodules in the periodontal ligament</p> Signup and view all the answers

    How does aging affect the permeability of cementum?

    <p>It decreases gradually</p> Signup and view all the answers

    What is the role of cementum in the periodontal ligament?

    <p>Securing the binding of the tooth root to the alveolar bone</p> Signup and view all the answers

    What is the primary function of fibroblasts during cementogenesis?

    <p>Collagen fiber production</p> Signup and view all the answers

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

    <p>Afibrillar cementum</p> 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?

    <p>30%</p> Signup and view all the answers

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

    <p>Exposure of the underlying root dentin</p> Signup and view all the answers

    Which type of cells are responsible for cementogenesis?

    <p>Cementoblasts, Cementocytes, Fibroblasts</p> Signup and view all the answers

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

    <p>Cementogenesis</p> Signup and view all the answers

    How does the mineralization process in cementogenesis occur?

    <p>As the first layer of matrix is formed</p> Signup and view all the answers

    What characterizes the cementodentinal junction in deciduous teeth?

    <p>It shows a scalloped appearance sometimes</p> Signup and view all the answers

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

    <p>Parallel to the long axis of fibers</p> 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.

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