Cementum: Introduction to Periodontium
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Questions and Answers

What is the percentage of teeth where cementum meets the cervical end of enamel in a knife edge-to-edge pattern?

  • 20%
  • 30% (correct)
  • 60%
  • 10%

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

  • Afibrillar cementum (correct)
  • Fibrillar cementum
  • Acellular cementum
  • Cellular cementum

    • What is the result of cementum not meeting enamel, where a zone of root dentin appears devoid of cementum?

  • Dental hypersensitivity (correct)
  • Tooth decay
  • Gingivitis
  • Periodontitis

    • What is the percentage of teeth where cementum overlaps enamel?

    <p>60%</p> Signup and view all the answers

    What is the characteristic of the dentin surface in deciduous teeth upon which cementum is deposited?

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

    How many phases does cementogenesis take place?

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

    What is the characteristic of the growth of cementum?

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

    What is the term for the uncalcified matrix secreted by cementoblasts during cementogenesis?

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

    What happens to cementoblasts after reaching full thickness?

    <p>They enter an aquiescent stage</p> Signup and view all the answers

    What is the term for abnormal thickening of cementum?

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

    What is the function of cementum in case of root fracture or resorption?

    <p>It serves as a reparative tissue</p> Signup and view all the answers

    What is the term for calcified oval or round nodules found in the PDL?

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

    What is the reason why cementum is more resistant to resorption?

    <p>Because of its low permeability</p> Signup and view all the answers

    What is the term for the fusion of cementum to alveolar bone with obliteration of PDL?

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

    What is the function of cementum in binding the tooth root to the alveolar bone?

    <p>By serving as a medium for the incorporation of principal periodontal fibers</p> Signup and view all the answers

    What happens to the permeability of cementum with aging?

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

    What is the primary function of cementoblasts?

    <p>To produce and maintain the cementum matrix.</p> Signup and view all the answers

    Which of the following statements is TRUE regarding cementocytes?

    <p>Cementocytes are interconnected by cytoplasmic processes.</p> Signup and view all the answers

    What is the significance of Salter lines in cementum?

    <p>They mark the boundaries between different types of cementum.</p> Signup and view all the answers

    Which type of cementum is typically found on the apical half of the root?

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

    What is a key characteristic that distinguishes intermediate cementum from cellular and acellular cementum?

    <p>It exhibits features of both dentin and cementum.</p> Signup and view all the answers

    Why is cementum considered an avascular tissue?

    <p>It does not contain any blood vessels.</p> Signup and view all the answers

    What type of cementum is formed when mesenchymal cells differentiate into cementoblasts and deposit cementum on the enamel surface?

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

    Which type of cementum is characterized by the presence of intrinsic fibers?

    <p>Intrinsic fibers cementum</p> Signup and view all the answers

    Which type of cementum is characterized by the presence of cementocytes within lacunae?

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

    Which of the following is NOT a type of cementum based on fibrillar content?

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

    What is the primary component of acellular cementum?

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

    Which of the following is TRUE regarding the location of acellular cementum?

    <p>It is primarily found on the cervical third or half of the root.</p> Signup and view all the answers

    What is the significance of the reduced enamel epithelium in the formation of cementum?

    <p>Its degeneration allows for the formation of afibrillar cementum.</p> Signup and view all the answers

    What is the primary function of Sharpey's fibers in cementum?

    <p>To anchor the cementum to the dentin.</p> Signup and view all the answers

    Which of the following statements regarding the formation of cementum is TRUE?

    <p>The type of cementum formed is determined by the location on the tooth.</p> Signup and view all the answers

    What is the Cementoenamel Junction (CEJ)?

    <p>The junction between the cementum and the enamel.</p> Signup and view all the answers

    What is the primary function of cementum in the periodontium?

    <p>Anchors the periodontal ligament to the tooth</p> Signup and view all the answers

    Which of the following statements about the thickness of cementum is correct?

    <p>It starts at 20 – 50μm at the CEJ and thickens towards the apex</p> Signup and view all the answers

    What is the primary chemical composition of cementum?

    <p>45-50% inorganic and 50-55% organic substances</p> Signup and view all the answers

    Which type of collagen is primarily found in the bulk of cementum?

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

    What distinguishes cellular cementum from acellular cementum?

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

    What is the coloration of cementum relative to other dental hard tissues?

    <p>Darker than dentin but lighter than enamel</p> Signup and view all the answers

    What happens to cementum's permeability with age?

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

    What are Sharpey's fibers in relation to cementum?

    <p>They are embedded collagen bundles of the periodontal ligament</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

    Learn about cementum, a part of the periodontium, and its role in the supporting and investing attachment system of teeth. Includes information on its composition and formation.

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