Dentine sheet part 1
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Questions and Answers

Where can peritubular or intratubular dentine be found?

  • On the enamel surface
  • Within the pulp chamber
  • At the walls of newly formed dentinal tubules at the pulp surface (correct)
  • At the root apex

    • What is the primary location of intratubular dentine?

  • Dentin-enamel junction
  • At the cementoenamel junction
  • Pulp-dentin junction
  • Pulp surface (correct)

    • Where is peritubular dentine predominantly present?

  • At the pulp surface (correct)
  • At the dentin-enamel junction
  • Along the root canal wall
  • In the enamel layer

    • Which type of dentine is situated specifically at the walls of newly formed dentinal tubules?

    <p>Mantle dentine</p> Signup and view all the answers

    In which area do we find newly formed dentinal tubules?

    <p>Pulp chamber</p> Signup and view all the answers

    Why are dentin crystals much smaller than enamel hydroxyapatite?

    <p>Dentin crystals don't stack with each other.</p> Signup and view all the answers

    What distinguishes the size of dentin crystals from enamel hydroxyapatite?

    <p>Dentin crystals lack rod formation.</p> Signup and view all the answers

    How does the arrangement of dentin crystals differ from enamel hydroxyapatite?

    <p>Dentin crystals do not stack together like enamel hydroxyapatite.</p> Signup and view all the answers

    What property of enamel hydroxyapatite contributes to its larger size compared to dentin crystals?

    <p>Enamel hydroxyapatite forms rods.</p> Signup and view all the answers

    In what way do dentin crystals differ structurally from enamel hydroxyapatite?

    <p>Dentin crystals do not align in a stacked manner.</p> Signup and view all the answers

    What is the diameter of the tubules at the pulpal end?

    <p>2.5um</p> Signup and view all the answers

    What happens to the odontoblasts as they retreat inwards?

    <p>They occupy a smaller area</p> Signup and view all the answers

    What is the diameter of the tubules at the DEJ?

    <p>1um</p> Signup and view all the answers

    What happens to the tubules as the odontoblasts retreat inwards?

    <p>They become closer together</p> Signup and view all the answers

    What is the main factor affecting the distance between the tubules?

    <p>The retreat of the odontoblasts</p> Signup and view all the answers

    What shape do the tubules form?

    <p>A curved S shape</p> Signup and view all the answers

    What is the term for the curved S shape of the tubules?

    <p>Primary curvature</p> Signup and view all the answers

    What is the role of the primary curvature?

    <p>It forms a curved S shape</p> Signup and view all the answers

    What is the term used to describe the curvature of the tubules?

    <p>Primary curvature</p> Signup and view all the answers

    What is the primary curvature a characteristic of?

    <p>The curved S shape of the tubules</p> Signup and view all the answers

    What type of proteins are found in dentine?

    <p>Glycoproteins/sialoproteins</p> Signup and view all the answers

    Which of the following proteins is NOT found in dentine?

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

    What is the function of the acidic proteins found in dentine?

    <p>Cell signaling</p> Signup and view all the answers

    Which of the following is a characteristic of dentine sialoprotein?

    <p>It is an acidic protein</p> Signup and view all the answers

    Which of the following proteins is also found in bones?

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

    Which glycosaminoglycan is listed as one of the main ones?

    <p>Chondroitin 4-sulphate</p> Signup and view all the answers

    What are the primary glycosaminoglycans found in dentine?

    <p>Chondroitin 4-sulphate and chondroitin 6-sulphate</p> Signup and view all the answers

    Which glycosaminoglycan mentioned is NOT one of the primary ones in dentine?

    <p>Chondroitin 6-sulphate</p> Signup and view all the answers

    What is a common glycosaminoglycan found in dentine that is NOT listed in the text?

    <p>Heparan sulfate</p> Signup and view all the answers

    Of the following options, which glycosaminoglycan is specifically mentioned as an 'imp'?

    <p>Dermatan sulfate</p> Signup and view all the answers

    What is the mineralization percentage of type I collagen in dentin compared to inter-tubular dentine?

    <p>5-12%</p> Signup and view all the answers

    Which type of collagen is primarily found in dentin?

    <p>Type III collagen</p> Signup and view all the answers

    What is the primary reason for dentin being more mineralized than inter-tubular dentine?

    <p>Less organic matrix</p> Signup and view all the answers

    In what way does the mineralization level of dentin impact its structural properties?

    <p>Improves resilience</p> Signup and view all the answers

    What is the main role of Phosphophoryn in dentine?

    <p>To facilitate mineralization</p> Signup and view all the answers

    Which of the following is a characteristic of Phosphophoryn?

    <p>It is the most acidic protein known</p> Signup and view all the answers

    What distinguishes Phosphophoryn from other proteins in dentine?

    <p>Its acidity</p> Signup and view all the answers

    How does Phosphophoryn contribute to the properties of dentine?

    <p>By promoting mineralization</p> Signup and view all the answers

    What makes Phosphophoryn significant in the study of dentine?

    <p>Its involvement in dentine formation</p> Signup and view all the answers

    Where are odontoblastic processes most heavily concentrated in the dentine?

    <p>Near the dentinoenamel junction</p> Signup and view all the answers

    What is the primary location of intratubular dentine?

    <p>Near the mineralising front</p> Signup and view all the answers

    What is a distinctive feature of dentin crystals compared to enamel hydroxyapatite?

    <p>Hexagonal shape</p> Signup and view all the answers

    Which type of proteins are primarily found in dentine?

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

    What property contributes to the larger size of enamel hydroxyapatite compared to dentin crystals?

    <p>Higher mineral content</p> Signup and view all the answers

    Which of the following is NOT a member of the SIBLING family?

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

    What is the primary function of the acidic proteins found in dentine?

    <p>Regulating mineralization</p> Signup and view all the answers

    Which of the following glycosaminoglycans is listed as one of the main ones in dentine?

    <p>Chondroitin sulfate</p> Signup and view all the answers

    Which of the following proteins is also found in bones?

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

    Which of the following is a characteristic of dentine sialoprotein?

    <p>Binding to integrins</p> Signup and view all the answers

    What is the primary difference between crystals in enamel and those in dentine?

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

    Which component makes up approximately 20% of the organic composition in dentine?

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

    Where is peritubular dentine predominantly located?

    <p>Around the tubules</p> Signup and view all the answers

    What is the distinctive feature of dentin crystals compared to enamel hydroxyapatite?

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

    What type of proteins are primarily present in dentine?

    <p>Acidic proteins</p> Signup and view all the answers

    What is the refractive index of water in relation to dentine in the described process?

    <p>Not specified in the given text</p> Signup and view all the answers

    Which protein, mentioned in the text, is NOT also found in bones?

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

    Which glycosaminoglycan is mentioned as an 'imp' in dentine?

    <p>Heparan sulphate</p> Signup and view all the answers

    What is the percentage of mineralization of type I collagen in dentin compared to inter-tubular dentine?

    <p>Not specified in the given text</p> Signup and view all the answers

    What happens to the regions with patent tubules when a ground section of a root is placed in water?

    <p>They fill with water and appear opaque</p> Signup and view all the answers

    Which protein is primarily found in intratubular dentine and differs from phosphophoryn?

    <p>Dentin phosphoprotein</p> Signup and view all the answers

    Which characteristic of dentine sialoprotein contributes to the unique structural properties of dentine?

    <p>Its ability to bind calcium</p> Signup and view all the answers

    Which glycosaminoglycan is mentioned as an 'imp' in dentine and what is its role?

    <p>Dermatan sulfate, regulating collagen fibril assembly</p> Signup and view all the answers

    Which protein found in dentine also plays a role in bone mineralization?

    <p>Collagen type I</p> Signup and view all the answers

    Which characteristic of enamel hydroxyapatite contributes to its larger size compared to dentin crystals?

    <p>Its lower organic content</p> Signup and view all the answers

    Which of the following mechanisms is likely responsible for the presence of more peritubular dentine at the DEJ?

    <p>An increased rate of formation of peritubular dentine due to higher mineralization</p> Signup and view all the answers

    Which protein is most likely responsible for the smaller size of odontoblastic processes at the DEJ?

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

    Which of the following mechanisms could explain the smaller diameter of tubules at the DEJ?

    <p>An increased deposition of peritubular dentine around the odontoblastic processes</p> Signup and view all the answers

    What is the significance of the smaller odontoblastic processes at the DEJ for the overall properties of dentine?

    <p>It enhances the overall strength of dentine in the DEJ region</p> Signup and view all the answers

    Which glycosaminoglycan is NOT likely to be involved in the regulation of mineralization at the DEJ, given the properties of this region?

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

    What is the specific role of phospholipids in the formation and growth of dentine crystals?

    <p>They act as a template for crystal nucleation.</p> Signup and view all the answers

    How do the structural differences between dentin crystals and enamel hydroxyapatite impact their properties?

    <p>Dentin crystals are smaller and less ordered, making them more susceptible to acid dissolution.</p> Signup and view all the answers

    What is the significance of Phosphophoryn in dentine mineralization and its structural properties?

    <p>Phosphophoryn promotes the formation of dentin crystals, contributing to dentine stiffness.</p> Signup and view all the answers

    How do the glycosaminoglycans found in dentine impact its structural and functional properties?

    <p>They provide flexibility and resilience to dentine.</p> Signup and view all the answers

    What is the impact of the primary curvature of the tubules on the structural properties of dentine?

    <p>The curvature enhances dentine's ability to distribute stress evenly.</p> Signup and view all the answers

    Study Notes

    Peritubular Dentine

    • Found at the walls of newly formed dentinal tubules at the pulp surface
    • Smaller than enamel hydroxyapatite, do not stack with each other, and do not form rods
    • Dentine tubules are 2.5 um in diameter at the pulpal end, decreasing to 1um or less at DEJ as odontoblasts retreat inwards

    Dentine Structure

    • Dentine tubules have a curved S shape, known as primary curvature, and are not straight
    • As odontoblasts retreat inwards, tubules become closer due to the smaller area occupied

    Dentine Composition

    • Contains acidic proteins, including osteonectin, osteopontin, and dentine sialoprotein
    • Main glycosaminoglycans are chondroitin 4-sulphate and chondroitin 6-sulphate
    • Made of highly mineralized type I collagen (5-12% more mineralized than inter-tubular dentine)

    Non-Collagenous Proteins

    • Phosphophoryn (PP-H): the main phosphoprotein in dentine, implicated in mineralization, and the most acidic protein known
    • Phosphophoryn is most heavily concentrated near the mineralizing front in predentine
    • SIBLING (small integrin-binding ligand N-linked glycoproteins) family includes osteopontin, bone sialoprotein, DMP-1, matrix extracellular phosphoglycoprotein, and dentine sialophosphoprotein

    Inorganic Material

    • Found on and between collagen fibrils

    Dentine Crystals

    • Different from enamel crystals

    Organic Composition

    • Accounts for 20% of dentine composition
    • Includes basic information about phospholipids, which are needlelike 'crystal ghosts' and may be involved in the formation and growth of crystals

    Translucent Dentine

    • Regions blocked by peritubular dentine appear translucent when a ground section of a root is placed in water
    • Regions with patent tubules appear opaque when filled with water

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