QUIZ 3 Periodontium II Flashcards Preview

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Flashcards in QUIZ 3 Periodontium II Deck (28)
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cementum serves to do what 2 things?

  • cover the root
  • provide PDL attachment


what are the origins of cementum?


describe the composition of cementum

  • very similar to bone
  • 50% organic, 50% inorganic
  • inorganice component: hydroxyapatite
  • organic component around 90% collagen type I
  • other collagens: type III and XII
  • bone-associated non-collagenous proteins


what are the bone-associated non-collagenous proteins of cementum?

  • bone sialoprotein (BSP)
  • osteopontin (OP)
  • osteocalcin (OC)
  • osteonectin (ON)


cementum is thinner at the CEJ and thicker at the apex.  what are the relative thicknesses?

  • CEJ: 20-50um
  • apex: 150-200um


cells in the ___ become cementoblasts

dental follicle


HERS cells that break off become ___.  HERS cells that remain attached to roots can form ___, which is ___.

  • cell rests of malassez
  • enamel pearls, which is enamel like material that remains attached to roots


what are two possible scenarios to explain how cells in the dental follicle become cementoblasts?

  1. HERS or dentin induces cells in the dental follicle to beome cementoblasts
  2. some HERS cells become cementoblasts themselves


describe the frequency of the 3 types of CEJs

  • cementum overlaps enamel - 60% (this is the ideal CEJ because dentin is not exposed)
  • cementum and enamel meet to form a blunt end - 30% 
  • there is a gap between cementum and enamel - 10%


what are the two cementum subtypes?

  • acellular (primary)
  • cellular (secondary)


describe the differences between acellular and cellular cementum

  • classified by the presence of encapsulated cells (cementoblasts) and the predominant origin of the collagen fibers
  • collagen fiber origin: extrinsic from the PDL, or intrinsic from the cementoblasts themselves
  • acellular has extrinsic fibers, cellular has intrinsic fibers
  • primary cementum - acellular extrinsic fiber cementum 
  • secondary cementum - cellular intrinsic fiber cementum


where is acellular and cellular cementum located?

  • acellular extrinsic fiber cementum - coronal 2/3 of root
  • cellular intrinsic fiber cementum - apical 1/3 of root


describe AEFC formation

  • predentin (unmineralized) forms in the roots
  • cementoblasts send processes into this predentin and produce collagen fibers, termed the "fibrous fringe"
  • mineralization occurs internally in the dentin and spreads into the cementum
  • thus cementum and dentin are mingled forming the CDJ
  • after 15-20um of deposition, collagen synthesis stops, and only non-collagenous protein is produced (to induce mineralization)
  • collagen fibers from the developing PDL fibroblasts merge with the fibrous fringe and mineralize in place forming Sharpey's Fibers (hence extrinsic fiber)
  • cementoblasts end up only on the surface of the cementum (hence acellular)


describe CIFC formation

  • starts very similar to AEFC with intermingling to create the CDJ
  • cementoblasts become entrapped in the advancing cementum and become cementocytes
  • form lacunae as in bone, but do not establish a complex cellular network like osteocytes (hence cellular)
  • cementoid visible at the surface
  • there is an initial rapid phase of cementum production, followed by a slower more regular deposition
  • the collage fibers present are produced by cementoblasts, not PDL fibroblasts (hence intrincis)
  • Sharpey's fibers can still be present: cementum forms around PDL collagen fibers
  • mixed cementum is also possible: alternating layers of AEFC and CIFC with both intrinsic and extrinsic fibers


inner cementoblasts are generally ___

non-vital (no vasculature)


describe the main differences between AEFC and CIFC

  • AEFC:
    • no cells inside, no cementoid, slower deposition, more mineralized
    • functionality: attachment of PDL to cementum
  • CIFC:
    • more laminar, cells encapsulated, cementoid visible, often absent in canines and incisors
    • functionality: some attachment, adaptation and adjustment for wear


what is intermediate cementum?

  • between granular layer of tomes and dnetal cementum proper
  • mineralization level higher
  • may function to seal the surface of root dentin: reduce sensitivity


what is mixed cementum?

  • alternating layers of AEFC and CIFC
  • extrinsic and intrinsic fibers, generally located apically
  • perhaps quite a lot of the secondary cementum is actually mixed


what is hypercementosis?

  • abnormal thickening of cementum
  • diffuse or circumferential around the whole root
  • can affect entire dentition, single tooth, or portions of one tooth
  • tooth can become ankylosed


in physiological and orthodontic tooth movement, cementum is more resistant to ___ than alveolar bone


thus, bone tends to be remodeled first, effectively moving teeth "through" bone


the periodontium is generally affected by what 5 types of tooth movements?

  • tipping
  • bodily movement
  • extrusive movement
  • intrusive movement
  • rotational movement


orthodontists effectively manipulate the ___



in tooth movements, what are the 3 factors that determine the degree of the effect of an applied force?

  • tranduction: efficiency of the conversion of physical force into biologic response
  • time: effect is time-dependent
  • magnitude of force: degree of force determines response


what are the 4 net results of tooth movements?

  • compression
  • tension
  • hyalinization
  • undermining resorption


describe compression that can result from tooth movement

  • resorption of alveolar bone on the side toward which the tooth moves


describe tension that can result from tooth movements

  • formation of alveolar bone on the side opposite to compression


describe hyalinization that can result from tooth movements

  • results from too great or too rapid a compression force (ex. visit to orthodontist)
  • loss of cell activity and vascularity


describe undermining resorption that can result from tooth movements

  • occurs in conjugation with hyalinization
  • resorption occurs on the opposite surface of compressed bone