Monday, November 7, 2011

An Illustrative Note & PowerPoint presentation on Cementum

PERIODONTIUM
PERIODONTIUM
TEETH IN-SITU
Periodontium (forms a specialized fibrous joint called Gomphosis)
         Cementum
         Periodontal Ligament
         Alveolar bone
         Gingiva facing the tooth
Histology of periodontium
Cementum
It is a hard avascular connective tissue that covers the roots of teeth
Role of Cementum
1.    It covers and protects the root dentin (covers the opening of dentinal tubules)
2.    It provides attachment of the periodontal fibers
3.    It reverses tooth resorption


Varies in thickness:  thickest in the apex and In the inter-radicular areas of multirooted teeth, and thinnest in the cervical area 10 to 15 mm in the cervical areas to 50 to 200 mm (can exceed > 600 mm) apically
        
Cementum simulates bone
          Organic fibrous framework, ground substance, crystal type, development
          Lacunae
          Canaliculi
          Cellular component
          Incremental lines (also known as “resting”  lines; they are  produced by continuous but            phasic, deposition of cementum)


Differences between cementum and bone
         Not vascularized – a reason for it being resistant to resorption
          Minor ability to remodel
          More resistant to resorption compared to bone
          Lacks neural component – so no pain
          70% of bone is made by inorganic salts (cementum only 45-50%)
          2 unique cementum molecules: Cementum attachment protein (CAP) and IGF
Clinical Correlation
Cementum is more resistant to resorption: Important in permitting orthodontic tooth movement


Development of Cementum

  • Cementum formation occurs along the entire tooth
  • Hertwig’s epithelial root sheath (HERS) –Extension of the inner and outer dentalepithelium
  • HERS sends inductive signal to ectomesenchymal pulp cells to secrete predentin by differentiating into odontoblasts
  • HERS becomes interrupted
  • Ectomesenchymal cells from the inner portion of the dental follicle come in with predentin by differentiating into cementoblasts
  • Cementoblasts lay down cementum 
PowerPoint presentation on Cementum




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