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HISTOLOGY OF SHEDDING

For dental students a slide for the histology of tooth shedding. <br><br>

Matthews2
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HISTOLOGY OF SHEDDING

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  1. HISTOLOGY OF SHEDDING

  2. Odontoclasts • They are multinucleated cells • Origin:blood monocytes or tissue macrophage • They are present in the root canals & pulp chambers • They resorb all hard dental tissue even Enamel Howships lacuna Dentin surface multinucleation

  3. Histochemically: The odontoclast have a high level of acid phosphatase activity

  4. Ruffled border ( arrows), • 1 Clear zone., • 2 Vesicular region., • 3 Basal region • Which contains multiple nuclei, Golgi saccules together with numerous mitochondria, some secretory vesicles, lysosomes, and small amount of rough endoplasmic reticulum 3 1 2

  5. Clast cells isolate an area of hard tissue using the clear zone &certain enzymes act as proton pumps

  6. An extracellular acidic environment is created leading to • Break down of the hydroxyapatite crystals of the inorganic component ( decalcification) • exposing the collagenous organic matrix • Prteolytic enzymes secreted & within the lysosomes are able to break down the collagenous organic matrix • TRANSPORT OF SOLUBLE PRODUCTS TO EXTRA CELLULAR FLUID OR THE BLOOD VESCULAR SYSTEM V

  7. RESORPTION OF DENTAL SOFT TISSUE • pulp& PDL • -Loss of the PDL is due to APOPTOTIC cell death. • Apoptosis: • -programmed cell death. • -shrinkage of the cells to be easily • phagocytosed by other cells.

  8. ligament fibroblasts exhibit morphologic features characteristic of apoptotic cell death. • Apoptosis involves condensation of the cell with its ultimate phagocytosis by neighboring macrophages or undamaged fibroblasts

  9. During active root resorption, coronal pulp tissue appears normal & odontoblast still line predentin surface (except that neural elements seem to be missing)

  10. Just before exfoliation, resorption ceases as odontoclasts migrate away from dentin & remaining pulp cells deposit cement-like tissue on it • Tooth may shed with some pulp tissue intact

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