The Periodontium

The Periodontium

1. Cementum

2. Periodontal ligament

   • Develops from dental folicle
     • Foms shortly after root formation
       • Starts with conective tissue/collagen fringes, extending to cementum
         • Fibroblasts secrete collagen which remodel fringes
   • Fibers change as tooth errupts, then thicken
     • Narrows with age
       • Thin in non functional teeth
         • Functions: Attachment, proprioreceptor, shock absorber
   • Composed of
     • Cells; Fibroblasts, epithelial cells (malassez,) Undifferenciated mesenchymal cells, Cementoblasts, Macrophages
       • Ectracellular; Colagen, elastin (immature only), Ground substance (glycoprotein, glycolipids.)
   • Fibroblasts synthesis/degrade collagen for rapid turnover
     • Mesenchymal cells are source of new PDL cells
       • Oesteoblasts/Oesteoclasts line bone
         • Cementoblasts line cementum.No Cementoclasts unless resorbtion of deciduos
   • Collagen, types 1,3+7. Remodelled withe stress forces
     • 5 principle types; Aveola crest, Horizontal, oblique, apical, inerridicular
       • They run from cementum-bone. Sharpeys fibres
         • Ground substance 70% water
   • Rich blood supply; main from superiour and inferiour alveolar arteries,More posteria and mandible, less ants and maxilla
     • 4 types of nerve endings, mostly free, Nocirecptors+ mechanicreceptor

3. Alveolar Bone

   • Consists of spongsiosa, sandwiched between buccal and ligual cortical plates
     • Bone lining known as Bundle bone as attaches PDL bundles
       • Perforated by forimina for nerves, vessels, known as cribiform plate or Lamina Dura on x-ray (white lining)

4. Gingivae

   • Gingivae fibres, insert into lamina propria
     • Groups include; Dentogingival, Alveologingival, circular, dentoperioestial,transseptal
   • Dentogingival Junction
     • Gingival tissue to tooth
       • Epithelial and connective parts
         • Epithelial part
           • Statified, squamous epithelial cells
             • Junctional epithelial, attached to tooth surface, forms collar, non keratinised
               • Sulclar epithelial, lines sulcus, non-keratinised
                 • Oral gingival is keratinised.
               • Junctional epithelial, Flattened cells, line tooth
                 • attached by hemidesmosomes and have high rate of turmover
                   • JE has pourous intercellular, can let through antigens, lined with immune cells.
           • Connective part
             • Different from other connective tissue orally, as contains immflamatory cells.
               • Monocytes continually migrate from vessels, through intercellular tissue, out to the sulcus
             • Col (interdental papilla,) identical to juntional epithelium
         • Decreases with age, due to constant low grade imflamatory- Gingival recession

5. Hyaline Layer