Vrahopoulos, TP, Barber, PM, Newman, HN. The Apical Border Plaque in Chronic Adult Periodontitis. An Ultrastructural Study: Morphology, Structure and Cell Content. J. Periodontol., 63:243-52, 1992

Aim

Examine the apical border plaque in relation to teeth affected by chronic periodontitis.

Materials and Methods

• 56 teeth from 24 untreated PT. with routine chronic adult periodontitis.
• After preparation, the 56 teeth were sliced b-L and corono-apically, stained, and viewed with a transmission electron microscope.

Results

• The apical border plaque was not discrete, with islands of bacteria in the so-called PFZ.
• 3-4 layers of bacteria immediate coronal to the border.
• Plaque layer nearest the cementum: Gram+ coccoid.
• Superficial plaque layer: G- rods and cocci G+ filaments in middle layer.
• Spirochetes random distributed.
• In the most superficial layer.

• Loss type:
  variety of forms. Spirochetes interspersed with G- filamore, cocci, rod-shape of cells. 'corn-rob' formation, 'rosettes', 'test-tube brushes' occurred.

• Dense type:
  g- and G variable cocci and rod-shaped bacteria.

• Very dense type:
  Closely-packed bacteria, predominance of g- and G-variable cocci, a 'barrier' of PMN

• The most apical organisms were lysed bacterial cell ghost.
• Plaque-cementum interface.

Discussion

• Plaque formation:
  1. Deep layer G(+) cocci in a palisade formation perpendicular to the cementum.
  2. The palisach appears to be the fundamental unit of plaque.
  3. Transition from deep to mixed middle layer: discrete no particular organization pattern.
  4. Superficial plaque: variations in density.
  5. The presence of the 'Corn-cob'. 'test-tube brush' is indicative of interbacterial interaction.
• Plaque-host interface. PMN on the superficial plaque: protective role in this location. PMN phagocytosing bacteria. PMN not in the apically-advanced microcolonies.
• Bacterial colonization of PFZ. Predominance of G(-) cocci and rods at the apical border and PFZ.
• Bacterial Morpho types associated with chronic periodontitis. G(-) cocci and rods are predominant morphotypes at the advancing front of the plaque and likely associated with disease progression. Antibacterial factors continue to mitigate against colonization of PFZ.

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