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Classification Of Edentulous Jaws

Cawood and Howell (1988) proposed a classification system for edentulous jaws based on a study of 300 dried skulls:

  • Class I: Dentate ridge
  • Class II: Ridge immediately after extraction
  • Class III: Broad and rounded ridge with adequate height and width
  • Class IV: Knife-edge ridge with sufficient height but inadequate width
  • Class V: Flat ridge with insufficient height and width
  • Class VI: Depressed ridge with a cup-shaped surface

Lekholm and Zarb (1985) classified the quality of residual alveolar bone into four types:

  • Type I: Full-thickness cortical bone
  • Type II: Thick cortical bone layer surrounding dense trabecular bone
  • Type III: Thin cortical bone layer surrounding dense trabecular bone
  • Type IV: Thin cortical bone layer surrounding sparse trabecular bone