It is the most frequently used bone classification. It takes into account bone volume and density.
Class A: Most of the bone is alveolar bone
Class B: Moderate resorption of the alveolar crest
Class C: Significant resorption of the alveolar crest
Class D: The beginning of resorption of the basal bone
Class E: Extreme resorption of the basal bone
Type I: The bone is made up mostly of compact bone and small spongy bone core (nucleus)
Type II: A thick layer of cortical bone surrounding a dense nucleus of spongy bone
Type III: A fine layer of cortical bone surrounding a low-density but resistant nucleus of spongy bone
Type IV: A fine layer of cortical bone surrounding a low-density nucleus of spongy bone
