There are different classifications of bone density (quality) in oral implantology.
Lekholm U, Zarb GA: Patient selection and preparation. In: Brånemark PI, Zarb GA, Albrektsson T. Tissue integrated Prostheses: Osseointegration in Clincal Dentistry. Chicago: Quintessence Publishing Co. Inc.; 1985:199-209.
Bone Density/Quality Types
I: Almost the entire jaw is comprised of homogenous compact bone.
II: A thick layer of compact bone surrounds a core of dense trabecular bone of favorable strength.
III: A thin layer of cortical bone surrounds a core of dense trabecular bone of favorable strength.
IV: A thin layer of cortical bone surrounds a core of low density trabecular bone.
D1 Comprised of almost all cortical bone
D2 Comprised of thick crestal layer of cortical bone and coarse trabecular bone
D3 Comprised of thin cortical bone on the crest and fine trabecular bone
D4 Comprised of almost all fine trabecular bone