ABSTRACT
The bones and teeth of mammals and most other vertebrates
are biologically engineered composite materials formed essentially
from nanoscale crystals of a carbonate-bearing calcium phosphate
apatite set in an organic matrix.1 In mammalian bone, in particular,
the carbonate hydroxylapatite nanocrystals are platelet shaped, and
the organic matrix is composed largely of type I collagen with
minor amounts of other collagens, glycoproteins, proteoglycans, and
sialoproteins. The matrix is generally considered to be a passive
scaffold and template for mineral formation. The mineral crystals
provide mechanical rigidity and load-bearing strength to bone,
whereas the matrix binds the apatite crystals together and accounts
for the elasticity and flexibility of bone. There is presently no general
consensus among biomaterial scientists on the appropriate name
for the inorganic component of bone, although “bone mineral,”
“biological apatite,” “hydroxylapatite,” and more rarely “dahllite” are
in general use.
