Stone Composition

Abstract

The ability of any bone to resist fracture under normal physiological load depends on bone mass, bone geometry, bone architecture , and bone composition. Bone is a composite made up of 65% mineral (mainly hydroxyapatite) and 35% organic matrix (collagen and other noncollagenous protein, bone cells, and water) (7). The inorganic component contributes to bone strength, while the organic matrix is responsible for toughness (i.e., crack resistance). The mechanical properties of any given bone can be fine-tuned according to the loading requirement by changing the ratio of inorganic, organic, and water content (8). Many examples [mineral content (inorganic)] in tooth enamel-97%, ossicles of the middle ear-90%, bone-65%, antler-30%) can be found in nature where the proportions of these three components are varied to obtain the desired mechanical property. One such interesting example pertains to a child's skeleton: the bones in children are less mineralized than in adults. A less mineralized bone will be more flexible (less brittle) and thus absorbs more energy. This helps children avoid fractures during their frequent falls (9). It is interesting to note that when the same bone mineral content (BMC) decreases in adults, the chance of fracture is very high during the first fall. The reason for this will be discussed in the following sections.