743 Microdamage observation in cortical bone applied to non-destructive overloads
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It is well known that microdamage is induced by in vivo stresses applied to bone tissues. Such microdamage is closely related not only to fatigue or stress fracture but also to bone homeostatic response. In order to gain basic insight into adverse effects of overloading on bone strength, in the present study, we observed bone microdamage induced by monotonic non-destructive overloading. Cylindrical cores obtained from bovine cortical bone were used for the experiment. Bone specimens were cyclically loaded between 0 and 10 N for the determination of the initial modulus (E_0) which is used to normalize the applied stress (σ) in loading tests. We monotonically applied a normalized compressive stress (σ/E_0) of 0.05 to specimens. Following the mechanical loading, microdamage was stained using a sequence of fluorochromes (alizarin and calcein) that allows differentiation of damage due to overloading. Microdamage observation was carried out using an epifluorescence microscopy. The results obtained show that non-destructive overloading induced linear microcracks and diffused damage area in bone tissues.
