Takashi Asaka1 and Hisao Kikugawa2
1Department of Applied Chemistry, School of Engineering, Tokai University, Hiratsuka 259-1292
To evaluate the physical properties of a bone, a specimen is often deep-frozen or chemically fixed with reagents such as formaldehyde solution (formalin) or ethanol for antisepsis and sterilization. However, formalin contains formic acid and dissolves bone minerals such as Ca and P into the fixative. To suppress bone mineral solution, we used neutral buffered formalin as the fixative solution. In this study, we investigated the effect of formalin and of neutral buffered formalin fixation on the fracture characteristics of bovine femoral compact bone during relatively long-term preservation. With both formalin and neutral buffered formalin fixation, bone mineral migrates rapidly into the fixative solution. Thus, formic acid is not solely responsible for the dissolution of bone minerals, but some aqueous solutions such as saline can also dissolve bone mineral. With neutral buffered formalin fixation, small calcium phosphate grains precipitate at the surface of blood vessels in the Haversian canal, as observed by scanning electron microscopy. An energy-dispersive spectroscopy also demonstrates the presence of Ca and P. Thus, the precipitated grains are assumed to be hydroxyapatite. In this study we evaluate the effect of formalin preservation, which is to reduce the fracture toughness of bovine femoral compact bone, and to form chemical bridges by the reaction of formaldehyde with the collagen fiber of bone. The collagen fiber was cured and hardened, resulting in a reduction in the fracture toughness of bovine femoral compact bone.
bone, mechanical properties, fracture toughness, mechanical test, formalin preservation, mineral elution, quantitative element analysis
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