Bone regeneration with demineralized bone preparations has demonstrated its potential in grafting procedures in surgical disciplines of both medicine and dentistry. To improve the osteogenic activity of a demineralized bone allograft, a new rapid
preparation method of demineralized bone allograft was evaluated using a hetertopic site in a rodent model.
The frozen preserved rat diaphyseal cortical bones measuring 0.5cm in length were demineralized in heated 0.6N Hcl at 50, 60℃, 70℃and 80℃ for 10, 20, and 30 minutes respectively using a controlledheat ultrasonic cleaner. The demineralized bone
allograft at each temperature, except for 70℃ and 80℃due to lysis of demineralized collagen bone matrix, were implanted after washing with normal saline solution in dorsal subcutaneous pouches of rats without any futher processing. The
undemineralized
bone allografts treated in distilled water in a similar demineralizing process served as controls.
The 162 Sprague-Dawley rats, divided into 18 demineralized allograft implant groups(n=3) and 36 undemineralized allograft implant groups(n=3), received subcutaneous implants of each preparation. The implants were harvested at 1, 2, and 3 weeks
and
prepared for routine LM and TEM examination.
The histologic analysis revealed active ectopic bone formation in the demineralized allograft at 60℃ for 20 and 30 mins. The demineralized allografts at 50℃for 30 mins and 60℃for 10mins also induced favorable bone formation. However, the
demineralized allografts at 50℃ for 10 and 20mins showed relatively poor osteoinductive activity. The ectopic bone formation induced by the demineralized allografts occured, confined within a fibrous capsule, through endochondral bone formation
procedure while the undemineralized allografts of each group induced no ectopic bone formation. All implants of each group revealed no remarkable inflammatory or immunologic reaction through all experimental periods.
These findings suggest that the simply and rapidly prepared heat-treated allografts in 60℃ 0.6N Hcl for 20 to 30 mins using a controlled-heat ultrasonic cleaner may enhance the healing capacity of large bone defects by maximizing of the
osteogenic
potential with a minimizing of antigenicity as well as exhibiting a sterilizing effect.
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