Dentistry needs new bone substitute materials. The purpose of this study was to prepare nano-hydroxyapatite/collagen composite (n-HAP/Col); and evaluate its usefulness as osteo-conductive bio-material by using animal model. We formed collagen control (Col) and n-HAP/Col specimens of 6 mm width and 1 mm height, by freeze-drying, de-hydrothermal cross-linking and punching. Critical-size bone defects (6 mm) were generated in the cranial bones of thirty-six 10-week-old Wistar rats, in which Col and n-HAP/Col specimens were implanted. After feeding for 1 day, 4 weeks, or 8 weeks, the rats were sacrificed (n=6). Micro-computed tomography (CT) revealed that at 4 and 8 weeks the defect zones implanted with Col had similar mean opacity values of around 105, compared to that of 70 after 1 day (p<0.05); whereas at 4 weeks those implanted with n-HAP /Col had a much larger mean opacity value of 149, compared to those of 109 at 1 day (p<0.05) and 123 at 8 weeks. Histological observations of the rat cranial defect zones implanted with n-HAP/Col for 8 weeks revealed that n-HAP/Col was completely eliminated, and new bone was partially formed. Taken together, it was considered that n-HAP/Col was osteo-conductive, most effective at 4 weeks while newly formed bone slightly decreased at 8 weeks. Withal limited experimental results, it can be concluded that n-HAP/Col could be used as new osteo-conductive bone substitute material. For better osteo-regeneration at cranial defects over 4 weeks, it was recommended to add growth factors and stem cells to n-HAP/Col in future studies.
Key words: nano-apatite, collagen composite, bone re-generation, micro-CT, histological observation