Bone Regeneration of Rat Critical-size Calvarial Defects Using a Collagen / Porous-apatite Composite: Micro-CT Analyses and Histological Observations

Abstract

We formed collagen/porous-HAP composite (Col/p-HAP) and collagen control (Col) specimens using freeze-drying technique and de-hydrothermal heat treatment. Critical-size bone defects (6 mm) were generated in the cranial bones of twelve 10-week-old Wistar rats, in which Col/p-HAP and Col specimens were implanted. After feeding for 4 weeks or 8 weeks, the rats were sacrificed (n=6 each), followed by micro-CT and histological analyses. Micro-CT revealed that the defect zones implanted with Col/p-HAP became significantly X-ray opaque with time whereas those with Col did not. Histological observations revealed that Col/p-HAP became considerably fragmented, exerting osteo-conductive effects in the defect zone at 8 weeks whereas Col was little osteo-conductive. Double staining showed dynamic new bone formation near p-HAP digested by nuclear cells in the defect zone. Col/p-HAP appears to be a useful new bone substitute material that is applicable to dental implantology.