In Vivo Evaluation of Noble Porous Apatite Disks Implanted in Rat Critical-size Calvarial Defects by Micro-CT and Histological Observations

13 INTRODUCTION Apatite block and granule that are produced by high-temperature sintering with macro dimensions of mm are basically non-absorbable in osseous defects. It takes much time beyond one to two years to replace these apatite materials by natural bone in vivo. One the contrary, as Watari et al. reported, nano-size apatite via high-temperature method becomes bio-absorbable because phagocytes (neutrophil and monocytes) can dissolve apatite nano particles. We have also already reported that self-blended commercial nanoapatite (n-HAP)/collagen disks in rat cranial defects were moderately osteoconductive in the period up to 4 weeks, but its trend declined during the period from 4 weeks to 8 weeks, reflecting In Vivo Evaluation of Noble Porous Apatite Disks Implanted in Rat Critical-size Calvarial Defects by Micro-CT and Histological Observations