Osseous cell response to electrostatic stimulations of poled hydroxyapatite ceramics in canine diaphyses

Cell responses of electrically charged surfaces of poled hydroxyapatite (HA) ceramics were investigated by implantation in wide defects of canine femora, compared with the uncharged surfaces. The HA ceramic specimens were poled in a dc field in air at 300-400degreesC. Base on the thermo stimulated current measurements, the stored charge and the half-value period of HA ceramics polarized at 300degreesC and 1.0 kVcm(-1) were 4.2 muCcm(-2) and 7.3x10(9) s (at 37.0degreesC), respectively. Although the non-polarized HA ceramic surfaces were still isolated from osteoid tissues by dominant fibrin multi-layers 7 days after the implantation, newly formed bone layers of 0.01-0.02 mm in thickness contacted the negatively charged surfaces without any inclusion. On the contrary, The osteoid tissues surrounded by osteoblastic cells occupied the gap between the positively charged surface and the cortical bone. We have demonstrated that the polarized HA ceramic had a large and long durable charge suitable for biomedical applications and that the HA surface charges induced by electrical polarization stimulated osseous cells and promoted bone reconstruction.