Extended bioactivity in the proximity of hydroxyapatite ceramic surfaces induced by polarization charges

Surface charges of electrically polarized hydroxyapatite (HAp) ceramics were demonstrated to enhance osteoconductivity in the wide gap of the canine bone whereas the bone formation processes varied according to the charge polarity. Cell reactions in the vicinity of the charged surfaces of HAp ceramics were not phagocytic absorption but rather bone formation by stimulated osteoblasts surrounding newly formed bone 7 days after implantation. The bone formation in direct contact with negatively charged ceramic surfaces suggests that the negative charges enhanced the osteobonding ability of the HAp ceramics. In the vicinity of the positively charged HAp surface, the formation of bones derived from osteoid tissues entirely occupied the 0.2-0.3-mm gaps between the HAp and the bone at 7 days. Surface charges induced by electrical polarization significantly cooperated with the innate bioactivity of HAp and reconstructed the wide bone defects more promptly than did the nonpolarized HAp ceramic surface.