Enhanced bone regeneration by electrical polarization of hydroxyapatite.

We examined osteogenic cell responses and new bone formation on electrically polarized hydroxyapatite (HAp) plates implanted into calvarial bone defects in rats. In the first group of rats, test pieces were placed with their positively charged surfaces face down on the dura mater. In a second group, test pieces were placed with their negatively charged surfaces facedown on the dura mater. A third group received noncharged test pieces. Histological examination was carried out to characterize the newly formed bone as well as quantification. Enzyme histochemistry involving the detection of alkaline phosphatase and tartrate-resistant acid phosphatase was performed to quantify osteogenic cell activity. Bone growth was enhanced in the groups that received polarized HAp plates, both at the negatively and positively charged surfaces. In addition to the electrostatic force that attracts Ca2+ to the negatively charged surfaces, the suppressive effects on osteoclasts proliferation on the positively charged surfaces may enhance bone formation.