Granular hydroxyapatite and allogeneic demineralized bone matrix in rabbit skull defect augmentation.

To study the effect of hydroxyapatite (HA) granules on new bone formation induced by allogeneic demineralized bone matrix (DBM) and to ascertain the specific dose response of bone regeneration in rabbit calvarial defects, implantation with different doses of DBM, HA granules and a mixture of DBM with HA, respectively, was undertaken. The results showed that the largest quantity of cartilage in the fourth week and woven and remodeled bone covering almost the whole area of the defect in the tenth and twelfth week, was visible in the 20-30 mg but not in the 40 mg DBM groups. New bone formation in the defects implanted with DBM and HA was markedly less than in those implanted with DBM alone and a large amount of fibrous tissue was initiated by HA granules. A significant negative correlation between new bone formation and fibrous tissue ingrowth was noted. HA granules, as disturbing the bone regeneration induced by DBM, are thus not a desirable combination, and a dose-block phenomenon according to the amount of DBM must be anticipated in repairing skull defects.