GRANULAR HYDROXYAPATITE AND ALLOGENEIC DEMINERALIZED BONE-MATRIX IN RABBIT SKULL DEFECT AUGMENTATION

To study the effect of hydroxyapatite (HA) granules on new bone format ion induced by allogeneic demineralized bone matrix (DBM) and to ascer tain the specific dose response of bone regeneration in rabbit calvari al defects, implantation with different doses of DBM, HA granules and a mixture of DBM with HA, respectively, was undertaken. The results sh owed that the largest quantity of cartilage in the fourth week and wov en 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 DB M 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 signi ficant negative correlation between new bone formation and fibrous tis sue ingrowth was noted. HA granules, as disturbing the bone regenerati on induced by DBM, are thus not a desirable combination, and a dose-bl ock phenomenon according to the amount of DBM must be anticipated in r epairing skull defects.