EFFECT(S) OF THE DEMINERALIZATION PROCESS ON THE OSTEOINDUCTIVITY OF DEMINERALIZED BONE-MATRIX

THE RELATIONSHIPS BETWEEN RESIDUAL calcium levels and particle size of ground demineralized bone matrix and its osteoinductive potential wer e investigated using in vitro and in vivo assays. The effects of varia ble residual calcium levels, variable particle sizes, and donor age an d gender were studied using a tissue culture-based bioassay (in vitro) as well as an athymic mouse (in vivo) bioassay. The osteoinductive po tential of the bone-derived biomaterial was assessed by measuring the degree of new bone formation (change in percent calcium content after 4 weeks of implantation) in the in vivo assay and levels of alkaline p hosphatase activity associated with cultures of human periosteal cells (HPO cells) in the in vitro assay, respectively. Slightly demineraliz ed bone matrix and overly demineralized bone matrix possessed a degree of osteoinductive potential whereas bone demineralized to levels of a pproximately 2% residual calcium provided for maximum osteoinductive p otential in both assay systems. The osteoinductive potential of ground demineralized bone varied relative to the particle size such that DBM particles ranging from 500 to 710 microns provided for the highest le vel of calcium deposition (increase of 8.1 weight percent calcium) aft er 4 weeks of implantation in muscle pouches of an athymic mouse, wher eas explanted particles less than 250 microns showed the lowest level of calcium deposition (increase of only 2.8 weight percent calcium). I n the donor age and gender study, DBM from different donors were divid ed into 5 age groups for both female and male donor derived bone: less than 20, 21 to 30, 31 to 40, 41 to 50, and 51 to 60 year old age grou ps. This study indicated that DBM from female donors in the 31 to 40 y ears old age group and male donors in the 41 to 50 year age group poss ess the highest osteoinductive potential, whereas DBM derived from don or bone from both female and male donors in the 51 to 60 year age grou p presented the lowest osteoinductive potential. DBM derived from male and female donors did not in general show significant differences in osteoinductive potential.