Quantitative comparison of osteoconduction of porous, dense A-W glass-ceramic and hydroxyapatite granules (effects of granule and pore sizes).

The osteoconductive potentials of dense, small porous and large porous apatite- and wollastonite-containing glass-ceramic (A-W GC) granules of various sizes implanted in rat tibiae were evaluated quantitatively, by determining their affinity indices. The average affinity indices of all types of A-W GC were high. The dense A-W GC granules had the highest values (97.0+/-5.5%), followed by the large porous (87.1+/-8.4%) and then the small porous granules (79.0+/-8.4%). There were no significant differences among the osteoconductive potentials of the different sizes of each form of A-W GC granule. The osteoconductive potentials of four types of commercially available porous hydroxyapatite (HA) granules were compared with those of the small porous A-W GC granules, using the affinity index and the proportion of newly formed bone relative to that of the granules in the bone defect. The values of the former parameter for three types of HA and those of the latter for four were significantly inferior to those of A-W GC. The difference between the osteoconductive potentials of A-W GC and HA was considered to be related to the rate of surface apatite layer formation.