Ultrastructure of the interface between alumina bead composite and bone

We developed a composite (ABC) consisting of alumina bead powder as an inor ganic filler and bisphenol-a-glycidyl dimethacrylate (Bis-GMA)-based resin as an organic matrix. Alumina bead powder was manufactured by fusing crushe d alpha-alumina powder and quenching it. The beads took a spherical form 3 mu m in average diameter. The proportion of filler in the composites was 70 % w/w. The composite was implanted into rat tibiae and cured in situ. Speci mens were prepared 1, 2, 4, and 8 weeks after the operation and observed by transmission electron microscopy, The results were compared with those of a bone composite made of alpha-alumina powder (alpha-ALC). In ABC-implanted tibiae, the uncured surface layer of Bis-GMA-based resin was completely fi lled with newly formed bonelike tissue 2 weeks after implantation. The alum ina bead fillers were surrounded by and in contact with bonelike tissue. No intervening soft tissue was seen. In alpha-ALC-implant ed tibiae, a gap wa s always observed between the alpha-ALC and the bonelike tissue. These resu lts indicate that the ABC has osteoconductivity, although the precise mecha nism is still unclear. (C) 2000 John Wiley & Sons, Inc.