Bone healing in porous implants: a histological and histometrical comparative study on sheep

Tissue integration in four types of porous implant materials (Interpore 200 or Corallin hydroxyapatite, hydroxyapatite blocks, hydroxyapatite granules and polymethylmethacrylate) was evaluated in vivo. Porous blocks measuring 20 mm x 10 mm x 8 mm were implanted in mandibles and iliac crests of sheep. Bone healing in porous blocks was studied at 2 and 6 months after implantation. The behavior of the material itself was also analyzed. Histological and histomorphometrical analysis revealed bone healing depending upon healing time and material. On the basis of analysis of variance, differences in amounts of bone ingrowth at 2 and 6 months were statistically significant (p=0.0039 in mandible; p=0.0351 in iliac crest). The longer the time span, the more mineralized tissues were observed in the specimen. Our data confirmed that hydroxyapatite has osteoconductive capacities. Porous PMMA was found to be biocompatible, but it showed less bonegrowth within the pores. Interpore 200, which had the highest surface to volume ratio was found to display the highest level of osseointegration and biodegradation.