Hydroxyapatite Dome for Bone Neoformation in Rabbit Tibia

Purpose: To evaluate supracortical bone neoformation with the use of hydroxyapatite (HA) hollow domes specially manufactured for osteogenesis promotion. Materials and Methods: Nine New Zealand rabbits were selected and 18 domes were placed, divided into three groups according to the filler: control (blood clot), vitamin complex, and particulate β-tricalcium phosphate (β-TCP). The healing period was 8 weeks, hence fluorescent markers were applied. After healing, the samples were embedded in resin to prepare slides for light and fluorescence microscopic evaluation of the amount of neoformed bone tissue. Energy dispersive spectroscopy was also used for chemical analysis of the material inside the domes. Results: The quality of neoformed bone tissue with active bone remodeling areas was observed. As a filler, β-TCP showed higher bone formation (14.1%), better quality of neoformed bone tissue with organized structures, and an area of mineralized tissue in the dome. Bone neoformation inside the dome filled with blood clot confirmed the osteoconductive property of HA, as indicated by the migration of osteogenic cells from the blood clot, without the action of another biomaterial (mean area of bone formation for blood clot filler = 7.5%). Bone neoformation was not favored in samples filled with vitamin complex because of the difficulty of blood penetration through the material. Conclusion: HA domes performed well as a scaffold for bone neoformation over the cortical bone of rabbits, and this is based on maintenance of good stability and good integration with bone tissue. β-TCP presented higher values of neoformed bone area compared with the blood clot. HA domes have osteoconductive properties, especially when filled with blood clot, because of the migration of osteogenic cells without action of any other biomaterial. In domes filled with vitamin complex, no bone formation was noted because of the absence of resorption. Keywords: bone neoformation, dome barrier, hydroxyapatite, osteoconduction