Bone modeling and cell-material interface responses induced by nickel-titanium shape memory alloy after periosteal implantation

The purpose of this study was to evaluate the new bone formation, modeling and cell-material interface responses induced by nickel-titanium shape memo ry alloy after periosteal implantation. We used a regional acceleratory phe nomenon (RAP) model, in which a periosteal contact stimulus provokes an ada ptive modelling response. NiTi has thermal shape memory and superelasticity properties uncommon in other implant alloys. So far, there are insufficien t data concerning the biocompatibility of NiTi as a bone implant. NiTi was compared to stainless steel (stst) and Ti-6Al-4V. The test implant was plac ed in contact with the intact femur periosteum, but it was not fixed inside the bone. Histomorphometry with digital image analysis was used to determi ne the bone formation and resorption parameters. The ultrastructural featur es of cell-material adhesion were analysed with scanning electron microscop y (FESEM). A typical peri-implant bone wall modelation was seen due to the normal RAP. The maximum new woven bone formation started earlier (2 weeks) in the Ti-6Al-4V group than in the NiTi (P < 0.01) group, but also decrease d earlier, and at 8 weeks the NiTi(P < 0.05) and stst (P < 0.005) groups ha d greater cortical bone width. At 12 and 26 weeks no statistical difference s were seen in the histomorphometric values. The histological response of t he soft tissues around the NiTi implant was also clearly non-toxic and non- irritating. Cell adhesion and focal contacts were similar between the mater ials studied by FESEM. We conclude that NiTi had no negative effect on tota l new bone formation or normal RAP after periosteal implantation during a 2 6-week follow-up. (C) 1999 Elsevier Science Ltd. All rights reserved.