The early remodeling phases around titanium implants: A histomorphometric assessment of bone quality in a 3- and 6-month study in sheep

The purpose of this study was to evaluate the quality of the bone matrix ar ound commercially pure titanium implants at 3 and 6 months postplacement in sheep. Implants were placed in the corticotrabecular areas of both femurs in 6 animals. Each animal received 4 Euroteknika implants in the right femu r and 4 Nobel Biocare implants in the left femur. Bone blocks containing th e implants were studied undecalcified after being embedded in methylmethacr ylate. Sections were stained with toluidine blue and basic fuchsin. The amo unt of bone around the implants, the contact interface between the implant and bone, and the mineral apposition rates were measured. The fractional am ount of woven bone could be quantified because of its high glycosaminoglyca n content. No differences could be observed between the 2 types of implants . Total bone volume did not increase around both types of implants between 3 and 6 months, indicating that ankylosis was rapidly achieved. In contrast , in the area in contact with the implant, the bone-titanium interface dras tically increased and the mineral apposition rate decreased. The fractional volume of woven bone around implants was considerably reduced alter 6 mont hs. Bone quality around implants was improved at 6 months (volume of woven bone near zero), and true osteonic structures were observed in close contac t with titanium. The remodeling process appeared to improve bone quality an d increase the bone-titanium interface around implants, while the net bone quantity necessary to immobilize implants was achieved rapidly and remained unchanged.