CRANIAL BONE APPOSITION AND INGROWTH IN A POROUS NICKEL-TITANIUM IMPLANT

A 5 x 5 x 1-mm uncoated porous nickel-titanium (nitinol) implant was p laced 4 mm to either side of the midsection of the frontal bone and 4 mm anterior to the coronal suture of the cranial bone of New Zealand W hite rabbits. In the other frontal location, a 5 x 5 x 1-mm coralline hydroxyapatite (HA) (Interpore 200, a well-known craniofacial implant material) implant was fitted. Rabbits were killed at each of three pos tsurgical intervals (2, 6, and 12 weeks), and the implants were evalua ted for gross biocompatibility, bony contact, and ingrowth. No adjacen t macrophage cells were observed for either implant type, and overlayi ng soft tissues and connective tissues readily adhered to the implants even after 2 weeks. Both materials made bone contact with the surroun ding cranial hard tissue, and percent ingrowth increased with surgical recovery time. Measurements of microhardness and bone histologic para meters indicated that bone in contact with and grown into the implants was similar in properties to the surrounding cranial bone. Porous nit inol implants therefore appear to allow for significant cranial bone i ngrowth after as few as 12 weeks, and thus nitinol appears to be suita ble for craniofacial applications. Compared to HA, the nitinol implant s demonstrated a trend for less total apposition and more total ingrow th after 6 and 12 weeks of implantation. (C) 1995 John Wiley and Sons, Inc.