Comparison of the tissue reaction to implants made of a beta titanium alloy and pure titanium. Experimental study on rabbits

Abstract

Commercially pure titanium (Ti cp) has been used successfully as an implant material in fracture fixation devices for many years. Ti cp is comparatively soft, but the mechanical properties, such as strength and ductility, can be adjusted by different means over a wide range. Titanium changes its crystal structure from a hexagonal (alpha) phase to the cubic (beta) phase at about 882 °C. Cubic titanium has the advantage of being very malleable (ductile), but in order to stabilize it at room temperature, additions of suitable alloying elements are required. In this study the soft tissue reaction to implants made from a beta titanium alloy (Ti−Mo−Zr−Al) with four different surface treatments is evaluated. The results are compared to Ti cp implants having the same surface conditions, and to electropolished stainless steel plates as controls. A minimum of four small plates of each group were implanted in rabbit tibiae for 3 months. Histomorphometric results show that the thickness of the soft tissue reaction layer, and the number of blood vessels, connective tissue cells (fibroblasts, fibrocytes), lymphocytes, and foreign body giant cells are not significantly different between beta titanium and Ti cp plates. For stainless steel plates the soft tissue reaction layer is thicker, and the numbers of macrophages and connective tissue cells are higher. Excellent biocompatibility was observed for this beta titanium alloy. The mechanical properties of this alloy surpass those of Ti cp, and because of the good tissue tolerance, this material seems to be advantageous and should enter into clinical testing.