Quantitative comparison of screw-shaped commercially pure titanium and zirconium implants in rabbit tibia

Screw-shaped implants with an outer diameter of 3.7 mm and a total length of 8 mm were made from rods of commercially pure titanium (c.p. Ti) and commercially pure zirconium (c.p. Zr). Prior to insertion in rabbit tibia for 12 weeks, the surface roughness of two randomly chosen c.p. Ti and two c.p. Zr machined implants of the batch were numerically and visually described with a TopScan 3-D system. Irrespective of implant material, they demonstrated rather similar surface roughnesses, for example, the R _a and R _q values (that describe the average deviation from the mean line) were 0.79 and 1.18 for c.p. Ti versus 0.56 and 0.86 for c.p. Zr. Each rabbit had four implants inserted; two made of c.p. Ti in one leg and two made of c.p. Zr in the other. The bone tissue reactions to the materials were qualitatively and quantitatively examined. Removal torque tests were performed on the distal implants and histomorphometrical evaluations of the proximal ones. No qualitative or quantitative bone differences were observed. Removal torque measurements demonstrated a mean of 26.2 N cm±9.6 for c.p. Ti versus a mean of 25.9 N cm±7.1 for the c.p.Zr implants. Histomorphometrical comparisons of the bone-to-metal contact revealed a mean of 29 ±10.2% for c.p. Ti and a mean of 19±5.5% for the c.p. Zr samples. The mean bone area in the threads around the c.p. Ti samples was 49±16.6% compared to 43±7.9% for the c.p. Zr group. Commercially pure titanium and zirconium implants seemed to be well accepted by the bone bed after 12 weeks of insertion in rabbit bone.