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 len gth 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 rab bit 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 imp lant material, they demonstrated rather similar surface roughnesses, f or example, the R(a) and R(q) values (that describe the average deviat ion 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 tis sue reactions to the materials were qualitatively and quantitatively e xamined. Removal torque tests were performed on the distal implants an d histomorphometrical evaluations of the proximal ones. No qualitative or quantitative bone differences were observed. Removal torque measur ements demonstrated a mean of 26.2 N cm +/- 9.6 for c.p. Ti versus a m ean 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 +/- 1 6.6% 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.