A quantitative comparison of machined commercially pure titanium and titanium-aluminum-vanadium implants in rabbit bone.

Screw-shaped implants made from rods of commercially pure titanium (grade 1) and titanium-aluminum-vanadium (grade 5) were machined, and the implant surface structures were numerically described before being placed in rabbit tibiae for healing periods of 1 months, 6 months, and 12 months. Quantitative comparisons of the removal torque (Ncm) necessary to loosen the implants from the bone bed were performed. Short-term (1 month) observations revealed no significant differences between the two tested materials. However, after 6 and 12 months, the commercially pure titanium implants were significantly more stable in the bone bed, as compared to the alloy samples. After 6 months, the commercially pure titanium had a mean removal torque of 29 Ncm versus 23 for the alloy (P = .01), and after 12 months, the mean removal torque was 38 Ncm for commercially pure titanium as compared to 35 Ncm for the alloy (P = .01). Quantifications of the bone tissue response to the materials did not show any significant differences; however, the commercially pure titanium showed a tendency to have a higher percentage of bone in contact with the implant as compared to the alloy screws. Bone volumes in the threads were similar. The absence of any quantitative light microscopic difference after 1 month following placement may relate to the fact that there was a sparse amount of bone, since the tissue was in the organization/granulation phase. After 6 and 12 months of follow-up, substantial bone formation had occurred, resulting in significantly increased removal torques for the commercially pure titanium samples.