Peripheral quantitative computer tomographic, histomorphometric, and removal torque analyses of two different non-coated implants in a rabbit model

The objectives of this study were (1) to investigate the bone-tissue response to zirconia and titanium implants at the implant-to-bone interface and at the periosteal level and (2) to quantitatively measure the mineral density of the peri-implant bone using peripheral quantitative computer tomography (pQCT).

Ten 3.5 mm × 6.6 mm screw-shaped threaded implants fabricated from titanium and zirconia were inserted into the mid-tibial diaphysis of five male New Zealand white rabbits. Calcein green was administered at 4 weeks post-implantation. The animals were sacrificed after 6 weeks and implants were retrieved and analyzed in terms of bone-to-implant contact (BIC), bone area (BA), mineralized surface (MS) percentage, inter-thread calcein labels, removal torque (RT) values, as well as pQCT measurements.

No statistically significant differences were detected between the zirconia and titanium implants in terms of BIC, RT, and pQCT. However, statistically significant higher BA and MS levels were found in the titanium group, while the higher amount of calcein labels occupying the threads were found in the zirconium group. Significant differences were also found in the quantity and the composition of bone at the bone-implant interfacial area vs. the region 1.5 mm away from the bone-implant interface, irrespective of the implant type.

Zirconia implants demonstrated a lower bone remodeling activity in the periosteal region. The bone at the bone-implant interface shows a significantly lower cortical bone density, a higher trabecular density, and trabecular mineral content. Finally, zirconia and titanium implants showed similar bone-implant responses in terms of BIC and RT.