Anchorage of titanium implants with different surface characteristics: an experimental study in rabbits

To compare the anchorage of titanium implants with different surface roughness and topography and to examine histologically the peri-implant bone after implant removal.

Screw implants with five different surface topographies were examined: (1) turned ("machined"), (2) TiO2-blasted with particles of grain size 10 to 53 microns; (3) TiO2-blasted, grain size 63 to 90 microns; (4) TiO2-blasted, grain size 90 to 125 microns; (5) titanium plasma-sprayed (TPS). The surface topography was determined by the use of an optical instrument. Twelve rabbits, divided into two groups, had a total of 120 implants inserted in the tibiae. One implant from each of the five surface categories was placed within the left tibia of each rabbit. By a second operation, implants were installed in the right tibia, after 2 weeks in group A and after 3 weeks in group B. Fluorochrome labeling was performed after 1 and 3 weeks. Removal torque (RMT) tests of the implants were performed 4 weeks after the second surgery in group A and 9 weeks after the second surgery in group B. Thus, in group A, two healing groups were created, representing 4 and 6 weeks, respectively. The corresponding healing groups in group B were 9 and 12 weeks. The tibiae were removed, and each implant site was dissected, fixed, and embedded in light-curing resin. Ground sections were made, and the peri-implant bone was analyzed using fluorescence and light microscopy.

The turned implants had the lowest Sa and Sy values, whereas the highest scores were recorded for the TPS implants. The corresponding Sa and Sy values for the TiO2-blasted implants were higher when a larger size of grain particles had been used for blasting. At all four observation intervals, the TPS implants had the highest and the turned implants the lowest RMT scores. The differences between the various TiO2-blasted implants were, in general, small, but the screws with the largest Sa value had higher RMT scores at 6, 9, and 12 weeks than implants with lower Sa values. The histologic analysis of the sections representing 6, 9, and 12 weeks revealed that fractures or ruptures were present in the marginal, cortical peri-implant bone. In such sections representing the TPS and TiO2-blasted implant categories, ruptures were frequently found in the zone between the old bone and the newly formed bone, as well as within the newly formed bone.

The present study demonstrated that a clear relation exists between surface roughness, described in Sa values, and implant anchorage assessed by RMT measurements. The anchorage appeared to increase with the maturation of bone tissue during healing.