Effects of surface roughness of titanium implants on bone remodeling activity of femur in rabbits.

We investigated the bone remodeling activity on titanium implants with different surface roughnesses using a confocal laser scanning microscope (CLSM). Two kinds of implants were used, the machined smooth-surfaced titanium and the plasma-sprayed rough-surfaced titanium. These implants were randomly inserted in a rabbit's femur from the lateral aspect of the diaphysis bicortically. Rabbits were killed at 6, 16, and 42 weeks after surgery. The implant-bone blocks were embedded in polyester resin, and were prepared to make undecalcified ground sections. Histomorphometric analyses were performed at the cortical bone-implant interface using the image obtained by CLSM. Percentages of direct bone-implant contact and bone volume (BV/TV) around the implant was greater in rough-surfaced titanium compared with the smooth-surfaced titanium at 42 weeks after implantation. On the contrary, the eroded surface (ES/BS) appeared to be less in the rough-surfaced titanium than in the smooth-surfaced titanium at 6 weeks after implantation, but thereafter, no difference was found between the two kinds of implants. Mineralizing surface (MS/BS) and mineral apposition rate (MAR) showed no significant differences throughout the experimental period. These results indicate that increased bone volume in the rabbits of rough-surfaced titanium implants is due to less remodeling activity during the early stage after implantation compared with the smooth-surfaced implants. The surface roughness of titanium is one factor which helps in determining the balance between bone formation and resorption of remodeling at the interface of the bone implants.