Nano size structures and enhanced bone formation

Objectives: To evaluate early bone response to titanium implants modified with nanostructures.

Methods: Titanium implants were inserted in the rabbit tibia and healing time was 4-weeks. Initially, smooth (Sa~ 150 nm) cylindrical-implant design was selected in order to control the macrothreads and microstructures. Thus, early bone response could be related to added nano-size-structures alone. Smooth implants were obtained through mechanical polishing and modified by nano-hydroxyapatite (HA) or nano-titania. Further, the effect of nanostructures on bone response was investigated to moderately-rough screw-shaped implants of similar microtopography (Sa~1.3 µm). The surface modifications included were: blasted with TiO2 (control), blasted fluoride-treated and blasted modified with nano-HA.

Results: Nanostructures diameter-height detected by AFM was 30-3 nm for nano-HA and 24-1 nm for nano-titania and; decreased nanostructures density (n/µm2) of 94 was observed for nano-HA compared to 721 for nano-titania smooth implants. SEM evaluation (X125.000) of the moderately-rough implants indicated the presence of nanostructures over the microstructures on the blasted fluoride-treated and blasted nano-HA, whereas the blasted implant failed to show these nanostructures. Histological analyses of the smooth implants demonstrated a tendency (p<0.1) for enhance bone formation to nano-titania compared to nano-HA implants. Screw-shaped moderately-rough implants; that exhibited particular nano structures (fluoride and nano-HA), showed higher removal torque values (p<0.05) compared to blasted-control implants, that lacked such structures.

Conclusion: Based on in vivo animal experiments, enhanced bone formation was demonstrated to smooth and moderately-rough titanium implants modified with nano-size-structures with different chemical composition. Thus, the presence of nanostructures of specific size and distribution, dependent on the surface modification, did modulate in vivo bone response.

Grants provided by Capes Research Foundation, Hjalmar Svensson Foundation and AstraTech-Sweden.