The aim of this study was to elucidate the relationship between the surface roughness and osteoconductivity of anodized titanium surfaces. Before anodizing, titanium substrates with different surface roughness were prepared by wet-polishing. These substrates were anodized at various voltages in H 3 PO 4 , H 2 SO 4 , and NaOH aqueous solutions, and their surface roughness was controlled simultaneously at the micron level. Surface roughness of these coatings was expressed with the arithmetical means (Ra). The osteoconductivity of anodized samples was evaluated by in vivo tests. In in vivo tests, samples were implanted in rats' tibia for 14 d. Anatase type TiO 2 films were formed on all of the anodized samples for in vivo tests. It was newly found that TiO 2 film with small Ra value exhibited high osteoconductivity than that with high Ra value, especially when Ra value was <0:3 mm. In addition, the osteoconductivity of anodized samples with Ra/mm > 0:3 was not improved by anodizing, showing the same low osteoconductivity of as-polished samples. These tendencies were observed for all of the TiO 2 films regardless of the type of electrolytes.

Various techniques for forming TiO2 coatings on Ti have been investigated for the improvement of the osteoconductivity of Ti implants. However, it is not clear how the oxidizing process affects this osteoconductivity. In this study, TiO2 coatings were prepared using the following three processes: anodizing in 0.1 M H3PO4 or 0.1 M NaOH aqueous solution; thermal oxidation at 673 K for 2 h in air; and a two-step process of anodizing followed by thermal oxidation. The oxide coatings were evaluated using SEM, XRD, and XPS. The water contact angle on the TiO2 coatings was measured as a surface property. The osteoconductivity of these samples was evaluated by measuring the contact ratio of formed hard tissue on the implanted samples (defined as the R B-I value) after 14 d implantation in rats' tibias. Anatase was formed by anodizing and rutile by thermal oxidation, but the difference in the TiO2 crystal structure did not influence the osteoconductivity. Anodized TiO2 coatings were hydrophilic, but thermally oxidized TiO2 coatings were less hydrophilic than anodized TiO2 coatings because they lacked in surface OH groups. The TiO2 coating process using anodizing without thermal oxidation gave effective improvement of the osteoconductivity of Ti samples.

The aim of this study was to elucidate the relationship between the surface roughness and osteoconductivity of anodized titanium surfaces. Before anodizing, titanium substrates with different surface roughness were prepared by wet polishing. These substrates were anodized at various voltages in H 3 PO 4 , H 2 SO 4 , and NaOH aqueous solutions, and their surface roughness was controlled simultaneously at the micron level. Surface roughness of these coatings was expressed with the arithmetical means (Ra ). The osteoconductivity of anodized samples was evaluated by in vivo tests. In in vivo tests, samples were implanted in rats' tibia for 14 d. Anatase type TiO 2 films were formed on all of the anodized samples for in vivo tests. It was newly found that TiO 2 film with small Ra value exhibited high osteoconductivity than that with high Ra value, especially when Ra value was ＜0.3 mm. In addition, the osteoconductivity of anodized samples with Ra/mm ＞0.3 was not improved by anodizing, showing the same low osteoconductivity of as polished samples. These tendencies were observed for all of the TiO 2 films regardless of the type of electrolytes.