Influence of custom made titanium meshes surface on bone regeneration using calcium phosphates

Abstract

In such a complex biological and mechanical procedure like GBR, all the variables involved assume a vital role in the final outcome. The use of custom-made titanium meshes with their biological and mechanical properties is, without a doubt, a major factor when applied in a bone augmentation technique. Since surface characteristics may influence the outcome and success of bone regeneration using custom-made titanium meshes, our work focused in some particular aspects of their physical and chemical characteristics, like roughness, corrosion resistance, cellular and bactericidal behavior. Starting out by comparing and analyzing individualized meshes produced by different companies allowed not only to characterize the surface of titanium meshes produced by SLM, but also how could they benefit of a surface treatment with Piranha Solution. On the other hand, it is also of great importance to avoid or minimize bacterial colonization, usually responsible for graft infection and loss. This led us to further investigate how could we treat the surface of those custom-made meshes in order to increase fibroblast adhesion (for a biological sealing without drawbacks) and, at the same time, reduce bacteria colonization. In our first published work, particular interest was given to the roughness studies. The results from the scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and the contact profilometry measurements were analyzed and cross-checked. The BoneEasy’s mesh was the one that presented the lowest Ra value and was the mesh that got the closest to the reported optimal roughness degree that enhances the osteoblasts’ affinity to the surface, reported as 0.5 μm. The reported differences between the surfaces were due to the divergent post-production superficial treatments applied. Mesh4U endured an electropolishing treatment of high quality that was able to deliver flawless smooth surfaces, as it delivers the mesh with the lowest Ra value, 0.61 ± 0.14 µm. Contrastingly, the BTK produced mesh also withstood the same polishing process but its surface displayed countless non-polished pits, exposing the less perfect treatment application. In addition, evidences of stainless-steel contamination were found on this mesh surface. The Yxoss CBR® mesh suffered a sandblasting treatment that, apart from introducing alumina and silicon impurities onto the surface, was responsible for the very high roughness values that were reported (Ra of 6.59 ± 0.76 µm). In our following work, results showed that the passivation of titanium meshes with Piranha solution improved their hydrophilicity and conferred a notably higher bactericidal activity in comparison with the meshes passivated with HCl. This unique response can be attributed to differences in the obtained nanotextures of the TiO2 layer. However, Piranha solution treatment decreased electrochemical stability and increased ion release as a result of the porous coating formed on the treated surfaces, which can compromise their corrosion resistance. Finally, in our third published work, the results showed that the samples treated with alumina particles by sandblasting at 200 micrometres were the ones that performed best with fibroblasts, in order to achieve a good biological sealing, and also with the number of bacterial colonies in both strains. Microbiological studies have determined that the roughness generated by these particles presents a behavior very similar to the polished samples with minimal bacterial colonies on their surface. It has been shown that increased roughness leads to increased contact angles by studying wettability and thus makes the surfaces more hydrophobic. Furthermore, this treatment shows a low bacterial adhesion (Streptococcus sanguinis and Lactobacillus salivarius) comparable to polished surfaces.