Biomimetic Zirconia with Cactus-Inspired Meso-Scale Spikes and Nano-Trabeculae for Enhanced Bone Integration

Biomimetic design provides novel opportunities for enhancing and functionalizing biomaterials. Here we created a zirconia surface with cactus-inspired meso-scale spikes and bone-inspired nano-scale trabecular architecture and examined its biological activity in bone generation and integration. Crisscrossing laser etching successfully engraved 60 μm wide, cactus-inspired spikes on yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) with 200–300 nm trabecular bone-inspired interwoven structures on the entire surface. The height of the spikes was varied from 20 to 80 μm for optimization. Average roughness (Sa) increased from 0.10 μm (polished smooth surface) to 18.14 μm (80 μm-high spikes), while the surface area increased by up to 4.43 times. The measured dimensions of the spikes almost perfectly correlated with their estimated dimensions (R2 = 0.998). The dimensional error of forming the architecture was 1% as a coefficient of variation. Bone marrow-derived osteoblasts were cultured on a polished surface and on meso- and nano-scale hybrid textured surfaces with different spike heights. The osteoblastic differentiation was significantly promoted on the hybrid-textured surfaces compared with the polished surface, and among them the hybrid-textured surface with 40 μm-high spikes showed unparalleled performance. In vivo bone-implant integration also peaked when the hybrid-textured surface had 40 μm-high spikes. The relationships between the spike height and measures of osteoblast differentiation and the strength of bone and implant integration were non-linear. The controllable creation of meso- and nano-scale hybrid biomimetic surfaces established in this study may provide a novel technological platform and design strategy for future development of biomaterial surfaces to improve bone integration and regeneration.

Considerations regarding the osseointegration of endosseous dental implants

Implant osseointegration has not been accepted over time, considering that in fact the implant integration is performed only in the soft tissue of the host. For this reason, the implant has never been sufficiently integrated into the host tissue immediately after insertion. Experiments performed in Branemark laboratories in the early 1960s, with a new type of implant, which required a direct anchorage to bone tissue for clinical function, this anchorage was called osseointegration. It has been shown that it is possible to achieve direct osseointegration if the Branemark method is considered, which was published a few years later in the first clinical report. The authors of this article come up with new contributions that validate the implant osseointegration process. Inside this article we present our methodology for evaluating the osseointegration of endosseous implants: ESEM (environmental scanning electron microscope) studies of the implant-bone tissue interface.

Effectiveness of Surface Treatment With Blasted Bioceramic Materials on Implants Surfaces

Hydroxyapatite (HA) and other forms of bioceramics coatings had been reported to stimulate bone healing, which helps in initial implant integration. This study was to evaluate the effectiveness of air blasting with two combinations of bioceramic powders (hydroxyapatite and calcium oxide) on the selected implant surfaces for surface deposition. Five different types of implant disks were tested, namely Commercially pure (Cp), Sandblasted (SB), Sandblasted and etched(SBE), SLActive®, Roxolid®. The studied samples were blasted with apatite abrasive bioceramic powders, 95% Hydroxyapatite (HA)/5% Calcium Oxide (CaO) and 90% Hydroxyapatite (HA)/10% Calcium Oxide (CaO). The surface and elemental differences between the blasted samples were compared using a Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS). Results after surface treatment had demonstrated changes in surface morphologies; most evidently on the Cp implant discs. All treated surfaces revealed a non-uniform distribution of the treatment on the surface layer, with dispersed patches of bioceramic powders over the surfaces. The experimental blasting method used in this study has demonstrated the ability to deposit bioceramic materials on different implant surfaces.

Sustained Calcium(II)-Release to Impart Bioactivity in Hybrid Glass Scaffolds for Bone Tissue Engineering

In this study, we integrated different calcium sources into sol-gel hybrid glass scaffolds with the aim of producing implants with long-lasting calcium release while maintaining mechanical strength of the implant. Calcium(II)-release was used to introduce bioactivity to the material and eventually support implant integration into a bone tissue defect. Tetraethyl orthosilicate (TEOS) derived silica sols were cross-linked with an ethoxysilylated 4-armed macromer, pentaerythritol ethoxylate and processed into macroporous scaffolds with defined pore structure by indirect rapid prototyping. Triethyl phosphate (TEP) was shown to function as silica sol solvent. In a first approach, we investigated the integration of 1 to 10% CaCl2 in order to test the hypothesis that small CaCl2 amounts can be physically entrapped and slowly released from hybrid glass scaffolds. With 5 and 10% CaCl2 we observed an extensive burst release, whereas slightly improved release profiles were found for lower Calcium(II) contents. In contrast, introduction of melt-derived bioactive 45S5 glass microparticles (BG-MP) into the hybrid glass scaffolds as another Calcium(II) source led to an approximately linear release of Calcium(II) in Tris(hydroxymethyl)aminomethane (TRIS) buffer over 12 weeks. pH increase caused by BG-MP could be controlled by their amount integrated into the scaffolds. Compression strength remained unchanged compared to scaffolds without BG-MP. In cell culture medium as well as in simulated body fluid, we observed a rapid formation of a carbonated hydroxyapatite layer on BG-MP containing scaffolds. However, this mineral layer consumed the released Calcium(II) ions and prevented an additional increase in Calcium(II) concentration in the cell culture medium. Cell culture studies on the different scaffolds with osteoblast-like SaOS-2 cells as well as bone marrow derived mesenchymal stem cells (hMSC) did not show any advantages concerning osteogenic differentiation due to the integration of BG-MP into the scaffolds. Nonetheless, via the formation of a hydroxyapatite layer and the ability to control the pH increase, we speculate that implant integration in vivo and bone regeneration may benefit from this concept.