Mineralized scaffolds are widely used as bone grafts with the assumption that bone marrow derived cells colonize and remodel them. This process is slow and often unreliable so we aimed to improve the biocompatibility of bone grafts by pre-seeding them with human mesenchymal stem cells from either bone marrow or dental pulp. Under standard cell culture conditions very low number of seeded cells remained on the surface of freeze-dried human or bovine bone graft or hydroxyapatite. Coating the scaffolds with fibronectin or collagen improved seeding efficiency but the cells failed to grow on the surface until the 18th day. In contrast, human albumin was a very potent facilitator of both seeding and proliferation on allografts which was further improved by culturing in a rotating bioreactor. Electron microscopy revealed that cells do not form a monolayer but span the pores, emphasizing the importance of pore size and microstructure. Albumin coated bone chips were able to unite a rat femoral segmental defect, while uncoated ones did not. Micro-hardness measurements confirmed that albumin coating does not influence the physical characteristics of the scaffold, so it is possible to introduce albumin coating into the manufacturing process of lyophilized bone allografts. ß

Background: The purpose of this research was to investigate the effects of disinfection and three different sterilization methods on the dimensional changes and mechanical properties of three-dimensional (3D) printed surgical guide for implant therapy. The objective was to assess the effects of sterilization procedures in 3D printed drill guide templates with destructive and non-destructive material testing. Methods: Fifteen identical drill guide templates were produced using a 3D printer. The surgical guides were classified into five groups: three controls, three disinfected (4% Gigasept®, 60 min), three plasma sterilized, three autoclave sterilized (+ 1 bar, 121°C, 20 min), and three autoclave sterilized (+ 2 bar, 134°C, 10 min). The templates were digitalized with a Steinbichler SCAN ST 3D scanner. Length was measured under an SZX16 stereomicroscope. A scanning electron microscope was used to study the surface morphology of the drill templates. The hardness, and flexural and compressive strength were measured to assess any changes in the physical characteristics of the material caused by sterilization. The drill guide templates were also examined with a Dage XiDAT 6600 X-ray. During the X-ray examinations, the following parameters were used: 100 kV voltage, 128 AVG averaging, 0.8 W power. One-way analysis of variance (ANOVA) was used to detect the difference between groups. Results: Evaluation of the hardness measurements of the various specimens shows that the hardness of the material was not changed by the plasma sterilization (p = 0.0680), steam sterilization on 121°C (p = 0.6033) or disinfection process (p = 0.1399). The statistical analysis revealed significant difference in hardness strength of the autoclave sterilized (134°C) specimens (p = 0.0002). There was no significant difference between the goups regarding the scanning electron microscopic and stereomicroscopic examinations. There was no significant difference regarding the X-ray visibility of the templates to the effect of the disinfection (p = 0.7844), plasma sterilization (p = 0.4091) and steam sterilization on 121°C (p = 0.9277) and steam sterilization on 131°C (p = 0.093). The effect of the sterilization was the same in case of both flexural and compressive strength of the material. Conclusions: Our findings indicate that plasma sterilization and steam sterilization at 121°C were both suitable for sterilizing the tested 3D printed surgical guides.

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The study aim was to assess the impact of different surface nanofeatures on otherwise smooth titanium surfaces on bacterial adhesion as well as on their osteogenic potential. Bacterial adhesion was assessed in the presence of saliva under static and dynamic conditions to approximate both sub- and supragingival conditions in the oral cavity as the gingival seal will be affected by implantation. The ultimate goal was to develop a surface that will reduce biofilm formation but still support osseointegration in vivo. To this end nanotubular or nanopitted surfaces were created on electropolished titanium via electrochemical anodization procedures. Sandblasted/acid etched surfaces (SBAE) were used as a microrough reference. Bacterial adhesion was studied using saliva-precoated samples with S. sanguinis as a typical early colonizer of the oral cavity; osteogenic differentiation was assessed with human bone marrow stromal cells. While bacterial adhesion was reduced on all microsmooth surfaces to an average of 17% surface coverage compared to 61% on SBAE under static conditions, under dynamic conditions the nanopitted surface had a significant impact on bacterial adhesion. Here fluid flow removed all bacteria. By comparison, the reduction on the nanotubular surface was only similar to that of the SBAE reference. We hypothesise the underlying cause to be an effect of the surface morphology on the structure and composition of the saliva precoating that reduces its stability, giving rise to a self-cleaning effect. In addition, no negative influence on the osteogenic potential of the nanopitted surface could be determined by alkaline phosphatase activity, mineralization behaviour or gene expression; it remained on a par with the tissue culture plastic control. Thus, nanopitting seems to be a promising surface treatment candidate for dental implants to reduce infection related complications without compromising the implant integration.