A balance of biocompatibility and antibacterial capability of 3D printed PEEK implants with natural totarol coating.

OBJECTIVE: Polyetheretherketone (PEEK), a biomaterial with appropriate bone-like mechanical properties and excellent biocompatibility, is widely applied in cranio-maxillofacial and dental applications. However, the lack of antibacterial effect is an essential drawback of PEEK material and might lead to infection and osseointegration issues. This study aims to apply a natural antibacterial agent, totarol coating onto the 3D printed PEEK surface and find an optimized concentration with balanced cytocompatibility, osteogenesis, and antibacterial capability. METHODS: In this study, a natural antibacterial agent, totarol, was applied as a coating to fused filament fabrication (FFF) 3D printed PEEK surfaces at a series of increasing concentrations (1 mg/ml, 5 mg/ml, 10 mg/ml, 15 mg/ml, and 20 mg/ml). The samples were then evaluated for cytocompatibility with L929 fibroblast and SAOS-2 osteoblast using live/dead staining and CCK-8 assay. The antibacterial capability was assessed by crystal violet staining, live/dead staining, and scanning electron microscopy (SEM) utilizing the oral primary colonizer S. gordonii and isolates of mixed oral bacteria in a stirring system simulating the oral environment. The appropriate safe working concentration for totarol coating is selected based on the results of the cytocompatibility and antibacterial test. Subsequently, the influence on osteogenic differentiation was evaluated by alkaline phosphatase (ALP) and alizarin red staining (ARS) analysis of pre-osteoblasts. RESULTS: Our results showed that the optimal concentration of totarol solution for promising antibacterial coating was approximately 10 mg/ml. Such surfaces could play an excellent antibacterial role by inducing a contact-killing effect with an inhibitory effect against biofilm development without affecting the healing of soft and hard tissues around FFF 3D printed PEEK implants or abutments. SIGNIFICANCE: This study indicates that the totarol coated PEEK has an improved antibacterial effect with excellent biocompatibility providing great clinical potential as an orthopedic/dental implant/abutment material.

Surface-Mediated Modulation of Different Biological Responses on Anatase-Coated Titanium.

Various surface modification strategies are being developed to endow dental titanium implant surfaces with micro- and nano-structures to improve their biocompatibility, and first of all their osseointegration. These modifications have the potential to address clinical concerns by stimulating different biological processes. This study aims to evaluate the biological responses of ananatase-modified blasted/etched titanium (SLA-anatase) surfaces compared to blasted/acid etched (SLA) and machined titanium surfaces. Using unipolar pulsed direct current (DC) sputtering, a nanocrystalline anatase layer was fabricated. In vitro experiments have shown that SLA-anatase discs can effectively promote osteoblast adhesion and proliferation, which are regarded as important features of a successful dental implant with bone contact. Furthermore, anatase surface modification has been shown to partially enhance osteoblast mineralization in vitro, while not significantly affecting bacterial colonization. Consequently, the recently created anatase coating holds significant potential as a promising candidate for future advancements in dental implant surface modification for improving the initial stages of osseointegration.

Biological Performance of Titanium Surfaces with Different Hydrophilic and Nanotopographical Features.

The micro- and nanostructures, chemical composition, and wettability of titanium surfaces are essential for dental implants' osseointegration. Combining hydrophilicity and nanostructure has been shown to improve the cell response and to shorten the healing time. This study aimed to investigate the biological response to different wettability levels and nanotopographical modifications in aged and non-aged titanium surfaces. By plasma etching titanium surfaces with the fluorine gas 2,3,3,3-tetrafluoropropene (R1234yF), additional nanostructures were created on the sample surfaces. Furthermore, this treatment resulted in sustained superhydrophilicity and fluoride accumulation. We examined the effect of various nanostructuring processes and aging using scanning electron microscopy, roughness analyses, and wettability measurement. In addition, all the surface modifications were tested for their effects on fibroblast adhesion, proliferation, and viability as well as osteoblast differentiation. Our study indicates that the plasma etching, with 2,3,3,3-tetrafluoropropene, of the machined and SLA surface neither favored nor had an adverse effect on the biological response of the SAOS-2 osteoblast cell line. Although the fluorine-plasma-etched surfaces demonstrated improved fibroblast cell viability, they did not lead to improved early osseointegration. It is still unclear which surface properties mainly influence fibroblast and osteoblast adhesion. Further physiochemical aspects, such as electrostatic interaction and surface tension, are crucial to be analyzed along with wettability and roughness.

Advanced co-culture model: Soft tissue cell and bacteria interactions at the transgingival dental implant interface.

OBJECTIVES: To better simulate and understand the clinical situation in which tissue cells and bacteria compete for settlement on an implant surface, the aim was to develop an improved transgingival co-culture model. METHODS: For this model human gingival fibroblasts (HGF) were seeded on different titanium surfaces in the presence of the early colonizer Streptococcus gordonii or mixed oral bacteria. Subsequently adhesion and viability of HGF cells was analyzed. RESULTS: Simultaneous co-culture showed no decrease in the viability of HGF cells at early stages compared to the control group. However, a moderate impact on HGF viability (76 ± 23 %) was observed after 4 h of co-culture, which then significantly decreased after 5 h (21 ± 2 %) of co-cultivation, resulting in cell death and detachment from the surface. Further experiments including saliva pre-treatment of smooth and structured titanium surfaces with Streptococcus gordonii or mixed oral bacteria suggested a cell-protective property of saliva. SIGNIFICANCE: Our study revealed that during simultaneous co-culture of cells and bacteria, which resembles the clinical situation the closest, the viability of gingival cells is considerably high in the early phase, suggesting that increasing initial cell adhesion rather than antibacterial functionality is a major goal and a relevant aspect in the development and testing of transgingival implant and abutment surface modifications.

Needle Penetration Simulation: Influence of Penetration Angle and Sample Stress on the Mechanical Behaviors of Polymers Applying a Cast Silicone and a 3D-Printed Resin.

For surgical catheterization training applications, realistic and effective materials are desired. In this study, the relevance of a needle puncture angle and a simulated wall stress on different elastic materials were determined in a previously developed experimental setup. Both settings were considered individually in two new setups. In addition, a control setup with neither angle nor prestress was designed. During the process of puncturing the samples of two materials (Replisil 9N and Formlabs Elastic 50A), force−displacement values were collected, and three predefined parameters evaluated. The differences between the angled/stressed groups and the control group were analyzed. The additively processed material required a significantly higher force to puncture than the conventional one (p < 0.001). Moreover, a needle angulation of 45° required more force than puncturing orthogonally. Prestressing the samples did not clearly influence the resulting force. An evaluation of relative parameters showed that the investigated materials behaved differently but not linearly differently under the influence of needle angle and prestress. Therefore, it is essential to evaluate the properties and suitability of materials for surgical training models in appropriate experimental setups considering multiple parameters.

Tailoring the biologic responses of 3D printed PEEK medical implants by plasma functionalization.

OBJECTIVE: The objective of this study was to determine the effect of two plasma surface treatments on the biologic responses of PEEK medical implants manufactured by fused filament fabrication (FFF) 3D printing technology. METHODS: This study created standard PEEK samples using an FFF 3D printer. After fabrication, half of the samples were polished to simulate a smooth PEEK surface. Then, argon (Ar) or oxygen (O2) plasma was used to modify the bioactivity of FFF 3D printed and polished PEEK samples. Scanning electron microscopy (SEM) and a profilometer were used to determine the microstructure and roughness of the sample surfaces. The wettability of the sample surface was assessed using a drop shape analyzer (DSA) after plasma treatment and at various time points following storage in a closed environment. Cell adhesion, metabolic activity, proliferation, and osteogenic differentiation of SAOS-2 osteoblasts were evaluated to determine the in vitro osteogenic activity. RESULTS: SEM analysis revealed that several spherical nanoscale particles and humps appeared on sample surfaces following plasma treatment. The wettability measurement demonstrated that plasma surface treatment significantly increased the surface hydrophilicity of PEEK samples, with only a slight aging effect found after 21 days. Cell adhesion, spreading, proliferation, and differentiation of SAOS-2 osteoblasts were also up-regulated after plasma treatment. Additionally, PEEK samples treated with O2 plasma demonstrated a higher degree of bioactivation than those treated with Ar. SIGNIFICANCE: Plasma-modified PEEK based on FFF 3D printing technology was a feasible and prospective bone grafting material for bone/dental implants.

Bacterial translocation and microgap formation at a novel conical indexed implant abutment system for single crowns.

OBJECTIVES: A conometric concept was recently introduced in which conical implant abutments hold the matching crown copings by friction alone, eliminating the need for cement or screws. The aim of this in vitro study was to assess the presence of microgap formation and bacterial leakage at the Acuris conometric restorative interface of three different implant abutment systems. MATERIAL AND METHODS: A total of 75 Acuris samples of three implant-abutment systems (Ankylos, Astra Tech EV, Xive) were subjected to microbiological (n = 60) and scanning electron microscopic (SEM) investigation (n = 15). Bacterial migration into and out of the conical coupling system were analyzed in an anaerobic workstation for 48, 96, 144, and 192 h. Bacterial DNA quantification using qrt-PCR was performed at each time point. The precision of the conometric coupling and internal fit of cemented CAD/CAM crowns on corresponding Acuris TiN copings were determined by means of SEM. RESULTS: qrt-PCR results failed to demonstrate microbial leakage from or into the Acuris system. SEM analysis revealed minute punctate microgaps at the apical aspect of the conometric junction (2.04 to 2.64 µm), while mean cement gaps of 12 to 145 µm were observed at the crown-coping interface. CONCLUSIONS: The prosthetic morse taper connection of all systems examined does not allow bacterial passage. Marginal integrity and internal luting gap between the ceramic crown and the coping remained within the clinically acceptable limits. CLINICAL RELEVANCE: Conometrically seated single crowns provide sufficient sealing efficiency, relocating potential misfits from the crown-abutment interface to the crown-coping interface.

Synthesis and Characterization of a Novel Biocompatible Alloy, Ti-Nb-Zr-Ta-Sn.

Many current-generation biomedical implants are fabricated from the Ti-6Al-4V alloy because it has many attractive properties, such as low density and biocompatibility. However, the elastic modulus of this alloy is much larger than that of the surrounding bone, leading to bone resorption and, eventually, implant failure. In the present study, we synthesized and performed a detailed analysis of a novel low elastic modulus Ti-based alloy (Ti-28Nb-5Zr-2Ta-2Sn (TNZTS alloy)) using a variety of methods, including scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and tensile test. Additionally, the in vitro biocompatibility of the TNZTS alloy was evaluated using SCP-1, SaOs-2, and THP-1 cell lines and primary human osteoblasts. Compared to Ti-6Al-4V, the elastic modulus of TNZTS alloy was significantly lower, while measures of its in vitro biocompatibility are comparable. O2 plasma treatment of the surface of the alloy significantly increased its hydrophilicity and, hence, its in vitro biocompatibility. TNZTS alloy specimens did not induce the release of cytokines by macrophages, indicating that such scaffolds would not trigger inflammatory responses. The present results suggest that the TNZTS alloy may have potential as an alternative to Ti-6Al-4V.

Impact of sterilization treatments on biodegradability and cytocompatibility of zinc-based implant materials.

Biodegradable zinc (Zn) and Zn-based alloys have been recognized as promising biomaterials for biomedical implants. Sterilization is an essential step in handling Zn-based implants before their use in clinical practice and there are various sterilization methods are available. However, how these treatments influence the Zn-based biomaterials remains unknown and is of critical relevance. In this study, three commonly-applied standard sterilization methods, namely gamma irradiation, hydrogen peroxide gas plasma and steam autoclave, were used on pure Zn and Zn3Cu (wt%) alloy. The treated Zn and ZnCu alloy were investigated to compare the different influences of sterilizations on surface characteristics, transient and long-term degradation behavior and cytotoxicity of Zn and Zn alloy. Our results indicate that autoclaving brought about apparently a formation of inhomogeneous zinc oxide film whereas the other two methods produced no apparent alterations on the material surfaces. Consequently, the samples after autoclaving showed significantly faster degradation rates and more severe localized corrosion, especially for the ZnCu alloy, owing to the incomplete covering and unstable zinc oxide layer. Moreover, the autoclave-treated Zn and ZnCu alloy exhibited apparent cytotoxic effects towards fibroblasts, which may be due to the excessive Zn ion releasing and its local concentration exceeds the cellular tolerance capacity. In contrast, gamma irradiation and hydrogen peroxide gas plasma had no apparent adverse effects on the biodegradability and cytocompatibility of Zn and ZnCu alloy. Our findings may have significant implications regarding the selection of suitable sterilization methods for Zn-based implant materials among others.

Flowability, Tear Strength, and Hydrophilicity of Current Elastomers for Dental Impressions.

This study investigates 2 polyethers (PE), 2 polyvinylsiloxanethers (VXSE), and 10 polyvinylsiloxanes (PVS), seven of which had a corresponding light-body consistency and seven of which had a corresponding heavy-body consistency. Each light-body elastomer underwent a flowability test using the shark fin method 20, 50, and 80 s after mixing. The tear strength test DIN 53504 was used after setting the time (T0). Next, 24 h later (T1), hydrophilicity testing was used with static contact angles in water drops during polymerization (20, 50, and 80 s, as well as after 10 min). The heavy-body elastomers underwent shark fin testing with a corresponding light-body material at 50 and 80 s after mixing. The results of light-body testing were combined in a score to describe their performance. The highest differences were detected within flowability in shark fin heights between PE and a PVS (means of 15.89 and 6.85 mm) within the maximum tear strengths at T0 between a PVS and PE (3.72 and 0.75 MPa), as well as within hydrophilicity during setting between VXSE and a PVS (15.09° and 75.5°). The results indicate that VSXE and novel PVS materials can significantly compensate shortcomings in PE towards tear strength and hydrophilicity, but not flowability.

Microstructural, mechanical, in vitro corrosion and biological characterization of an extruded Zn-0.8Mg-0.2Sr (wt%) as an absorbable material.

Zinc (Zn) alloys seem to be promising candidates for application in orthopaedic or cardiovascular medical implants. In this area, high standards are required regarding the biocompatibility as well as excellent mechanical and tailored degradation properties. In the presented study, a novel Zn-0.8Mg-0.2Sr (wt%) alloy has been fabricated by the combination of casting, homogenization annealing and extrusion at 200 °C. As a consequence of its fine-grained homogenous microstructure, the prepared material is characterized by an excellent combination of tensile yield strength, ultimate tensile strength and elongation corresponding to 244 MPa, 324 MPa and 20% respectively. The in vitro corrosion rates of the Zn-0.8Mg-0.2Sr alloy in the physiological solution and the simulated body fluid were 244 µm/a and 69.8 µm/a, respectively. Furthermore, an extract test revealed that Zn-0.8Mg-0.2Sr extracts diluted to 25% had no adverse effects towards L929 fibroblasts, TAg periosteal cells and Saos-2 osteoblasts. Moreover, the Zn-0.8Mg-0.2Sr surface showed effective inhibition of initial Streptococcus gordonii adhesion and biofilm formation. These results indicated the Zn-0.8Mg-0.2Sr alloy, which has superior mechanical properties, might be a promising candidate for materials used for load-bearing applications.

Appropriately adapted properties of hot-extruded Zn-0.5Cu-xFe alloys aimed for biodegradable guided bone regeneration membrane application.

Appropriately adapted comprehensive mechanical properties, degradation behavior and biocompatibility are prerequisites for the application of Zn-based biodegradable implants. In this study, hot-extruded Zn-0.5Cu-xFe (x = 0.1, 0.2 and 0.4 wt%) alloys were fabricated as candidates for biodegradable materials for guided bone regeneration (GBR) membranes. The hot-extrusion process and Cu alloying were expected mostly to enhance the mechanical properties, and the Fe alloying was added mainly for regulating the degradation. The microstructure, mechanical properties and in vitro degradation behavior were systematically investigated. The ZnCuFe alloys were composed of a Zn matrix and FeZn13 phase. With increasing Fe content, a higher FeZn13 phase precipitation with larger particles was observed. Since elongation declined significantly until fracture with increasing Fe content up to 0.4 wt%, the ZnCuFe (0.2 wt%) alloy achieved a good balance between mechanical strength and ductility, with an ultimate tensile strength of 202.3 MPa and elongation at fracture of 41.2%. Moreover, the addition of Fe successfully accelerated the degradation of ZnCuFe alloys. The ZnCuFe (0.2 wt%) alloy showed relatively uniform corrosion in the long-term degradation test. Furthermore, extracts of the ZnCuFe (0.2 wt%) alloy showed no apparent cytotoxic effects against L929 fibroblasts, Saos-2 osteoblasts or TAg periosteal cells. The ZnCuFe (0.2 wt%) alloy exhibited the potential to inhibit bacterial adhesion of Streptococcus gordonii and mixed oral bacteria. Our study provides evidence that the ZnCuFe (0.2 wt%) alloy can represent a promising material for the application as a suitable GBR membrane.

Correction: Li, P. et al. Mechanical Characteristics, In Vitro Degradation, Cytotoxicity, and Antibacterial Evaluation of Zn-4.0Ag Alloy as a Biodegradable Material. Int. J. Mol. Sci. 2018, 19, 755.

The authors wish to make the following corrections to this paper [...].

Establishment of Collagen: Hydroxyapatite/BMP-2 Mimetic Peptide Composites.

Extensive efforts were undertaken to develop suitable biomaterials for tissue engineering (TE) applications. To facilitate clinical approval processes and ensure the success of TE applications, bioinspired concepts are currently focused on. Working on bone tissue engineering, we describe in the present study a method for biofunctionalization of collagen/hydroxyapatite composites with BMP-2 mimetic peptides. This approach is expected to be fundamentally transferable to other tissue engineering fields. A modified BMP-2 mimetic peptide containing a negatively charged poly-glutamic acid residue (E7 BMP-2 peptide) was used to bind positively charged hydroxyapatite (HA) particles by electrostatic attraction. Binding efficiency was biochemically detected to be on average 85% compared to 30% of BMP-2 peptide without E7 residue. By quartz crystal microbalance (QCM) analysis, we could demonstrate the time-dependent dissociation of the BMP-2 mimetic peptides and the stable binding of the E7 BMP-2 peptides on HA-coated quartz crystals. As shown by immunofluorescence staining, alkaline phosphatase expression is similar to that detected in jaw periosteal cells (JPCs) stimulated with the whole BMP-2 protein. Mineralization potential of JPCs in the presence of BMP-2 mimetic peptides was also shown to be at least similar or significantly higher when low peptide concentrations were used, as compared to JPCs cultured in the presence of recombinant BMP-2 controls. In the following, collagen/hydroxyapatite composite materials were prepared. By proliferation analysis, we detected a decrease in cell viability with increasing HA ratios. Therefore, we chose a collagen/hydroxyapatite ratio of 1:2, similar to the natural composition of bone. The following inclusion of E7 BMP-2 peptides within the composite material resulted in significantly elevated long-term JPC proliferation under osteogenic conditions. We conclude that our advanced approach for fast and cost-effective scaffold preparation and biofunctionalization is suitable for improved and prolonged JPC proliferation. Further studies should prove the functionality of composite scaffolds in vivo.

Application of totarol as natural antibacterial coating on dental implants for prevention of peri-implantitis.

Peri-implantitis is the most important issue threatening the long-term survival rate of dental implants. Various efforts have been made to reduce implant surface plaque formation, which is one of the essential causes of peri-implantitis. In our study, we applied the natural antibacterial agent totarol as a coating on experimental silicon wafer and titanium implant surfaces. To analyze the interaction between the totarol coating and the oral primary colonizer S. gordonii and isolates of mixed oral bacteria, samples were incubated in a model system simulating the oral environment and analyzed by Live/Dead staining, crystal violet staining and scanning electron microscopy (SEM). After 4 d, 8 d, 12 d, 16 d, and 24 d salivary incubation, the stability and antibacterial efficiency of totarol coating was evaluated through SEM. The results indicated that totarol coatings on both silicon wafer and Ti surfaces caused efficient contact killing and an inhibition effect towards S. gordonii and mixed oral bacterial film growth after 4 h, 8 h, 24 h, and 48 h incubation. After longtime salivary incubation of 12 d, the bactericidal effect started to weaken, but the anti-adhesion and inhibition effect to biofilm development still exist after 24 d of salivary incubation. The application of a totarol coating on implant or abutment surfaces is a promising potential prophylactic approach against peri-implantitis.

Response of human periosteal cells to degradation products of zinc and its alloy.

Zinc (Zn) and its alloys are proposed as promising resorbable materials for osteosynthesis implants. Detailed studies should be undertaken to clarify their properties in terms of degradability, biocompatibility and osteoinductivity. Degradation products of Zn alloys might affect directly adjacent cellular and tissue responses. Periosteal stem cells are responsible for participating in intramembranous ossification during fracture healing. The present study aims at examining possible effects emanating from Zn or Zn-4Ag (wt%) alloy degradation products on cell viability and osteogenic differentiation of a human immortalized cranial periosteal cell line (TAg cells). Therefore, a modified extraction method was used to investigate the degradation behavior of Zn and Zn-4Ag alloys under cell culture conditions. Compared with pure Zn, Zn-4Ag alloy showed almost fourfold higher degradation rates under cell culture conditions, while the associated degradation products had no adverse effects on cell viability. Osteogenic induction of TAg cells revealed that high concentration extracts significantly reduced calcium deposition of TAg cells, while low concentration extracts enhanced calcium deposition, indicating a dose-dependent effect of Zn ions. Our results give evidence that the observed cytotoxicity effects were determined by the released degradation products of Zn and Zn-4Ag alloys, rather than by degradation rates calculated by weight loss. Extracellular Zn ion concentration was found to modulate osteogenic differentiation of TAg cells. These findings provide significant implications and guidance for the development of Zn-based alloys with an optimized degradation behavior for Zn-based osteosynthesis implants.

Evaluation of a Zn-2Ag-1.8Au-0.2V Alloy for Absorbable Biocompatible Materials.

Zinc (Zn) and Zn-based alloys have been proposed as a new generation of absorbable metals mainly owing to the moderate degradation behavior of zinc between magnesium and iron. Nonetheless, mechanical strength of pure Zn is relatively poor, making it insufficient for the majority of clinical applications. In this study, a novel Zn-2Ag-1.8Au-0.2V (wt.%) alloy (Zn-Ag-Au-V) was fabricated and investigated for use as a potential absorbable biocompatible material. Microstructural characterization indicated an effective grain-refining effect on the Zn alloy after a thermomechanical treatment. Compared to pure Zn, the Zn-Ag-Au-V alloy showed significantly enhanced mechanical properties, with a yield strength of 168 MPa, an ultimate tensile strength of 233 MPa, and an elongation of 17%. Immersion test indicated that the degradation rate of the Zn-Ag-Au-V alloy in Dulbecco's phosphate buffered saline was approximately 7.34 ± 0.64 µm/year, thus being slightly lower than that of pure Zn. Biocompatibility tests with L929 and Saos-2 cells showed a moderate cytotoxicity, alloy extracts at 16.7%, and 10% concentration did not affect metabolic activity and cell proliferation. Plaque formation in vitro was reduced, the Zn-Ag-Au-V surface inhibited adhesion and biofilm formation by the early oral colonizer Streptococcus gordonii, indicating antibacterial properties of the alloy.

An In Vitro Study of Osteoblast Response on Fused-Filament Fabrication 3D Printed PEEK for Dental and Cranio-Maxillofacial Implants.

Polyetheretherketone (PEEK) is a prime candidate to replace metallic implants and prostheses in orthopedic, spine and cranio-maxillofacial surgeries. Fused-filament fabrication (FFF) is an economical and efficient three-dimensional (3D) printing method to fabricate PEEK implants. However, studies pertaining to the bioactivity of FFF 3D printed PEEK are still lacking. In this study, FFF 3D printed PEEK samples were fabricated and modified with polishing and grit-blasting (three alumina sizes: 50, 120, and 250 µm) to achieve varying levels of surface roughness. In vitro cellular response of a human osteosarcoma cell line (SAOS-2 osteoblasts, cell adhesion, metabolic activity, and proliferation) on different sample surfaces of untreated, polished, and grit-blasted PEEK were evaluated. The results revealed that the initial cell adhesion on different sample surfaces was similar. However, after 5 days the untreated FFF 3D printed PEEK surfaces exhibited a significant increase in cell metabolic activity and proliferation with a higher density of osteoblasts compared with the polished and grit-blasted groups (p < 0.05). Therefore, untreated FFF 3D printed PEEK with high surface roughness and optimal printing structures might have great potential as an appropriate alloplastic biomaterial for reconstructive cranio-maxillofacial surgeries.

Selection of extraction medium influences cytotoxicity of zinc and its alloys.

Zinc (Zn) alloys have been considered as promising absorbable metals, mainly due to their moderate degradation rates ranging between magnesium alloys and iron alloys. The degradation behavior depends on the specific physiological environment. Released metallic ions and corrosion products directly influence biocompatibility. The initial contact of orthopedic implants or vascular stents after implantation will be with blood. In this study, fetal bovine serum (FBS) was used as a model system of blood components. We investigated the influence of FBS on in vitro degradation behavior and cytotoxicity of pure Zn, and Zn-4Ag and Zn-2Ag-1.8Au-0.2 V (wt%) alloys. The initial degradation rates in FBS were assessed and compared with the degradation and toxicity in four other common physiological model systems: DMEM cell culture medium ±â€¯FBS and McCoy's 5A medium ±â€¯FBS. Test samples in pure FBS showed the highest initial degradation rates, and accordingly, FBS supplemented media accelerated the degradation process as well. Moreover, an extract test according to ISO 10993-5 and -12 with L929 and Saos-2 cells was performed to investigate the role of FBS in the extraction medium. The cytotoxic effects observed in the tests were correlated with FBS-mediated Zn2+ release. These findings have significant implications regarding the selection of appropriate media for in vitro degradation and cytotoxicity evaluation of Zn and its alloys. STATEMENT OF SIGNIFICANCE: Metallic zinc and its alloys have been considered as promising biodegradable metals, mainly due to their moderate degradation rates. However, in vitro cytotoxicity tests according to the current ISO 10993 standard series are not suitable to predict biocompatibility of Zn alloys due to the inconsistent correlation between in vitro and in vitro biocompatibility. In this study, we show that the outcomes of standardized in vitro cytotoxicity tests of Zn and Zn alloys are influenced by fetal bovine serum in the extraction vehicle because FBS promotes Zn2+ release during the extraction process. The results of the study provide significant information for selection of appropriate model systems to evaluate in vitro degradation behavior and cytotoxicity.

Carbon Fiber Reinforced PEEK Composites Based on 3D-Printing Technology for Orthopedic and Dental Applications.

Fused deposition modeling (FDM) is a rapidly growing three-dimensional (3D) printing technology and has great potential in medicine. Polyether-ether-ketone (PEEK) is a biocompatible high-performance polymer, which is suitable to be used as an orthopedic/dental implant material. However, the mechanical properties and biocompatibility of FDM-printed PEEK and its composites are still not clear. In this study, FDM-printed pure PEEK and carbon fiber reinforced PEEK (CFR-PEEK) composite were successfully fabricated by FDM and characterized by mechanical tests. Moreover, the sample surfaces were modified with polishing and sandblasting methods to analyze the influence of surface roughness and topography on general biocompatibility (cytotoxicity) and cell adhesion. The results indicated that the printed CFR-PEEK samples had significantly higher general mechanical strengths than the printed pure PEEK (even though there was no statistical difference in compressive strength). Both PEEK and CFR-PEEK materials showed good biocompatibility with and without surface modification. Cell densities on the "as-printed" PEEK and the CFR-PEEK sample surfaces were significantly higher than on the corresponding polished and sandblasted samples. Therefore, the FDM-printed CFR-PEEK composite with proper mechanical strengths has potential as a biomaterial for bone grafting and tissue engineering applications.