Carbon Fiber-reinforced Polyetheretherketone Research Articles

Compressive properties and biocompatibility of additively manufactured lattice structures by using bioactive materials

Porous bioactive materials were widely used in orthopedic implant fields because of their excellent mechanical properties and porous spaces. However, most porous types are predominantly stacked in two-dimensional configurations, which significantly limits their mechanical property range and adversely affects the modulus matching between the porous implants and surrounding bone tissues. Hence, various lattice structures were prepared using 3D printing technology with bioactive materials, and characterized by mechanical and biological tests. Numerical simulations were conducted to analyze the effect of relative density and geometric parameters on the equivalent compressive properties of the lattice structures. The results showed that the lattice structure exhibited a broad elastic modulus range, which can be adjusted to align with the mechanical properties of human cortical and cancellous bones, thereby helping to mitigate stress shielding in orthopedic implants. The biocompatibility of the 3D-printed solid materials was assessed in vitro using a cell counting assay kit-8 (CCK-8). The results indicated that poly-ether-ether-ketone (PEEK), carbon fiber reinforced PEEK (CFR/PEEK), nylon, and titanium (Ti) alloy all exhibited good biocompatibility, with no significant differences observed among the four materials. This study further enhances the understanding of bioactive lattice structures in the biomedical field and offers new possibilities for orthopedic repair.

Intelligent Supramolecular Modification for Implants: Endogenous Regulation of Bone Defect Repair in Osteoporosis.

Addressing osteoporosis-related bone defects, a supramolecular strategy is innovated for modifying carbon fiber reinforced polyether ether ketone (CF/PEEK) composites. By covalently attaching intelligent macromolecules via in situ RAFT polymerization, leveraging the unique pathological microenvironment in patients with iron-overloaded osteoporosis, intelligent supramolecular modified implant surface possesses multiple endogenous modulation capabilities. After implantation, surface brush-like macromolecules initially resist macrophage adhesion, thereby reducing the level of immune inflammation. Over time, the molecular chains undergo conformational changes due to Fe (III) mediated supramolecular self-assembly, transforming into mechanistic signals. These signals are then specifically transmitted to pre-osteoblast cell through the binding capacity of the KRSR short peptide at the molecular terminus, induced their osteogenic differentiation via the YAP/β-catenin signaling axis. Furthermore, osteoblasts secrete alkaline phosphatase (ALP), which significantly hydrolyzes phosphate ester bonds in surface macromolecular side groups, resulting in the release of alendronate (ALN). This process further improves the local osteoporotic microenvironment. This intelligent surface modification tailors bone repair to individual conditions, automatically realize multiple endogenous regulation once implanted, and truly realize spontaneous activation of a series of responses conducive to bone repair in vivo. It is evidenced by improved bone regeneration in iron-overloaded osteoporotic rabbits and supported by in vitro validations.

Clinical performance of implanted devices used in surgical treatment of patients with spinal tumors: a systematic review

PurposeImplanted devices used in metastatic spine tumor surgery (MSTS) include pedicle screws, fixation plates, fixation rods, and interbody devices. A material to be used to fabricate any of these devices should possess an array of properties, which include biocompatibility, no toxicity, bioactivity, low wear rate, low to moderate incidence of artifacts during imaging, tensile strength and modulus that are comparable to those of cortical bone, high fatigue strength/long fatigue life, minimal or no negative impact on radiotherapy (RT) planning and delivery, and high capability for fusion to the contiguous bone. The shortcomings of Ti6Al4V alloy for these applications with respect to these desirable properties are well recognized, opening the field for an investigation about novel biomaterials that could replace the current gold standard. Previously published reviews on this topic have exhibited significant shortcomings in the studies they included, such as a small, heterogenous sample size and the lack of a cost-benefit analysis, extremely useful to understand the practical possibility of applying a novel material on a large scale. Therefore, this review aims to collect information about the clinical performance of these biomaterials from the most recent literature, with the objective of deliberating which could potentially be better than titanium in the future, with particular attention to safety, artifact production and radiotherapy planning interference. The significant promise showed by analyzing the clinical performance of these devices warrants further research through prospective studies with a larger sample size also taking into account each aspect of the production and use of such materials.MethodsThe Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines were used to improve the reporting of the review. The search was performed from March 2022 to September 2023.ResultsAt the end of the screening process, 20 articles were considered eligible for this study. Polyetheretherketone (PEEK), Carbon-fibre reinforced polyetheretherketone (CFR-PEEK), long carbon fiber reinforced polymer (LCFRP), Polymethylmethacrylate (PMMA), and carbon screw and rods were used in the included studies.ConclusionCFR-PEEK displays a noninferior safety and efficacy profile to titanium implanted devices. However, it also has other advantages. By decreasing artifact production, it is able to increase detection of local tumor recurrence and decrease radiotherapy dose perturbation, ultimately bettering prognosis for patients necessitating adjuvant treatment. Nonetheless, its drawbacks have not been explored fully and still require further investigation in future studies. This does not exclude the fact that CFR-PEEK could be a valid alternative to titanium in the near future.

An Experimental Study on the Thermomechanical Coupling Effects of Carbon-Fiber-Reinforced Polyetheretherketone under Dynamic Impact.

Carbon-fiber-reinforced polyetheretherketone (CF/PEEK) composites are widely utilized in aerospace, medical devices, and automotive industries, renowned for their superior mechanical properties and high-temperature resistance. Despite these advantages, the thermomechanical coupling behavior of CF/PEEK under dynamic loading conditions is not well understood. This study aims to explore the thermomechanical coupling effects of CF/PEEK at elevated strain rates, employing Hopkinson bar impact tests and scanning electron microscopy (SEM) for detailed characterization. Our findings indicate that an increase in temperature led to significant reductions in the yield strength, peak stress, and specific energy absorption of CF/PEEK, while fracture strain had no significant effect. For instance, at 200 °C, the yield strength, peak stress, and specific energy absorption decreased by 39%, 37%, and 38%, respectively, compared to their values at 20 °C. Furthermore, as the strain rate increased, the yield strength, peak stress, specific energy absorption, and fracture strain all exhibited strain-hardening effects. However, as the strain rate further increased, above 4000 s-1, the enhancing effect of the strain rate on the yield strength and peak stress gradually diminished. The interaction of the temperature and strain rate significantly affected the mechanical performance of CF/PEEK under high-speed impact conditions. While the strain rate generally enhanced these properties, the strain-hardening effect on the yield strength weakened as the temperature increased, and both the temperature and strain rate contributed to the increase in specific energy absorption. Microdamage mechanism analysis revealed that interface debonding and sliding between the fibers and the matrix were more pronounced under static compression than under dynamic compression, thereby diminishing the efficiency of stress transfer. Additionally, higher temperatures caused the PEEK matrix to soften and exhibit increased viscoelastic behavior, which in turn affected the material's toughness and the mechanisms of stress transfer. These insights hold substantial engineering significance, particularly for the optimization of CF/PEEK composite design and applications in extreme environments.

Thermo-oxidative crosslinking of carbon fiber reinforced PEEK (Polyetheretherketone) for additive manufactured ceramic matrix composites

Carbon fiber reinforced polyetheretherketone (CF-PEEK) samples were fabricated using material extrusion. These additive manufactured green bodies are later processed to their final application as ceramic matrix composites (CMC) by the liquid silicon infiltration (LSI) route. Past studies showed that the application of material extrusion for the fabrication of CMC requires an additional stabilization-step after 3D-printing in order to prevent the remelting of CF-PEEK during the high temperature process of pyrolysis. The thermally induced crosslinking of the CF-PEEK parts ensured shape accuracy and avoided remelting during the pyrolysis afterwards but is limited by the melting temperature of PEEK (T m ∼ 343 °C). The study revealed a correlation between the annealing conditions time and temperature and the degree of crosslinking. Based on the analytical results from differential scanning calorimetry (DSC), a kinetic model was calculated, allowing predictions in dependence of the annealing temperature and time. Rheological and shape stability investigations of thermally annealed specimens verified the analytic results. The main findings of the study highlight an increasing degree of crosslinking with increasing annealing temperature and time.

Bone healing under different lay-up configuration of carbon fiber-reinforced PEEK composite plates.

Secondary healing of fractured bones requires an application of an appropriate fixator. In general, steel or titanium devices are used mostly. However, in recent years, composite structures arise as an attractive alternative due to high strength to weight ratio and other advantages like, for example, radiolucency. According to Food and Drug Administration (FDA), the only unidirectionally reinforced composite allowed to be implanted in human bodies is carbon fiber (CF)-reinforced poly-ether-ether-ketone (PEEK). In this work, the healing process of long bone assembled with CF/PEEK plates with cross- and angle-ply lay-up configurations is studied in the framework of finite element method. The healing is simulated by making use of the mechanoregulation model basing on the Prendergast theory. Cells transformation is determined by the octahedral shear strain and interstitial fluid velocity. The process runs iteratively assuming single load cycle each day. The fracture is subjected to axial and transverse forces. In the computations, the Abaqus program is used. It is shown that the angle-ply lamination scheme of CF/PEEK composite seems to provide better conditions for the transformation of the soft callus into the bone tissue.

Pomegranate-like ZnMn2O4 nanospheres/carbon fiber network for interface enhancement structure-function PEEK composites with good electromagnetic interference shielding and thermal conductivity

The functionalization of structural carbon fiber reinforced polymer (CFRP) composites remains a significant challenge. In this work, the integration of structure-function was achieved in carbon fiber reinforced PEEK (CF/PEEK) composite by introducing a ZnMn2O4-based interface with the functionalities of electromagnetic interference (EMI) shielding and thermal conductivity (TC). The ZnMn2O4 nanospheres/CF network was constructed by introducing ZnMn2O4 nanospheres on the CF surface, realizing a significantly strengthened composite interface. Notably, the interlayer shear strength (ILSS) of the UCF-Z125/PEEK composite has reached 85.38 MPa, marking a 47.51 % increase over the Unsized CF/PEEK composite. In addition, the EMI shielding and the TC performances of the CF/PEEK composite have also improved, with the EMI shielding of the composite enhanced by 54.67 % and the through-plane TC increased by 47.17 %. This structure-function integrated composite can be used not only as structural materials in aerospace applications but also as high-performance bifunctional materials in semiconductor and artificial intelligence industries.

Mechanical property of powder bed fusion printed carbon fiber reinforced polyetheretherketone and enhanced interlayer strength by post‐processing

AbstractAdditive Manufacturing (AM) of carbon fiber reinforced polyetheretherketone (CF/PEEK) composites with excellent performance by Powder Bed Fusion (PBF) has great potential in the applications where high strength and high service temperature are required. However, the reinforcement mechanisms of CF/PEEK composites based on the PBF process are complex and show significant differences from traditional processing methods. In this paper, the mechanical properties of CF/PEEK prepared by PBF were investigated. The results showed that its X‐axis tensile strength and modulus were approximately equal to or a bit lower than the theoretical value with randomly distributed CF, but much lower than the theoretical value with unidirectional distribution of CF in composites. Meanwhile, mechanical strength anisotropy was observed. The composites' Y‐axis tensile strength was slightly lower than X‐axis, and the lowest strength existed in Z‐axis. To improve the weak Z‐axis strength, post‐processing of annealing and solvent‐induced crystallization were carried out, and the Z‐axis tensile strength of post‐processed parts reached 50 MPa, which was 62% higher than untreated samples. Consequently, suitable CF and proper post‐ processing for AM of high strength CF/PEEK were proposed, which would promote the industrial application of this technology.Highlights The effect of CF on mechanical property of CF/PEEK prepared by PBF were studied. The optimal CF for PBF of high strength CF/PEEK were obtained. The post‐processing method for improving the Z‐axis strength were proposed. CF/PEEK with comprehensive mechanical property was successfully prepared by PBF.

Comparison between CFR-PEEK and titanium plate for proximal humeral fracture: A meta-analysis.

The aim of the present meta-analysis was to compare the efficacy and safety of the carbon fiber-reinforced polyetheretherketone (CFR-PEEK) and titanium plate for the treatment of proximal humeral fractures (PHFs) from clinical comparative trials. A comprehensive search of English databases was carried out, such as PubMed, Web of Science, ScienceDirect, Springer and Cochrane Library databases. The RevMan version 5.1 software was applied for statistical analysis, and the mean difference (MD) and risk difference (RD) as the combined variables, and "95%" as the confidence interval (CIs). One randomized-controlled trial and five retrospective controlled studies including 282 PHFs were considered eligible and finally included. Meta-analysis demonstrated that there were significant differences in Constant score (CS) (MD=9.23; 95% CI: 5.02, 13.44; p<0.0001), anterior elevation (MD=18.83; 95% CI: 6.27, 31.38; p=0.003), lateral elevation (MD=18.42; 95% CI: 3.64, 33.19; p=0.01) and adduction (MD=3.53; 95% CI: 0.22, 6.84; p=0.04). No significant differences were observed regarding Constant score compared to the contralateral shoulder, Oxford Shoulder Score, internal rotation, external rotation, screw perforation and cutout, varus/valgus malalignment, humeral head collapse/necrosis, implant removal, and revision surgery between the two groups. Compared to titanium plate, CFR-PEEK plate showed better Constant score, anterior elevation, lateral elevation and adduction in treating PHFs. The complications are comparable to those achieved with conventional titanium plates.

CF/PEEK skins assembly by induction welding for thermoplastic composite sandwich panels

A method to assemble sandwich panels made of carbon fibre reinforced poly-ether-ether-ketone (CF/PEEK) facesheets and 3D-printed poly-ether-imide (PEI) honeycomb cores using induction welding is presented. Induction heating patterns inside CF/PEEK laminates of variable dimensions are first evaluated with a thermal camera and compared to a COMSOL Multiphysics model. Sandwich samples are then prepared by vacuum-assisted continuous induction welding under parameters selected from the modelling effort. Joining of sandwich panels made of CF/PEEK facesheets by induction welding under vacuum is demonstrated. Facesheets do not deconsolidate in the process and core crushing is avoided. Flatwise skin/core strength of the welded samples reaches up to 7 MPa, above reported performance for thermoset or thermoplastic composite sandwich panels.

Biomechanical Effects of Titanium and Carbon Fiber Reinforced PEEK as Dental Implant Material: A Finite Element Analysis.

The aim of this study is to examine the stresses on the peri-implant bone under occlusal forces of 30% Carbon fiber reinforced PEEK (Cfr-PEEK) and 60% Cfr-PEEK materials that can be used as an alternative to titanium dental implants by finite element analysis. Single-tooth implants of 30% Cfr-PEEK, 60% Cfr-PEEK and titanium were modeled in each of the maxillary anterior, maxilla posterior, mandibular posterior regions. As a result of the applied vertical and oblique forces; Von Misses stress, maximum principal stress and minimum principal stress values and stress distributions in the implant, cortical bone and spongious bone in each of the models were examined. 30% Cfr-PEEK implants stress in the surrounding bone was higher than titanium and 60% Cfr-PEEK implants. The 60% Cfr-PEEK material displayed lower stress distribution on both cortical and spongious peri-implant bone in all models. Titanium and 60% Cfr- PEEK implants exhibited biomechanically similar behavior and these implants conducted stresses to bone more homogeneous than the 30% Cfr-PEEK implants. Overall, oblique forces had more destructive effect than vertical forces and denser bone structure showed better stress distribution against incoming forces. For the routine use of Cfr-PEEK material as dental implant material; animal and long-term clinical studies are needed.

Effects of grinding mode on grinding performance of anisotropic CF/PEEK composites

AbstractGrinding could be used to enhance accuracy and quality of carbon fiber‐reinforced poly‐ether‐ether‐ketone (CF/PEEK) composites. However, the grinding mode, namely up‐grinding (UG) or down‐grinding (DG), is usually neglected while unbefitting grinding mode choice may cause inferior surface quality. To investigate effects of grinding modes on grinding performance of anisotropic CF/PEEK, grinding experiments in UG and DG were carried out under different fiber orientation angles θ. Experimental results indicated that maximum grinding temperatures and normal grinding forces in UG were lower than DG regardless of the abrasive grit sizes. Material removal mechanisms of CF/PEEK affected by grinding mode were revealed by analyzing morphologies of surface, chip and grinding wheel. When θ = 0°, the dominant mechanisms in DG were extrusion fracture and fiber deformation, while they were interface shear debonding and bending fracture in UG. When θ = 90°, the dominant mechanisms in DG included interface layer separation and bending fracture, while they were shear and extrusion fracture of well‐supported fibers in UG. Thus, UG was more favorable for material removal, obtaining lower surface roughness values, fewer machining defects and less wheel wear than DG. This study will provide technical guidance for high‐quality grinding of carbon fiber‐reinforced thermoplastic composites.Highlights The effects of grinding modes (DG and UG) on the grinding performance of anisotropic CF/PEEK composites were investigated. Material removal mechanisms of CF/PEEK affected by grinding mode were revealed under different fiber orientation angles. The maximum grinding temperatures and normal grinding forces in UG were lower than DG. UG was more favorable for material removal in grinding, and could produce better ground surface quality than DG.

Finite Element Analysis of the Stress and Deformation in Bone Caused by CFR-PEEK, Titanium, and Zirconia Ceramic Implants

ABSTRACT Introduction: Glass or carbon fiber-reinforced polyetheretherketone (CFR-PEEK) composites and zirconia ceramic have been offered as more modern implant biomaterials. Objectives: This study examined the effects of zirconia ceramic implants, titanium, and CFR-PEEK on bone stress and deformation. Materials and Methods: A geometric model of a mandibular molar replaced with an implant-supported crown was created for this in vitro finite element analysis investigation. The dimensions of the implant employed in the study are 11.0 mm in length and 4.5 mm in diameter. Using finite element analysis, three implant assemblies composed of zirconium, titanium, and CFR-PEEK were produced. 150 N loads were applied both vertically and obliquely on the long axis of the implant. The von-Mises stresses and deformation were compared using ANSYS Workbench 18.0 and finite element software, with a significance threshold of P &lt; 0.05. Results: All three implant assemblies—zirconia, titanium, and CFR-PEEK—showed comparable stresses and deformation in bone with no appreciable variations. Conclusion: Zirconia and PEEK reinforced with carbon fibers (CFR-PEEK) have been found to be viable replacements for titanium in implant biomaterials.

Emerging role of carbon fiber-reinforced polyetheretherketone instrumentation in spinal oncology: A systematic review

Spinal metastases are increasing in incidence with affected patients experiencing significant pain and disability. Continuous research and innovation in the field of spinal oncology have given rise to an increase in personalized treatment based on tumor characteristics and various patient-specific factors. Carbon fiber-reinforced polyetheretherketone (CFR-PEEK) instrumentation has gained popularity as an alternative to titanium-based implants primarily due to their ability to minimize imaging artifact. A literature search was performed to find articles that examined the use of CFR-PEEK screws in spinal fusion procedures in oncologic patients. Data from each study were compiled to compare complication rates, durability, and effects on postoperative imaging in patients treated with CFR-PEEK instrumentation to those treated with traditional titanium implants. Overall, CFR-PEEK-based products were similar to titanium hardware in terms of durability and complication rates while CFR-PEEK allows for improved postoperative tumor surveillance and radiosurgical planning.

Dental implant and abutment in PEEK: stress assessment in single crown retainers on anterior region.

Stress distribution assessment by finite elements analysis in poly(etheretherketone) (PEEK) implant and abutment as retainers of single crowns in the anterior region. Five 3D models were created, varying implant/abutment manufacturing materials: titanium (Ti), zirconia (Zr), pure PEEK (PEEKp), carbon fiber-reinforced PEEK (PEEKc), glass fiber-reinforced PEEK (PEEKg). A 50N load was applied 30o off-axis at the incisal edge of the upper central incisor. The Von Mises stress (σvM) was evaluated on abutment, implant/screw, and minimum principal stress (σmin) and maximum shear stress (τmax) for cortical and cancellous bone. The abutment σvM lowest stress was observed in PEEKp group, being 70% lower than Ti and 74% than Zr. On the implant, PEEKp reduced 68% compared to Ti and a 71% to Zr. In the abutment screws, an increase of at least 33% was found in PEEKc compared to Ti, and of at least 81% to Zr. For cortical bone, the highest τmax values were in the PEEKp group, and a slight increase in stress was observed compared to all PEEK groups with Ti and Zr. For σmin, the highest stress was found in the PEEKc. Stress increased at least 7% in cancellous bone for all PEEK groups. Abutments and implants made by PEEKc concentrate less σvM stress, transmitting greater stress to the cortical and medullary bone. The best stress distribution in PEEKc components may contribute to decreased stress shielding; in vitro and in vivo research is recommended to investigate this.

Strength-plasticity synergetic CF/PEEK composites obtained by adjusting melt flow rate

Short carbon fiber reinforced PEEK (CF/PEEK) composite materials with the advantages of excellent mechanical properties and easy processing, have been widely applied in the fields of aeronautics and astronautics, automotive engineering, and so on. However, their development in microinjection molding is hindered by the incompatibility between excellent plasticity and high mechanical properties. Herein, strength-plasticity synergetic CF/PEEK composites are prepared by adjusting the melt fluidity and crystallization behaviors, based on PEEK with different melt flow rate (MFR) and T800 carbon fiber. The rheological results showed that the melt viscosity of CF/PEEK composite was negatively related to the MFR of PEEK. Moreover, the mechanical properties of composites were increased by the crystallinity of PEEKs with high MFR. This work presents strength-plasticity synergetic CF/PEEK composites suitable for microinjection molding thin-walled and intricate components, offering new opportunities for next-generation portable electronic.

Performance parametric formulation of carbon fiber-reinforced composite locking bone implant plates based on finite-element analysis

The treatment of Giant Cell Tumor (GCT) in the distal radius poses challenges due to the intricate anatomical features of the bone. It often necessitates the use of long implant plates or the interconnection of multiple short plates after tumor excision. However, the deployment of metal plates may increase the risk of screw loosening and various complications. To address these challenges, this study proposes the adoption of carbon fiber-reinforced PEEK (CFRP) as the base material. As a unique strategy, performance parameters (PP) were developed to compare CFRP implant plates with a Ti-6Al-4V plate using the Finite-element Method. The focus was on four elements: the screw axial force, bone growth, callus formation, and bone resorption. The investigation into the screw axial force involved analyzing the internal force of the screw. The remaining parameters were evaluated using the stress, strain, or elastic energy induced in the bones. The findings showed that the second screw endured the largest screw axial force, measuring 10.16 N under a 90-degree 10-N loading at the translocated bone. The model without a callus exerted a significantly greater force on the screw than the model with a callus, leading to screw loosening in the early stage of treatment. The maximum PP, reached 1.62, was achieved with an angle-ply [456 /−456 ] laminate, featuring a weighting fraction of 0.7 for bone growth and 0.1 for the other parameters. This study provides a generalized methodology for assessing the performances of CFRP implants and offers guidelines for future development in composite implant plate technology.

Thermal-force coupling simulation of carbon fibre-reinforced poly-ether-ether-ketone thermoplastic composites during the laser-assisted automated tape placement process

To reveal the thermal-force coupling characteristics of the laser in-situ consolidation (ISC) of carbon fibre-reinforced poly-ether-ether-ketone (CF/PEEK) composites, a two-dimensional transient thermal-force model of CF/PEEK composites was constructed using COMSOL Multiphysics finite element simulation software to calculate the temperature history and the thermal stress variation of CF/PEEK composites during the laser-assisted automated tape placement (LATP) process. The results show that the temperature field formed on the surface of each layer by the laser spot during LATP is stable, and the temperature gradient at the front of the spot movement direction is higher than that at the back edge. The maximum stresses in the laminate occur on both sides of the first CF/PEEK layer and the stresses are unevenly distributed along the length and thickness directions of the lay-up. The composite material on both sides of the laminate tends to ‘shrink’ compared to its original position.

Investigation on grinding temperature characteristics of CF/PEEK and material removal mechanism under temperature treatments

Carbon fiber reinforced thermoplastic (CFRTP) composites grinding temperatures could even exceed the glass transition temperature (Tg) of the material due to heat accumulation, combined with the unknown material removal mechanism, resulting in machining defects. To investigate the grinding temperature distribution and maximum temperatures of carbon fiber-reinforced poly-ether-ether-ketone (CF/PEEK) composites, as a typical kind of CFRTP, an analytical temperature model considering the anisotropy was proposed based on the moving heat source theory, verified by the experimental results measured by the infrared camera. Further, the material removal mechanism under temperature treatments (below and above Tg) was also studied. In high temperatures (above Tg), there were many defects on surfaces after grinding, including resin smearing, severe deflection, fiber distortion, and grinding wheel clogging. Therefore, to reduce the grinding temperature below Tg, the vortex tube cooling-assisted grinding method was proposed in the research. The proposed method could reduce the grinding temperature in the grinding area, suppress resin smearing, improve the surface quality, enhance the elastic modulus and nano-hardness of the workpiece, and reduce the clogging of grinding wheels. This study provided a better understanding of the CF/PEEK grinding temperature characteristics and suggested a method to improve the grinding quality.

Inflammatory tissue response in human soft tissue is caused by a higher particle load near carbon fiber-reinforced PEEK compared to titanium plates

Titanium as the leading implant material in locked plating is challenged by polymers such as carbon fiber-reinforced polyetheretherketone (CFR-PEEK), which became the focus of interest of researchers and manufacturers in recent years. However, data on human tissue response to these new implant materials are rare.Osteosynthesis plates and peri‑implant soft tissue samples of 16 healed proximal humerus fractures were examined (n = 8 CFR-PEEK, n = 8 titanium). Soft tissue was analyzed by immunohistochemistry and µCT. The entrapped foreign bodies were further examined for their material composition by FTIR. To gain insight into their origin and formation mechanism, explanted and new plates were evaluated by SEM, EDX, profilometry and HR-CT.In the peri‑implant soft tissue of the CFR-PEEK plates, an inflammatory tissue reaction was detected. Tissues contained foreign bodies, which could be identified as tantalum wires, carbon fiber fragments and PEEK particles. Titanium particles were also found in the peri‑implant soft tissue of the titanium plates but showed a less intense surrounding tissue inflammation in immunohistochemistry. The surface of explanted CFR-PEEK plates was rougher and showed exposed and broken carbon fibers as well as protruding and deformed tantalum wires, especially in used screw holes, whereas scratches were identified on the titanium plate surfaces.Particles were present in the peri‑implant soft tissue neighboring both implant materials and could be clearly assigned to the plate material. Particles from both plate materials caused detectable tissue inflammation, with more inflammatory cells found in soft tissue over CFR-PEEK plates than over titanium plates. Statement of significanceOsteosynthesis plates are ubiquitously used in various medical specialties for the reconstruction of bone fractures and defects and are therefore indispensable for trauma surgeons, ENT specialists and many others. The leading implant material are metals such as titanium, but recently implants made of polymers such as carbon fiber-reinforced polyetheretherketone (CFR-PEEK) have become increasingly popular. However, little is known about human tissue reaction and particle generation related to these new implant types. To clarify this question, 16 osteosynthesis plates (n = 8 titanium and n = 8 CFR-PEEK) and the overlying soft tissue were analyzed regarding particle occurrence and tissue inflammation. Tissue inflammation is clinically relevant for the development of scar tissue, which is discussed to cause movement restrictions and thus contributes significantly to patient outcome.