Developments of PEEK (Polyetheretherketone) as a biomedical material: A focused review

Effects of porosity distribution on mechanical properties and osseointegration of porous polyetheretherketone

Porous polyetheretherketone (P-PEEK) is widely used as the material for making implant screws, and yet its mechanical properties and osseointegration for ultilization are still unsatisfied. In this work, the effects of the porosity distribution on the mechanical properties and osseointegration were investigated. Functionally graded P-PEEK (FGP-PEEK) and uniform P-PEEK (UP-PEEK) were developed by infiltration casting technology. The mechanical properties of the P-PEEK were studied by compressive and bending tests, and the osseointegration was evaluated by in vitro and rabbit femur experiments. The prepared FGP-PEEK was composed of the central dense part and its surrounding porous one where the pores were isodiametric and interconnected. Both the compressive strength and bending strength of the FGP-PEEK with graded porosity were higher than those of the UP-PEEK with uniform porosity. The mechanical properties of the FGP-PEEK were comparable to that of the human cancellous bone. The in vitro and in vivo experiments indicated the FGP-PEEK had no cytotoxicity, and its osseointegration was better than the UP-PEEK. The results demonstrated that the graded porosity had a superiority in the mechanical properties and osseointegration of the P-PEEK scaffolds compared to the uniform porosity. The influencing mechanisms of the porosity distribution on the mechanical properties and osseointegration were also clarified. Additionally, the osseointegration of the FGP-PEEK gradually increased as the surface porosity increased from 30 % to 50 %. The 50 %-surface porosity FGP-PEEK was a promising material on the application of the implant screws.

Biomedical Device Surface Treatment by Laser-Driven Hydroxyapatite Penetration-Synthesis Technique for Gapless PEEK-to-Bone Integration

Polyetheretherketone (PEEK), a bioinert polymer known for its mechanical properties similar to bone, is capable of averting stress shielding. Due to these attributes, it finds applications in diverse fields like orthopedics, encompassing cervical disc replacement for the neck and spine, along with dentistry and plastic surgery. However, due to insufficient bonding with bone, various methods such as hydroxyapatite (HA) coating on the surface are attempted. Nonetheless, the interface between the polymer and ceramic, two different materials, tended to delaminate after transplantation, posing challenges in preventing implant escape or dislodgement. This research delves into the laser-driven hydroxyapatite penetration-synthesis technique. Differing from conventional coating methods that bond layers of dissimilar materials like HA and PEEK, this technology focuses on synthesizing and infiltrating ionized HA within the PEEK substrate resulting in an interface-free HA-PEEK surface. Conversely, HA-PEEK with this technology applied achieves complete, gap-free direct bone-implant integration.  Our research involved the analysis of various aspects. By means of these, we quantitatively assesed the enhanced bone bonding characteristics of HA-PEEK surfaces treated with this approach and offered and explanation for the mechanism responsible for direct bone integration.

Investigating the Impact of Pore Size and Specification on Soft Tissue Ingrowth in 3D-Printed PEEK Material

Bone pelvis tumor resection and reconstruction is a complex surgical procedure that poses challenges in soft tissue reconstruction despite advancements in stabilizing pelvic structure. This study aims to investigate the potential of using Polyetheretherketone (PEEK) material in repairing and reconstructing soft tissues surrounding pelvic implants. Specifically, the study focuses on exploring the effectiveness of 3D printed porous PEEK material in promoting cell growth and adhesion. The interaction between PEEK materials with different pore sizes (200, 400, 600 µm) and different specifications (through-hole (T)/non-through-hole (C)) is evaluated by cell experiments and animal experiments. The soft tissue ingrowth potential of PEEK materials is evaluated by cell growth and adhesion observation. The findings indicate that PEEK material, particularly the T400 variant, exhibits stronger interaction with muscle tissue compared to its interaction with bone and fibrous tissue. The moderately sized pores present in the T400 material facilitate enhanced cell adhesion and penetration, thereby promoting cell growth and differentiation. PEEK materials with through-hole structures show promise for applications involving the repair and reconstruction of soft tissues and muscle tissue. The study provides valuable insights into the development and application of biomedical materials, specifically PEEK, contributing to the advancement of pelvic tumor resection and reconstruction techniques.

Effect of the degree of polymerization, crystallinity and sulfonation on the thermal behaviour of PEEK: a molecular dynamics-based study

The safe and efficient working of fuel cells depends on the thermal management of the heat generated during the electrochemical process. The aim of the article is to study the thermal transport phenomenon in polyether ether ketone (PEEK) using molecular dynamics (MD) based simulations. MD simulations were performed in conjunction with hybrid force fields. The effect of the degree of polymerization, crystallinity, sulfonation and the concentration of water on the thermal conductivity of PEEK was explored in this article. The Müller-Plathe algorithm was used to predict the thermal transport phenomenon in PEEK and S-PEEK. It was predicted from the simulations that the degree of polymerization and crystallinity significantly affect the thermal conductivity of PEEK, whereas the attachment of a sulfur group mitigates the thermal transport in S-PEEK. Addition of water molecules to PEEK and S-PEEK configurations leads to an enhancement in the thermal conductivity, and the effect is more prominent in S-PEEK configurations. The efficient thermal transport in the polymeric membranes of fuel cells helps in improving the working and lifecycle of the membranes.

Surface Treatment of Additively Manufactured Polyetheretherketone (PEEK) by Centrifugal Disc Finishing Process: Identification of the Key Parameters

Polyetheretherketone is a promising material for implants due to its good mechanical properties and excellent biocompatibility. Its accessibility to a wide range of applications is facilitated by the ability to process it with an easy-to-use manufacturing process such as fused filament fabrication. The elimination of disadvantages associated with the manufacturing process, such as a poor surface quality, is a main challenge to deal with. As part of the mass finishing process, centrifugal disc finishing has demonstrated good results in surface optimization, making it a promising candidate for the post-processing of additively manufactured parts. The objective of this study is to identify the key parameters of the centrifugal disc finishing process on the waviness of additively manufactured PEEK specimens, which has not been investigated previously. The waviness of the specimen was investigated by means of confocal laser scanning microscopy (CLSM), while weight loss was additionally tracked. Six parameters were investigated: type, amount and speed of media, use of compound, amount of water and time. Type of media, time and speed were found to significantly influence waviness reduction and weight loss. Surface electron microscopy images demonstrated the additional effects of deburring and corner rounding. Results on previous studies with specimens made of metal showed similar results. Further investigation is required to optimize waviness reduction and polish parts in a second post-processing step.

High-Performance Monovalent Selective Cation Exchange Membranes with Ionically Cross-Linkable Side Chains: Effect of the Acidic Groups

Inspired by the charge-governed protein channels located in the cell membrane, a series of polyether ether ketone-based polymers with side chains containing ionically cross-linkable quaternary ammonium groups and acidic groups have been designed and synthesized to prepare monovalent cation-selective membranes (MCEMs). Three acidic groups (sulfonic acid, carboxylic acid, and phenolic hydroxyl) with different acid dissociation constant (pKa) were selected to form the ionic cross-linking structure with quaternary ammonium groups in the membranes. The ionic cross-linking induced the nanophase separation and constructed ionic channels, which resulted in excellent mechanical performance and high cation fluxes. Interesting, the cation flux of membranes increased as the ionization of acidic groups increase, but the selectivity of MCEMs did not follow the same trend, which was mainly dependent on the affinity between the functional groups and the cations. Carboxyl group-containing MCEMs exhibited the best selectivity (9.01 for Li+/Mg2+), which was higher than that of the commercial monovalent cation-selective CIMS membrane. Therefore, it is possible to prepare stable MCEMs through a simple process using ionically cross-linkable polymers, and tuning acidic groups in the membranes provided an attractive approach to improving the cation flux and selectivity of MCEMs.

Graphene Oxide-Silver-Coated Sulfonated Polyetheretherketone (Ag/GO-SPEEK): A Broad-Spectrum Antibacterial Artificial Bone Implants

Polyetheretherketone (PEEK), particularly its sulfonated form (SPEEK), has emerged as a promising synthetic biomaterial for artificial bone implants, providing an alternative to conventional titanium metal. However, postoperative infections pose a critical challenge, driven by diverse and antibiotic-resistant bacteria. To address this issue, we propose the modification of the SPEEK surface using a thin graphene oxide (GO) film containing silver (Ag) ions. The resulting coating exhibits substantial antibacterial effects against various pathogens, including Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Candida albicans. Experimental assessments elucidate the coating's impact on bacterial adhesion, biofilm formation, and morphology. The results suggest that hindered bacterial growth stems from reduced biofilm production and the controlled release of Ag ions facilitated by the GO coating. The Ag/GO-SPEEK material holds promise as a bioactive implant, addressing the challenges associated with bacterial targeting in bone tissue engineering applications.

Effects of Nd: YAG LASER irradiation and O2 plasma on the adhesive performance of poly-ether-ether-ketone (PEEK)

PURPOSE

To evaluate the effects of neodymium-doped yttrium aluminum garnet (Nd: YAG) LASER irradiation and oxygen (O2) plasma on the adhesive performance of polyether ether ketone (PEEK) and resin adhesive.

METHODS

Nd: YAG LASERs of varying powers and O2 plasma for different durations were used to modify PEEK. A total of 168 PEEK specimens were randomly divided into seven groups (n = 24/group): (A) Control group: untreated PEEK, (B) L0.75 group: PEEK modified with 0.75 W Nd: YAG LASER, (C) L1 group: PEEK modified with 1.0 W Nd: YAG LASER, (D) L1.25 group: PEEK modified with 1.25 W Nd: YAG LASER, (E) P15 group: PEEK modified with 15 min of O2 plasma, (F) P25 group: PEEK modified with 25 min of O2 plasma, and (G) P35 group: PEEK modified with 35 min of O2 plasma. The surface characteristics of the materials were comprehensively analyzed using a scanning electron microscope (SEM), profilometer, energy-dispersive spectrometer (EDS), and contact angle tester. The adhesive specimens were bonded with Variolink N resin adhesive in all groups and each group was further divided into two subgroups (n = 12/group): (a) water storage for 56 h at 37 °C and (b) thermal cycling 5000 times. Shear bond strength (SBS) was tested using a universal testing machine, and the fracture modes were observed using an automated chemiluminescence analysis system to assess the effects of Nd: YAG LASER and O2 plasma on the bond strength of PEEK to resin adhesive.

RESULTS

Both Nd: YAG LASER and O2 plasma treatments altered the surface characteristics of PEEK and significantly increased the SBS between PEEK and Variolink N resin adhesive. The L0.75 group (Nd: YAG LASER) and the P35 group (O2 plasma) achieved the highest SBS, respectively. Furthermore, the SBS of the L0.75 group was higher than that of the P35 group. Following thermal cycling, SBS values decreased compared to the water storage subgroups. The fracture modes of the specimens in each group were predominantly interfacial and mixed, with no cohesive fractures observed.

CONCLUSIONS

Nd: YAG LASER irradiation and O2 plasma treatments can improve the SBS between PEEK and resin adhesive, with the 0.75 W Nd: YAG LASER being the preferred treatment method.

Methods to improve antibacterial properties of PEEK: A review

As a thermoplastic and bioinert polymer, polyether ether ketone (PEEK) serves as spine implants, femoral stems, cranial implants, and joint arthroplasty implants due to its mechanical properties resembling the cortical bone, chemical stability, and radiolucency. Although there are standards and antibiotic treatments for infection control during and after surgery, the infection risk is lowered but can not be eliminated. The antibacterial properties of PEEK implants should be improved to provide better infection control. This review includes the strategies for enhancing the antibacterial properties of PEEK in four categories: immobilization of functional materials and functional groups, forming nanocomposites, changing surface topography, and coating with antibacterial material. The measuring methods of antibacterial properties of the current studies of PEEK are explained in detail under quantitative, qualitative, andin vivomethods. The mechanisms of bacterial inhibition by reactive oxygen species generation, contact killing, trap killing, and limited bacterial adhesion on hydrophobic surfaces are explained with corresponding antibacterial compounds or techniques. The prospective analysis of the current studies is done, and dual systems combining osteogenic and antibacterial agents immobilized on the surface of PEEK are found the promising solution for a better implant design.

Chemically heparinized PEEK via a green method to immobilize bone morphogenetic protein-2 (BMP-2) for enhanced osteogenic activity

Osseointegration remains one of the major challenges in the success of bone-related implants. Recently, polyetheretherketone (PEEK) has emerged as an alternative material in orthopedic and dental applications due to its bone-mimicking mechanical properties. However, its bioinertness resulting in poor osseointegration has limited its potential application. So, the surface modification of PEEK with bone morphogenetic protein-2 (BMP-2) can be a potential approach for improving osseointegration. In this study, we proposed the chemical modification of heparin onto PEEK through an environmentally benign method to exploit the BMP-2 binding affinity of heparin. The heparin was successfully functionalized on the PEEK surface via a combination of ozone and UV treatment without using organic solvents or chemicals. Furthermore, BMP-2 was efficiently immobilized on PEEK and exhibited a sustained release of BMP-2 compared to the pristine PEEK with enhancement of bioactivity in terms of proliferation as well as osteogenic differentiation of MG-63. The significant synergistic effect of BMP-2 and heparin grafting on osteogenic differentiation of MG-63 was observed. Overall, we demonstrated a relatively safe method where no harsh chemical reagent or organic solvent was involved in the process of heparin grafting onto PEEK. The BMP-2 loaded, heparin-grafted PEEK could serve as a potential platform for osseointegration improvement of PEEK-based bone implants.

Surface characteristics of 3D printed PEEK polymer using atomic force microscopy

High-performance polymer three-dimensional printing is becoming more popular for producing unique parts suitable for different applications. It has been utilized extensively in biomedical applications such as dental prosthetics, surgical equipment, and implants. However, the performance of the material is significantly influenced by its surface qualities, particularly in aspects of its adhesion and biocompatibility. This study involves the fabrication of PEEK specimens S1, S2, S3, and S4 with different printing parameters such as layer height of 0.10 and 0.15 mm and printing speed of 20 and 25 mm/s using a fused deposition modeling process. The surface roughness of the fabricated specimens is measured using atomic force microscopy. The results showed that the printing parameters significantly impact the surface roughness of the PEEK specimens. The surface roughness of specimen S3, printed at a layer height of 0.15 mm and a speed of 20 mm/s, has a low roughness value of 0.017 μm, which is considerable in comparison to the other specimens. In addition to the measurement of surface roughness from roughness profile, the force curve separation graph was plotted and the adhesion force values were calculated for all the specimens to determine the interlayer bonding strength.

Conditioning of PEEK Implant Abutment Surfaces Using Photodynamic Therapy, Nd:YAG Laser, and Conventional Methods to Evaluate Shear Bond Strength

Objective: This study was done to evaluate shear bond strength (SBS) and modes of failures after different surface treatment modalities on polyetheretherketone (PEEK) implant abutments. Materials and methods: Seventy-five PEEK implant abutment specimens were randomly distributed into five groups based on surface treatment methods: Group I: No treatment, Group II: methylene blue-mediated photodynamic therapy (MB-PDT), Group III: neodymium-doped yttrium aluminum garnet (Nd:YAG) laser, Group IV: Sulfuric acid (H2SO4), and Group V: Sandblasting (Sb). The measurements for SBS and failure modes for PEEK implant abutment specimens were evaluated via Universal Testing Machine and Stereomicroscope, respectively. Two-way analysis of variance and Tukey's post-hoc test (p > 0.05) were used for the statistical analysis. Moreover, the Shapiro-Wilk normality test was also performed for normality. Results: The SBS mean values and standard deviations in megapascals (MPa) for PEEK abutment specimens with different surface pretreatment groups are shown in Table 1 and Fig. 1. The control group had the lowest SBS (9.67 ± 2.1 MPa), while the highest SBS was observed in Group II (MB-PDT; 17.21 ± 1.32 MPa). SBS values for Group IV (H2SO4; 15.83 ± 0.63 MPa) and Group III (Nd:YAG laser; 16.91 ± 2.10 MPa) were similar to Group II (MB-PDT; p > 0.05). The SBS values for the sandblasted specimens (13.90 ± 1.87 MPa) were not significantly different from the control group (p > 0.05). Conclusions: The PEEK implant abutment surfaces treated with MB-PDT and Nd:YAG laser expressed significantly improved SBS.

Biomedical Applications of Titanium Alloys: A Comprehensive Review

Titanium alloys have emerged as the most successful metallic material to ever be applied in the field of biomedical engineering. This comprehensive review covers the history of titanium in medicine, the properties of titanium and its alloys, the production technologies used to produce biomedical implants, and the most common uses for titanium and its alloys, ranging from orthopedic implants to dental prosthetics and cardiovascular devices. At the core of this success lies the combination of machinability, mechanical strength, biocompatibility, and corrosion resistance. This unique combination of useful traits has positioned titanium alloys as an indispensable material for biomedical engineering applications, enabling safer, more durable, and more efficient treatments for patients affected by various kinds of pathologies. This review takes an in-depth journey into the inherent properties that define titanium alloys and which of them are advantageous for biomedical use. It explores their production techniques and the fabrication methodologies that are utilized to machine them into their final shape. The biomedical applications of titanium alloys are then categorized and described in detail, focusing on which specific advantages titanium alloys are present when compared to other materials. This review not only captures the current state of the art, but also explores the future possibilities and limitations of titanium alloys applied in the biomedical field.

A New Promising Material for Biological Applications: Multilevel Physical Modification of AgNP-Decorated PEEK

In the case of polymer medical devices, the surface design plays a crucial role in the contact with human tissue. The use of AgNPs as antibacterial agents is well known; however, there is still more to be investigated about their anchoring into the polymer surface. This study describes the changes in the surface morphology and behaviour in the biological environment of polyetheretherketone (PEEK) with immobilised AgNPs after different surface modifications. The initial composites were prepared by immobilising silver nanoparticles from a colloid solution in the upper surface layers of polyetheretherketone (PEEK). The prepared samples (Ag/PEEK) had a planar morphology and were further modified with a KrF laser, a GaN laser, and an Ar plasma. The samples were studied using the AFM method to visualise changes in surface morphology and obtain information on the height of the structures and other surface parameters. A comparative analysis of the nanoparticles and polymers was performed using FEG-SEM. The chemical composition of the surface of the samples and optical activity were studied using XPS and UV-Vis spectroscopy. Finally, drop plate antibacterial and cytotoxicity tests were performed to determine the role of Ag nanoparticles after modification and suitability of the surface, which are important for the use of the resulting composite in biomedical applications.

Evaluation of Cytocompatibility of PEEK-Based Composites as a Function of Manufacturing Processes

The biocompatible polymer polyetheretherketone (PEEK) is a suitable candidate to be part of potential all-polymer total joint replacements, provided its use is associated with better osseointegration, mechanical performance, and wear resistance. Seeking to meet the aforementioned requirements, respectively, we have manufactured a PEEK composite with different fillers: carbon fibers (CF), hydroxyapatite particles (HA) and graphene platelets (GNP). The mechanical outcomes of the composites with combinations of 0, 1.5, 3.0 wt% GNP, 5 and 15 wt% HA and 30% of wt% CF concentrations pointed out that one of the best filler combinations to achieve the previous objectives was 30 wt% CF, 8 wt% HA and 2 wt% of GNP. The study compares the bioactivity of human osteoblasts on this composite prepared by injection molding with that on the material manufactured by the Fused Filament Fabrication 3D additive technique. The results indicate that the surface adhesion and proliferation of human osteoblasts over time are better with the composite obtained by injection molding than that obtained by 3D printing. This result is more closely correlated with morphological parameters of the composite surface than its wettability behavior.

Compression properties and constitutive model of short glass fiber reinforced poly-ether-ether-ketone (PEEK)

To analyze the deformation behavior of short glass fiber-reinforced poly-ether-ether-ketone (SGFR-PEEK) under various conditions through numerical simulations, it is crucial to construct a constitutive model that can describe its stress-strain behavior over a wide range of strain rates and temperatures. In this study, quasi-static compression tests were conducted on SGFR-PEEK composites with varying mass fractions, and dynamic tests were performed using a Split Hopkinson Pressure Bar to acquire the material's compressive stress-strain response under quasi-static and dynamic conditions. The results indicate that, under compression, the yield stress of SGFR-PEEK composites increases with an augmentation in glass fiber content, rises with increasing strain rate, and decreases with elevated temperature. Based on experimental findings, a modified Johnson-Cook constitutive model was established to characterize the mechanical performance of SGFR-PEEK. In comparison to the traditional Johnson-Cook intrinsic structure model, the modified model takes into account the glass fiber mass fraction as comprehensively as possible and better predicts the material's flow behavior at high strain rates. Finally, this modified constitutive model was implemented in the ABAQUS software using the user-defined subroutine VUMAT to simulate the compression behavior of SGFR-PEEK composites under different loading conditions, and the model was validated. This research provides valuable insights for the practical application of SGFR-PEEK composites in engineering.

Effect of Ridge Splitting of Mandibular Knife Edge Ridges with Two-implant Retained Overdenture with Locator Attachments on Peri-implant Bone Level and Posterior Ridge Resorption: A One-year Preliminary Study

AIM

This study was conducted to evaluate peri-implant bone height changes and posterior ridge resorption by using two-implant retained polyetheretherketone (PEEK) overdentures with locator attachments following expansion of mandibular knife edge ridges by ridge splitting.

MATERIALS AND METHODS

Eighteen patients were selected for ridge splitting followed by expansion, implant placement, and bone graft application. Six months later, the fabrication of PEEK overdentures retained by locator attachments was accomplished. Friedman test, Wilcoxon signed-rank test, and Spearman correlation were used to evaluate the changes over time.

RESULTS

Peri-implant bone height loss increased significantly with the advance of time between 6 and 12 months following denture insertion. Posterior area index changes were significant over time when measured at the time of denture insertion and twelve months following denture insertion.

CONCLUSION

The effect of using PEEK as overdenture base material retained with two locator attachments allowed sharing the load between the peri-implant bone anteriorly and residual ridge posteriorly in cases with ridge splitting technique.

CLINICAL SIGNIFICANCE

Using PEEK as an overdenture base material is a successful means of bone preservation. How to cite this article: Helmy MA, El-Shaheed NH, El Waseef FA, et al. Effect of Ridge Splitting of Mandibular Knife Edge Ridges with Two-implant Retained Overdenture with Locator Attachments on Peri-implant Bone Level and Posterior Ridge Resorption: A One-year Preliminary Study. J Contemp Dent Pract 2023;24(11):834-839.

Progress in Nanostructured Mechano-Bactericidal Polymeric Surfaces for Biomedical Applications

Bacterial infections and antibiotic resistance remain significant contributors to morbidity and mortality worldwide. Despite recent advances in biomedical research, a substantial number of medical devices and implants continue to be plagued by bacterial colonisation, resulting in severe consequences, including fatalities. The development of nanostructured surfaces with mechano-bactericidal properties has emerged as a promising solution to this problem. These surfaces employ a mechanical rupturing mechanism to lyse bacterial cells, effectively halting subsequent biofilm formation on various materials and, ultimately, thwarting bacterial infections. This review delves into the prevailing research progress within the realm of nanostructured mechano-bactericidal polymeric surfaces. It also investigates the diverse fabrication methods for developing nanostructured polymeric surfaces with mechano-bactericidal properties. We then discuss the significant challenges associated with each approach and identify research gaps that warrant exploration in future studies, emphasizing the potential for polymeric implants to leverage their distinct physical, chemical, and mechanical properties over traditional materials like metals.

Virtual Design of 3D-Printed Bone Tissue Engineered Scaffold Shape Using Mechanobiological Modeling: Relationship of Scaffold Pore Architecture to Bone Tissue Formation

Large bone defects are clinically challenging, with up to 15% of these requiring surgical intervention due to non-union. Bone grafts (autographs or allografts) can be used but they have many limitations, meaning that polymer-based bone tissue engineered scaffolds (tissue engineering) are a more promising solution. Clinical translation of scaffolds is still limited but this could be improved by exploring the whole design space using virtual tools such as mechanobiological modeling. In tissue engineering, a significant research effort has been expended on materials and manufacturing but relatively little has been focused on shape. Most scaffolds use regular pore architecture throughout, leaving custom or irregular pore architecture designs unexplored. The aim of this paper is to introduce a virtual design environment for scaffold development and to illustrate its potential by exploring the relationship of pore architecture to bone tissue formation. A virtual design framework has been created utilizing a mechanical stress finite element (FE) model coupled with a cell behavior agent-based model to investigate the mechanobiological relationships of scaffold shape and bone tissue formation. A case study showed that modifying pore architecture from regular to irregular enabled between 17 and 33% more bone formation within the 4-16-week time periods analyzed. This work shows that shape, specifically pore architecture, is as important as other design parameters such as material and manufacturing for improving the function of bone tissue scaffold implants. It is recommended that future research be conducted to both optimize irregular pore architectures and to explore the potential extension of the concept of shape modification beyond mechanical stress to look at other factors present in the body.

Effect of carbon-fiber-reinforced polyetheretherketone on stress distribution in a redesigned tumor-type knee prosthesis: a finite element analysis

Background: Surgery for bone tumors around the knee often involves extensive resection, making the subsequent prosthetic reconstruction challenging. While carbon fiber-reinforced polyetheretherketone (CF-PEEK) has been widely used in orthopedic implants, its application in tumor-type prosthesis is limited. This study aims to evaluate the feasibility of using 30wt% and 60wt% carbon fiber-reinforced polyetheretherketone (CF30-PEEK and CF60-PEEK) as materials for a redesigned tumor-type knee prosthesis through numerical analysis. Methods: A knee joint model based on CT data was created, and the resection and prosthetic reconstruction were simulated. Three finite element models of the prostheses, representing the initial and updated designs with CoCrMo and CFR-PEEK components, were constructed. Loading conditions during standing and squatting were simulated with forces of 700 N and 2800 N, respectively. Finite element analysis was used to analyze the von Mises stress and stability of all components for each prosthesis type. Results: After improvements in both material and design, the new Type 3 prosthesis showed significantly lower overall stress with stress being evenly distributed. Compared with the initial design, the maximum von Mises stress in Type 3 was reduced by 53.9% during standing and 74.2% during squatting. In the standing position, the maximum stress in the CF30-PEEK femoral component decreased by 57.3% compared with the initial design which was composed of CoCrMo, while the stress in the CF60-PEEK cardan shaft remained consistent. In the squatting position, the maximum stress in the femoral component decreased by 81.9%, and the stress in the cardan shaft decreased by 46.5%. Conclusion: The incorporation of CF30-PEEK effectively transmits forces and reduces stress concentration on the femoral component, while CF60-PEEK in the redesigned cardan shaft significantly reduces stress while maintaining stiffness. The redesigned prosthesis effectively conducts loading force and demonstrates favorable biomechanical characteristics, indicating the promising potential of utilizing CF30-PEEK and CF60-PEEK materials for tumor-type knee prostheses. The findings of this study could provide novel insights for the design and development of tumor-type knee prostheses.

Continuous monitoring of multiple biomarkers with an ultrasensitive 3D-structured wearable biosensor

Chronic diseases call for routine management of frequent monitoring of specific biomarkers. Traditional in vitro diagnostics technologies suffer from complex sampling processes and long detection intervals, which cannot meet the need of continuous monitoring. Wearable devices taking advantage of compact size, rapid detection process, and small sample consumption are promising to take the place of endpoint detection, providing more comprehensive information about human health. Here, we proposed a fully integrated wearable system with an ultrasensitive 3D-structured biosensor for real-time monitoring of multiple metabolites. The 3D-structured biosensor shows wide linear ranges of 400-1,400 μM and 0.1-8 mM and high sensitivities of 460.5 and 283.09 μA/(mM·cm2) for lactate and glucose detection, respectively. We have conducted in vivo animal experiments, and the proposed wearable biosensor demonstrated high consistency with established methods. We envision that this system could provide a real-time wearable detection platform for multiple biomarker detection.

An overview of the tribological and mechanical properties of PEEK and CFR-PEEK for use in total joint replacements

Poly-ether-ether-ketone (PEEK) and PEEK composites are outstanding candidates for biomedical applications, such as orthopedic devices, where biocompatibility and modulus match with surrounding tissue are requisite for long-term success. The mechanical properties can be optimized by incorporating fillers such as continuous and chopped carbon fibers. While much is known about the mechanical and tribological behavior of PEEK composites, there are few articles that summarize the viability of using PEEK reinforced with carbon fibers in orthopedic implants. This paper reviews biocompatibility, tribological, and mechanical studies on PEEK and their composites with carbon fibers, notably PEEK reinforced with polyacrylonitrile (PAN)-based carbon fibers and PEEK reinforced with pitch-based carbon fibers, for application in orthopedics and total joint replacements (TJRs). The main objectives of this review are two-fold. Firstly, this paper aims to assist designers in making informed decisions on the suitability of using PEEK and PEEK composites in orthopedic applications; as it is not well understood how these materials perform on the whole in orthopedics and TJRs. Secondly, this paper aims to serve as a centralized paper in which researchers can gain information on the tribological and mechanical advancements of PEEK and PEEK composites.

Advances in Biodegradable Polymers and Biomaterials for Medical Applications-A Review

The introduction of new materials for the production of various types of constructs that can connect directly to tissues has enabled the development of such fields of science as medicine, tissue, and regenerative engineering. The implementation of these types of materials, called biomaterials, has contributed to a significant improvement in the quality of human life in terms of health. This is due to the constantly growing availability of new implants, prostheses, tools, and surgical equipment, which, thanks to their specific features such as biocompatibility, appropriate mechanical properties, ease of sterilization, and high porosity, ensure an improvement of living. Biodegradation ensures, among other things, the ideal rate of development for regenerated tissue. Current tissue engineering and regenerative medicine strategies aim to restore the function of damaged tissues. The current gold standard is autografts (using the patient's tissue to accelerate healing), but limitations such as limited procurement of certain tissues, long operative time, and donor site morbidity have warranted the search for alternative options. The use of biomaterials for this purpose is an attractive option and the number of biomaterials being developed and tested is growing rapidly.

Effect of coping materials zirconia or polyetheretherketone with different techniques of fabrication on vertical marginal gap and fracture resistance of posterior crowns with composite veneering

BACKGROUND

Insufficient research has been conducted in the literature assessing the performance of zirconia and polyetheretherketone (PEEK) crowns in relation to the essential requirements of successful restorations, such as fracture resistance or margin adaptation. The purpose of this study was to evaluate the effect of the coping materials zirconia or PEEK with different fabrication techniques on the vertical marginal gap and fracture resistance of posterior crowns with composite veneering.

METHODS

Ceramic copings (n = 18) restoring mandibular first molar were fabricated from zirconia (Zircon.x, Presidentdental, Germany), milled PEEK (PEEK CAD) (breCAM.BioHPP, Bredent, Germany) and pressed PEEK (PEEK Press) (BioHPP Granules, Bredent, Germany) six specimens each (n = 6). The copings were veneered with high impact polymer composite (HIPC) material (breCAM.HIPC, Bredent, Germany). The vertical marginal gap was captured under a magnification of 40X. Five equidistant marks on each surface of the die distinguished the points of measurement for a total of 20 readings per sample. The analysis was completed using an image analysis system (ImageJ 1.53t, National Institute of Health, USA). The specimens were loaded to failure at a crosshead speed of 1 mm/min and the load at failure was recorded to measure the fracture resistance.

RESULTS

The marginal gap was analyzed using one-way ANOVA followed by Tukey's post hoc test. Fracture resistance was analyzed using Welch one-way ANOVA followed by the Games-Howell post hoc test. Marginal gap values showed a significant difference between the tested groups, with zirconia having significantly lower gap values (48.67 ± 11.98 µm) than both the PEEK CAD (108.00 ± 20.08 µm) and Press groups (108.00 ± 25.10 µm) (p < 0.001). However, the results of fracture resistance showed no significant difference (p = 0.06) with 1687.47 ± 253.29 N, 2156.82 ± 407.64 N, 2436.72 ± 725.93 N for zirconia, PEEK CAD, and Press, respectively. The significance level was p < 0.05.

CONCLUSIONS

Zirconia framework crowns have a smaller vertical marginal gap than milled and pressed PEEK crowns. Crowns fabricated from zirconia, PEEK CAD, or PEEK Press frameworks and veneered with composite resin have comparable fracture resistance lower than the maximum biting force in the posterior region.

CLINICAL RELEVANCE

Posterior crowns with zirconia frameworks are preferred over milled and pressed PEEK frameworks regarding margin adaptation, although all can safely survive the maximum occlusal forces without fracture.

Solid implantable devices for sustained drug delivery

Implantable drug delivery systems (IDDS) are an attractive alternative to conventional drug administration routes. Oral and injectable drug administration are the most common routes for drug delivery providing peaks of drug concentrations in blood after administration followed by concentration decay after a few hours. Therefore, constant drug administration is required to keep drug levels within the therapeutic window of the drug. Moreover, oral drug delivery presents alternative challenges due to drug degradation within the gastrointestinal tract or first pass metabolism. IDDS can be used to provide sustained drug delivery for prolonged periods of time. The use of this type of systems is especially interesting for the treatment of chronic conditions where patient adherence to conventional treatments can be challenging. These systems are normally used for systemic drug delivery. However, IDDS can be used for localised administration to maximise the amount of drug delivered within the active site while reducing systemic exposure. This review will cover current applications of IDDS focusing on the materials used to prepare this type of systems and the main therapeutic areas of application.

Polyetheretherketone development in bone tissue engineering and orthopedic surgery

Polyetheretherketone (PEEK) has been widely used in the medical field as an implant material, especially in bone tissue engineering and orthopedic surgery, in recent years. This material exhibits superior stability at high temperatures and is biosecured without harmful reactions. However, the chemical and biological inertness of PEEK still limits its applications. Recently, many approaches have been applied to improve its performance, including the modulation of physical morphology, chemical composition and antimicrobial agents, which advanced the osteointegration as well as antibacterial properties of PEEK materials. Based on the evolution of PEEK biomedical devices, many studies on the use of PEEK implants in spine surgery, joint surgery and trauma repair have been performed in the past few years, in most of which PEEK implants show better outcomes than traditional metal implants. This paper summarizes recent studies on the modification and application of biomedical PEEK materials, which provides further research directions for PEEK implants.

Mechanical performance and bioactivation of 3D-printed PEEK for high-performance implant manufacture: a review

Polyetheretherketone (PEEK) has stood out as the leading high-performance thermoplastic for the replacement of metals in orthopaedic, trauma and spinal implant applications due to its high biocompatibility and mechanical properties. Despite its potential for custom-made medical devices, 3D-printed PEEK's mechanical performance depends on processing parameters and its bioinertness may hinder bone opposition to the implant. Concerning these challenges, this review focuses on the available literature addressing the improvement of the mechanical performance of PEEK processed through "fused filament fabrication" (FFF) along with literature on bioactivation of PEEK for improved osseointegration. The reviewed research suggests that improvements can be achieved in mechanical performance of 3D-printed PEEK with adequate FFF parametrization while different bioactivation techniques can be used to improve the bioperformance of 3D-printed PEEK. The adequate approaches towards these procedures can increase PEEK's potential for the manufacture of high-performance custom-made implantable devices that display improved bone-implant integration and prevent stress shielding of the treated bone.

Calcium Silicate Whiskers-Enforced Poly(Ether-Ether-Ketone) Composites with Improved Mechanical Properties and Biological Activities for Bearing Bone Reconstruction

Poly (ether-ether-ketone) (PEEK) displays promising potential application in bone tissue repair and orthopedic surgery due to its good biocompatibility and chemical stability. However, the bio-inertness and poor mechanical strength of PEEK greatly limit its application in load-bearing bones. In this study, calcium silicate whiskers (CSws) are synthesized and then compounded with PEEK to fabricate the PEEK/CSw composites with excellent mechanical properties, biological activity. Compared with PEEK, the PEEK/CSw composites exhibited higher hydrophilicity and ability to deposit hydroxyapatite on the surface. CSws are evenly dispersed in the PEEK matrix at 10 wt% content and the mechanical strength of the PEEK/CSw composite is ≈96.9 ± 2.4 MPa, 136.3 ± 2.4 MPa, and 266.0 ± 3.2 MPa, corresponding to tensile strength, compressive strength, and bending strength, respectively, which is 20%, 18%, and 52% higher than that of pure PEEK. The composites improve the adhesion, proliferation, and osteogenic differentiation of BMSCs. Furthermore, PEEK/CSw composite remarkably improves bone formation and osteointegration, which has higher bone repair capacity than PEEK. These results demonstrate that the PEEK/CSw scaffolds display superior abilities to integrate with the host bone and promising potential in the field of load bearing bone repair.

The Use of the Three-Dimensional Printed Polyether Ether Ketone Implant in Secondary Craniosynostosis Revision

BACKGROUND

Skull deformities may be seen in patients years after craniosynostosis correction. These deformities cause psychosocial distress in affected patients. In this series, the authors describe the use of patient specific polyether ether ketone (PEEK) implants for correction of skull deformities after cranial vault remodeling for craniosynostosis.

METHODS

A chart review was conducted for 3 revision procedures performed by 1 plastic surgeon in collaboration with 1 neurosurgeon, both affiliated with Northwell Health. Preoperative computed tomography scans were used to design three-dimensional (3D) printed PEEK implants manufactured by KLS Martin. Implants were used to correct frontal and orbital asymmetry and skull deformities in each patient. Outcomes were assessed at 1 week, 1 month, and 3 months post-operation.

RESULTS

Two males and 1 female, ages 13, 17, and 19, underwent revision cranioplasty or orbital rim reconstruction using a custom, single piece 3D printed PEEK implant. All 3 patients underwent cranial vault remodeling in infancy; 1 was treated for coronal craniosynostosis and 2 were treated for metopic craniosynostosis. Revision cranioplasty operative times were 90, 105, and 147 minutes, with estimated blood loss of 45 mL, 75 mL, and 150 mL, respectively. One patient went home on post op day 1 and 2 patients went home on post op day 2. All patients had an immediate improvement in structural integrity and cranial contour, and all patients were pleased with their aesthetic results.

CONCLUSIONS

Custom 3D printed PEEK implants offer a single piece solution in revision cranioplasty surgery to correct skull deformities after cranial vault remodeling for craniosynostosis.

Early Osteogenic Marker Expression in hMSCs Cultured onto Acid Etching-Derived Micro- and Nanotopography 3D-Printed Titanium Surfaces

Polyetheretherketone (PEEK) titanium composite (PTC) is a novel interbody fusion device that combines a PEEK core with titanium alloy (Ti6Al4V) endplates. The present study aimed to investigate the in vitro biological reactivity of human bone-marrow-derived mesenchymal stem cells (hBM-MSCs) to micro- and nanotopographies produced by an acid-etching process on the surface of 3D-printed PTC endplates. Optical profilometer and scanning electron microscopy were used to assess the surface roughness and identify the nano-features of etched or unetched PTC endplates, respectively. The viability, morphology and the expression of specific osteogenic markers were examined after 7 days of culture in the seeded cells. Haralick texture analysis was carried out on the unseeded endplates to correlate surface texture features to the biological data. The acid-etching process modified the surface roughness of the 3D-printed PTC endplates, creating micro- and nano-scale structures that significantly contributed to sustaining the viability of hBM-MSCs and triggering the expression of early osteogenic markers, such as alkaline phosphatase activity and bone-ECM protein production. Finally, the topography of 3D-printed PTC endplates influenced Haralick's features, which in turn correlated with the expression of two osteogenic markers, osteopontin and osteocalcin. Overall, these data demonstrate that the acid-etching process of PTC endplates created a favourable environment for osteogenic differentiation of hBM-MSCs and may potentially have clinical benefit.

The Single-Step Fabrication of a Poly (Sodium Vinylsulfonate)-Grafted Polyetheretherketone Surface to Ameliorate Its Osteogenic Activity

Polyetheretherketone (PEEK) is considered a potential material for replacing traditional biomedical metals used in orthopedic implants because of its similar elastic modulus to human bone. However, the poor osteogenic activity of PEEK itself hinders its clinical application. In this study, a PEEK surface was grafted with poly (sodium vinylsulfonate) through a single-step ultraviolet-initiated graft polymerization method to ameliorate its osteogenic activity. X-ray photoelectron spectroscopy and water contact angle measurements confirmed that different amounts of poly (sodium vinylsulfonate) were grafted onto the PEEK surface upon varying the ultraviolet irradiation time. Atomic force microscopy revealed that the surface topography and roughness of PEEK before and after surface grafting did not change significantly. The in vitro results showed that grafting with poly (sodium vinylsulfonate) rendered the PEEK surface with improved MC3T3-E1 osteoblast compatibility and osteogenic activity. Moreover, a PEEK surface with a higher grafting amount of poly (sodium vinylsulfonate) was observed to be more beneficial to the proliferation and osteogenic differentiation of MC3T3-E1 osteoblasts. Collectively, by employing this simple and one-step method, the osteogenic activity of PEEK can be enhanced, paving the way for the clinical application of PEEK in orthopedic implants.

Alloplastic temporomandibular joint replacement: present status and future perspectives of the elements of embodiment

Medical device embodiment involves the following elements: materials, design, and manufacturing. Failure of any one of these elements can result in failure of the device, despite the others being satisfactory. The abundance of clinical and basic science literature published since 1986, demonstrates the safety and efficacy of alloplastic temporomandibular joint replacement (TMJR). Currently, there are 19 countries producing 41 TMJR devices. More than 75% are custom designed, and 27% are additively manufactured. In light of the increasing number of TMJR devices being designed and manufactured around the world, this paper will discuss TMJR embodiment so that clinicians understand their present status as well as the prospects for the future of new and/or improved TMJR devices, to ensure that these devices continue to be safe and effective long-term surgical options for the management of end-stage TMJ pathologies.

Cenospheres-Reinforced PA-12 Composite: Preparation, Physicochemical Properties, and Soaking Tests

The main aim of this research was the preparation of a polymer–ceramic composite with PA-12 as the polymer matrix and modified aluminosilicate cenospheres (CSs) as the ceramic filler. The CSs were subjected to an early purification and cleaning process, which was also taken as a second objective. The CSs were surface modified by a two-step process: (1) etching in Piranha solution and (2) silanization in 3-aminopropyltriethoxysilane. The composite was made for 3D printing by FDM. Raw and modified CSs and a composite with PA-12 were subjected to the following tests: surface development including pores (BET), real density (HP), chemical composition and morphology (SEM/EDS, FTIR), grain analysis (PSD), phase composition (XRD), hardness (HV), and static tensile tests. The composites were subjected to soaking under simulated body fluid (SBF) conditions in artificial saliva for 14, 21, and 29 days. Compared to pure PA-12, PA-12_CS had generally better mechanical properties and was more resistant to SBF at elevated temperatures and soaking times. These results showed this material has potential for use in biomedical applications. These results also showed the necessity of developing a kinetic aging model for aging in different liquids to verify the true value of this material.

Tribological and Antibacterial Properties of Polyetheretherketone Composites with Black Phosphorus Nanosheets

Over the past few decades, polyetheretherketone (PEEK) artificial bone joint materials faced problems of poor wear resistance and easy infection, which are not suitable for the growing demand of bone joints. The tribological behavior and wear mechanism of polyetheretherketone (PEEK)/polytetrafluoroethylene (PTFE) with black phosphorus (BP) nanosheets have been investigated under dry sliding friction. Compared with pure PEEK, the COF of PEEK/10 wt% PTFE/0.5 wt% BP was reduced by about 73% (from 0.369 to 0.097) and the wear rate decreased by approximately 95% (from 1.0 × 10⁻⁴ mm³/(N m) to 5.1 × 10⁻⁶ mm³/(N m)) owing to the lubrication of the BP transfer film. Moreover, BP can endow the PEEK composites with excellent biological wettability and antibacterial properties. The antibacterial rate of PEEK/PTFE/BP was assessed to be over 99.9%, which might help to solve the problem of PEEK implant inflammation. After comprehensive evaluation in this research, 0.5 wt% BP nanosheet-filled PEEK/PTFE material displayed the optimum lubrication and antibacterial properties, and thus could be considered as a potential candidate for its application in biomedical materials.

3D PEEK Objects Fabricated by Fused Filament Fabrication (FFF)

PEEK (poly ether ether ketone) materials printed using FFF 3D printing have been actively studied on applying electronic devices in satellites owing to their excellent light weight and thermal resistance. However, the PEEK FFF process generated cavities inside due to large shrinkage has degraded both mechanical integrity and printing reliability. Here, we have investigated the correlations between nozzle temperatures and PEEK printing behaviors such as the reliability of printed line width and surface roughness. As the temperature increased from 360 to 380 °C, the width of the printed line showed a tendency to decrease. However, the width of PEEK printed lines re-increased from 350 to 426 μm at the nozzle temperatures between 380 and 400 °C, associated with solid to liquid-like phase transition and printed out distorted and disconnected lines. The surface roughness of PEEK objects increased from 49 to 55 μm as the nozzle temperature increased from 380 to 400 °C, where PEEK is melted down and quickly solidified based on more energy and additional heating time at higher printing temperatures at 400 °C. Based on these printing trends, a reliability analysis of the printed line was performed. The printed line formed the most uniform width at 380 °C and had a highest Weibull coefficient of 28.6 using the reliability analysis technique called Weibull modulus.

Facilitating GL13K Peptide Grafting on Polyetheretherketone via 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide: Surface Properties and Antibacterial Activity

In the present work, the antimicrobial peptide (AMP) of GL13K was successfully coated onto a polyetheretherketone (PEEK) substrate to investigate its antibacterial activities against Staphylococcus aureus (S. aureus) bacteria. To improve the coating efficiency, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) was mixed with a GL13K solution and coated on the PEEK surface for comparison. Both energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) data confirmed 30% greater peptide coating on PEEK/GL13K-EDC than PEEK without EDC treatment. The GL13K graft levels are depicted in the micrograms per square centimeter range. The PEEK/GL13K-EDC sample showed a smoother and lower roughness (Rq of 0.530 µm) than the PEEK/GL13K (0.634 µm) and PEEK (0.697 µm) samples. The surface of the PEEK/GL13K-EDC was more hydrophilic (with a water contact angle of 24°) than the PEEK/GL13K (40°) and pure PEEK (89°) samples. The pure PEEK disc did not exhibit any inhibition zone against S. aureus. After peptide coating, the samples demonstrated significant zones of inhibition: 28 mm and 25 mm for the PEEK/GL13K-EDC and PEEK/GL13K samples, respectively. The bacteria-challenged PEEK sample showed numerous bacteria clusters, whereas PEEK/GL13K contained a little bacteria and PEEK/GL13K-EDC had no bacterial attachment. The results confirm that the GL13K peptide coating was able to induce antibacterial and biofilm-inhibitory effects. To the best of our knowledge, this is the first report of successful GL13K peptide grafting on a PEEK substrate via EDC coupling. The present work illustrates a facile and promising coating technique for a polymeric surface to provide bactericidal activity and biofilm resistance to medical implantable devices.

Comparison of the dose perturbation arising from conventional and the novel PEEK prosthesis materials during high energy radiotherapy with 15 MV photons

Aim:

This study aimed to evaluate the dosimetric effects of the metal prosthesis in radiotherapy by Siemens Primus 15 MV linac accelerator. In addition, it proposed the new material could lead to less dose perturbation.

Materials and methods:

The depth dose distributions of typical hip prostheses were calculated for 15 MV photons by MCNP-4C code. Five metal prostheses were selected to reveal the correlation between material type, density and dose perturbations of prostheses. Furthermore, the effects of the location and thickness of the prosthesis on the dose perturbation were also discussed and analysed.

Results:

The results showed that the Co-Cr-Mo alloy as the prosthesis had more influence on the dose at the interface of metal tissue. The dose increased at the entrance of this prosthesis and experienced the reduction when passed through it. Finally, the impact of the new PEEK biomedical polymer materials was also investigated, and the lowest dose perturbations were introduced based on the obtained results.

Conclusion:

It was found that the mean relative dose before and after of PEEK prosthesis was 99·2 and 97·1%, respectively. Therefore, this new biomedical polymer material was proposed to replace the current metal implants.

Thermo-Mechanical Behavior of Poly(ether ether ketone): Experiments and Modeling

Observations are reported on poly(ether ether ketone) (PEEK) in uniaxial tensile tests, relaxation tests and creep tests with various stresses in a wide interval of temperatures ranging from room temperature to 180 °C. Constitutive equations are developed for the thermo-mechanical behavior of PEEK under uniaxial deformation. Adjustable parameters in the governing equations are found by matching the experimental data. Good agreement is demonstrated between the observations and results of numerical simulation. It is shown that the activation energies for the elastoplastic, viscoelastic and viscoelastoplastic responses adopt similar values at temperatures above the glass transition point.