Polyetheretherketone Specimens Research Articles

Differentiation of human mesenchymal stem cells on plasma-treated polyetheretherketone

Polyetheretherketone (PEEK) generally exhibits physical and chemical characteristics that prevent osseointegration. To activate the PEEK surface, we applied oxygen and ammonia plasma treatments. These treatments resulted in surface modifications, leading to changes in nanostructure, contact angle, electrochemical properties and protein adhesion in a plasma power and process gas dependent way. To evaluate the effect of the plasma-induced PEEK modifications on stem cell adhesion and differentiation, adipose tissue-derived mesenchymal stem cells (adMSC) were seeded on PEEK specimens. We demonstrated an increased adhesion, proliferation, and osteogenic differentiation of adMSC in contact to plasma-treated PEEK. In dependency on the process gas (oxygen or ammonia) and plasma power (between 10 and 200W for 5min), varying degrees of osteogenic differentiation were induced. When adMSC were grown on 10 and 50W oxygen and ammonia plasma-treated PEEK substrates they exhibited a doubled mineralization degree relative to the original PEEK. Thus plasma treatment of PEEK specimens induced changes in surface chemistry and topography and supported osteogenic differentiation of adMSC in vitro. Therefore plasma treated PEEK holds perspective for contributing to osseointegration of dental and orthopedic load-bearing PEEK implants in vivo.

Biomimetic hydroxyapatite grown on biomedical polymer coated with titanium dioxide interlayer to assist osteocompatible performance

A widely utilized spinal implant material, polyetheretherketone (PEEK), with its bio-inert and hydrophobic surface was persistently paid attention for bioactive surface modification. Hydroxyapatite (HAp), exhibiting excellent osteoconductive property, has also been regarded as a promising candidate for biomedical applications. The present study employed an arc ion plating (AIP) technique to respectively deposit rutile-rich titanium dioxide (R-TiO2) and anatase-rich titanium dioxide (A-TiO2) as an interlayer onto PEEK substrates for inducing HAp layer growth in simulated body fluid (SBF) at low temperature. Consequently, this materials are expected to promote osteoblast compatibility for PEEK to be used as spinal implants. For comparison, microstructure characterization of the as-grown HAp are examined and growth mechanism is proposed. Finally, osteocompatibility test are carried out to evaluate the effect of HAp grown on the TiO2-coated PEEK specimens.Experimental results showed that HAp growth can effectively be enhanced by adopting TiO2 interlayer in SBF environment, with the crystallinity and film thickness of the grown HAp layer proportional to immersion time. It was also worth to note that the R-TiO2/PEEK specimen exhibit superior ability to induce HAp formation, due most likely to the pre-absorbed negatively charged –OH− groups on R-TiO2 coating surface at early growth stage. This also accounts for the ultimate osteocompatibility provided by the R-TiO2 as the interlayer for growing the fastest and the highest crystallinic HAp.

Strength of poly-ether-ether-ketone: Effects of sterilisation and thermal ageing

This paper investigates the strength of polyether-ether-ketone (PEEK) after sterilisation and thermal ageing. PEEK specimens were divided into five groups, according to whether the specimens had been annealed, sterilised or aged. Specimens were subjected to either static or dynamic three-point bend tests. Static tests involved loading the specimens until a maximum displacement of 40 mm was reached. Dynamic tests involved applying a sinusoidally varying force at a frequency of 5 Hz. The maximum force applied to a specimen was based on a percentage of the static yield strength. Testing continued until failure or run out of 10 million cycles. Sterilisation and ageing resulted in no significant change in the static yield strength. Annealing was found to significantly increase the yield strength. For the dynamic tests, the fatigue strength was in the range 99.4 to 107.4 MPa; sterilisation and thermal ageing were found to have no effect on fatigue strength.

Polyetheretherketone-A suitable material for fixed dental prostheses?

To study the surface properties of polyetheretherketone (PEEK) and its bond strength with two veneering resins after different conditioning methods as well as fracture load of PEEK three-unit fixed dental prostheses (FDPs). Two hundred and twenty five PEEK specimens were fabricated and divided into five groups: no treatment (A), etching with 98% sulfuric acid for 1 min (B), air-abrasion for 10 s with either 50 or 110 μm alumina (C and D, respectively), and silica coating using the Rocatec System (E). On 15 specimens of each conditioning method, contact angle and surface roughness were determined. The remaining 150 specimens of each conditioning method were divided into two groups for the veneering procedure with the composites Gradia (GC Europe) and Sinfony (3M ESPE). Shear bond strength (SBS) was measured and failure types were assessed. In addition, 15 FDPs were milled and the fracture load was tested. Data were analyzed using descriptive statistics, one-way ANOVA (Scheffé test), two sample Student's t-test, and Weibull statistics (p < 0.05). Silica-coated PEEK surfaces showed the highest wettability. The highest roughness and lowest contact angles were observed for 110 μm air-abraded and silica-coated PEEK surfaces. The highest SBS values were, however, achieved in the acid-etched group. PEEK three-unit FDPs showed a mean fracture load of 1383 N with a plastic deformation starting approximately at 1200 N. Acid etching should be applied when PEEK is used as substructure material and composite veneering material is applied. In this combination, PEEK might be a suitable material for FDPs, especially in load-bearing areas.

ASTM F2624—Evaluating Alternate Fixtures for Flexion/Extention, Lateral Bending, and Axial Rotation Testing of Extra Discal Motion Preserving Implants

Abstract ASTM F2624-07 prescribes applying flexion/extension (FE), lateral bending (LB), and axial rotation (AR) moments to test and evaluate extra discal motion preserving implants (EDMPI), but parameters such as fixture design and load parameters are left to the user to define. A set of fixtures to conduct FE, LB, and AR testing rotation of EDMPI devices about a fixed center of rotation were developed by Aesculap Implant Systems. Their design was shared, and a set of these fixtures were manufactured and evaluated independently at Empirical Testing Corp. Testing was conducted to quantify the loads applied to an EDMPI in the FE and LB fixtures, determine whether results are frequency dependent, and evaluate whether EDMPI of different stiffnesses can be differentiated when using the fixtures. Miniature load cells were mounted to FE and LB fixtures to quantify load applied to an EDMPI during testing at several different applied loads and at two testing frequencies (2 Hz and 5 Hz). The load cells were replaced with cylindrical test specimens made of stainless steel, titanium, polyether ether ketone (PEEK), or a polyethylene cable slipped inside a polyurethane tube and the testing repeated. Results indicated that loads measured during FE testing were similar in magnitude to those recorded during LB testing but 90 degrees out of phase. No frequency effects were observed. Differences in displacement amplitude when testing the stainless steel, titanium, and PEEK specimens in FE and LB testing at both 2 Hz and 5 Hz were not discernable. The displacement amplitude of the polyethylene (PE) cord specimen was different than the other specimens, but no frequency effect was noted. The fixtures developed by Aesculap are a reasonable attempt to conduct EDMPI testing in FE, LB, and AR motions. Potential users of these fixtures should conduct further studies to determine whether their use is appropriate to test their specific EDMPI device.

Low-cycle fatigue damage mechanisms of FCC and BCC polycrystals: homologous behaviour?: Magnin, T., Ramade, C., Lepinoux, J. and Kubin, L. P. Mater. Sci. Eng. A Oct. 1989 A118, (1–2), 41–51

In this study, the effects of microstructural inclusions on fatigue life of polyether ether ketone (PEEK) was investigated. Due to the versatility of its material properties, the semi-crystralline PEEK polymer has been increasingly adopted in a wide range of applications particularly as a biomaterial for orthopedic, trauma, and spinal implants. To obtain the cyclic behavior of PEEK, uniaxial fully-reversed strain-controlled fatigue tests were conducted at ambient temperature and at 0.02 mm/mm to 0.04 mm/mm strain amplitudes. The microstructure of PEEK was obtained using the optical and the scanning electron microscope (SEM) to determine the microstructural inclusion properties in PEEK specimen such as inclusion size, type, and nearest neighbor distance. SEM analysis was also conducted on the fracture surface of fatigue specimens to observe microstructural inclusions that served as the crack incubation sites. Based on the experimental strain-life results and the observed microstructure of fatigue specimens, a microstructure-sensitive fatigue model was used to predict the fatigue life of PEEK that includes both crack incubation and small crack growth regimes. Results show that the employed model is applicable to capture microstructural effects on fatigue behavior of PEEK.

High strain fatigue crack growth in nickel-base alloys: Marchand, N. J. and Pelloux, R. M. Res. Mech. 1989 27, (4), 285–308

In this study, the fatigue behavior of a semi-crystalline thermoplastic polyether ether ketone (PEEK) is investigated. A series of tests at ambient temperature, including uniaxial monotonic (tension and compression) at different strain rates and uniaxial fully-reversed strain-controlled cyclic tests at strain amplitudes ranging from 0.02 mm/mm to 0.04 mm/mm at various frequencies, were conducted. The frequency influence on the strain-controlled fatigue lives of unfilled PEEK specimens was found to be highly dependent on the strain level. A minimal frequency effect was observed at a lower strain amplitude of 0.02 mm/mm, whereas increasing the test frequency at higher strain amplitudes resulted in longer fatigue lives. Additionally, load-controlled cyclic tests that utilized applied loads corresponding to stress responses obtained from the strain-controlled fatigue tests were performed. The cyclic behavior under the two control modes were compared and discussed. Three types of fatigue models, including a strain-based (Coffin–Manson) model, a strain–stress-based (Smith–Watson–Topper) model, and an energy-based model, were employed to correlate the data in this study. Among the three fatigue models, the energy approach was found to better correlate the PEEK experimental data at various frequencies.