Biomechanical analyses of one-piece dental implants composed of titanium, zirconia, PEEK, CFR-PEEK, or GFR-PEEK: Stresses, strains, and bone remodeling prediction by the finite element method.

This work aimed to assess the biomechanics, using the finite element method (FEM), of traditional titanium Morse taper (MT) dental implants compared to one-piece implants composed of zirconia, polyetheretherketone (PEEK), carbon fiber-reinforced PEEK (CFR-PEEK), or glass fiber-reinforced PEEK (GFR-PEEK). MT and one-piece dental implants were modeled within a mandibular bone section and loaded on an oblique force using FEM. A MT implant system involving a Ti6Al4V abutment and a cp-Ti grade IV implant was compared to one-piece implants composed of cp-Ti grade IV, zirconia (3Y-TZP), PEEK, CFR-PEEK, or GFR-PEEK. Stress on bone and implants was computed and analyzed while bone remodeling prediction was evaluated considering equivalent strain. In comparison to one-piece implants, the traditional MT implant revealed higher stress peak (112 MPa). The maximum stresses on the one-piece implants reached ~80 MPa, regardless their chemical composition. MT implant induced lower bone stimulus, although excessive bone strain was recorded for PEEK implants. Balanced strain levels were noticed for reinforced PEEK implants of which CFR-PEEK one-piece implants showed proper biomechanical behavior. Balanced strain levels might induce bone remodeling at the peri-implant region while maintaining low risks of mechanical failures. However, the strength of the PEEK-based composite materials is still low for long-term clinical performance.

Chitosan/ß-TCP composites scaffolds coated with silk fibroin: a bone tissue engineering approach.

Bone regeneration and natural repair are long-standing processes that can lead to uneven new tissue growth. By introducing scaffolds that can be autografts and/or allografts, tissue engineering provides new approaches to manage the major burdens involved in this process. Polymeric scaffolds allow the incorporation of bioactive agents that improve their biological and mechanical performance, making them suitable materials for bone regeneration solutions. The present work aimed to create chitosan/beta-tricalcium phosphate-based scaffolds coated with silk fibroin and evaluate their potential for bone tissue engineering. Results showed that the obtained scaffolds have porosities up to 86%, interconnectivity up to 96%, pore sizes in the range of 60-170 µm, and a stiffness ranging from 1 to 2 MPa. Furthermore, when cultured with MC3T3 cells, the scaffolds were able to form apatite crystals after 21 d; and they were able to support cell growth and proliferation up to 14 d of culture. Besides, cellular proliferation was higher on the scaffolds coated with silk. These outcomes further demonstrate that the developed structures are suitable candidates to enhance bone tissue engineering.

Biomechanical behavior of functionally graded S53P4 bioglass-zirconia dental implants: Experimental and finite element analyses.

OBJECTIVES: The aim of this work was to evaluate the biomechanical behavior of one-piece zirconia implants with a functionally graded bioglass (BG) layer as compared to monolithic zirconia and BG-coated implants, using the finite element method (FEM). METHODS: Zirconia disks were infiltrated with bioglass S53P4 and then morphologically inspected by scanning electron microscopy (SEM) followed by mechanical analyses on micro-indentation tests for further biomechanical validation using the finite element method (FEM). On modeling, zirconia dental implants anchored into mandibular bone were simulated on occlusal loading as recorded under mastication. Three types of implants were simulated: i) free of BG coating, ii) with 100 µm or 150 µm thick conventional BG coatings; and iii) with graded BG coatings involving 3 different chemical composition distributions. The stress state at both implant and bone were evaluated using the FEM. The mechanically-induced bone remodelling was analyzed through the bone strain results. RESULTS: Infiltration of BG into a zirconia structure resulted in a ∼100 µm thick layer with an exponential-like gradation of chemical composition and properties. Regarding the FEM calculations, the BG coating induced up to 30% decrease on stress in the implant body when compared to the monolithic zirconia implant. The gradient of chemical composition also improved the stresses' distribution. The stresses distribution towards the BG-coatings were significantly high and could lead to failure. Stresses on the bone were recorded down to its strength threshold, with insignificant influence of the coating layer. The bone strain values on all models indicates further bone remodelling although BG-coated and BG-graded zirconia implants showed the highest strain magnitude that may enhance the mechanical stimulation for bone maintenance. SIGNIFICANCE: Graded BG-zirconia dental implants showed enhanced overall biomechanical behaviour as compared to the BG-coated or monolithic zirconia dental implants. Also, such biomechanical improvements noticed for the BG-graded system should be considered in combination with the well-known osseointegration benefits of bioactive glasses.

Three-dimensional bioactive hydrogel-based scaffolds for bone regeneration in implant dentistry.

Bone tissue requires a range of complex mechanisms to allow the restoration of its structure and function. Bone healing is a signaling cascade process, involving cells secreting cytokines, growth factors, and pro-inflammatory factors in the defect site that will, subsequently, recruit surrounding stem cells to migrate, proliferate, and differentiate into bone-forming cells. Bioactive functional scaffolds could be applied to improve the bone healing processes where the organism is not able to fully regenerate the lost tissue. However, to be optimal, such scaffolds should act as osteoconductors - supporting bone-forming cells, providing nutrients, and sustaining the arrival of new blood vessels, and act as osteoinducers - slowly releasing signaling molecules that stimulate mesenchymal stem cells to differentiate and deposit mineralized bone matrix. Different compositions and shapes of scaffolds, cutting-edge technologies, application of signaling molecules to promote cell differentiation, and high-quality biomaterials are reaching favorable outcomes towards osteoblastic differentiation of stem cells in in vitro and in vivo researches for bone regeneration. Hydrogel-based biomaterials are being pointed as promising for bone tissue regeneration; however, despite all the research and high-impact scientific publications, there are still several challenges that prevent the use of hydrogel-based scaffolds for bone regeneration being feasible for their clinical application. Hence, the objective of this review is to consolidate and report, based on the current scientific literature, the approaches for bone tissue regeneration using bioactive hydrogel-based scaffolds, cell-based therapies, and three-dimensional bioprinting to define the key challenges preventing their use in clinical applications.

On the synergistic effect of sulfonic functionalization and acidic adhesive conditioning to enhance the adhesion of PEEK to resin-matrix composites.

OBJECTIVE: The objective of this study was to evaluate the combined effect of the sulfuric acid etching and an acidic adhesive conditioning on the shear bond strength of PEEK to a resin-matrix composite. MATERIALS AND METHODS: Forty PEEK specimens were assigned randomly to 4 groups for H2SO4 etching followed by universal adhesive (pH at 2.5) conditioning for 0, 1, 3, and 5 min. Thirty PEEK specimens were divided into 3 groups for only acidic adhesive conditioning for 0, 1, 3, and 5 min. After the light-curing of the adhesive, a nanohybrid resin composite was applied onto the surfaces and then light-cured following the manufacturer`s guidelines. All specimens were stored in distilled water at 37 °C for 24 h mechanical testing. Shear bond strength tests were performed using a universal testing machine. Surfaces were analyzed by SEM, light interferometry, FTIR, and liquid contact angle measurement. Statistical analysis was performed by one-way ANOVA and Tukey's post hoc tests (p < 0.05). RESULTS: No adhesion was achieved between untreated PEEK a resin-matrix composite, regardless of the adhesive conditioning time points. Shear bond strength of H2SO4-etched PEEK to resin-matrix composite increased with time (0 mmin. 4.95 ± 2.86 MPa < 1 min: 9.35 ± 2.26 MPa < 3 min: 17.84 ± 2.82 MPa < 5 min: 21.43 ± 5.00 MPa). SEM images revealed a significant modification of PEEK surface topography after the H2SO4 etching. SIGNIFICANCE: The acidic adhesive was unable to modify the untreated PEEK surface to establish an effective adhesion although a synergistic effect was noticed when the universal (acidic) adhesive was applied over a H2SO4-etched PEEK surface, thus improving the PEEK to resin-matrix composite adhesion.

In-vitro mechanical and biological evaluation of novel zirconia reinforced bioglass scaffolds for bone repair.

Bone defects resulting from infections, tumors, or traumas represent a major health care issue. Tissue engineering has been working togehter with medicine to develop techniques to repair bone damage and increase patient's life quality. In that context, scaffolds composed of bioactive ceramics have been explored, although their poor mechanical properties restrain their clinical applications as highly porous structures. As an alternative solution, this study aimed to evaluate the mechanical properties and biological response of novel zirconia reinforced bioactive glass scaffolds (ZRBG) manufactured by the replica method. The microstructure, chemical composition, compressive strength, density, in-vitro bioactivity, and cell viability were analyzed and compared to scaffolds made of monolithic zirconia of similar architecture (45, 60 and 85 ppi). The microstructure of ZRGB scaffolds consisted of a bioactive glass matrix with dispersed zirconia particles (~33% glassy phase) and the compressive strength values (ZRBG scaffolds: 0.33 ± 0.11, 0.41 ± 0.20 and 0.48 ± 0.6 MPa; ZRBG scaffolds with extra BG coating: 0.38 ± 0.13, 0.45 ± 0.11 and 0.50 ± 0.14 MPa for 45, 60 and 80 ppi, respectively) were not statistically different from those of zirconia scaffolds (0.25 ± 0.14 MPa for 45 ppi, 0.32 ± 0.11 MPa for 60 ppi and 0.44 ± 0.07 MPa for 80 ppi). No bioactivity was exhibited by monolithic zirconia scaffolds while significant bioactive response was found for ZRBG scaffolds. The cell viability of ZRBG scaffolds in osteogenic medium was improved up to 171% over zirconia scaffolds. This work provides promosing results for further exploring this technique for implant dentistry.

Adhesion behavior of conventional and high-translucent zirconia: Effect of surface conditioning methods and aging using an experimental methodology.

OBJECTIVE: Evaluate the adhesive behavior of conventional and high-translucent zirconia after surface conditioning and hydrothermal aging. MATERIALS AND METHODS: Conventional (ZrC) and high-translucent zirconia (ZrT) specimens were divided into six groups: without surface treatment (ZrC and ZrT), air-borne particle abrasion with 50-µm Al2 O3 sized particles (ZrC-AO and ZrT-AO), and tribochemical treatment with 30-µm silica modified Al2 O3 sized particles (ZrC-T and ZrT-T). Zirconia specimens were treated using an MDP-containing universal adhesive and bonded to two resins blocks with an adhesive luting cement. Microbar specimens with cross-sectioned areas of 1 mm2 were achieved. Half of the microbars were subjected to hydrothermal aging. Bond strength was evaluated by microtensile bond strength test and statistically evaluated by the Weibull analysis. RESULTS: Roughness of the ZrC-AO and ZrT-AO groups were statistically higher. Bond strength analysis revealed higher bond strength for ZrC-AO and ZrC-T groups compared to ZrT-AO and ZrT-T, respectively. Mixed failure was the most frequent for the mechanically treated groups, while no cohesive failures were obtained. CONCLUSION: Lower values of bond strength were obtained for the mechanically treated high-translucent zirconia groups when compared to their conventional zirconia counterparts. Mechanical surface treatment significantly improved the bond strength to conventional and high-translucent zirconia. CLINICAL SIGNIFICANCE: Mechanical surface treatment (air-borne particle abrasion or tribochemical treatment) associated with the use of universal adhesives containing MDP could provide a durable bonding to conventional and high-translucent zirconia.

Production and characterization of zirconia structures with a porous surface.

The aim of this study was to produce zirconia structures with a porous surface by the dip coating technique and assess the mechanical properties of the structures as well as the integrity of the porous layers. Surface porous layers with homogenous and graded porosity were produced over zirconia substrate discs using zirconia powders with different average sizes (d50 = 40 µm; d50 = 70 µm and d50 = 100 µm) and without pore forming fugitive phases. Specimens were inspected using Scanning Electron Microscopy. Bending strength of specimens was obtained from biaxial flexural tests (B3B). Porous layers were successfully produced on zirconia discs substrates and the bending strength of these specimens were ~35% lower than uncoated specimens. Delamination occurred especially in layers with higher thickness and made of bigger particles. Practical application examples were provided in this paper showing the versatility of these porous surfaces in the production of multifunctional surfaces for stronger interfaces.

Release of simvastatin from scaffolds of poly(lactic-co-glycolic) acid and biphasic ceramic designed for bone tissue regeneration.

The aim of this study was to evaluate the release of simvastatin from scaffolds composed of poly(lactic-co-glycolic) acid (PLGA) and biphasic ceramic designed for bone engineering and to assess the physico-chemical and mechanical properties of the scaffolds. Samples with 30% and 70% porosity were obtained with 0, 2, 5, and 8 wt %. of simvastatin through the solvent evaporation technique and leaching of sucrose particles. Scaffold degradation and simvastatin release were evaluated in phosphate-buffered saline. Scaffolds were analyzed by scanning electron microscopy and microtomography for two-dimensional and three-dimensional morphological characterization of the porosity, connectivity, and intrinsic permeability. The mechanical characterization was conducted based on the compressive strength and the chemical characterization by differential scanning calorimetry and energy dispersive X-ray spectroscopy. Gradual and prolonged simvastatin release from the scaffolds was observed. The release followed the Korsmeyer kinetics model with the predominance of case II transport for 30% porosity scaffolds, and anomalous behavior for the 70% porosity samples. Simvastatin release was also influenced by the slow scaffold degradation due to the strong chemical interaction between simvastatin and PLGA, as observed by differential scanning calorimetry. The scaffolds presented spherical and sucrose crystal-shaped pores that resulted in a homogenous porosity, with a predominance of open pores, ensuring interconnectivity. Simvastatin incorporation into the scaffolds and increased porosity did not influence the mechanical properties. The scaffolds presented gradual and prolonged simvastatin release, with satisfactory physico-chemical and mechanical properties. The scaffolds presented gradual and prolonged simvastatin release, with satisfactory physico-chemical and mechanical properties, a promise for applications in bone regeneration. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2152-2164, 2019.

Mechanical integrity of cement- and screw-retained zirconium-lithium silicate glass-ceramic crowns to Morse taper implants.

STATEMENT OF PROBLEM: The improved esthetics of ceramic dental prostheses has increased their popularity, although their high elastic modulus and low fracture toughness and tensile strength may reduce the long-term performance of dental prostheses. PURPOSE: The purpose of this in vitro study was to assess the mechanical integrity of zirconium-lithium silicate glass-ceramic crowns cement- and screw-retained to a titanium implant-abutment after fatigue. MATERIAL AND METHODS: Forty titanium implants were placed in polyacetal to mimic bone support. Abutments were tightened to the implants to 20 Ncm by using a digital handheld torque meter. The implant abutment assemblies received a pressed maxillary premolar crown, either lithium disilicate (LD) or zirconium-lithium silicate glass-ceramic (LZS). The specimens (n=10) were subjected to fatigue at 200 N and 5 Hz for 500 000 cycles in a Ringer electrolytic solution (37°C). After fatigue, the crowns were removed to evaluate removal torque values on the implant-abutment connection. The remaining crown-implant-abutment assemblies were cross-sectioned at 90 degrees to the implant-abutment joint for inspection of cracks and the micro-gaps by scanning electron microscopy. RESULTS: Removal torque values before fatigue were recorded at 18 ±1.63 Ncm for the LD group and 18.2 ±0.81 Ncm for the LZS group. After fatigue, the removal torque values decreased significantly (12.8 ±1.6 Ncm for LD, 14.9 ±1.08 Ncm for LZS; P<.05). Micro-gaps at the implant-abutment connections were measured at 0.9 ±0.3 µm before fatigue and at 4.2 ±0.9 µm after fatigue. Cracks were detected at the crown adhesive or at the adhesive-abutment interface for both systems after fatigue. CONCLUSIONS: Cement- and screw-retained implant zirconium-lithium silicate glass-ceramic crowns revealed effective fatigue resistance on mean cyclic loading in an electrolyte solution. However, mechanical instability of the crown-adhesive-abutment interfaces and implant-abutment joints was detected after fatigue.

Influence of laser structuring of PEEK, PEEK-GF30 and PEEK-CF30 surfaces on the shear bond strength to a resin cement.

OBJECTIVES: The aim of this study was to evaluate the influence of a surface conditioning technique using laser ablation and acid etching on PEEK substrate on its bonding strength to a resin cement. MATERIALS AND METHODS: Cylindrical specimens of unfilled PEEK, 30% glass fiber reinforced PEEK and 30% carbon fiber reinforced PEEK were separated in four groups according to the following surface treatments: acid etching with H2SO4, laser ablation with 200 µm holes spaced 400 µm apart (D2E4), laser ablation with 200 µm holes spaced 600 µm apart (D2E6), and laser ablation (D2E4) followed by acid etching. A dual-curing resin cement (Allcem CORE) was then applied to the PEEK surface. Specimens were aged in distilled water at 37 °C for 24 h. Shear bond strength tests were performed to the fracture of the samples. Two-way ANOVA statistical analysis was performed with a significance level of 0.05. Scanning electron microscopy analysis was performed to analyse the conditioned and fracture surfaces. RESULTS: SEM images of the test interfaces showed that the resin cement could not flow in the holes designed by the laser ablation on the PEEK surface. The shear bond strength of PEEK to resin cement was not improved by the surface modification of the PEEK. Also, there was a statistically significant decrease in shear bond strength for unfilled PEEK specimens. On carbon or glass reinforced PEEK, the change was not significant. SEM images of the fracture surfaces revealed that the failure mode was mainly adhesive. CONCLUSIONS: Although laser ablation promoted the PEEK surface modification by the formation of retentive holes, the test resin cement could not thoroughly flow on the rough modified surfaces to establish an effective mechanical interlocking. That negatively affected the shear bonding strength of PEEK to the resin cement. Further studies should be carried out to increase the bonding between PEEK and resin cements.

Bond strength enhancement of zirconia-porcelain interfaces via Nd:YAG laser surface structuring.

OBJECTIVES: The aim of this study was to evaluate the effect of laser surface structuring on the bond strength of feldspar-based porcelain to zirconia, as compared to conventional sandblasting treatment. MATERIALS AND METHODS: Thirty cylindrical zirconia substrates, previously sintered, were divided in three groups according to the type of surface conditioning: 1) sandblasting with 50 µm Al2O3; 2) laser structuring (Ø25 µm holes); and 3) laser structuring (Ø50 µm holes). Porcelain was injected onto the zirconia substrates. X-ray diffractometry (XRD) was used to evaluate the influence of the laser treatment on zirconia crystallographic phases. Shear bond strength test was performed. Micrographs using SEM were used to evaluate the zirconia surface after each surface treatment and to evaluate the fracture surface after the shear test. RESULTS: The laser-structured groups presented the highest shear bond strength (65 ±â€¯16 MPa and 65 ±â€¯11 MPa, for the 25 µm and 50 µm holes, respectively). The sandblasting samples presented shear bond strength of 37 ±â€¯16 MPa. XRD analysis showed that there was no phase transformation on the thermally affected surface due to laser action. Microcracks were created at some holes due to the high temperature gradient generated by laser. SIGNIFICANCE: Laser structuring significantly increased (up to 75%) the shear bond strength of zirconia to veneering porcelain as compared to conventional sandblasting treatment. Therefore, laser structuring arises as a surface conditioning method for producing stronger and long lasting zirconia-porcelain interfaces.

Mesoporous bioactive glass embedding propolis and cranberry antibiofilm compounds.

The aim of this study was to evaluate the chemical reactivity of 58S mesoporous bioactive glass (MBG) particles in as-synthesized condition and after embedding propolis and cranberry antibiofilm compounds at different concentrations. MBG 58S was synthesized by alkali sol-gel method with the addition of the triblock pluronic copolymer P123 as surfactant. Samples were characterized by physicochemical properties measurement, N2 adsorption/desorption analysis, and field emission gun scanning electron microscopy (FEGSEM) observations. MBG powders were immersed into 5 and 10 µg/mL propolis or cranberry solutions for 24 h. The chemical reactivity of the specimens was evaluated by FEGSEM, EDX, FTIR, Ca/P ratio, XRD, and sample weight gain analysis after being immersed in simulated body fluid (SBF) for 8, 24, and 72 h. MBG particles exhibited the expected chemical composition with a particle size distribution ranging from 1.44 to 955 µm, and a mean particle size of 154 µm. MBG particles exhibited a pore volume of 0.8 cc/g, pore radius of ∼2 nm, and surface area of 350.2 m2 /g, according to BJH and BET analyses. A hydroxyl-carbonate apatite (HCAp) layer was formed on all samples after SBF immersion for 72 h. Pure MBG showed the highest chemical reactivity after 72 h, with the resulting apatite layer exhibiting a Ca/P ratio of ∼1.6 in accordance to stoichiometric biological apatite. MBG embedding propolis and cranberry can be considered for future microbiological analysis since the presence of propolis or cranberry did not interfere with MBG's ability to develop a HCAp layer, which is an essential feature for bone regeneration applications. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1614-1625, 2018.

On the synthesis and characterization of ß-tricalcium phosphate scaffolds coated with collagen or poly (D, L-lactic acid) for alveolar bone augmentation.

OBJECTIVES: After tooth loss, dimensional alterations on the alveolar bone ridge can occur that can negatively affect the placement of dental implants. The purpose of this study was to evaluate the synthesis, and mechanical properties of ß-tricalcium phosphate (ß-TCP) scaffolds coated with bioabsorbable polymers, namely, collagen and poly (D, L-lactic acid) (PDLLA). MATERIALS AND METHODS: ß-TCP powder was obtained by reactive milling and then characterized by X-ray diffraction and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS). ß-TCP scaffolds were obtained by replica method, in which polyurethane foams are immersed in ß-TCP suspension and thereafter submitted to a thermal treatment to remove the polyurethane and sinter the ceramic. Type-I collagen or PDLLA were used to coat the ß-TCP scaffolds by dip-coating method. Scaffolds were separated in four groups depending on the coating material: noncoated (Group A), double immersion in collagen (Group B), double immersion in PDLLA (Group C), and ten immersions in PDLLA (Group D). Samples were characterized by compressive tests and SEM/EDS. Data were statistically analyzed through two-way ANOVA (p = 0.05). RESULTS: Chemical and microscopic analyses revealed proper morphology and chemical composition of powder particles and scaffolds with or without polymeric coatings. Scaffolds coated with PDLLA showed higher compressive strength (0.11 ± 0.054 MPa) than those of collagen (0.022 ± 0.012 MPa) or noncoated groups (0.024 ± 0.012 MPa). CONCLUSIONS: The coating method of ß-TCP with PDLLA revealed a potential strategy to increase the mechanical strength of porous ceramic materials while collagen can enhance cell migration.

Physicochemical and biological assessment of PEEK composites embedding natural amorphous silica fibers for biomedical applications.

The main aim of this study was to assess the physicochemical and biological properties of a novel poly(ether ether ketone) (PEEK) composite containing 30%wt natural amorphous silica fibers (NASF). PEEK and NASF powders were previously functionalized by atomization and citric acid in order to enhance adhesion between polymeric matrix and fillers. Then, composites were produced by cold compression molding technique at 350°C for 3h. Materials were characterized by chemical, microstructural, thermophysical, mechanical and cytotoxic analysis. The results of the mechanical assays showed that the incorporation fibers increased the elastic modulus of the resultant PEEK composite in 56% while its microhardness increased in 26.7%. Chemical and microscopic analyses detected a good interfacial adhesion between PEEK and NASF. The results of the cytotoxicity assays indicated that PEEK/NASF composites stimulated the metabolic activity of fibroblasts and therefore a high cytocompatibility was noticed. PEEK composites embedding natural amorphous silica fibers revealed a high potential to be used in medicine and dentistry replacing several polymeric and composite materials.

Biofilm behavior on sulfonated poly(ether-ether-ketone) (sPEEK).

Poly(ether-ether-ketone) (PEEK) has also shown to be very attractive for incorporating therapeutic compounds thanks to a sulfonation process which modifies the material structure resulting in a sulfonated-PEEK (sPEEK). Concerning biomedical applications, the objective of this work was to evaluate the influence of different sulfonation degree of sPEEK on the biofilm growth. PEEK samples were functionalized by using sulphuric acid (98%) and then dissolved into dimethyl-sulfoxide. A dip coating technique was used to synthesize sPEEK thin films. The sulfonation degree of the materials was analyzed by FT-IR, H NMR, TG and IEC. The surfaces were characterized by scanning electron microscopy, profilometry and contact angle analyses. Subsequently, the biofilm formation on sulfonated-PEEK based on Streptococcus mutans and Enterococcus faecalis was measured by spectrophotometry, colony forming units (CFUmL-1) and SEM. Results obtained from thermal and chemical analyses showed an intensification in sulfonation degree for sPEEK at 2 and 2.5h. The E. faecalis or S. mutans biofilm growth revealed statistically significant differences (p<0.05) between 2 and 3h sulfonation groups. A significant decrease (p<0.05) in CFUmL-1 was recorded for S. mutans or E. faecalis biofilm grown on 2.5 or 3h sPEEK. Regarding the thermal-chemical and microbiologic analyses, the sulfonation degree of sPEEK ranging from 2 up to 3h was successful capable to decrease the biofilm growth. That revealed an alternative strategy to embed anti-biofilm and therapeutic compounds into PEEK avoiding infections in biomedical applications.

Chemical, microscopic, and microbiological analysis of a functionalized poly-ether-ether-ketone-embedding antibiofilm compounds.

Poly-ether-ether-ketone (PEEK) is currently introduced as an alternative material for orthopedic implants due to its biocompatibility and low elastic modulus compared to titanium. Also, a sulphonation treatment can functionalize PEEK to embed therapeutical substances. The objective of this work was to functionalize a PEEK film to incorporate novel lactam-based antibiofilms compounds. PEEK samples were functionalized by sulphuric acid treatment and then dissolved in dimethylsulfoxide, where lactams were added to be incorporated into the polymer. A dip-coating technique was used to synthesize a thin film on a glass-based substrate. The degree of sulfonation (DS) and the incorporation of lactams into sulphonated PEEK (sPEEK) were analyzed by Fourier transform infrared spectroscopy, nuclear magnetic resonance, thermogravimetric analysis (TGA), and scanning electron microscopy. A DS of 65% was obtained and TGA curves confirmed the presence of SO3 H and lactams in the sPEEK structure. The growth of Streptococcus mutans biofilm decreased on sPEEK surface containing lactams when compared to sPEEK free of lactams. That indicated the antibiofilm activity of those compounds was maintained after incorporation into sPEEK. Planktonic growth analysis showed no long distant effects of sPEEK containing lactams, indicating that no systemic effects should be expected upon clinical uses of medical devices produced with lactam-treated sPEEK. Results revealed that inclusion of lactams into sPEEK represents a good alternative for the production of biomaterials resistant to bacterial accumulation. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 3015-3020, 2016.

In vivo human electrochemical properties of a NiTi-based alloy (Nitinol) used for minimally invasive implants.

The development of a homemade device for in vivo human determination of the open circuit potential (OCP) of Nitinol is described. Pseudo-reference electrodes (316L stainless steel and Pt) were initially tested and validated in vitro using simulated body fluids. As judged from the excellent electrochemical responses in terms of both accuracy and precision, the most ideal system comprised the combination of sterilized Pt (pseudo-reference) and Nitinol (working) needle-shaped electrodes. The average in vivo human OCP determined from independent measurements on six human patients with indication of direct arterial surgery was -0.334 +/- 0.030 V/SCE. This value was in good agreement with data recorded in vitro using simulated body fluids (-0.313 +/- 0.003 V/SCE in AFNOR S90-701 artificial saliva; -0.334 +/- 0.001 V/SCE in artificial urine; -0.239 +/- 0.007 V/SCE in Ringer's solution). The thin surface film protecting the bulk NiTi alloy is therefore not susceptible to active dissolution at rest as long as the break down potentials (>>0.0 V/SCE) so far reported are well above OCP measured in this study. These results highlight the importance of evaluating the corrosion resistance of Nitinol under realistic conditions (mechanical loads, wear and fatigue) in order to establish multifaceted mechanisms that might lead to accelerated dissolution and failure of implanted stents.