Isabella da Silva Vieira Marques

Production of a biofunctional titanium surface using plasma electrolytic oxidation and glow-discharge plasma for biomedical applications

In this study, the authors tested the hypotheses that plasma electrolytic oxidation (PEO) and glow-discharge plasma (GDP) would improve the electrochemical, physical, chemical, and mechanical properties of commercially pure titanium (cpTi), and that blood protein adsorption on plasma-treated surfaces would increase. Machined and sandblasted surfaces were used as controls. Standard electrochemical tests were conducted in artificial saliva (pHs of 3.0, 6.5, and 9.0) and simulated body fluid. Surfaces were characterized by scanning electron microscopy, energy-dispersive spectroscopy, x-ray photoelectron spectroscopy, atomic force microscopy, x-ray diffraction, profilometry, Vickers microhardness, and surface energy. For biological assay, the adsorption of blood serum proteins (i.e., albumin, fibrinogen, and fibronectin) was tested. Higher values of polarization resistance and lower values of capacitance were noted for the PEO and GDP groups (p < 0.05). Acidic artificial saliva reduced the corrosion resistance of cpTi (p < 0.05). PEO and GDP treatments improved the surface properties by enrichment of the surface chemistry with bioactive elements and increased surface energy. PEO produced a porous oxide layer (5-μm thickness), while GDP created a very thin oxide layer (0.76-μm thickness). For the PEO group, the authors noted rutile and anatase crystalline structures that may be responsible for the corrosion barrier improvement and increased microhardness values. Plasma treatments were able to enhance the surface properties and electrochemical stability of titanium, while increasing protein adsorption levels.

Tribocorrosion behavior of biofunctional titanium oxide films produced by micro-arc oxidation: Synergism and mechanisms

Dental implants, inserted into the oral cavity, are subjected to a synergistic interaction of wear and corrosion (tribocorrosion), which may lead to implant failures. The objective of this study was to investigate the tribocorrosion behavior of Ti oxide films produced by micro-arc oxidation (MAO) under oral environment simulation. MAO was conducted under different conditions as electrolyte composition: Ca/P (0.3M/0.02M or 0.1M/0.03M) incorporated with/without Ag (0.62g/L) or Si (0.04M); and treatment duration (5 and 10min). Non-coated and sandblasted samples were used as controls. The surfaces morphology, topography and chemical composition were assessed to understand surface properties. ANOVA and Tukey׳s HSD tests were used (α=0.05). Biofunctional porous oxide layers were obtained. Higher Ca/P produced larger porous and harder coatings when compared to non-coated group (p<0.001), due to the presence of rutile crystalline structure. The total mass loss (Kwc), which includes mass loss due to wear (Kw) and that due to corrosion (Kc) were determined. The dominant wear regime was found for higher Ca/P groups (Kc/Kw≈0.05) and a mechanism of wear-corrosion for controls and lower Ca/P groups (Kc/Kw≈0.11). The group treated for 10min and enriched with Ag presented the lowest Kwc (p<0.05). Overall, MAO process was able to produce biofunctional oxide films with improved surface features, working as tribocorrosion resistant surfaces.

Surface-treated commercially pure titanium for biomedical applications: Electrochemical, structural, mechanical and chemical characterizations.

Modified surfaces have improved the biological performance and biomechanical fixation of dental implants compared to machined (polished) surfaces. However, there is a lack of knowledge about the surface properties of titanium (Ti) as a function of different surface treatment. This study investigated the role of surface treatments on the electrochemical, structural, mechanical and chemical properties of commercial pure titanium (cp-Ti) under different electrolytes. Cp-Ti discs were divided into 6 groups (n = 5): machined (M—control); etched with HCl + H2O2 (Cl), H2SO4 + H2O2 (S); sandblasted with Al2O3 (Sb), Al2O3 followed by HCl + H2O2 (SbCl), and Al2O3 followed by H2SO4 + H2O2 (SbS). Electrochemical tests were conducted in artificial saliva (pHs 3; 6.5 and 9) and simulated body fluid (SBF—pH 7.4). All surfaces were characterized before and after corrosion tests using atomic force microscopy, scanning electron microscopy, energy dispersive microscopy, X-ray diffraction, surface roughness, Vickers microhardness and surface free energy. The results indicated that Cl group exhibited the highest polarization resistance (Rp) and the lowest capacitance (Q) and corrosion current density (Icorr) values. Reduced corrosion stability was noted for the sandblasted groups. Acidic artificial saliva decreased the Rp values of cp-Ti surfaces and produced the highest Icorr values. Also, the surface treatment and corrosion process influenced the surface roughness, Vickers microhardness and surface free energy. Based on these results, it can be concluded that acid-etching treatment improved the electrochemical stability of cp-Ti and all treated surfaces behaved negatively in acidic artificial saliva.

Effect of nonthermal plasma treatment on surface chemistry of commercially-pure titanium and shear bond strength to autopolymerizing acrylic resin

The effect of nonthermal plasma on the surface characteristics of commercially pure titanium (cp-Ti), and on the shear bond strength between an autopolymerizing acrylic resin and cp-Ti was investigated. A total of 96 discs of cp-Ti were distributed into four groups (n=24): Po (no surface treatment), SB (sandblasting), Po+NTP and SB+NTP (methane plasma). Surface characterization was performed through surface energy, surface roughness, scanning microscopy, energy dispersive spectroscopy, and X-ray diffraction tests. Shear bond strength test was conducted immediately and after thermocycling. Surface treatment affected the surface energy and roughness of cp-Ti discs (P<.001). SEM-EDS showed the presence of the carbide thin film. XRD spectra revealed no crystalline phase changes. The SB+NTP group showed the highest bond strength values (6.76±0.70 MPa). Thermocycling reduced the bond strength of the acrylic resin/cp-Ti interface (P<.05), except for Po group. NTP is an effective treatment option for improving the shear bond strength between both materials.

Fit and Stability of Screw-Retained Implant-Supported Frameworks Under Masticatory Simulation: Influence of Cylinder Type

PURPOSE The aim of the study was to evaluate the effect of a prosthetic cylinder and casting on the misfit and loosening torque of screw-retained multiple-unit implant-supported dental prostheses under masticatory simulation. MATERIALS AND METHODS Screw-retained, three-unit fixed dental prostheses (FDP) and screw-retained full-arch FDP frameworks were waxed using calcinable (plastic cylinders) or overcasted (premachined cast-on cylinders) on the dental implant abutments. The cylinders were cast in Co-Cr alloy to obtain four groups according to cylinder type and prosthesis type (n = 10). The screws were tightened with 20 N/cm (abutment) and 10 N/cm (prosthetic) torque according to the manufacturers recommendation. After 24 hours, the initial loosening torque was analyzed. The initial misfit measurements were performed according to the Schiffleger test. The screws were retightened, and the specimens were submitted to 10(6) mechanical cycles (2 Hz/280 N). Loosening torque and misfit were reevaluated (final measurements), and data were submitted to ANOVA, Tukeys HSD, and Pearsons correlation tests (α = 0.05). RESULTS The calcinable three-unit FDP demonstrated greater misfit (initial: 107.53 ± 40.36 μm; final: 99.00 ± 40.85 μm) than did the overcasted three-unit FDP frameworks (initial: 51.50 ± 22.98 μm; final: 44.33 ± 14.14 μm) (initial: p = 0.0005; final: p = 0.0007). No difference was noted between the calcinable and overcasted full-arch FDP frameworks (p > 0.05). Masticatory simulation did not affect the misfit (p > 0.05). The overcasted full-arch FDP presented a lower abutment screw loosening torque (12.05 ± 1.80 N/cm) than did the calcinable ones (14.75 ± 1.72 N/cm) in the final measurement (p = 0.0024). The calcinable groups presented a lower prosthetic screw loosening torque than did the overcasted groups in the final evaluation (p < 0.05). After masticatory simulation, the prosthetic screw loosening torque of the calcinable three-unit FDP decreased (initial: 5.49 ± 1.07 N/cm; final: 3.73 ± 1.15 N/cm; p = 0.0044). Correlation between misfit and loosening was observed only for the prosthetic screws (p < 0.05). CONCLUSIONS The overcasted components provided a better fit in three-unit FDPs but did not influence the fit of full-arch FDPs. Prosthetic screws of overcasted frameworks presented higher stability, whereas masticatory simulation did not influence misfit but did reduce the prosthetic screw loosening torque of calcinable three-unit FDP frameworks.

Transparent TiO2 nanotubes on zirconia for biomedical applications

Tissue discoloration in dental implant patients with thin gingival tissue is one of the many causes of dental implants’ revision surgery. Therefore, the purpose of this study is to address this issue by developing a surface that has a “tooth like bright colored” appearance while at the same time enhancing the bone implant integration. A biomimetic surface is fabricated by forming transparent TiO2 nanotubes on zirconia (TTNZ) that can enhance the proliferation and attachment of human mesenchymal stem cells (hMSCs) as compared to roughened ZrO2. This surface treatment was aimed to resolve tissue discoloration and aesthetic appearance problems for dental implant patients, while also enhancing biocompatibility. TiO2 nanotubes (TNTs) were formed using an electrochemical anodization technique in an electrolyte comprised of NH4F, ethylene glycol and water. The presence of TNTs on the ZrO2 substrate was detected by field emission scanning electron microscopy (FESEM). Optical images of longer anodized (20 and 30 min) samples show the white colored appearance characteristic of ZrO2 and FESEM confirmed the presence of TNTs on anodized samples. Surface characteristics of all samples were analyzed using water contact angle analysis, Fourier-transform infrared spectroscopy, white light interferometry and FESEM. Quantitative and qualitative biocompatibility analysis of treated and non-treated ZrO2 surfaces were obtained by performing FESEM, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay and fluorescence microscopy. FESEM revealed well-elongated and well-spread cell morphology on the nanotubular surface as compared to roughened ZrO2. Additionally, MTT assay showed a significantly high cell proliferation for anodized Ti–ZrO2 surface as compared to roughened ZrO2 after 7 days of incubation.

The effect of casting and masticatory simulation on strain and misfit of implant-supported metal frameworks.

The influence of casting and masticatory simulation on marginal misfit and strain in multiple implant-supported prostheses was evaluated. Three-unit screw retained fixed dental prosthesis (FDP) and screw retained full-arch fixed dental prosthesis (FAFDP) frameworks were made using calcinable or overcasted cylinders on conical dental implant abutment. Four groups were obtained according to the cylinder and prosthesis type (n=10). Frameworks were casted in CoCr alloy and subjected to strain gauge analyses and marginal misfit measurements before and after 10(6) mechanical cycles (2 Hz/280 N). Results were submitted to ANOVA, Tukeys HSD and Pearson correlation test (α=0.05). No difference was found on misfit among all groups and times (p>0.05). Overcasted frameworks showed higher strain than the calcinable ones (FDP - Initial p=0.0047; Final p=0.0004; FAFDP - Initial p=0.0476; Final p=0.0115). The masticatory simulation did not influence strain (p>0.05). No correlation was observed between strain and misfit (r=0.24; p>0.05). In conclusion, the marginal misfit value in the overcasted full-arch frameworks was higher than clinical acceptable data. It proved that overcasted method is not an ideal method for full-arch prosthesis. Overcasted frameworks generate higher strain upon the system. The masticatory simulation had no influence on misfit and strain of multiple prostheses.

Incorporation of Ca, P, and Si on bioactive coatings produced by plasma electrolytic oxidation: The role of electrolyte concentration and treatment duration.

The objectives of the present study were to produce bioactive coatings in solutions containing Ca, P, and Si by plasma electrolytic oxidation (PEO) on commercially pure titanium, to investigate the influence of different electrolytes concentration and treatment duration on the produced anodic films and to evaluate biocompatibility properties. The anodic films were characterized using scanning electron microscopy, energy-dispersive spectroscopy, atomic force microscopy, and x-ray diffraction and x-ray photoelectron spectroscopies. The surface energy and roughness were also evaluated. PEO process parameters influenced the crystalline structure formation and surface topography of the anodic films. Higher Ca content produced larger porous (volcanolike appearance) and thicker oxide layers when compared to the lower content. Treatment duration did not produce any topography difference. The treatment modified the surface chemistry, producing an enriched oxide layer with bioactive elements in the form of phosphate compounds, which may be responsible for mimicking bone surface. In addition, a rough surface with increased surface energy was generated. Optimal spreading and proliferation of human mesenchymal stem cells was achieved by PEO treatment, demonstrating excellent biocompatibility of the surface. The main finding is that the biofunctionalization with higher Ca/P on Ti-surface can improve surface features, potentially considered as a candidate for dental implants.

Biomimetic coatings enhance tribocorrosion behavior and cell responses of commercially pure titanium surfaces

Biofunctionalized surfaces for implants are currently receiving much attention in the health care sector. Our aims were (1) to create bioactive Ti-coatings doped with Ca, P, Si, and Ag produced by microarc oxidation (MAO) to improve the surface properties of biomedical implants, (2) to investigate the TiO2 layer stability under wear and corrosion, and (3) to evaluate human mesenchymal stem cells (hMSCs) responses cultured on the modified surfaces. Tribocorrosion and cell experiments were performed following the MAO treatment. Samples were divided as a function of different Ca/P concentrations and treatment duration. Higher Ca concentration produced larger porous and harder coatings compared to the untreated group (p < 0.001), due to the presence of rutile structure. Free potentials experiments showed lower drops (-0.6 V) and higher coating lifetime during sliding for higher Ca concentration, whereas lower concentrations presented similar drops (-0.8 V) compared to an untreated group wherein the drop occurred immediately after the sliding started. MAO-treated surfaces improved the matrix formation and osteogenic gene expression levels of hMSCs. Higher Ca/P ratios and the addition of Ag nanoparticles into the oxide layer presented better surface properties, tribocorrosive behavior, and cell responses. MAO is a promising technique to enhance the biological, chemical, and mechanical properties of dental implant surfaces.

Surface Treatment Influences Electrochemical Stability Of Cpti Exposed To Mouthwashes

The role of surface treatment on the electrochemical behavior of commercially pure titanium (cpTi) exposed to mouthwashes was tested. Seventy-five disks were divided into 15 groups according to surface treatment (machined, sand blasted with Al2O3, and acid etched) and electrolyte solution (artificial saliva — control, 0.12% chlorhexidine digluconate, 0.05% cetylpyridinium chloride, 0.2% sodium fluoride, and 1.5% hydrogen peroxide) (n = 5). Open-circuit-potential and electrochemical impedance spectroscopy were conducted at baseline and after 7 and 14 days of immersion in each solution. Potentiodynamic test and total weight loss of disks were performed after 14 days of immersion. Scanning electron microscopy, energy dispersive spectroscopy, white light interferometry and profilometry were conducted for surface characterization before and after the electrochemical tests. Sandblasting promoted the lowest polarization resistance (Rp) (P b .0001) and the highest capacitance (CPE) (P b .006), corrosion current density (Icorr) and corrosion rate (P b .0001). In contrast, acid etching increased Rp and reduced CPE, independent to the mouthwash; while hydrogen peroxide reduced Rp (P b .008) and increased Icorr and corrosion rate (P b .0001). The highest CPE values were found for hydrogen peroxide and 0.2% sodium fluoride. Immersion for longer period improved the electrochemical stability of cpTi (P b .05). In conclusion, acid etching enhanced the electrochemical stability of cpTi. Hydrogen peroxide and sodium fluoride reduced the resistance to corrosion of cpTi, independent to the surface treatment. Chlorhexidine gluconate and cetylpyridinium chloride did not alter the corrosive behavior of cpTi.