Evaluation of metal ion release from Ti6Al4V and Co-Cr-Mo casting alloys: in vivo and in vitro study

Morphology of Nanostructured Tantalum Oxide Controls Stem Cell Differentiation and Improves Corrosion Behavior

Tantalum is receiving increasing attention in the biomedical field due to its biocompatible nature and superior mechanical properties. However, the bioinert nature of tantalum still poses a challenge and limits its integration into the bone tissue. To address these issues, we fabricated nanotubular (NT), nanocoral (NC), and nanodimple morphologies on tantalum surfaces via anodization. The size of these nanofeatures was engineered to be approximately 30 nm for all anodized samples. Thus, the influence of the anodized nanostructured morphology on the chemical and biological properties of tantalum was evaluated. The NT and NC samples exhibited higher surface roughness, surface energy, and hydrophilicity compared to the nonanodized samples. In addition, the NT samples exhibited the highest corrosion resistance among all of the investigated samples. Biological experiments indicated that NT and NC samples promoted human adipose tissue-derived mesenchymal stem cell (hADMSC) spreading and proliferation up to 5 days in vitro. ALP, COL1A1, and OSC gene expressions as well as calcium mineral synthesis were upregulated on the NT and NC samples in the second and third weeks in vitro. These findings highlight the significance of nanostructured feature morphology for anodized tantalum, where the NT morphology was shown to be a potential candidate for orthopedic applications.

Enhanced bone tissue regeneration using a 3D-printed poly(lactic acid)/Ti6Al4V composite scaffold with plasma treatment modification

The mechanical and biological properties of polylactic acid (PLA) need to be further improved in order to be used for bone tissue engineering (BTE). Utilizing a material extrusion technique, three-dimensional (3D) PLA-Ti6Al4V (Ti64) scaffolds with open pores and interconnected channels were successfully fabricated. In spite of the fact that the glass transition temperature of PLA increased with the addition of Ti64, the melting and crystallization temperatures as well as the thermal stability of filaments decreased slightly. However, the addition of 3-6 wt% Ti64 enhanced the mechanical properties of PLA, increasing the ultimate compressive strength and compressive modulus of PLA-3Ti64 to 49.9 MPa and 1.9 GPa, respectively. Additionally, the flowability evaluations revealed that all composite filaments met the print requirements. During the plasma treatment of scaffolds, not only was the root-mean-square (Rq) of PLA (1.8 nm) increased to 60 nm, but also its contact angle (90.4°) significantly decreased to (46.9°). FTIR analysis confirmed the higher hydrophilicity as oxygen-containing groups became more intense. By virtue of the outstanding role of plasma treatment as well as Ti64 addition, a marked improvement was observed in Wharton's jelly mesenchymal stem cell attachment, proliferation (4',6-diamidino-2-phenylindole staining), and differentiation (Alkaline phosphatase and Alizarin Red S staining). Based on these results, it appears that the fabricated scaffolds have potential applications in BTE.

Minimization of Adverse Effects Associated with Dental Alloys

Metal alloys are one of the most popular materials used in current dental practice. In the oral cavity, metal structures are exposed to various mechanical and chemical factors. Consequently, metal ions are released into the oral fluid, which may negatively affect the surrounding tissues and even internal organs. Adverse effects associated with metallic oral appliances may have various local and systemic manifestations, such as mouth burning, potentially malignant oral lesions, and local or systemic hypersensitivity. However, clear diagnostic criteria and treatment guidelines for adverse effects associated with dental alloys have not been developed yet. The present comprehensive literature review aims (1) to summarize the current information related to possible side effects of metallic oral appliances; (2) to analyze the risk factors aggravating the negative effects of dental alloys; and (3) to develop recommendations for diagnosis, management, and prevention of pathological conditions associated with metallic oral appliances.

Diffusion of Vanadium Ions in Artificial Saliva and Its Elimination from the Oral Cavity by Pharmacological Compounds Present in Mouthwashes

In this study, diffusion coefficients of ammonium vanadate at tracer concentrations in artificial saliva with and without sodium fluoride, at different pH values, were measured using an experimental model based on the Taylor dispersion technique. Ternary mutual diffusion coefficients (D11, D22, D12, and D21) for four aqueous systems {NH4VO3 (component 1) + β-cyclodextrin (β-CD) (component 2),} {NH4VO3 (component 1) + β-cyclodextrin (HP-β-CD) (component 2)}, {NH4VO3 (component 1) + sodium dodecyl sulphate (SDS) (component 2)} and {NH4VO3 (component 1) + sodium hyaluronate (NaHy) (component 2)} at 25.00 °C were also measured by using the same technique. These data showed that diffusion of ammonium vanadate was strongly affected in all aqueous media studied. Furthermore, a significant coupled diffusion of this salt and β-CD was observed through the non-zero values of the cross-diffusion coefficients, D12, allowing us to conclude that there is a strong interaction between these two components. This finding is very promising considering the removal, from the oral cavity, of vanadium resulting from tribocorrosion of Ti-6Al-4V prosthetic devices.

Behavior of rat bone marrow stem cells on titanium surfaces modified by laser-beam and deposition of calcium phosphate

OBJECTIVES

The aim of this study was to evaluate the behavior of rat bone marrow stem cells seeded on a Ti-15Mo alloy surface modified by laser-beam irradiation followed by calcium phosphate deposition.

MATERIALS AND METHODS

A total of four groups were evaluated: polished commercially pure titanium (cpTi): Ti-P; laser irradiation + calcium phosphate deposition on cpTi: Ti-LCP; polished Ti-15Mo alloy: Ti15Mo-P; and laser irradiation + calcium phosphate deposition on Ti-15Mo alloy: Ti15Mo-LCP. Before and after laser irradiation and calcium phosphate deposition on the surfaces, physicochemical and morphological analyses were performed: Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDX). The wettability of the samples was evaluated by contact angle measurement. In addition, the behavior of osteoblast-like cells to these surfaces was evaluated for cell morphology, adhesion, proliferation and viability, evaluation of alkaline phosphatase formation and gene expression of osteogenesis markers.

RESULTS

Surfaces wet-abrade with grit paper (P) showed oriented groves, while the laser irradiation and calcium phosphate deposition (LCP) produced porosity on both cpTi and Ti15Mo alloy groups with deposits of hydroxyapatite (HA) crystals (SEM). EDX showed no contamination after surface modification in both metal samples. A complete wetting was observed for both LCP groups, whereas P surfaces exhibited high degree of hydrophobicity. There was a statistical difference in the intragroup comparison of proliferation and viability (p < 0.05). The ALP activity showed higher values in the Ti15Mo alloy at 10 days of culture. The gene expression of bone related molecules did not present significant differences at 7 and 14 days among different metals and surface treatments.

CONCLUSION

Ti15-Mo seems to be an alternative alloy to cpTi for dental implants. Surface treatment by laser irradiation followed by phosphate deposition seems to positively interact with bone cells.

CLINICAL RELEVANCE

Ti-15Mo alloy surface modified by laser-beam irradiation followed by calcium phosphate deposition may improve and accelerate the osseointegration process of dental implants.

Gradient nanostructured titanium stimulates cell responses in vitro and enhances osseointegration in vivo

Background

Though titanium (Ti) is widely used as dental materials in the clinic, effective methods to treat Ti for higher surface biological activity still lack. Through Surface mechanical attrition treatment (SMAT) technology we could endow Ti with gradient nanostructured surface (GNS Ti). To investigate the biocompatibility of GNS Ti for its further application in dental implant field, we study the effects of GNS Ti on cell responses in vitro and osseointegration of the implant with surrounding bone tissues in vivo.

Methods

In this study, GNS Ti was fabricated by SMAT. In vitro experiment, we co-cultured GNS Ti with bone mesenchymal stem cells (BMSCs), surface characterization was detected by transmission electron microscope (TEM). Adhesion, proliferation and differentiation of BMSCs were evaluated by scanning electron microscope (SEM), MTT, flow cytometry (FCM), alkaline phosphatase (ALP) and osteocalcin (OCN) tests. In vivo experiment, the GNS Ti was implanted into the rabbit mandible. Osteogenesis and osseointegration were evaluated by Micro CT, toluidine blue staining, and immunohistochemical staining at 4, 8, and 12 weeks postoperatively.

Results

Both results showed that compared with the coarse grained (CG) Ti, the GNS Ti stimulated the adhesion, proliferation, and differentiation of BMSCs and improved osteogenesis and osseointegration.

Conclusions

This study indicates that gradient nanostructured Ti is a promising material for dental implant application.

A Multi-Element-Doped Porous Bioactive Glass Coating for Implant Applications

Objectives: The objectives of the study were (1) to develop a novel multi-element-doped porous 58S bioactive glass coating for titanium implants and (2) to investigate the physiochemical, cell cytotoxic and antibacterial properties of this novel coating for titanium implants. Methods: This study employed the sol–gel method to develop a silver-, cobalt (II) oxide- and titanium dioxide-doped 58S bioactive glass coating. The surface topography and in vitro bioactivity of the new bioactive glass-coated implants were studied using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy. The surface nanohardness and coating degradation were evaluated using atomic force microscopy (AFM) and inductively coupled plasma atomic emission spectroscopy (ICP-AES), respectively. The cell cytotoxicity was assessed using cell viability of osteoblast-like mouse cells. The antibacterial property was examined using colony-forming units (CFUs) of the implant coating against Porphyromonas gingivalis. Results: The multi-element-doped porous 58S bioactive glass-coated titanium implant was synthesized. SEM showed that calcium phosphate was formed on the novel coating but not on the 58S bioactive glass coating. The mean surface nanohardness of the novel coating and the 58S coating were 124 ± 24 and 50 ± 17 MPa, respectively (p < 0.001). ICP-AES showed that the releases of Si, Ca and P ions of the novel coating were significantly higher than that of a 58S bioactive glass-coated implant. No significant difference in cell cytotoxicity was found between the novel coating and the 58S coating (p > 0.1). The mean CFUs of the novel coating and the conventional coating were 120 × 10⁶ and 49 × 10⁶ /mL. Conclusion: A novel multielement-doped porous bioactive glass coating for titanium implants was developed. The coating displays promising biocompatibility and antibacterial activity. Clinical significance: the coating can be used to improve the clinical success of dental implants for patient care if it shows success in clinical trials.

Effect of chemical passivation on corrosion behavior and ion release of a commercial chromium-cobalt alloy

Background. Corrosion resistance and ion release of alloys play a crucial role in biomedical applications. The present study aimed to investigate an increase in corrosion resistance and reduction in ion release in a commercial Co-Cr-Mo alloy by the chemical passivation method. Methods. Based on ADA97, 20 samples of Flexicast alloy were cast, surface-polished, and electrolytically passivated at room temperature for 24 h in a sodium sulfate solution. Corrosion and ion release of the alloys before and after passivation were studied in normal saline solution. Corrosion resistance and the ion release rates were measured by the weight loss method and atomic absorption spectroscopy, respectively, before and after passivation after 1, 2, 3, and 4 weeks. The surface morphology of the samples was examined using scanning electron microscopy (SEM). The results were analyzed with Kruskal-Wallis and Mann-Whitney tests using SPSS 20 at a significance level of <0.05. Results. The corrosion rate in the passivated samples was significantly lower than the non-passivated samples at the intervals (1, 2, 3, and 4 weeks) (P<0.05). The passivation of the alloy significantly reduced Co and Cr ion release in the first and fourth weeks, and in the first, second, and fourth weeks, respectively (P<0.05). SEM images revealed localized pitting associated with the corrosion, which was less significant in passivated samples. Conclusion. Chemical passivation of the CR-Co alloy significantly reduced corrosion and ionic release of Cr and Co over time.