Prediction of tribocorrosion processes in titanium-based dental implants using acoustic emission technique: Initial outcome.

The use of dental implants is growing rapidly for the last few decades and Ti-based dental implants are a commonly used prosthetic structure in dentistry. Recently, the combined effect of corrosion and wear, called tribocorrosion, is considered as a major driving process in the early failure of dental implants. However, no previous study has reported the prediction of tribocorrosion processes in advance. Therefore, this study is a novel investigation on how the acoustic emission (AE) technique can predict tribocorrosion processes in commercially-pure titanium (cpTi) and titanium-zirconium (TiZr) alloys. In this study, tribocorrosion tests were performed under potentiostatic conditions and AE detection system associated with it captures AE data. Current evolution and friction coefficient data obtained from the potentiostatic evaluations were compared with AE absolute energy showcased the same data interpretation of tribocorrosion characteristics. Other AE data such as duration, count, and amplitude, matched more closely with other potentiostatic corrosion evaluations and delivered more promising results in the detection of tribocorrosion. Hence, AE can be consider as a tool for predicting tribocorrosion in dental implants. Experimental results also reveal Ti5Zr as one of the most appropriate dental implant materials while exposing Ti10Zr's lower effectiveness to withstand in the simulated oral environment.

Comprehensive Characterization of Titania Nanotubes Fabricated on Ti-Nb Alloys: Surface Topography, Structure, Physicomechanical Behavior, and a Cell Culture Assay.

In this study, hybrid composites based on ß-alloy Ti-xNb and oxide nanotubes (NTs) have been successfully prepared. NTs of different sizes were grown on Ti-Nb substrates with different Nb contents (5, 25, and 50 wt %) via electrochemical anodization at 30 and 60 V. Scanning electron microscopy imaging revealed that vertically aligned nanotubular structures form on the surface of Ti-Nb alloy substrates and influence Nb content in alloys based on NT length. X-ray diffraction analysis confirmed the formation of the anodized TiO2 layer and revealed several phases as the Nb content increased, starting with α' for low Nb content (5 wt %), the martensite α″ for intermediate Nb content (25 wt %), and the ß phase for the highest Nb content (50 wt %). Nanoindentation testing was used to evaluate the changes in mechanical properties of oxide NTs grown on Ti-Nb alloys with different compositions. NT arrays showed wide variations in Young's modulus and hardness depending upon the anodization voltage and the Nb content. The hardness and Young's modulus strongly correlated with NT morphology and structure. The highly dense morphology formed at a lower anodization voltage results in increased elastic modulus and hardness values compared with the surfaces prepared at higher anodization voltages. The nanostructurization of Ti-Nb surface substrates favored improved surface properties for the enhanced adhesion and proliferation of human mesenchymal stem cells (hMSCs). In vitro adhesion, spreading, and proliferation of hMSCs revealed the improved surface properties of the NTs prepared at an anodization voltage of 30 V compared with the NTs prepared at 60 V. Thus it can be concluded that NTs with diameters of ∼50 nm (at 30 V) are more favorable for cell adhesion and growth compared with NTs with diameters of 80 ± 20 nm (at 60 V). The surfaces of Ti-25Nb substrates anodized at 30 V promoted enhanced cell growth, as the further increase in Nb content in Ti-Nb substrate (Ti-50Nb) led to reduced cell proliferation. The application of NTs on Ti-Nb substrates leads to significant reductions in mechanical properties compared with those on the Ti-Nb alloy and improves cell adhesion and proliferation, which is vitally important for successful application in regenerative medicine.

Characterization of chemically treated Ti-Zr system alloys for dental implant application.

Materials and surfaces developed for dental implants need to withstand degradation processes that take place in the oral cavity. Therefore, the aim of the study was to develop and evaluate the topographical, mechanical, chemical, electrochemical and biological properties of Ti-xZr alloys (x = 5, 10, and 15 wt%) with two surface features (machined and double acid etched). Commercially pure titanium (cpTi) and Ti-6Al-4V alloy were used as controls. Surface characterization was performed using dispersive energy spectroscopy, X-ray diffraction, scanning electron microscopy, atomic force microscopy, profilometry and surface energy. The mechanical properties were assessed using Vickers microhardness, elastic modulus and stiffness. The electrochemical behavior analysis was conducted in a body fluid solution (pH 7.4). In addition, MC3T3-E1 cells were used to determine the impact of material and surface treatment on cell morphology by SEM analysis. Data were analyzed by two-way ANOVA and Bonferroni test (α = 0.05). Ti-Zr alloys showed lower surface roughness, elastic modulus and stiffness, as well as higher hardness and surface energy when compared to cpTi. Ti-Zr system increased the polarization resistance values and significantly decreased the capacitance, corrosion current density (icorr), and passivation current density (ipass) values. The acid treatment increased the resistance and corrosion potential of the oxide layer. SEM data analysis demonstrated that Ti-Zr alloys displayed normal cell attachment/spreading and slightly changed cell morphology in the double etched surface. In conclusion, Zr addition and surface treatment altered surface, mechanical, biological and electrochemical properties of Ti material.

Development of binary and ternary titanium alloys for dental implants.

OBJECTIVE: The aim of this study was to develop binary and ternary titanium (Ti) alloys containing zirconium (Zr) and niobium (Nb) and to characterize them in terms of microstructural, mechanical, chemical, electrochemical, and biological properties. METHODS: The experimental alloys - (in wt%) Ti-5Zr, Ti-10Zr, Ti-35Nb-5Zr, and Ti-35Nb-10Zr - were fabricated from pure metals. Commercially pure titanium (cpTi) and Ti-6Al-4V were used as controls. Microstructural analysis was performed by means of X-ray diffraction and scanning electron microscopy. Vickers microhardness, elastic modulus, dispersive energy spectroscopy, X-ray excited photoelectron spectroscopy, atomic force microscopy, surface roughness, and surface free energy were evaluated. The electrochemical behavior analysis was conducted in a body fluid solution (pH 7.4). The albumin adsorption was measured by the bicinchoninic acid method. Data were evaluated through one-way ANOVA and the Tukey test (α=0.05). RESULTS: The alloying elements proved to modify the alloy microstructure and to enhance the mechanical properties, improving the hardness and decreasing the elastic modulus of the binary and ternary alloys, respectively. Ti-Zr alloys displayed greater electrochemical stability relative to that of controls, presenting higher polarization resistance and lower capacitance. The experimental alloys were not detrimental to albumin adsorption. SIGNIFICANCE: The experimental alloys are suitable options for dental implant manufacturing, particularly the binary system, which showed a better combination of mechanical and electrochemical properties without the presence of toxic elements.

Influence of Oxygen Content and Microstructure on the Mechanical Properties and Biocompatibility of Ti-15 wt%Mo Alloy Used for Biomedical Applications.

The Ti-15Mo alloy has its mechanical properties strongly altered by heat treatments and by addition of interstitial elements, such as, oxygen, for example. In this sense, the objective of this paper is to analyze the effect of the introduction of oxygen in selected mechanical properties and the biocompatibility of Ti-15Mo alloy. The samples used in this study were prepared by arc-melting and characterized by density measurements, X-ray diffraction, scanning electron microscopy, microhardness, modulus of elasticity, and biocompatibility tests. Hardness measurements were shown to be sensitive to concentration of oxygen. The modulus results showed interstitial influence in value; this was verified under several conditions to which the samples were exposed. Cytotoxicity tests conducted in vitro showed that the various processing conditions did not alter the biocompatibility of the material.

The Influence of Small Quantities of Oxygen in the Structure, Microstructure, Hardness, Elasticity Modulus and Cytocompatibility of Ti-Zr Alloys for Dental Applications.

The mechanical properties of Ti alloys are changed significantly with the addition of interstitial elements, such as oxygen. Because oxygen is a strong stabilizer of the α phase and has an effect on hardening in a solid solution, it has aroused great interest in the biomedical area. In this paper, Ti-Zr alloys were subjected to a doping process with small amounts of oxygen. The influence of interstitial oxygen in the structure, microstructure and some selected mechanical properties of interest for use as biomaterial and biocompatibility of the alloys were analyzed. The results showed that in the range of 0.02 wt% to 0.04 wt%, oxygen has no influence on the structure, microstructure or biocompatibility of the studied alloys, but causes hardening of the alloys, increasing the values of the microhardness and causing variation in the elasticity modulus values.

Glass transition and degree of conversion of a light-cured orthodontic composite.

OBJECTIVE: This study evaluated the glass transition temperature (Tg) and degree of conversion (DC) of a light-cured (Fill Magic) versus a chemically cured (Concise) orthodontic composite. MATERIAL AND METHODS: Anelastic relaxation spectroscopy was used for the first time to determine the Tg of a dental composite, while the DC was evaluated by infrared spectroscopy. The light-cured composite specimens were irradiated with a commercial LED light-curing unit using different exposure times (40, 90 and 120 s). RESULTS: Fill Magic presented lower Tg than Concise (35-84 masculineC versus 135 masculineC), but reached a higher DC. CONCLUSIONS: The results of this study suggest that Fill Magic has lower Tg than Concise due to its higher organic phase content, and that when this light-cured composite is used to bond orthodontic brackets, a minimum energy density of 7.8 J/cm(2) is necessary to reach adequate conversion level and obtain satisfactory adhesion.

Glass transition and degree of conversion of a light-cured orthodontic composite

OBJECTIVE: This study evaluated the glass transition temperature (Tg) and degree of conversion (DC) of a light-cured (Fill Magic) versus a chemically cured (Concise) orthodontic composite. MATERIAL AND METHODS: Anelastic relaxation spectroscopy was used for the first time to determine the Tg of a dental composite, while the DC was evaluated by infrared spectroscopy. The light-cured composite specimens were irradiated with a commercial LED light-curing unit using different exposure times (40, 90 and 120 s). RESULTS: Fill Magic presented lower Tg than Concise (35-84ºC versus 135ºC), but reached a higher DC. CONCLUSIONS: The results of this study suggest that Fill Magic has lower Tg than Concise due to its higher organic phase content, and that when this light-cured composite is used to bond orthodontic brackets, a minimum energy density of 7.8 J/cm² is necessary to reach adequate conversion level and obtain satisfactory adhesion.