Study of the corrosion behavior of titanium and some of its alloys for biomedical and dental implant applications

The influence of alloying elements and the potential on the corrosion resistance of Ti and other Ti-based biomedical implant alloys under simulated physiological conditions is presented. Ti and its following alloys: Ti10Mo, Ti10Mo10Al, Ti7Al4.5V and Ti5Al4.5V and Ti5Al2.5Fe were studied. Electrochemical impedance spectroscopy was used and the experimental results were compared with those obtained by potentiostatic and potentiodynamic techniques. All the measurements were made in Ringer’s solution at pH 7.8 and at different potentials (E_corr, ?650, ?500, 0, +200 and +400 mV vs. SCE). Under these conditions, all the Ti-based alloys exhibited spontaneous passivity. It was evident that Mo, V and Fe improved passivity and limited the active corrosion of the β-phase of Ti while Al enrichment of the α-phase was found to be detrimental to the passivity and corrosion resistance of Ti.     

Corrosion properties of low carbon CoCrMo and additively manufactured CoCr alloys for dental applications

ObjectivesAdditive manufacturing (AM) is being applied to metallic biomaterials and dental alloys, including CoCrMo. CoCrMo mechanical properties and corrosion resistance are vital to the structural integrity of implants and dental appliances. The goal of this work is to assess the resistivity of AM cobalt chromium alloys by comparing them with traditional CoCrMo, regarding electrochemical properties resulting from microstructural and oxide film differences.MethodsIn this work, selective laser melting (SLM), was used to manufacture CoCrMoW. The corrosion characteristics of AM alloy were compared to that of wrought LC CoCrMo (ASTM F-1537) in both phosphate buffered saline (PBS) and PBS with 10 mM H₂O₂ to simulate increased inflammatory conditions. Anodic polarization and electrochemical impedance spectroscopy (EIS) were performed.ResultsBoth alloys were substantially similar in corrosion behavior in both solutions. They exhibited changes with the different solutions. Polarization resistances were statistically lower (R_p^AM = 1.4 MΩcm² (PBS) vs. 0.72 MΩcm² (H₂O₂), R_p^LC = 1.86 MΩcm² (PBS) vs. 0.55 MΩcm² (H₂O₂)), and open circuit potentials (OCP’s) were statistically higher in 10 mM H₂O₂ for both alloys (0.20 V (in H₂O₂) vs. ? 0.09 V in PBS). Chemistry variations were revealed by the corrosion tests indicating that wrought LC CoCrMo retained its casting-based chemical heterogeneity, while AM CoCrMoW had sub-cell structures within the solidified grains.SignificanceAs novel production methods like AM arise, it is necessary to understand any microstructural differences that may diminish the corrosion resistance properties. AM CoCrMoW alloys hold significant promise for use in dentistry where complex geometries are required.     

Attachment of Porphyromonas gingivalis to Corroded Commercially Pure Titanium and Titanium‐Aluminum‐Vanadium Alloy

Background: Titanium dental material can become corroded because of electrochemical interaction in the oral environment. The corrosion process may result in surface modification. It was hypothesized that a titanium surface modified by corrosion may enhance the attachment of periodontal pathogens. This study evaluates the effects of corroded titanium surfaces on the attachment of Porphyromonas gingivalis. Methods: Commercially pure titanium (cp‐Ti) and titanium‐aluminum‐vanadium alloy (Ti‐6Al‐4V) disks were used. Disks were anodically polarized in a standard three‐electrode setting in a simulated oral environment with artificial saliva at pH levels of 3.0, 6.5, or 9.0. Non‐corroded disks were used as controls. Surface roughness was measured before and after corrosion. Disks were inoculated with P. gingivalis and incubated anaerobically at 37°C. After 6 hours, the disks with attached P. gingivalis were stained with crystal violet, and attachment was expressed based on dye absorption at optical density of 550 nm. All assays were performed independently three times in triplicate. Data were analyzed by two‐way analysis of variance, the Tukey honestly significant difference test, t test, and Pearson's correlation test (α = 0.05). Results: Both cp‐Ti and Ti‐6Al‐4V alloy‐corroded disks promoted significantly more bacterial attachment (11.02% and 41.78%, respectively; P <0.0001) than did the non‐corroded controls. Significantly more (11.8%) P. gingivalis attached to the cp‐Ti disks than to the Ti‐6Al‐4V alloy disks (P <0.05). No significant difference in P. gingivalis attachment was noted among the corroded groups for both cp‐Ti and Ti‐6Al‐4V alloy (P >0.05). There was no significant correlation between surface roughness and P. gingivalis attachment. Conclusion: A higher degree of corrosion on the titanium surface may promote increased bacterial attachment by oral pathogens.     

Metallurgical and electrochemical characterization of contemporary silver-based soldering alloys

Objective:To investigate the microstructure, hardness, and electrochemical behavior of four contemporary Ag-based soldering alloys used for manufacturing orthodontic appliances.Materials and Methods:The Ag-based alloys tested were Dentaurum Universal Silver Solder (DEN), Orthodontic Solders (LEO), Ortho Dental Universal Solder (NOB), and Silver Solder (ORT). Five disk-shaped specimens were produced for each alloy, and after metallographic preparation their microstructural features, elemental composition, and hardness were determined by scanning electron microscopy with energy-dispersive X-ray (EDX) microanalysis, X-ray diffraction (XRD) analysis, and Vickers hardness testing. The electrochemical properties were evaluated by anodic potentiodynamic scanning in 0.9% NaCl and Ringer''s solutions. Hardness, corrosion current (I_corr), and corrosion potential (E_corr) were statistically analyzed by one-way analysis of variance and Tukey test (α  =  .05).Results:EDX analysis showed that all materials belong to the Ag-Zn-Cu ternary system. Three different mean atomic contrast phases were identified for LEO and ORT and two for DEN and NOB. According to XRD analysis, all materials consisted of Ag-rich and Cu-rich face-centered cubic phases. Hardness testing classified the materials in descending order as follows: DEN, 155 ± 3; NOB, 149 ± 3; ORT, 141 ± 4; and LEO, 136 ± 8. Significant differences were found for I_corr of NOB in Ringer''s solution and E_corr of DEN in 0.9% NaCl solution.Conclusion:Ag-based soldering alloys demonstrate great diversity in their elemental composition, phase size and distribution, hardness, and electrochemical properties. These differences may anticipate variations in their clinical performance.     

The influence of SiO2 and SiO2–TiO2 intermediate coatings on bond strength of titanium and Ti6Al4V alloy to dental porcelain

ObjectivesThe purpose of this study was to evaluate the bond strength of commercially pure CPTi and Ti6Al4V alloy with SiO₂ and SiO₂–TiO₂ intermediate coatings to Triceram low-fusing dental porcelain.MethodsThe multilayered systems were characterized from the standpoint of microstructure analysis (SEM), the mode of failure, the nature of bonding and the influence of intermediate coatings on the improvement of bond strength. The SiO₂ and SiO₂–TiO₂ intermediate coatings were applied on the substrate materials by the sol–gel dipping technique. The metal–ceramic bond strength was investigated according to ISO 9693 standards using the three-point flexure bond test.ResultsStatistically significant higher bond strength of the metal–porcelain for Ti6A14V alloy (28.24 MPa), Ti6Al4V/SiO₂ (32.17 MPa) and Ti6Al4V/SiO₂–TiO₂ (36.09 MPa) was noted in comparison to CPTi (23.04 MPa), CPTi/SiO₂ (27.98 MPa) and CPTi/SiO₂–TiO₂ (28.84 MPa), respectively. The nature of metal-intermediate coating–porcelain bonding was both mechanical and chemical. The failure in all systems was cohesive and adhesive, mainly adhesive.SignificanceThe application of SiO₂ and SiO₂–TiO₂ intermediate coatings, produced by the sol–gel method, to both CPTi and Ti6Al4V alloy significantly improves the bond strength of metal–porcelain systems in comparison to the metal substrate only after sandblasting, and may have clinical use.     

两种口腔致病菌对钴铬和镍铬合金的体外腐蚀行为

目的 通过体外实验，探讨白色念珠菌和变形链球菌对钴铬合金和镍铬合金耐腐蚀性能的影响。方法 将10 mm×10 mm×2 mm的钴铬合金和镍铬合金试片高度抛光后分别浸泡于实验组(A组：白色念珠菌组，B组：变形链球菌组)及对照组(C组：BHI培养液组)中8周，应用电化学法测定各组试件片的自腐蚀电流(I_corr)及极化电阻(R_p)，并利用扫描电镜观察表面形态。结果 电化学法显示钴铬合各组的I_corr依次为A组>B组>C组，R_p结果显示A组corr>钴铬合金，而R_p<钴铬合金，上述差异均具有统计学意义(P<0.05)。结论 白色念珠菌、变形链球菌对钴铬合金和镍铬合金有腐蚀作用，相同条件下钴铬合金耐腐蚀性能优于...     

Effects of a fluoride etchant and a phosphate primer on bonding of veneering composite to Ti–6Al–4V alloy for CAD/CAM restorations

PurposeTitanium abutments and superstructures are commonly veneered or covered with esthetic materials. The present investigation was carried out to evaluate the effects of an experimental surface treatment using etchant and primer on bond strength between a resin composite and Ti–6Al–4V alloy.MethodsDisk-shaped Ti–6Al–4V alloy was machine milled, the surface was air abraded with alumina, and the alloy was chemically etched with 5wt% ammonium hydrogen fluoride (F-etch) for 30 s. A phosphate primer (MDP-primer) was applied to the bonding area, and then a resin composite, with or without milled-fiber resin composite (FRC), was veneered on the specimen. Shear bond strengths were determined after thermocycling for 20,000 cycles. Bond strength data were analyzed by means of ANOVA and a multiple comparison test (α = 0.05). The surface of Ti–6Al–4V alloy was observed using a scanning electron microscope before and after the etching procedure.ResultsNo-FRC/F-etch/MDP-primer exhibited the highest bond strength (28.2 MPa), followed by No-FRC/No-etching/MDP-primer (24.2 MPa), FRC/F-etch/MDP-primer (19.9 MPa), FRC/No-etching/MDP-primer (17.8 MPa), No-FRC/No-etching/No-primer (13.6 MPa), while FRC/No-etching/No-primer (2.5 MPa) resulted in the lowest value. Microphotographs showed that numerous micro and nano pits were created on the Ti–6Al–4V alloy surface modified with F-etch.ConclusionsThe bond strength between Ti–6Al–4V alloy and the veneering resin composite was the highest when the alloy surface was modified with alumina blasting, fluoride etchant, and phosphate primer successively.     

Assessment of nickel titanium and beta titanium corrosion resistance behavior in fluoride and chloride environments

Objective:To assess the influence of fluoride concentration on the corrosion behavior of nickel titanium (NiTi) superelastic wire and to compare the corrosion resistance of NiTi with that of beta titanium alloy in physiological solution with and without addition of fluoride.Materials and Methods:NiTi corrosion resistance was investigated through electrochemical impedance spectroscopy and anodic polarization in sodium chloride (NaCl 0.15 M) with and without addition of 0.02 M sodium fluoride (NaF), and the results were compared with those associated with beta titanium. The influence of fluoride concentration on NiTi corrosion behavior was assessed in NaCl (0.15 M) with and without 0.02, 0.04, 0.05, 0.07, and 0.12 M NaF solution. Galvanic corrosion between NiTi and beta titanium were investigated. All samples were characterized by scanning electron microscopy.Results:Polarization resistance decreased when NaF concentration was increased, and, depending on NaF concentration, NiTi can suffer localized or generalized corrosion. In NaCl solution with 0.02 M NaF, NiTi suffer localized corrosion, while beta titanium alloys remained passive. Current values near zero were observed by galvanic coupling of NiTi and beta titanium.Conclusions:There is a decrease in NiTi corrosion resistance in the presence of fluoride. The corrosion behavior of NiTi alloy depends on fluoride concentration. When 0.02 and 0.04 M of NaF were added to the NaCl solution, NiTi presented localized corrosion. When NaF concentration increased to 0.05, 0.07, and 0.12 M, the alloy presented general corrosion. NiTi corrosion resistance behavior is lower than that of beta titanium. Galvanic coupling of these alloys does not increase corrosion rates.     

山花、84消毒液对Ti-6Al-4V合金表面点蚀的能谱及电镜分析

目的：观察８４、山花消毒液对Ｔｉ－６Ａｌ－４Ｖ合金表面的腐蚀。方法：将Ｔｉ－６Ａｌ－４Ｖ合金试件分别浸泡在山花、８４消毒液中保持１５、３０、６０ｍｉｎ。对照组置于蒸馏水中，取出清洗，扫描电镜观察并行能谱分析。结果：Ｔｉ－６Ａｌ－４Ｖ合金浸泡在山花、８４消毒液中１５、３０ｍｉｎ，扫描电镜观察无点蚀，浸泡６０ｍｉｎ表面出现明显点蚀坑。对点蚀部位进行能谱分析发现主要元素为铝、磷、硫、钛。结论：用山花、８     

Corrosion behavior of pure titanium and titanium alloys in various concentrations of Acidulated Phosphate Fluoride (APF) solutions

The corrosion behaviors of Ti, Ti-6Al-7Nb and Ti-6Al-4V alloys, and an experimentally produced Ti-0.5Pt alloy in 0.05% to 2.0% concentrations of Acidulated Phosphate Fluoride (APF) solutions (corresponding to 226 to 9,050 ppm fluoride at pH 3.5 or 3.6) were examined. While the corrosion of Ti, Ti-6Al-7Nb and Ti-6Al-4V alloys might occur easily even in a diluted 0.05% APF solution, dissolution of Ti from the Ti-0.5Pt alloy was observed only in test solutions with APF concentration exceeding 0.2%. When Ti-6Al-7Nb and Ti-6Al-4V alloys were immersed in 2.0% APF solution, their surfaces were entirely covered by compact corrosion products of Na3TiF6 due to severe corrosion. As a result, Ti dissolution was prevented and the amount of Ti dissolved decreased. However, since Ti was covered by porous, large-sized corrosion products of Na3TiF6 and that Ti-0.5Pt alloy was not covered with any corrosion product, the amount of Ti dissolved increased in the 2.0% APF solution.     

氟离子对2种牙科用钛合金耐腐蚀性的影响

目的在模拟口腔环境下,探讨氟离子对Ti-12Zr合金和Ti-6Al-4V合金耐腐蚀性的影响。方法2种钛合金在含有不同浓度NaF（0%、0.05%、0.1%、0.2%）的酸性人工唾液（pH=4.0）电解池中测得极化曲线;然后将试件浸泡于恒温的实验溶液中,扫描电镜（SEM）下观察各组试件的表面形貌。结果2种钛合金在酸性人工唾液中的自腐蚀电位、极化电阻随着NaF浓度的升高而减小,自腐蚀电流密度随着NaF浓度的升高而增大;且当NaF浓度高于0.1%时2种钛合金的自腐蚀电位、极化电阻以及自腐蚀电流密度的变化明显（P＜0.05）;同时,扫描电镜结果显示当NaF浓度高于0.1%时2种钛合金表面开始发生严重的腐蚀;Ti-12Zr合金在NaF浓度为0.2%酸性人工唾液中的极化电阻明显高于Ti-6Al-4V合金（P＜0.05）。结论氟离子可降低Ti-12Zr合金及Ti-6Al-4V合金的耐腐蚀性,且在NaF浓度高于0.1%时更为明显。     

Effect of Cu and Ti electrodes on surface and electrochemical properties of Electro Discharge Machined (EDMed) structures made of Co-Cr and Ti dental alloys

ObjectivesPrevious studies have shown that the use of Cu electrodes compromises the electrochemical properties of Co-Cr and Ti alloys used for the fabrication of implant retained superstructures by Electro Discharge Machining (EDM). A possible solution is the use of Ti instead of Cu electrodes and thus the aim of this study was to evaluate the effect of Cu and Ti electrodes on surface and electrochemical properties of two types of dental alloys used for fabrication of implant retained superstructures after EDM.MethodsThree full arch frameworks were prepared from a Co–Cr and three from Ti6Al7Nb alloy. One framework from each alloy was used as control, one was subjected to EDM with Cu electrodes and the last one with Ti electrodes. Morphological and elemental characterization was studied by SEM/EDX. The electrochemical properties of the alloys were evaluated by Open Circuit Potential (OCP) and Linear Sweep Voltammetry (LSV) in Ringer’s solution. Electrochemical data were analyzed statistically by one way ANOVA and SNK multiple comparison tests at a = 0.05ResultsAll groups demonstrate the typical surface after EDM treatment with almost circular valleys and an increase in C and O content compared to control groups. Both alloys demonstrated an uptake of C and Cu by Cu electrodes and C and Ti after treatment with Ti electrodes. The use of Cu electrodes had a detrimental effect on corrosion resistance of Ti alloy.SignificanceThe use of Ti electrodes mitigates the degradation of electrochemical properties compared to Cu electrodes and from this standpoint is safer for the EDM of implant retained superstructures made of Co-Cr and Ti alloys.     

Influence of surface layer on mechanical and corrosion properties of nickel-titanium orthodontic wires

Objective:To analyze the effect of various coating formulations on the mechanical and corrosion properties of nickel-titanium (NiTi) orthodontic wires.Materials and Methods:Uncoated, rhodium-coated, and nitrified NiTi wires were observed with a three-point-bend test, surface roughness (Ra) measurement, scanning electron microscopy, energy dispersive spectroscopy, and electrochemical testing (open circuit potential, electrochemical impedance spectroscopy, and cyclic polarization scan). Differences in the properties of tested wire types were analyzed with analysis of variance and Tukey post hoc test.Results:Uncoated and nitrified NiTi wires showed similar mechanical and anticorrosive properties, while rhodium-coated NiTi wires showed the highest Ra and significantly higher modulus of elasticity, yield strength, and delivery of forces during loading but not in unloading. Rhodium-coated NiTi wires also had the highest corrosion current density and corrosion potential, lowest impedance modulus, and two time constants on Bode plot, one related to the Rh/Au coating and the other to underlying NiTi.Conclusion:Working properties of NiTi wires were unaffected by various coatings in unloading. Nitrification improved corrosion resistance. Rhodium coating reduced corrosion resistance and pronounced susceptibility to pitting corrosion in artificial saliva because of galvanic coupling between the noble coating and the base alloy.     

The development of Ti alloys for dental implant with high corrosion resistance and mechanical strength

The corrosion behaviors of Ti and Ti-6Al-4V, Ti-6Al-7Nb, Ti-0.5Pt, Ti-6Al-4V-0.5Pt, and Ti-6Al-7Nb-0.5Pt alloys were examined using an electrochemical analyzer in artificial saliva containing 0.1 and 0.2% NaF at a pH of 4.0. The SEM observations revealed that the surfaces of the alloys containing 0.5 wt% Pt were not affected in fluoride-containing environments, whereas the surfaces of Ti, Ti-6A1-4V, and Ti-6Al-7Nb alloys were markedly rough. In artificial saliva containing 0.1% NaF at a pH of 4.0, the amounts of Ti dissolved from the Ti, Ti-6Al-4V, and Ti-6Al-7Nb alloys were about 50 times larger than those of the alloys containing 0.5 wt% Pt. The tensile strengths of the alloys containing 0.5 wt% Pt were equal to or higher than those of pure Ti or the alloys without Pt. The Ti-0.5Pt, Ti-6Al-4V-0.5Pt, and Ti-6Al-7Nb-0.5 alloys are expected to be useful in clinical dentistry as new Ti alloys with high corrosion resistance and mechanical strength.     

Galvanic interaction between titanium and gallium alloy or dental amalgam.

OBJECTIVES: The objective was to examine in vitro the galvanic interaction between titanium and a high-copper dental amalgam or a gallium-based direct filling alloy at different area ratios, and to relate the observed interactions to the electrochemical characteristics of the alloys. METHODS: The tested materials were cast titanium, a single-composition, spherical high-copper amalgam, and a gallium-based direct filling alloy. Polarization curves were recorded. The galvanic couples were prepared at Ti/filling alloy ratios of 1:1, 2:1, 4:1 and 6:1. The couples were exposed to synthetic saliva at 37 degrees C and the galvanic currents and potentials were measured as a function of time. The results were analyzed by ANOVA and Tukey tests (p < or = 0.05). RESULTS: Freshly abraded titanium initially was anodic to both the amalgam and the gallium alloy, but the polarity reversed after a period of exposure. The galvanic potential and current density increased with the increasing Ti/alloy area ratio. The potential increase was smaller and the current increase larger for the Ga alloy than for the amalgam. The difference was consistent with the polarization characteristics. The galvanic current density was of the order of 10(-8) A/cm2 for the Ti/amalgam couple, and 10(-7) to 10(-6) A/cm2 for the Ti/gallium alloy couple. SIGNIFICANCE: The results show that the galvanic interaction between titanium and direct filling alloys is small. High copper dental amalgams should suffer little galvanic corrosion when in contact with Ti. For gallium direct filling alloys, the galvanic interaction may be more detrimental because of the inherently lower corrosion resistance.     

In vitro biocompatibility of CoCrMo dental alloys fabricated by selective laser melting

Objective

Selective laser melting (SLM) is increasingly used for the fabrication of customized dental components made of metal alloys such as CoCrMo. The main aim of the present study is to elucidate the influence of the non-equilibrium microstructure obtained by SLM on corrosion susceptibility and extent of metal release (measure of biocompatibility).

Methods

A multi-analytical approach has been employed by combining microscopic and bulk compositional tools with electrochemical techniques and chemical analyses of metals in biologically relevant fluids for three differently SLM fabricated CoCrMo alloys and one cast CoCrMo alloy used for comparison.

Results

Rapid cooling and strong temperature gradients during laser melting resulted in the formation of a fine cellular structure with cell boundaries enriched in Mo (Co depleted), and suppression of carbide precipitation and formation of a martensitic ? (hcp) phase at the surface. These features were shown to decrease the corrosion and metal release susceptibility of the SLM alloys compared with the cast alloy. Unique textures formed in the pattern of the melting pools of the three different laser melted CoCrMo alloys predominantly explain observed small, though significant, differences. The susceptibility for corrosion and metal release increased with an increased number (area) of laser melt pool boundaries.

Significance

This study shows that integrative and interdisciplinary studies of microstructural characteristics, corrosion, and metal release are essential to assess and consider during the design and fabrication of CoCrMo dental components of optimal biocompatibility. The reason is that the extent of metal release from CoCrMo is dependent on fabrication procedures.     

Elucidating the corrosion-related degradation mechanisms of a Ti-6Al-4V dental implant

ObjectiveThe Ti-6Al-4V (TAV) alloy is commercially used as a dental implant material. This work seeks to elucidates the origins of degradation of Ti-6Al-4V (TAV) implant alloys that result in peri-implant bone loss. Methods: In this work, a combination of microstructure, surface, and solution analyses was utilized to study the corrosion mechanism of the TAV alloy in oral environments. The corrosion of TAV alloys in the F^--enriched environment of a crevice was evaluated through nanoscale surface analysis. And, the findings were further rationalized via electrochemical means. ResultsOur results suggest the bone loss was caused by crevice corrosion and the consequential release of by-products, and the crevice corrosion was potentially induced by the buildup of corrosive species such as fluorides, which are common additives in dental products. In turn, the corrosion properties of the TAV alloy were evaluated in fluoride enriched environments. Nanoscale analysis of corroded surfaces, carried out using vertical scanning interferometry (VSI) showed that the corrosion susceptibility of the constituent phases dictates the corrosion product species. In specific, the aluminum-rich α phase preferentially dissolves under potential-free conditions and promotes the formation of insoluble Al-Ti oxides. Notably, under conditions of applied potential, oxidative dissolution of the vanadium-rich β phase is favored, and the vanadium release is promoted. SignificanceThese findings elucidate the origins of degradation of TAV-implants that result in the release of corrosion by-products into the local biological environment. More important, they offer guidelines for materials design and improvement to prevent this nature of degradation of dental implants.     

Corrosion behavior of pure titanium and titanium alloys in fluoride-containing solutions

The effects of fluoride concentrations and pH on the corrosion behavior of pure titanium, Ti-6Al-4V, Ti-6Al-7Nb alloys and a new Ti alloy adding palladium, which is expected to promote a repassivation of Ti were examined by anodic polarization and corrosion potential measurements. The amount of dissolved Ti was analyzed by inductively coupled plasma mass spectroscopy. The surface of the specimen was analyzed by X-ray photoelectron spectroscopy before and after the measurement. Pure Ti, Ti-6Al-4V and Ti-6Al-7Nb alloys were easily corroded even in a low fluoride concentration in an acidic environment. The corrosion resistance of Ti-0.2Pd alloy was greater than those of pure Ti, Ti-6Al-4V and Ti-6Al-7Nb alloys in the wide range of pH and fluoride concentrations. The high corrosion resistance of Ti-0.2Pd alloy was caused by the surface enrichment of Pd promoting a repassivation of Ti. The Ti-0.2Pd alloy is expected to be useful as a new Ti alloy with high corrosion resistance in dental use.     

Formation of carbon-added anatase-rich TiO2 layers on titanium and their antibacterial properties in visible light

ObjectiveTo avoid risk of infections associated with dental implants, thermal oxidation processes for practical dental Ti alloys were studied for both high bonding strength and antibacterial properties in visible light.MethodsTwo-step thermal oxidation, comprising carburization (first step of treatment: in Ar-1%CO gas) and subsequent oxidation (second step of treatment: in air), was conducted on commercially pure (CP) Ti, Ti-6Al-4V (Ti64), and Ti-6Al-7Nb (Ti67) alloys to form TiO₂ layers. Their bonding strengths and antibacterial properties against Escherichia coli (E. coli) in visible light (λ ≥ 400 nm) were evaluated.ResultsTiO₂ layers formed on each metal were composed of anatase and/or rutile. Anatase fraction and carbon concentration in the layers decreased with increasing temperature in the second step of treatment. Antibacterial properties of the TiO₂ layers were dependent on the temperature in the second step of treatment. An approximate antibacterial activity value of 2 (killing ～99% bacteria) was obtained when the temperatures in the second step of treatment were 673 and 773 K for CP Ti, 773 K for Ti64, and 773 and 873 K for Ti67. It was found that the TiO₂ layer must contain carbon and be anatase-rich to exhibit excellent antibacterial properties. Bonding strength between the substrate and TiO₂ layers formed at 773 K in the second step of treatment exceeded 80 MPa and was independent of substrate type.SignificanceTiO₂ layers, possessing both high bonding strength and excellent antibacterial properties, were successfully formed on practical dental Ti alloys via two-step thermal oxidation.     

An evaluation of the biocompatibility and osseointegration of novel glass fiber reinforced composite implants: In vitro and in vivo studies

Objectives

The aim of this study was to evaluate the in vitro biocompatibility and in vivo osseointegration of three novel bioactive glass fiber reinforced composite (GFRC) implants and to compare these with metal (Ti6Al4V) implants.