Surface treatment influences electrochemical stability of cpTi exposed to mouthwashes

Micro-arc driven porous ZrO2 coating for tailoring surface properties of titanium for dental implants application

Titanium (Ti) is an ideal material for dental implants due to its excellent properties. However, corrosion and mechanical wear lead to Ti ions and particles release, triggering inflammatory responses and bone resorption. To overcome these challenges, surface modification techniques are used, including micro-arc oxidation (MAO). MAO creates adherent, porous coatings on Ti implants with diverse chemical compositions. In this context, zirconia element stands out in its wear and corrosion properties associated with low friction and chemical stability. Therefore, we investigated the impact of adding zirconium oxide (ZrO2) to Ti surfaces through MAO, aiming for improved electrochemical and mechanical properties. Additionally, the antimicrobial and modulatory potentials, cytocompatibility, and proteomic profile of surfaces were investigated. Ti discs were divided into four groups: machined - control (cpTi), treated by MAO with 0.04 M KOH - control (KOH), and two experimental groups incorporating ZrO2 at concentrations of 0.04 M and 0.08 M, composing the KOH@Zr4 and KOH@Zr8 groups. KOH@Zr8 showed higher surface porosity and roughness, even distribution of zirconia, formation of crystalline phases like ZrTiO4, and hydrophilicity. ZrO2 groups showed better mechanical performance including higher hardness values, lower wear area and mass loss, and higher friction coefficient under tribological conditions. The formation of a more compact oxide layer was observed, which favors the electrochemical stability of ZrO2 surfaces. Besides not inducing greater biofilm formation, ZrO2 surfaces reduced the load of pathogenic bacteria evidenced by the DNA-DNA checkerboard analysis. ZrO2 surfaces were cytocompatible with pre-osteoblastic cells. The saliva proteomic profile, evaluated by liquid chromatography coupled with tandem mass spectrometry, was slightly changed by zirconia, with more proteins adsorbed. KOH@Zr8 group notably absorbed proteins crucial for implant biological responses, like albumin and fibronectin. Incorporating ZrO2 improved the mechanical and electrochemical behavior of Ti surfaces, as well as modulated biofilm composition and provided suitable biological responses.

Exploring the effect of chlorhexidine concentration on the biocorrosion behavior of Ti6Al4V for dental implants

Corrosion of dental implants is one of the most critical factors in the failure of implant treatments. Generally, corrosion depends on the type of material used in implants and the chemical composition of the oral environment. Due to the antibacterial activities, mouthwashes and chlorhexidine gels are often used after implant surgery. Ti6Al4V is commonly used in manufacturing dental implants. The present study aims to investigate the corrosion behavior of the Ti6Al4V alloy under different concentrations of chlorhexidine (0.12%, 0.2%,and 2%) during 2- and 24-h immersion. This way corrosion may be minimized while obtaining an antibacterial environment around the implant. In this regard, the electrochemical behavior of the specimens was investigated using polarization and impedance tests, and then their morphology, cross-section and nano-tribological behavior were evaluated using atomic force microscopy, scanning electron microscopy, energy dispersive x-ray spectroscopy, and nano-scratch test. The results show that using chlorhexidine solution with a concentration of 0.12% could yield a lower corrosion rate and material loss after implant surgery. RESEARCH HIGHLIGHTS: Open circuit potential values increase with immersion time, which suggests multistage passivation of the surface during immersion in chlorhexidine. Specimens in 0.12% chlorhexidine show improved thermodynamic corrosion resistance. Nano-scratch testing demonstrates higher scratch resistance for specimens in 0.12% chlorhexidine solution after 2-h immersion. Higher chlorhexidine concentration than 0.12% and longer immersion times decrease the resistance of the formed passive layer.

Effect of Enterococcus faecalis Biofilm on Corrosion Kinetics in Titanium Grade 4 Alloys with Different Surface Treatments

E. faecalis has been associated with bacteremia, sepsis, and bacterial endocarditis and peri-implantitis. This microorganism can remain in the alveolus even after extraction of the root remnant. This study aimed to evaluate the corrosion on different surfaces of commercially pure titanium (Ti) grade 4 (Ticp-G4) as a function of the bacterial biofilm effect of Enterococcus faecalis. A total of 57 discs were randomly divided according to their surface finish (n = 19). For microbiological analysis (n = 9), the discs were placed in 12-well plates containing E. faecalis culture and incubated at 37 °C for 7 days. The results show that for the intergroup analysis, considering the "electrolyte" factor, there was a difference between the groups. There was greater biofilm formation for the D.A.Zir group, with greater electrochemical exchange for Biofilm, and the presence of biofilm favored greater electrochemical exchange with the medium.

The Progress in Tribocorrosion Research (2010-21): Focused on the Orthopedics and Dental Implants

Tribocorrosion is an integration of two areas-tribology and corrosion. It can be defined as the material degradation caused by the combined effect of corrosion and tribological process at the material interfaces. Significant development has occurred in the field of tribocorrosion over the past years. This development is due to its applications in various fields, such as aerospace, marine, biomedical, and space. Focusing on biomedical applications, tribocorrosion finds its applications in the implants used in cardiovascular, spine, orthopedics, trauma, and dental areas. It was reported that around 7.2 million Americans are living with joint implants. Implant surgery is a traumatic and expensive procedure. Tribocorrosion can affect the lifespan of the implants, thus leading to implant failure and a potential cause of revision surgery. Hence, it is essential to understand how tribocorrosion works, its interaction with the implants, and what procedures can be implemented to protect materials from tribocorrosion. This paper discusses how tribocorrosion research has evolved over the past 11 years (2010-2021). This is a comprehensive overview of tribocorrosion research in biomedical applications.

Bio-Tribocorrosion of Titanium Dental Implants and Its Toxicological Implications: A Scoping Review

Bio-tribocorrosion is a phenomenon that combines the essentials of tribology (friction, wear, and lubrication) and corrosion with microbiological processes. Lately, it has gained attention in implant dentistry because dental implants are exposed to wear, friction, and biofilm formation in the corrosive oral environment. They may degrade upon exposure to various microbial, biochemical, and electrochemical factors in the oral cavity. The mechanical movement of the implant components produces friction and wear that facilitates the release of metal ions, promoting adverse oro-systemic reactions. This review describes the bio-tribocorrosion of the titanium (Ti) dental implants in the oral cavity and its toxicological implications. The original research related to the bio-tribo or tribocorrosion of the dental implants was searched in electronic databases like Medline (Pubmed), Embase, Scopus, and Web of Science. About 34 studies included in the review showed that factors like the type of Ti, oral biofilm, acidic pH, fluorides, and micromovements during mastication promote bio-tribocorrosion of the Ti dental implants. Among the various grades of Ti, grade V, i.e., Ti6Al4V alloy, is most susceptible to tribocorrosion. Oral pathogens like Streptococcus mutans and Porphyromonas gingivalis produce acids and lipopolysaccharides (LPS) that cause pitting corrosion and degrade the TiO2. The low pH and high fluoride concentration in saliva hinder passive film formation and promote metal corrosion. The released metal ions promote inflammatory reactions and bone destruction in the surrounding tissues resulting in peri-implantitis, allergies, and hyper-sensitivity reactions. However, further validation of the role of bio-tribocorrosion on the durability of the Ti dental implants and Ti toxicity is warranted through clinical trials.

Insight Into Corrosion of Dental Implants: From Biochemical Mechanisms to Designing Corrosion-Resistant Materials

Purpose of Review

Despite advanced technologies to avoid corrosion of dental implants, the mechanisms toward the release of metals and their role in the onset of peri-implant diseases are still under-investigated. Effective knowledge on the etiopathogenesis of corrosive products and preventive strategies mitigating the risks for surface degradation are thus in dire need. This review aimed to summarize evidence toward biocorrosion in the oral environment and discuss the current strategies targeting the improvement of dental implants and focusing on the methodological and electrochemical aspects of surface treatments and titanium-based alloys.

Recent Findings

Recent studies suggest the existence of wear/corrosion products may correlate with peri-implantitis progress by triggering microbial dysbiosis, the release of pro-inflammatory cytokines, and animal bone resorption. Furthermore, current clinical evidence demonstrating the presence of metal-like particles in diseased tissues supports their possible role as a risk factor for peri-implantitis. For instance, to overcome the drawback of titanium corrosion, researchers are primarily focusing on developing corrosion-resistant alloys and coatings for dental implants by changing their physicochemical features.

Summary

The current state-of-art discussed in this review found corrosion products effective in affecting biofilm virulence and inflammatory factors in vitro. Controversial and unstandardized data are limitations, making the premise of corrosion products being essential for peri-implantitis onset. On the other hand, when it comes to the strategies toward reducing implant corrosion rate, it is evident that the chemical and physical properties are crucial for the in vitro electrochemical behavior of the implant material. For instance, it is foreseeable that the formation of films/coatings and the incorporation of some functional compounds into the substrate may enhance the material’s corrosion resistance and biological response. Nevertheless, the utmost challenge of research in this field is to achieve adequate stimulation of the biological tissues without weakening its protective behavior against corrosion. In addition, the translatability from in vitro findings to clinical studies is still in its infancy. Therefore, further accumulation of high-level evidence on the role of corrosion products on peri-implant tissues is expected to confirm the findings of the present review besides the development of better methods to improve the corrosion resistance of dental implants. Furthermore, such knowledge could further develop safe and long-term implant rehabilitation therapy.

Assessment of Nickel and Chromium Level in Gingival Crevicular Fluid in Patients Undergoing Orthodontic Treatment with or without Fluoridated Tooth Paste

BACKGROUND

Release of metallic ions, especially nickel and chromium, present in orthodontic fixed appliance attachments such as brackets and archwires has been a basis of concern in current years. The present study was conducted to assess nickel and chromium level in gingival crevicular fluid in patients undergoing orthodontic treatment.

MATERIALS AND METHODS

Forty patients undergoing fixed orthodontic treatment were divided into 2 groups of 20 each. Group I was fixed orthodontic treatment group and was given nonfluoridated toothpaste and Group II was fixed orthodontic treatment group and was given fluoridated toothpaste. The assessment of salivary nickel and chromium levels was done using inductively coupled plasma mass spectrometry.

RESULTS

In group I, there were 6 male and 14 female and in group II 7 males and 13 females. The mean nickel level (ng/ml) before treatment in group I was 0.49 and in group II was 0.52, on 7^th day was 0.52 and 0.54, on 30^th day was 13.4 and 100.2, and on 6^th month was 0.54 and 0.52 in Group I and II, respectively. The mean chromium level (ng/ml) before treatment in Group I was 0.48 and in Group II was 0.52, on 7^th day was 0.52 and 0.53, on 30^th day was 40.6 and 62.4 and on 6^th month was 4.9 and 0.52 in Group I and II, respectively. The difference was significant (P < 0.05).

CONCLUSION

The release of metal ions such as nickel and chromium was more with fluoridated toothpaste as compared to nonfluoridated toothpaste in patients undergoing fixed orthodontics.

Efficacy of 0.05% Chlorhexidine and 0.05% Cetylpyridinium Chloride Mouthwash to Eliminate Living Bacteria on In Situ Collected Biofilms: An In Vitro Study

Chlorhexidine (CHX) mouthwashes are frequently used as an adjunctive measure for the treatment of periodontitis and peri-implantitis, as well as in patients on maintenance therapy. However, their prolonged use is associated with several side effects. This study aimed at evaluating if a mouthwash with a reduced concentration of CHX combined with cetylpyridnium chloride (CPC) was as effective as a conventional CHX mouthwash in the reduction in living cells in oral biofilms attached to hydroxyapatite (HA) and micro-rough titanium (Ti) surfaces. Four healthy volunteers wore a customized acrylic appliance containing HA and Ti discs for in situ plaque accumulation. Biofilms were grown on the discs for 24 or 48 h and then randomly exposed for 60 s to: 0.05% CHX + 0.05% CPC, 0.1% CHX (positive control) or sterile saline (negative control). Viability assay and live-dead staining were performed to quantify bacterial viability and to distinguish live and dead cells, respectively. At both time points, contrary to saline, CHX, both alone and in combination with CPC, exhibited high antibacterial properties and induced a significant reduction in biofilm viability. This study demonstrates the potential of mouthwashes containing a low concentration of CHX combined with CPC as effective antibacterial agents for long-term applications with reduced undesired side effects.

Synthesis of bioactive glass-based coating by plasma electrolytic oxidation: Untangling a new deposition pathway toward titanium implant surfaces

HYPOTHESIS

Although bioactive glass (BG) particle coatings were previously developed by different methods, poor particle adhesion to surfaces and reduced biological effects because of glass crystallization have limited their biomedical applications. To overcome this problem, we have untangled, for the first time, plasma electrolytic oxidation (PEO) as a new pathway for the synthesis of bioactive glass-based coating (PEO-BG) on titanium (Ti) materials.

EXPERIMENTS

Electrolyte solution with bioactive elements (Na₂SiO₃-5H₂O, C₄H₆O₄Ca, NaNO₃, and C₃H₇Na₂O₆P) was used as a precursor source to obtain a 45S5 bioglass-like composition on a Ti surface by PEO. Subsequently, the PEO-BG coating was investigated with respect to its surface, mechanical, tribological, electrochemical, microbiological, and biological properties, compared with those of machined and sandblasted/acid-etched control surfaces.

FINDINGS

PEO treatment produced a coating with complex surface topography, Ti crystalline phases, superhydrophilic status, chemical composition, and oxide layer similar to that of 45S5-BG (~45.0Si, 24.5 Ca, 24.5Na, 6.0P w/v%). PEO-BG enhanced Ti mechanical and tribological properties with higher corrosion resistance. Furthermore, PEO-BG had a positive influence in polymicrobial biofilms, by reducing pathogenic bacterial associated with biofilm-related infections. PEO-BG also showed higher adsorption of blood plasma proteins without cytotoxic effects on human cells, and thus may be considered a promising biocompatible approach for biomedical implants.

Surface analysis and corrosion behavior of pure titanium under fluoride exposure

STATEMENT OF PROBLEM

The corrosive effects of oral fluoride products on titanium have been reported, and chronic fluorosis, which causes hyperfluoemia, is one of the world's health problems. Nevertheless, the relationship between high serum fluoride and corrosion on the titanium surface, which might have adverse effects on titanium implant osseointegration, has not been elucidated.

PURPOSE

The purpose of this in vitro study was to investigate the corrosion behavior of pure titanium exposed to high serum fluoride with different pH values based on surface analysis.

MATERIAL AND METHODS

Pure titanium specimens, exposed to different electrolytes with 0.04 and 0.4 ppm NaF at pH 7.3 and 5.0 values, were examined for surface microstructure by using scanning electron microscopy (SEM) and for surface element composition with X-ray photoelectron spectroscopy (XPS). The corrosion behavior and metal ion release of specimens immersed in the Hanks' balanced salt solution (HBSS) containing 0.04 and 0.4 ppm serum fluoride concentrations (NaF) at 7.3 and 5.0 pH values were measured by electrochemical impedance spectroscopy (EIS) and inductively coupled plasma atomic emission spectrometry (ICP-AES).

RESULTS

Pitting holes were observed on pure titanium surfaces exposed to high serum fluoride. The surfaces became rougher with the increase of serum fluoride concentration, especially under acidic conditions. XPS analysis revealed a reduction of dominant titanium dioxide (TiO₂) on the pure titanium surface under serum fluoride exposure, corresponding to an increase in the relative level of F. EIS data showed an active corrosion behavior of pure titanium exposed to high serum fluoride and gradually decreased corrosion resistance with increasing concentration of serum fluoride, which was more severe under acidic conditions. The release of titanium ions was also induced by high serum fluoride and acidic conditions.

CONCLUSIONS

High serum fluoride had a negative influence on the corrosion behavior of pure titanium. The titanium oxide film barrier could be broken down in the fluoride ions condition, and the corrosion resistance of pure titanium decreased with the increasing concentration of serum fluoride. The increased corrosion susceptibility of pure titanium accelerated the release of titanium ions after exposure to high serum fluoride; this was more pronounced in an acidic environment.

Electrochemical evaluation of the hydrogen peroxide- and fluoride-induced corrosive property and its recovery on the titanium surface

PURPOSE

This study aimed to elucidate the effects of hydrogen peroxide (H₂O₂) and sodium fluoride (NaF) on titanium surfaces under conditions mimicking those encountered during dental treatment.

METHODS

Titanium samples were immersed in artificial saliva (AS), 1M H₂O₂, 1M H₂O₂ with catalase, 1000ppmF NaF, 1M H₂O₂ with 1000ppmF NaF, or 9000ppmF NaF (9000ppmF NaF: pH 5.3, other solutions: pH 6.5) for 3min. The electrochemical properties of the titanium samples were analyzed before and after the immersion procedures using a potentiostat. The amounts of titanium eluted into each solution were measured using inductively coupled plasma mass spectrometry. The post-immersion color changes (ΔE*ab) and gloss values of the titanium samples were determined using spectrophotometry. Moreover, the solution-treated titanium samples were subsequently immersed in AS and analyzed electrochemically at 1, 2, 3, 4, 6, 8, and 24h.

RESULTS

The immersion of titanium in any of the solutions except 1000ppmF NaF caused significant increases in corrosive and passive currents and significant reductions in polarization resistance. No titanium elution or color changes were observed, except when 9000ppmF NaF was used. After immersion in AS, the electrochemical properties of all of the titanium samples, except the 9000ppmF NaF-treated samples, recovered within 24h.

CONCLUSIONS

One M H₂O₂ and 1000ppmF NaF can be used alone or in combination in the clinical setting without causing significant titanium corrosion because the corrosive properties they induce is reversible. However, highly concentrated acidic fluorides can cause irreversible corrosion.

Initial investigation of the corrosion stability of craniofacial implants

STATEMENT OF PROBLEM

Although craniofacial implants have been used for retention of facial prostheses, failures are common. Titanium undergoes corrosion in the oral cavity, but the corrosion of craniofacial implants requires evaluation.

PURPOSE

The purpose of this in vitro study was to investigate the corrosion stability of commercially pure titanium (CP Ti) exposed to simulated human perspiration at 2 different pH levels (5.5 and 8).

MATERIAL AND METHODS

Fifteen titanium disks were divided into 3 groups (n=5 per group). The control group was subjected to simulated body fluid (SBF) (control). Disks from the 2 experimental groups were immersed in simulated alkaline perspiration (SA_KP) and simulated acidic perspiration (SA_CP). Electrochemical tests, including open circuit potential (3600 seconds), electrochemical impedance spectroscopy, and potentiodynamic tests were performed according to the standardized method of 3-cell electrodes. Data were analyzed by 1-way ANOVA and the Tukey honestly significant difference tests (α=.05).

RESULTS

Simulated human perspiration reduced the corrosion stability of CP Ti (P<.05). The SBF group presented the lowest capacitance values (P<.05). SA_KP and SA_CP groups showed increased values of capacitance and showed no statistically significant differences (P>.05) from each other. The increase in capacitance suggests that the acceleration of the ionic exchanges between the CP Ti and the electrolyte leads to a lower corrosion resistance. SA_KP reduced the oxide layer resistance of CP Ti (P<.05), and an increased corrosion rate was noted in both simulated human perspiration groups.

CONCLUSIONS

Craniofacial implants can corrode when in contact with simulated human perspiration, whereas alkaline perspiration shows a more deleterious effect. Perspiration induces a more corrosive effect than simulated body fluid.