Judy Chia Chun Yuan

Stability of cp-Ti and Ti-6Al-4V alloy for dental implants as a function of saliva pH - an electrochemical study

OBJECTIVES To investigate the role of different levels of pH of artificial saliva under simulated oral environment on the corrosion behavior of commercially pure titanium (cp-Ti) and Ti-6Al-4V alloy. Special attention is given to understand the changes in corrosion kinetics and surface characterization of Ti by using electrochemical impedance spectroscopy (EIS). MATERIALS AND METHODS Fifty-four Ti disks (15-mm diameter, 2-mm thickness) were divided into six groups (n = 9) as a function of saliva pH (3, 6.5, and 9) and Ti type. Samples were mechanically polished using standard metallographic procedures. Standard electrochemical tests, such as open circuit potential, EIS, and potentiodynamic tests were conducted in a controlled environment. Data were evaluated by two-way ANOVA, Tukey multiple comparison test, and independent t-test (α = 0.05). Ti surfaces were examined using white-light-interferometry microscopy and scanning electron microscopy (SEM). RESULTS Saliva pH level significantly affected the corrosion behavior of both Ti types. At low pH, acceleration of ions exchange between Ti and saliva, and reduction of resistance of Ti surface against corrosion were observed (P < 0.05). Corrosion rate was also significantly increased in acidic medium (P < 0.05). Similar corrosion behavior was observed for both Ti types. The white-light-interferometry images of Ti surfaces show higher surface changes at low pH level. SEM images do not show detectable changes. No pitting corrosion was observed for any group. CONCLUSIONS The pH level of artificial saliva influences the corrosion behavior of cp-Ti and Ti-6Al-4V alloy in that lower pH accelerates the corrosion rate and kinetics. The corrosion products may mitigate the survival rate of dental implants.

The Role of Lipopolysaccharide on the Electrochemical Behavior of Titanium

Lipopolysaccharide (LPS) may induce peri-implantitis and implant failure. However, the role of LPS in titanium (Ti) electrochemical behavior remains unknown. We hypothesized that LPS in saliva with different pHs affects Ti corrosion properties. Thirty-six Ti discs (15 mm × 3 mm) were divided into 12 groups according to saliva pH (3, 6.5, and 9) and Escherichia coli LPS concentration (0, 0.15, 15, and 150 µg/mL). Electrochemical tests, such as open circuit potential, potentiodynamic, and electrochemical impedance spectroscopy, were conducted in a controlled environment. Data were evaluated by Pearson correlation and regression analysis (α = 0.05). LPS and pH affected Ti corrosive behavior. In general, lower pH and higher LPS concentration accelerated Ti corrosion. In the control group, the increase of pH significantly reduced the corrosion rate and increased the capacitance of the double layer. In LPS groups, the decrease of pH significantly increased the corrosion rate of Ti. LPS negatively influenced Ti corrosion behavior. Abbreviations: Cdl, capacitance of double layer; Ecorr, corrosion potential; EIS, electrochemical impedance spectroscopy; Icorr, corrosion current density; Ipass, passivation current density; LPS, lipopolysaccharide; OCP, open circuit potential; Rp, polarization resistance; Ti, titanium.

Fabrication of Anti-Aging TiO2 Nanotubes on Biomedical Ti Alloys

The primary objective of this study was to fabricate a TiO2 nanotubular surface, which could maintain hydrophilicity over time (resist aging). In order to achieve non-aging hydrophilic surfaces, anodization and annealing conditions were optimized. This is the first study to show that anodization and annealing condition affect the stability of surface hydrophilicity. Our results indicate that maintenance of hydrophilicity of the obtained TiO2 nanotubes was affected by anodization voltage and annealing temperature. Annealing sharply decreased the water contact angle (WCA) of the as-synthesized TiO2 nanotubular surface, which was correlated to improved hydrophilicity. TiO2 nanotubular surfaces are transformed to hydrophilic surfaces after annealing, regardless of annealing and anodization conditions; however, WCA measurements during aging demonstrate that surface hydrophilicity of non-anodized and 20 V anodized samples decreased after only 11 days of aging, while the 60 V anodized samples maintained their hydrophilicity over the same time period. The nanotubes obtained by 60 V anodization followed by 600 °C annealing maintained their hydrophilicity significantly longer than nanotubes which were obtained by 60 V anodization followed by 300 °C annealing.

Effects of Dextrose and Lipopolysaccharide on the Corrosion Behavior of a Ti-6Al-4V Alloy with a Smooth Surface or Treated with Double-Acid-Etching

Diabetes and infections are associated with a high risk of implant failure. However, the effects of such conditions on the electrochemical stability of titanium materials remain unclear. This study evaluated the corrosion behavior of a Ti-6Al-4V alloy, with a smooth surface or conditioned by double-acid-etching, in simulated body fluid with different concentrations of dextrose and lipopolysaccharide. For the electrochemical assay, the open-circuit-potential, electrochemical impedance spectroscopy, and potentiodynamic test were used. The disc surfaces were characterized by scanning electron microscopy and atomic force microscopy. Their surface roughness and Vickers microhardness were also tested. The quantitative data were analyzed by Pearsons correlation and independent t-tests (α = 0.05). In the corrosion parameters, there was a strong lipopolysaccharide correlation with the Ipass (passivation current density), Cdl (double-layer capacitance), and Rp (polarization resistance) values (p<0.05) for the Ti-6Al-4V alloy with surface treatment by double-acid-etching. The combination of dextrose and lipopolysaccharide was correlated with the Icorr (corrosion current density) and Ipass (p<0.05). The acid-treated groups showed a significant increase in Cdl values and reduced Rp values (p<0.05, t-test). According to the topography, there was an increase in surface roughness (R2 = 0.726, p<0.0001 for the smooth surface; R2 = 0.405, p = 0.036 for the double-acid-etching-treated surface). The microhardness of the smooth Ti-6Al-4V alloy decreased (p<0.05) and that of the treated Ti-6Al-4V alloy increased (p<0.0001). Atomic force microscopy showed changes in the microstructure of the Ti-6Al-4V alloy by increasing the surface thickness mainly in the group associated with dextrose and lipopolysaccharide. The combination of dextrose and lipopolysaccharide affected the corrosion behavior of the Ti-6Al-4V alloy surface treated with double-acid-etching. However, no dose-response corrosion behavior could be observed. These results suggest a greater susceptibility to corrosion of titanium implants in diabetic patients with associated infections.

Authorship, Collaboration, and Funding Trends in Implantology Literature: Analysis of Five Journals From 2005 to 2009

Purpose:To identify the trend of authorship in dental implant by exploring the prevalence of coauthored articles and to investigate the collaboration efforts, trends in funding involved in original articles, and their relationships. Materials:Articles published in the Clinical Oral Implants Research, International Journal of Oral & Maxillofacial Implants, Clinical Implant Dentistry and Related Research, Implant Dentistry, and Journal of Oral Implantology from 2005 to 2009 were reviewed. Nonoriginal articles were excluded. For each included articles, number of authors, collaboration efforts, and extramural funding were recorded. Descriptive and analytical statistics (&agr; = 0.05), including logistic regression analysis and &khgr;2 test, were used. Results:From a total of 2085 articles, 1503 met the inclusion criteria. Publications with 5 or more authors increased over time (P = 0.813). The amount of collaboration among different disciplines, institutions, and countries all increased. The greatest increase of collaboration was seen among institutions (P = 0.09). Nonfunding studies decreased over time (P = 0.031). There was a strong association between collaboration and funding for the manuscripts during the years studied (OR, 1.5). Conclusion:The number of authors per articles and collaborative studies increased over time in implant-related journals. Collaborative studies were more likely to be funded.

The role of nicotine, cotinine and caffeine on the electrochemical behavior and bacterial colonization to cp-Ti

Although smoking promotes deleterious effect to bone healing, there is a lack of study investigating its role on the implant structure and biofilm growth. We hypothesized that nicotine, cotinine and caffeine would impair the corrosion resistance of commercially-pure titanium (cp-Ti) and would enhance Streptococcus sanguinis biofilm growth. Neither the smoking products nor the caffeine affected the corrosion tendency (P>.05) and the oxide layer resistance (P=.762) of cp-Ti. Lower capacitance values were noted in the presence of nicotine (P=.001) and cotinine (P=.0006). SEM showed no pitting corrosion, and the EDS spectra did not differ among groups. Nicotine (300μg/mL) induced higher surface roughness (P=.03) and greater surface change of cp-Ti. Nicotine at 3μg/mL, and cotinine at 0.3 and 3μg/mL increased the number of viable cells (P<.05). Biofilm exposed to nicotine (0.3, 3 and 30μg/mL) (P=.025, .030, .040, respectively) and cotinine (3 and 30μg/mL) (P=.027, .049, respectively) enhanced carbohydrate content. Biofilm biomass and protein content were similar among groups (P>.05). These findings suggest a greater biofilm accumulation in smokers, a risk factor that may lead to peri-implantitis.

Occlusion for implant-supported fixed dental prostheses in partially edentulous patients: a literature review and current concepts

Implant treatment has become the treatment of choice to replace missing teeth in partially edentulous areas. Dental implants present different biological and biomechanical characteristics than natural teeth. Occlusion is considered to be one of the most important factors contributing to implant success. Most literature on implant occlusal concepts is based on expert opinion, anecdotal experiences, in vitro and animal studies, and only limited clinical research. Furthermore, scientific literature regarding implant occlusion, particularly in implant-supported fixed dental prostheses remains controversial. In this study, the current status of implant occlusion was reviewed and discussed. Further randomized clinical research to investigate the correlation between implant occlusion, the implant success rate, and its risk factors is warranted to determine best clinical practices.

An electrochemical investigation of TMJ implant metal alloys in an artificial joint fluid environment: The influence of pH variation

OBJECTIVE To investigate the corrosion behaviour of commonly used TMJ implants alloys (CoCrMo and Ti6Al4V) under simulated physiological conditions. METHODS Corrosion behaviour was evaluated using standard electrochemical corrosion techniques and galvanic corrosion techniques as per ASTM standards. Standard electrochemical tests (E(corr), I(corr), R(p) and C(f)) were conducted in bovine calf serum (BCS), as a function of alloys type and different pHs. Galvanic corrosion tests were conducted in BCS at a pH of 7.6. Alloy surfaces were characterized using white-light interferometry (WLI) and scanning electron microscopy (SEM). RESULTS The potentiodynamic test results exhibited the enhanced passive layer growth and a better corrosion resistance of Ti6Al4V compared to CoCrMo. Electrochemical impedance spectroscopy measurements demonstrated the influence of protein as a function of pH on corrosion mechanisms/kinetics. Galvanic coupling was not a major contributor to corrosion. SEM and WLI images demonstrated a significantly higher in surface roughness in CoCrMo after corrosion. CONCLUSIONS The results of this study suggest that Ti6Al4V shows superior corrosion behaviour to CoCrMo due to its strong passive layer, simulated joint fluid components can affect the electrochemical nature of the metal/electrolyte interface as a function of pH, and the galvanic effect of coupling CoCrMo and Ti6Al4V in a single joint is weak.

Corrosion kinetics and topography analysis of Ti-6Al-4V alloy subjected to different mouthwash solutions

This study evaluated the corrosion kinetics and surface topography of Ti-6Al-4V alloy exposed to mouthwash solutions (0.12% chlorhexidine digluconate, 0.053% cetylpyridinium chloride and 3% hydrogen peroxide) compared to artificial saliva (pH6.5) (control). Twenty Ti-6Al-4V alloy disks were used and divided into 4 groups (n=5). For the electrochemical assay, standard tests as open circuit potential and electrochemical impedance spectroscopy (EIS) were applied at baseline, 7 and 14days after immersion in the solutions. Scanning electron microscopy, atomic force microscopy and profilometry (average roughness - Ra) were used for surface characterization. Total weight loss of disks was calculated. Data were analyzed by ANOVA and Bonferronis test (α=0.05). Hydrogen peroxide generated the lowest polarization resistance (Rp) values for all periods (P<0.05). For the capacitance (Cdl), similar results were observed among groups at baseline (P=0.098). For the 7 and 14-day periods, hydrogen peroxide promoted the highest Cdl values (P<0.0001). Hydrogen peroxide promoted expressive superficial changes and greater Ra values than the others (P<0.0001). It could be concluded that solutions containing cetylpyridinium chloride and chlorhexidine digluconate might be the mouthwashes of choice during the post-operatory period of dental implants. However, hydrogen peroxide is counter-indicated in these situations. Further studies evaluating the dynamics of these solutions (tribocorrosion) and immersing the disks in daily cycles (two or three times a day) to mimic a clinical situation closest to the application of mouthwashes in the oral cavity are warranted to prove our results.

Influence of corrosion on lipopolysaccharide affinity for two different titanium materials.

STATEMENT OF PROBLEM Titanium is subject to corrosion in the oral cavity, which could contribute to periimplantitis. However, the effect of corrosion on the lipopolysaccharide affinity for titanium remains unknown. PURPOSE This study evaluated the role of corrosion (in artificial saliva at pHs 3, 6.5, and 9) on the lipopolysaccharide (LPS) affinity for commercially pure titanium (cp-Ti) and Ti-6Al-4V alloy. MATERIAL AND METHODS Seventy-two titanium disks were anodically polarized in a controlled environment (n=9). Control specimens were not corroded. Deionized water with different concentrations of LPS (1.5, 15, and 150 μg/mL) were used to treat the disks for 24 hours to investigate LPS adherence (n=3). Then specimens were immersed in LPS-free water to evaluate LPS elution at 24, 48, and 72 hours. Data were analyzed by the 2-way, 3-way, and 3-way repeated measures ANOVA, t tests, and the Tukey honestly significant difference (HSD) tests (α=.05). RESULTS A greater corrosion rate of cp-Ti and Ti-6Al-4V alloy and a higher LPS adherence to titanium surfaces (P<.05) were noted at acidic pH. The LPS affinity was higher for the Ti-6Al-4V alloy than for cp-Ti (P<.05). More LPS was eluted from titanium surfaces after a 24-hour interval. CONCLUSION Lipopolysaccharide affinity for cp-Ti and Ti-6Al-4V alloy is influenced by the corrosion process.