Cortino Sukotjo

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.

Influence of pH on the tribocorrosion behavior of CpTi in the oral environment: synergistic interactions of wear and corrosion †

UNLABELLED Dental implants made of titanium alloys have been used as a predictable therapy approach to replace missing teeth. The oral environment subjects titanium implants to varying conditions like changes in pH, temperature, and saliva contamination leading to chemical corrosion together with mastication process. OBJECTIVE In this study, the combined effect of chemical corrosion and wear (so-called tribocorrosion) in the degradation of dental implant material (CpTi) under varying pH oral environment was investigated. METHODS Titanium (CpTi) discs were subjected to sliding tests in artificial saliva at varying pHs: 3.0, 6.0, and 9.0. A custom made tribocorrosion apparatus was used to perform the tests. The tribological system consisted of a ceramic ball of 28 mm diameter articulating against the flat face (titanium). RESULTS Electrochemical impedance spectroscopy results indicated an increase in electrochemical double layer capacitance (C(dl)) at pH 3.0 and 6.0 after sliding. Surprisingly, in the presence of tribological stresses, the measured current evolution was highest and fluctuated the most at pH 6.0. In addition, the greatest weight loss was measured at pH 6.0. CONCLUSIONS Despite reports of CpTi being electrochemically stable down to pH 2.0, this study suggests degradation peaks at near neutral pH values in the presence of motion. At pH 6.0, the passive film layer, typically protecting the surface of titanium may not be reformed cohesively, resulting in more tribocorrosion products at the surface, which are easily sheared off. These findings elevate concern with regard to dental implants because the average pH of the oral cavity is 6.3.

Effects of nicotine on gene expression and osseointegration in rats

BACKGROUND While many studies have focused on the hazardous effects of smoking, there is little direct evidence regarding the specific detrimental effects of the nicotine on the osseointegration of implants. OBJECTIVE To understand the effects of nicotine on gene expression and osseointegration of titanium implants in rats. MATERIAL AND METHODS Forty-four rats were administered with nicotine or saline for a period of 8 weeks. The femurs were then harvested and analyzed using a three-point bending test. Osseointegration level was determined using bone/implant contact ratio at 2 or 4 weeks after implants were placed. Expression levels of bone matrix-related genes were measured by quantitative real-time polymerase chain reaction. RESULTS The results of the three-point bending showed that there was no significant difference detected in stiffness between control and nicotine groups at 8 weeks post-saline/nicotine delivery (P=0.705). The bone/implant contact ratio in nicotine-delivered group was significantly decreased compared with those in the control group at 4 weeks (P<0.05). Also, expression levels of osteopontin, type II collagen, bone morphogenic protein-2, bone sialoprotein, and core-binding factor α-1 were significantly down-regulated in the nicotine-delivered group compared with the control. CONCLUSIONS Although systemic exposure to nicotine did not affect rat bone development, bone wound healing around the implant after placement was affected. These findings suggest that nicotine might inhibit the bone matrix-related gene expressions required for wound healing and thereby diminish implant osseointegration at late stage.

Biophysical evaluation of cells on nanotubular surfaces: the effects of atomic ordering and chemistry.

After the implantation of a biomaterial in the body, the first interaction occurs between the cells in contact with the biomaterial surface. Therefore, evaluating the cell–substrate interface is crucial for designing a successful implant. In this study, the interaction of MC3T3 osteoblasts was studied on commercially pure and alloy (Ti6Al4V) Ti surfaces treated with amorphous and crystalline titanium dioxide nanotubes. The results indicated that the presence of nanotubes increased the density of osteoblast cells in comparison to bare surfaces (no nanotubes). More importantly, our finding shows that the chemistry of the substrate affects the cell density rather than the morphology of the cells. A novel approach based on the focused ion beam technique was used to investigate the biophysical cell–substrate interaction. The analysis revealed that portions of the cells migrated inside the crystalline nanotubes. This observation was correlated with the super hydrophilic properties of the crystalline nanotubes.

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.

The Effect of Systemic Nicotine on Osseointegration of Titanium Implants in the Rat Femur

The purpose of this study was to determine whether high levels of plasma nicotine, delivered via subcutaneously placed mini-osmotic pumps, had an effect on bone development and osseointegration of a titanium implant in rat femurs in both the short and long term. In this study, we hypothesized that systemic nicotine may not affect bone development, but may affect osseointegration in both the short and long term. Thirty rats were assigned to 4 groups. Group 1 (n = 10) was subdivided into 2 groups, which both received nicotine during the duration of the experiment. Half of the group (n = 5) was sacrificed at 2 weeks after implant placement, and the other half (n = 5) was sacrificed at 4 weeks after implant placement. Group 2 (n = 10) was treated identically; however, this group was given saline placebo rather than nicotine. Nicotine/saline was administered via subcutaneous mini-osmotic pumps. Serum analysis was assessed biweekly and weight was assessed weekly. Implant placement consisted of mini-implant placement in the femur of the rats under general anesthesia. After sacrifice, the femurs were harvested and analyzed. Biomechanical push-in test was used to determine the degree of osseointegration by evaluating the breakpoint load. Micro-CT was performed on the femurs of the remaining 10 rats to determine the bone density and architecture. Micro-CT showed no significant difference in bone morphometric analysis. Push-in test showed significant difference in axial load force required to dislodge the implant between the nicotine-treated and control rats both at 2 and at 4 weeks after implant placement. The evidence indicates that while there was no significant difference in bone development and remodeling with exposure to systemic nicotine, there was a significant difference in bone wound healing, specifically with the osseointegration of titanium implants at both 2 and 4 weeks after implant placement. In conclusion, systemic nicotine may have a significant impact on the osseointegration of implants in the rat femur. Additional studies need to be conducted to further understand the specific way in which nicotine adversely affects wound healing on the molecular level.

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.

Electrochemical behavior of titanium in artificial saliva: Influence of pH

Titanium is the most common material chosen for dental implants because it is highly corrosion resistant because it constantly reforms a protective passive film layer. The formation and composition of the passive film layer is dependent on the environmental conditions. If the stable oxide layer is damaged, the titanium surface underneath can corrode. The purpose of this study was to determine if basic corrosion of commercially pure titanium (CpTi) alloy in artificial saliva was affected by pH and to understand the corrosion kinetics/mechanisms of CpTi as a function of pH. In this study, titanium alloy discs were subjected to corrosion tests. Before the tests, all samples were cleaned and polished using standard metallographic preparation methods. Artificial saliva was used as the testing medium. The following pH values were tested: 3.0, 4.5, 6.0, 6.5, 7.5, and 9.0. Different pH values were achieved by adding lactic acid (acidic) or NaOH (basic) in appropriate amounts. Potentiodynamic curves indicated behavior change at each pH. In addition, the corrosion current density value determined from the potentiodynamic curve exhibited the poorest corrosion resistance for pH 7.5. The Nyquist plot (from the electrochemical impedance spectroscopy results) indicated that pH 7.5 had the poorest resistance. Scanning electron microscopy images indicated that pH levels of 6.5, 7.5, and 9.0 had considerable surface corrosion. The results showed that the medias pH significantly influenced the corrosion behavior of CpTi. The poor corrosion behavior at the neutral pHs invites some concerns and highlights the need for further study.