Antimicrobial behavior of titanium coating with chlorhexidine-doped thin film exposed to a biofilm supplemented with nicotine.

Because nicotine upregulates the growth of most oral bacteria, this in vitro study investigated the antimicrobial effect of chlorhexidine-doped thin film on commercially pure titanium against Fusobacterium nucleatum (F. nucleatum) biofilm supplemented with different concentrations of nicotine (0, 1, and 2 mg/mL). Biofilms were formed on a chlorhexidine-doped thin film on commercially-pure-titanium discs and compared to the control groups. Biofilm viability, total biofilm growth using a spectrophotometer, extracellular polysaccharide content, and pH variations were assessed as dependent variables. Data were submitted to ANOVA and Tukey honest significant difference tests (α=0.05). F. nucleatum biofilm growth was inhibited when exposed to chlorhexidine-doped thin film (p<0.05). Biofilm supplemented with nicotine did not impact the synthesis of EPS on the same type of treatment (p>0.05). The pH values were significantly increased with the increase of nicotine concentration (p<0.05). Chlorhexidine-doped thin film was effective in reducing F. nucleatum biofilm supplemented with nicotine.

Nicotine is a potent extracellular polysaccharide inducer in Fusobacterium nucleatum biofilms

The purpose of this in vitro study was to analyze the influence of nicotine on the extracellular polysaccharides in Fusobacterium nucleatum biofilm. Methods: F. nucleatum (ATCC 10953) biofilms supplemented with different concentrations of nicotine (0, 0.5, 1, 2, 4, and 8 mg/mL) were grown in two different BHI broth conditions [no sucrose and 1% sucrose]. Extracellular polysaccharides assay, pH measurements, and a spectrophotometric assay were performed. Data were submitted for ANOVA and Tukey honestly significant difference analyses (HSD) tests (α =.05). Results: Extracellular polysaccharides synthesis was influenced by an interaction between nicotine concentrations and growth medium solution containing sucrose (P<.05). The pH values declined in the sucrose-exposed biofilm were greater than in the group exposed only to nicotine (P<.05). The biofilm exposed to sucrose and nicotine had a higher total biofilm growth (P<.05) than the nicotine-treated biofilm without sucrose. Conclusions: Regardless of sucrose exposure, biofilms exposed to different nicotine concentrations influenced the amount of extracellular polysaccharides

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.

Synthesis of multifunctional chlorhexidine-doped thin films for titanium-based implant materials.

Our goal was to create bio-functional chlorhexidine (CHX)-doped thin films on commercially pure titanium (cpTi) discs using the glow discharge plasma approach. Different plasma deposition times (50, 35 and 20 min) were used to create bio-functional surfaces based on silicon films with CHX that were compared to the control groups [no CHX and bulk cpTi surface (machined)]. Physico-chemical and biological characterizations included: 1. Morphology, roughness, elemental chemical composition, film thickness, contact angle and surface free energy; 2. CHX-release rate; 3. Antibacterial effect on Streptococcus sanguinis biofilms at 24, 48 and 72 h; 4. Cytotoxicity and metabolic activity using fibroblasts cell culture (NIH-F3T3 cells) at 1, 2, 3 and 4 days; 5. Protein expression by NIH-F3T3 cells at 1, 2, 3 and 4 days; and 6. Co-culture assay of fibroblasts cells and S. sanguinis to assess live and dead cells on the confocal laser scanning microscopy, mitochondrial activity (XTT), membrane leakage (LDH release), and metabolic activity (WST-1 assay) at 1, 2 and 3 days of co-incubation. Data analysis showed that silicon films, with or without CHX coated cpTi discs, increased surface wettability and free energy (p < 0.05) without affecting surface roughness. CHX release was maintained over a 22-day period and resulted in a significant inhibition of biofilm growth (p < 0.05) at 48 and 72 h of biofilm formation for 50 min and 20 min of plasma deposition time groups, respectively. In general, CHX treatment did not significantly affect NIH-F3T3 cell viability (p > 0.05), whereas cell metabolism (MTT assay) was affected by CHX, with the 35 min of plasma deposition time group displaying the lowest values as compared to bulk cpTi (p < 0.05). Moreover, data analysis showed that films, with or without CHX, significantly affected the expression profile of inflammatory cytokines, including IL-4, IL-6, IL-17, IFN-y and TNF-α by NIH-F3T3 cells (p < 0.05). Co-culture demonstrated that CHX-doped film did not affect the metabolic activity, cytotoxicity and viability of fibroblasts cells (p > 0.05). Altogether, the findings of the current study support the conclusion that silicon films added with CHX can be successfully created on titanium discs and have the potential to affect bacterial growth and inflammatory markers without affecting cell viability/proliferation rates.

Bond strength of lithium disilicate after cleaning methods of the remaining hydrofluoric acid.

BACKGROUND: Different ceramic surface cleaning methods have been suggested after the acid conditioning. The aim was to evaluate the effect of different protocols used to remove the remaining hydrofluoric acid on the shear bond strength (SBS) between lithium disilicate and resin cement. MATERIAL AND METHODS: Forty-four specimens of lithium disilicate (IPS e.max Press) were divided in 4 groups (n=11): group C (control, no treatment); group HF+S (5% hydrofluoric acid + silane); group HF+US+S (5% hydrofluoric acid + ultrasound cleaning + silane); group HF+PH+S (5% hydrofluoric acid + 37% phosphoric acid + silane). Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were performed to characterize the surface morphology. The SBS test was performed on the resin/ceramic interface, and the failure mode was characterized. SBS values were submitted to 1-way ANOVA and the Tukey test (α=.05). The relation between surface treatment and failure modes was analyzed using the chi-squared test (α=.05). RESULTS: The surface treatment type interfered in the shear strength (p<.001) and higher SBS values were observed for the groups HF+US+S (17.87 MPa) and HF+PH+S (16.37 MPa). The surface treatment did not influence the failure mode (p=.713). No fluorsilicate salts were observed after ultrasound cleaning. CONCLUSIONS: The utilization of ultrasound cleaning was an effective procedure to remove remaining fluorsilicate salts, promoting the highest SBS values. Key words:Bond strength, ceramics, fluorsilicate, lithium disilicate, resin cement.

Influence of a light-activated glaze on the adhesion of Streptococcus sanguinis to the surface of polymers used in fabrication of interim prostheses.

AIM: This study aimed to investigate the adhesion of Streptococcus sanguinis to the surface of interim prostheses that were treated or not treated with a light-activated glaze, and subjected or not subjected to a thermocycling procedure. METHODS: 36 specimens of each resin were divided into 4 groups: heat-activated acrylic resin; chemically-activated acrylic resin; bis-acryl composite resin (Protemp; 3M ESPE); and bis-GMA (Charisma; Heraeus Kulzer). Half of the specimens underwent application of glaze and the other half underwent mechanical polishing. Specimens were randomly distributed into groups (N = 9) with and without thermocycling (2000 cycles). Surface energy, roughness and microbiological analyses were performed. RESULTS: Groups treated with glaze showed lower roughness when compared with the same groups without glaze treatment, before and after thermocycling, except for the bis-acryl groups after thermocycling. Surface energy values were higher in the groups treated with glaze, except the bis-acryl group before and after thermocycling. After thermocycling, the values of bacterial adhesion decreased numerically, with the exception of the chemically-activated acrylic resin group treated with glaze and the heat-activated acrylic resin group without glaze treatment. CONCLUSION: The application of glaze and the thermocycling do not influence, in a statistically significant manner, the bacterial adhesion on polymer surfaces.

Electrochemical behavior of titanium exposed to a biofilm supplemented with different sucrose concentrations.

STATEMENT OF PROBLEM: Biofilms can reduce the corrosion resistance of titanium because of the bacterial metabolism of fermentable carbohydrates, including sucrose. However, studies evaluating whether biofilms exposed to higher sucrose concentrations can affect the electrochemical behavior of titanium are lacking. PURPOSE: The purpose of this in vitro study was to test the electrochemical behavior of titanium previously exposed to biofilm supplemented with different sucrose concentrations. MATERIAL AND METHODS: Streptococcus mutans UA159 biofilms were formed on commercially pure titanium (cpTi) surfaces and supplemented constantly with different sucrose concentrations (0%, 1%, 10%, and 40%) for 7 days (experimental groups) (n=12 per group). CpTi disks without biofilm were used as a control (n=12). The standard electrochemical tests open-circuit potential, electrochemical impedance spectroscopy, and potentiodynamic curve were performed. Data were submitted to ANOVA and the Tukey honestly significant difference (HSD) tests (α=.05). RESULTS: The biofilm exposed to sucrose had an increased biofilm dry weight (P<.05). The polysaccharide amount and the pH drop were higher in the groups exposed to sucrose (P<.05). No difference was noted between the control and experimental groups for the electrochemical properties of cpTi (P>.05). CONCLUSIONS: Biofilms exposed to greater carbohydrate concentration did not alter the corrosive behavior of titanium.

Comparative analysis of ceramic flexural strength in co-cr and ni-cr alloys joined by TIG welding and conventional brazing

Aims: The purpose of the present study was to evaluate the flexural strength of specimens made of nickel-chromium(Ni-Cr) and cobalt-chromium (Co-Cr) alloys and joined by tungsten inert gas (TIG) welding and conventional brazing. Ni­Cr and Co­Cr base metal specimens (n = 40, each) were cast and welded by TIG or brazing. The specimens were divided into six groups (2 base metals, four welded specimens). Ceramic systems were applied to the central part of all the specimens. A three-point bending test with a velocity of 0.5 mm/m was performed on the specimens up to the point of the first ceramic bond failure by measuring the flexural strength. Data were analyzed using two-way ANOVA and Bonferroni's tests. Conventional welding showed the lowest flexural strength results for both alloys, while the TIG weld and the control group presented with varying bond strengths for the alloys studied. We concluded that TIG welding was superior to the conventional welding method for both Ni­Cr and Co­Cr alloys with regard to the flexural strength of the ceramic (AU)

Surface analysis and shear bond strength of zirconia on resin cements after non-thermal plasma treatment and/or primer application for metallic alloys.

There is no established protocol for bonding zirconia (Y-TZP) with resin cements. Non-thermal plasma (NTP) may be an alternative for the clinical problems related to adhesion. The purpose of the present study was to characterize the surface of Y-TZP exposed to methane (CH4) NTP or coated with a layer of primer for metal alloys and the association between the two methods and to evaluate the effect of NTP treatment on bond strength between Y-TZP and two resin cements. A total of 235 Y-TZP discs (8×2mm) were distributed into five groups: Co (no surface treatment), Pr (primer), NTP (methane plasma), Pr+NTP and NTP+Pr. The effect of the treatment type on the surface free energy, morphology, topography and chemical composition of the Y-TZP discs was investigated. The discs were cemented to composite resin substrates using Panavia F2.0 or RelyX U200. Shear bond strength (n=10) analyses were performed (1mm/min) before and after thermocycling (5-55°C, 2000cycles) on the bonded specimens. The data were analyzed with one and three-way ANOVAs and Bonferroni tests (α=0.05). NTP reduced the surface energy and roughness of the Y-TZP discs. SEM-EDS and XPS analyses showed the presence of the organic thin film, which significantly improved the bond strength results when Rely X U200 was used, whereas the primer treatment was more effective with Panavia F2.0. Thermocycling significantly reduced the bond strength results of the NTP and Pr+NTP groups cemented with Rely X U200 and the Pr and NTP+Pr groups cemented with Panavia F2.0. Nonthermal plasma improves the bond strength between Rely X U200 and Y-TZP and also seems to have water-resistant behavior, whereas Panavia F2.0 showed better results when associated with primer.

Effect of nonthermal plasma treatment on surface chemistry of commercially-pure titanium and shear bond strength to autopolymerizing acrylic resin.

The effect of nonthermal plasma on the surface characteristics of commercially pure titanium (cp-Ti), and on the shear bond strength between an autopolymerizing acrylic resin and cp-Ti was investigated. A total of 96 discs of cp-Ti were distributed into four groups (n=24): Po (no surface treatment), SB (sandblasting), Po+NTP and SB+NTP (methane plasma). Surface characterization was performed through surface energy, surface roughness, scanning microscopy, energy dispersive spectroscopy, and X-ray diffraction tests. Shear bond strength test was conducted immediately and after thermocycling. Surface treatment affected the surface energy and roughness of cp-Ti discs (P<.001). SEM-EDS showed the presence of the carbide thin film. XRD spectra revealed no crystalline phase changes. The SB+NTP group showed the highest bond strength values (6.76±0.70 MPa). Thermocycling reduced the bond strength of the acrylic resin/cp-Ti interface (P<.05), except for Po group. NTP is an effective treatment option for improving the shear bond strength between both materials.