载银多聚赖氨酸-海藻酸钠静电自组装多层膜修饰钛表面及其抗菌研究

目的 利用层层自组装技术在钛表面构建聚L赖氨酸（PLL）-海藻酸钠（ALG）多层膜,并在膜层中导入纳米银颗粒,以评价其杀菌效果。方法 利用层层自组装的方法将带正电荷的PLL与带负电荷的ALG在钛片上交替吸附沉积形成聚电解质多层膜,再用盐诱导相分离技术在多层膜中形成一定尺寸的微孔并在其中包裹纳米银粒子。扫描电子显微镜（SEM）、傅立叶红外光谱（FTIR）和能谱分析（EDX）对表面进行表征。并与变形链球菌共培养,观察对细菌的粘附和杀灭的作用。结果 SEM、FTIR和EDX分析证实：多层膜成功沉积在钛片表面,并且纳米银粒子被包裹于其中。荧光显微镜显示纯钛表面有大量的活细菌,沉积聚电解质多层膜后细菌数量减少,导入纳米银离子之后附着于钛片上的细菌数量更少,并且随着膜层数的增多,银离子含量增加,抗菌效果也增强。SEM结果与荧光结果一致。结论 通过层层自组装的方法在钛金属表面沉积载银PLL-ALG聚电解质多层膜,能抑制细菌的粘附。同时,随着膜层数的增加,银粒子含量增加,抗菌效果增强。     

钛表面接枝 大分子季铵盐抗菌性的研究

目的:在钛表面接枝大分子季铵盐,以增强钛种植体的表面抗菌效果。方法:采用表面引发原子转移自由基聚合反应(ATRP)引发甲基丙烯酸 N,N-二甲氨基乙酯 (DMAEMA)单体在钛片表面聚合,获得含叔胺基团的高分子聚合物刷,然后与十六烷基溴发生季铵化反应,在钛表面形成通过共价键连接的季铵盐涂层。用用静态接触角仪、傅立叶红外光谱仪(FTIR)、X射线光电子能谱(XPS)对改性的钛表面进行表征;以纯钛为对照组,季铵化后的钛片作实验组,分别在其表面进行变形链球菌(S.m)和大肠杆菌(E. coli )培养,4、 24 h后用荧光显微镜和扫描电镜 检测钛片表面的细菌活性。 结果:静态接触角仪、傅立叶红外光谱仪、X射线光电子能谱仪等结果证明大分子季铵盐被接枝到钛片表面。荧光显微镜显示无论是G⁺变形链球菌还是G^-大肠杆菌,纯钛表面均有大量的活细菌;而实验组上细菌几乎全为死菌。SEM显示实验组钛片表面的细菌比空白组钛表面量明显少些,结果与荧光显微镜结果一致。结论:钛表面成功接枝大分子季铵盐物季铵盐,接枝大分子季铵盐的钛表面对变形链球菌和大肠杆菌具有显著的杀菌作用。     

应用IBAD方法制备纯钛表面多孔TCP／HA涂层材料的微观分析

目的:为了改善钛种植体的生物相容性,对纯钛表面沉积多孔磷酸三钙/羟基磷灰石(Tricalciumphosphate/hydroxyapatite,TCP/HA)复合涂层材料的表面结构和化学成分进行分析,并与沉积羟基磷灰石(Hydroxyapatite,HA)的钛表面进行对比。方法:用离子束辅助沉积方法(Ionbeamassisteddeposition,IBAD)在纯钛表面沉积HA和TCP/HA涂层材料,通过扫描电镜(Scanningelectronmicroscope,SEM)、原子力显微镜(Atomicforcemicroscopy,AFM)、X射线能谱分析(EnergydispersiveX-rayanalysis,EDX)以及X射线衍射(X-raydiffraction,XRD)技术,检测两种涂层材料表面的微观形态和化学成分,并进行比较。结果:SEM和AFM显示TCP/HA涂层材料表面存在多孔结构,表面化学成分分析显示TCP/HA涂层的钙磷比低于HA,XRD证实TCP/HA涂层内同时存在TCP和HA两种化合物。结论:用IBAD方法在纯钛表面成功地沉积了具有多孔结构的TCP/HA复合涂层材料,该涂层材料和基体材料的结合牢固,改善了基体材料的生物相容性,是一种有应用前景的种植体表面涂层材料。     

不同种植体表面改性对细菌生物膜的影响

目的:研究临床常用的3种钛种植体不同表面处理对口腔内常见菌群牙龈卟啉单胞菌(Porphyromanusgingivalis,P.gingivalis)、具核梭杆菌(Fusobacterium nucleatum,F.nucleatum)及血链球菌(Streptococcus sanguis,S.sanguis)生物膜黏附的影响。方法:将钛片分成3组进行表面改性处理,分别为:电解沉积羟基磷灰石(HA)组、微弧氧化(MAO)组和大颗粒喷砂酸蚀(SLA)组,进行表面性能检测;在3组钛片上分别培养Pg、Fn及Ss 4 d,通过菌落形成单位(CFU)法、噻唑蓝(MTT)法和扫描电子显微镜(SEM)探究细菌的黏附情况。结果:(1)SEM观察表面形貌可见HA组表面大量不规则的棒状结构;MAO表面“火山口”样结构,孔径在0.1~1μm之间;SLA表面为不规则凹陷,大小不一且边缘锋利。3组表面粗糙度Ra值:SLA组0.05);Pg生物膜在MAO组钛片上活性最高,与另外2组有统计学差异(P<0.01)。(3)利用SEM观察显示,细菌活性与种植体表面形态结构有关。结论:细菌在种植体表面黏附受到表面形貌影响,与粗糙度及物理构型有关。对于Pg、Ss和Fn 3种细菌,SLA在3种表面处理中细菌粘附量最少。     

纯钛表面微弧氧化膜的结构与成分分析

目的:探讨纯钛表面应用微弧氧化技术进行改性的效果。方法:应用微弧氧化技术在纯钛表面制备陶瓷膜层,并用扫描电镜(SEM)观察其表面和横断面形貌,X射线能谱(EDS)及X射线衍射(XRD)分析其元素成分和晶相结构。结果:微弧氧化处理后,纯钛表面生成微孔结构的氧化膜,膜层厚度约20μm,由O,Ti,Ca,P四种元素组成。膜层表面有火山丘状的微孔分布,直径约0.1μm-5μm。膜层由锐钛矿型和金红石型二氧化钛及少量结晶相羟基磷灰石组成。结论:经微弧氧化技术处理后,纯钛种植体表面生成了内层致密外层多孔的晶相二氧化钛膜,含有少量羟基磷灰石。此结论可供今后开发新型口腔种植材料参考。     

纯钛阳极氧化及表面薄层羟基磷灰石形成技术的研究——Ⅰ.氧化膜的制备及羟基磷灰石涂层的形成

目的：初步了解制备纯钛表面阳极氧化膜和沉积HA薄涂层的技术路线。方法：商业纯钛片经抛光、除油、酸洗后,置于电解槽中进行阳极氧化,采用β－磷酸甘油钠和醋钙作为电解质,阳极化条件为直流电压200V－400V,电流密度≤50mA/cm^2,时间15分钟,阳极氧化完毕后将钛片经高温水热处理2小时（180℃－300℃）。结果：在阳极化后的钛片表达出现蜂窝状孔隙,孔径约1μm-3μm,周围为较规则的突起;X射线衍射图谱（XRD）显示钛表面有金红石和锐钛矿两种氧化钛形态,能谱分析（EDAX）表明钛表面氧化膜内含Ca、P元素;水热处理后,在钛表面出现了结晶物,XRD证明其为HA。结论：阳极氧化可以在纯钛表面形成呈蜂窝状孔隙的、含Ca、P的氧化膜,经水热处理后,在氧化膜表面沉积了HA薄涂层。     

紫外线光照射促进微弧氧化纯钛诱导磷灰石形成及细胞矿化

目的评估紫外线照射效应对微弧氧化纯钛诱导磷灰石形成及细胞矿化的影响。 方法Ⅱ级商用纯钛片进行微弧氧化（MAO）处理,作为空白对照组,记为MAO;微弧氧化结合紫外线（UV）照射处理2 h的钛片作为实验组,记为MAO+UV 2 h。采用扫描电镜（SEM）观察钛片浸泡在DMEM/F12培养液中材料表面磷灰石形成情况;将钛片与大鼠脂肪间质干细胞矿化诱导条件下共培养,观察细胞矿化情况。 结果浸泡在培养液中21 d后,MAO组仅在SEM高倍镜下见少量散在微小磷灰石结晶颗粒;MAO+UV 2 h组颗粒明显增大增多且叠层沉积,除微弧氧化形成的孔径外周高点外,氧化膜层几乎全部被磷灰石晶体层覆盖,且孔径内沉积大量晶体使孔径明显缩小。SEM观察细胞矿化物的形成情况,发现MAO组未见明显矿化物形成,但MAO+UV 2 h组细胞材料表面可见较多针状结晶,能谱分析（EDS）提示为磷灰石结晶。 结论紫外线照射可增强微弧氧化纯钛表面在体外诱导磷灰石沉积的能力且促进脂肪间质干细胞的体外矿化。     

纯钛钛片表面胶原/透明质酸聚电解质复合膜涂层的构建

目的尝试在纯钛钛片表面构建胶原/透明质酸聚电解质复合膜涂层,并评价其生物相容性。方法纯钛钛片表面经打磨抛光及氧化性混酸溶液处理,得到表面富含钛羟基的基底面(设为对照组),在此基础上接着通过层层自组装技术将I型胶原和透明质酸引入到钛片表面(设为实验组)。采用扫描电镜(SEM)、X射线光电子能谱(XPS)和接触角实验对两组钛片的表面进行表征。最后,在两组钛片表面培养成骨前体细胞,检测其早期粘附、增殖及分化的能力。结果 SEM结果显示,对照组钛片的表面非常平整,高倍镜下发现其表面有很多直径为数十纳米的颗粒状结构。而实验组钛片的表面也很光滑,高倍镜下也可见很多纳米颗粒,但其直径较对照组为小。XPS分析发现实验组钛片表面元素成分氮的含量随着组装层数的增加而不断升高。接触角实验显示实验组钛片表面的可湿性随着钛片表面聚电解质组装层数的变化而不断变化,实验组钛片表面的接触角较对照组小。实验组钛片明显促进了成骨细胞的早期粘附(P<0.05),而且培养在实验组钛片表面的细胞增殖得更快(P<0.05)。同时,在实验组钛片表面生长的成骨细胞分化能力更强。结论 I型胶原和透明质酸能够被成功的组装到纯钛钛片表面,该涂层结构有利于成骨前体细胞的生长,显示了良好的生物相容性。     

纯钛表面纳米HA涂层的制备及生物学评价

目的采用电化学法在粗化钛片表面制备纳米HA(Nano-HA)涂层并进行生物学评价。方法钛片表面粗化,采用电化学法在粗化钛片表面沉积Nano-HA涂层。通过场发射扫描电子显微镜(FSEM)、傅立叶红外光谱(FTIR)和X射线衍射仪(XRD)观察涂层晶体形貌、化学结构及组成;通过大鼠骨髓基质干(BMSCs)细胞培养验证该涂层的生物活性。结果 FSEM证实Nano-HA沉积在粗化钛片表面,直径约70～80nm,棒状晶粒截面为规则的六变形。FTIR和XRD分析表明该涂层为HA。与对照组相比,Nano-HA能够明显促进碱性磷酸梅(ALP)和骨钙素(OC)的表达。结论采用电化学法可在粗化纯钛表面制备Nano-HA涂层,并可促进BMSCs成骨分化。     

电解液Ca,P浓度对纯钛表面微弧氧化膜结构和特性的影响

目的:研究电解液不同Ca,P浓度对纯钛表面微弧氧化膜结构和特性的影响.方法:根据电解液中Ca,P浓度的不同,将纯钛试件分成A,B和C共3组,通过微弧氧化技术制备纯钛表面氧化膜,D组作对照组.使用扫描电镜(SEM)检测氧化膜的表面及横断面形貌,用X射线能谱仪(EDS)检测氧化膜的元素成分,用X射线衍射仪((XRD)检测氧...     

The effect of a decontamination protocol on contaminated titanium dental implant surfaces with different surface topography in edentulous patients

Objectives: To investigate if it is possible to achieve complete decontamination of dental implant surfaces with different surface characteristics.

Materials and methods: Twelve implant pieces with an Osseotite^® surface and 12 implant pieces with a Ti-Unite^® surface were attached on to the complete lower dentures of six patients and were allowed to accumulate plaque for 30 days. When retrieved, the implant decontamination protocol used, involved both mechanical (PeriBrush?) and chemical (3% H₂O₂) decontamination. The number of colony forming units per millilitre was determined and the dominant micro-organisms in selected samples was identified by 16s rRNA gene amplicon sequencing. The effect of the titanium brush on the implant surface was examined by SEM.

Results: Complete decontamination was achieved in five out of 24 implants (four Osseotite^® and one Ti-Unite^®). The mean CFU/ml detected after decontamination were 464.48 for Osseotite^® and 729.09 for Ti-Unite^® implants. On the surface of the implants in which complete decontamination was not achieved, all of the predominant bacteria identified were streptococci except for one which was identified as micrococcus. SEM images revealed that the surface features of the decontaminated implants were not significantly altered.

Conclusions: Mechanical decontamination using a titanium brush supplemented with chemical treatment for one minute (3% H₂O₂) can achieve complete decontamination of implant surfaces in edentulous patients.     

Interfacial Characterization of Dentin Conditioned with Chitosan Hydroxyapatite Precursor Nanocomplexes Using Time-of-flight Secondary Ion Mass Spectrometry

IntroductionThe purpose of this study was to evaluate the effect of chitosan-hydroxyapatite precursor (C-HA) nanocomplex conditioning on the chemical modifications at the tricalcium silicate sealer-dentin interface using time-of-flight secondary ion mass spectrometry.MethodsDentin slabs from human premolar root dentin were prepared, demineralized, and randomly distributed between control and C-HA nanocomplex conditioned groups. Tricalcium silicate sealer was applied, and the slabs were allowed to set in 100% humidity for 10 days. The cross-sectional area was exposed, and the sealer-dentin interface was characterized for chemical/ultrastructural evaluation with time-of-flight secondary ion mass spectrometry and transmission electron microscopy, respectively.ResultsChemical analysis revealed the presence of an ion-rich layer constituted of abundant phosphates (PO₂⁻, PO₃⁻, and PO₄⁻), hydroxide (OH⁻), and chitosan fragments (C₂H₄NO⁻, C₃H₄NO₂^−, C₂H₅O₂⁺, C₂H₆NO⁺, C₄H₆NO₂⁺, C₅H₆NO⁺, and C₅H₅O₂⁺) on the dentin surface at the sealer-dentin interface and subsurface dentin after conditioning with C-HA nanocomplexes. In contrast, a decreased interfacial presence of calcium (Ca⁺) and calcium phosphates (CaPO₂⁺, CaPO₃⁺, CaPO₄⁺, and Ca₂PO₃⁺) and the absence of phosphate fragments in the control were noted. Ultrastructural evaluation showed an interfacial layer (<1 μm) with interrupted mineral aggregates in the controls as opposed to a continuous (5 μm) mineral layer formation on the conditioned dentin.ConclusionsC-HA nanocomplex conditioning of dentin before tricalcium silicate sealer application resulted in a chemically modified dentin substrate with an ion-rich layer consisting of phosphate, calcium, calcium phosphates, and chitosan that chemically modified the dentin surface/subsurface.     

Effect of surface treatments on adhesion of low-fusing porcelain to titanium as determined by strain energy release rate

Objective

This study evaluated the effect of different chemical surface treatments on the surface characteristics of commercially pure titanium (cp Ti) and the adhesion of the porcelain–titanium system by means of strain energy release rate (G-value, J/m²). Surface roughness and morphology of treated cp Ti were additionally evaluated.

Methods

Two hundred and thirty specimens of machined cp Ti plates grade II were prepared. The specimens were divided into ten groups in each test according to the surface treatment used; Gr 1 (control; machined), Gr 2 (sandblasted), Gr 3 (CH₂Cl₂ for 5 min), Gr 4 (CH₂Cl₂ for 10 min), Gr 5 (10% H₂O₂ for 5 min), Gr 6 (10% H₂O₂ for 10 min), Gr 7 (30% H₂O₂ for 5 min), Gr 8 (30% H₂O₂ for 10 min), Gr 9 (9% HF for 5 min) and Gr 10 (9% HF for 10 min). Titanium–porcelain (Vita Titankeramik) was applied to each group for testing the adhesion. The G-value (J/m²) was measured with a four-point bending configuration. Following fracture testing specimens were examined with a scanning electron microscope (SEM). Surface roughness and SEM analysis were carried out. Data were analyzed using ANOVA and Tukey's test.

Results

Groups treated with 9% HF or CH₂Cl₂ baths for 10 or 5 min showed the highest adhesion values (J/m²) (34.23 ± 4.31, 30.75 ± 4.91, 28.92 ± 4.33 and 22.54 ± 3.58) respectively among the groups. The machined groups demonstrated the lowest value (8.18 ± 1.95) (J/m²). SEM analysis indicated a combination of cohesive and adhesive fractures for 9% HF, CH₂Cl₂, sandblasted and 30% H₂O₂ (10 min) groups, while mainly adhesive fractures were found with the other groups. There was no direct correlation between surface roughness and adhesion.

Significance

Adhesion between porcelain and cp Ti can be improved by the use of certain chemical surface treatments prior to porcelain firing as alternative techniques to sandblasting treatment.     

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

ObjectiveTo investigate the corrosion behaviour of commonly used TMJ implants alloys (CoCrMo and Ti6Al4V) under simulated physiological conditions.MethodsCorrosion 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).ResultsThe 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.ConclusionsThe 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.     

De novo synthetic short antimicrobial peptides against cariogenic bacteria

ObjectiveAntimicrobial peptides (AMPs) have shown the ability to inhibit planktonic bacteria and biofilms. The objectives of this study were to de novo design and synthesize a series of cationic, amphipathic α-helical AMPs that would be shorter, less cytotoxic, and more potent than existing AMPs against cariogenic bacteria.DesignThree short AMPs (GH8, GLLWHLLH-NH₂; GH12, GLLWHLLHHLLH-NH₂; and GH16, GLLWHLLHHLLHLLHH-NH₂) were designed, synthesized and characterized structurally. Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) against eight major cariogenic bacteria were tested to select the most promising peptide. Scanning electron microscopy (SEM) was used to observe the bacterial membrane after treatment with selected peptides. The bactericidal kinetics, effects on biofilm and cytotoxity were further investigated.ResultsOf the three AMPs, GH12 had the most balanced structural parameters and a high content of α-helical structure. GH12 had a MIC of 4.0-8.0 μg/mL and MBC of 8.0-32.0 μg/mL. The corresponding values for the other two AMPs were 2- to 64- fold higher. In time-kill assays, GH12 killed all bacterial strains within 60 min at 4- fold MBC. SEM observed lysis and pore formation of the cytomembrane after treatment with GH12. 8.0 μg/mL GH12 inhibited Streptococcus mutans biofilm formation. Confocal laser scanning microscopy showed that GH12 effectively reduced the biomass of 1-day-old S. mutans biofilm. Cytotoxicity assays indicated that GH12 showed little toxic effect on the viability of human gingival fibroblasts.ConclusionThese results indicate that GH12 shows antimicrobial activity against cariogenic bacteria and biofilms in vitro.     

Electrochemical study of methylalkylviologens using an electrochemical quartz crystal microbalance

The electrochemical behavior of various 1-methyl-1′-alkylviologens (C₁C_nV²⁺: n=1, 7, 8, 9, 10, 12, 14, 16 and 18) was studied using an electrochemical quartz crystal microbalance (EQCM). Three different types of the frequency change-potential (Δf–E) curves were observed depending on the length of alkyl substituent during the cyclic voltammetry (CV) of the first redox step: for n=1 and 7, Δf was less than 30 Hz (reversible); for n=9, 10, 12 and 14, Δf=200 Hz indicating electrodeposition of C₁C_nV⁺; for n=16 and 18, Δf=5000 Hz with two anodic peaks implying reorientation of the electrodeposited C₁C_nV⁺ occurring on the electrode surface. These results are consistent with our previous report where apparent dimerization of C₁C_nV⁺ was observed. The effect of cyclodextrins (CDs) on the frequency change-potential (Δf–E) curves was also investigated. Δf for 1 mM C₁C₁₆V²⁺ solution was 6000 Hz, while Δf was below 100 Hz in the presence of 13 mM of α-CD. However, Δf was 5000 Hz in the presence of 13 mM of β-CD. This implies that the complexation ability between C₁C₁₆V⁺/C₁C₁₆V²⁺ and α-CD is larger than that of β-CD through the tighter binding as per the report by Diaz et al. (J. Phys. Chem., 92 (1988) 3537). Comproportionation between C₁C₇V²⁺ and C₁C₇V⁰ in the presence of α- and β-CD was also carried out. A negligible effect was observed in the CV or Δf–E curve by α-CD. With β-CD, the anodic stripping wave (C₁C₇V⁰?e^?→C₁C₇V⁺) disappeared, however, Δf was 9500 Hz (1100 Hz without CDs). It is clear that the complexation ability between C₁C₇V⁰ and β-CD is larger than that of α-CD. This might be due to the limited solubility of β-CD upon complexation with C₁C₇V⁰. A similar result was obtained in a 1 mM C₁C₄V²⁺ with 30 mM γ-CD experiment. The mechanism of the cyclodextrin-induced comproportionation reaction as well as electrodeposition pathways are discussed in this paper based on EQCM and spectroelectrochemical experimental results.     

Electrogenerated chemiluminescence of sterically hindered porphyrins in aqueous media

A sterically hindered water-soluble porphyrin, tetrakis(3-sulfonatomesityl)porphyrin (H₂TSMP), could form stable radical cation in aqueous media after electrochemical one electron oxidation. The anodic oxidation of H₂TSMP in the presence of tripropylamine or C₂O₄^2? as a coreactant in aqueous solution produces electrogenerated chemiluminescence (ECL) with maxima at 640 and 700 nm. The same emission spectrum of ECL and fluorescence indicates that the ECL emission is from the singlet state of H₂TSMP. The annihilation reactions of ZnTSMP⁺and ZnTSMP^?, which are generated electrochemically, in CH₃CN+H₂O (1:1) mixed solution results in an emission which is identical to the photoluminescence. Protection of the active sites against the nucleophilic attack of water or OH^? by sterical hinderance is a successful strategy in designing new ECL-active compounds in aqueous media. Both ECL reaction mechanisms are proposed.     

Characterization of copper hexabromoplatinate films and their electrocatalytic properties with dopamine,NADH, and S2O32−

Copper(II) hexabromoplatinate (CuPtBr₆) films have been prepared by mixing Cu²⁺ and PtBr₆^2? ions in an aqueous KBr solution. An electrochemical quartz crystal microbalance (EQCM), a rotating ring-disk electrode, UV–visible absorption spectroscopy and cyclic voltammetry were used to study the deposition and growth mechanism of the copper(II) hexabromoplatinate films. The electrochemical and EQCM properties of the films indicate that a single redox process was confined to the immobilized copper(II) hexabromoplatinate films. The deposition of a copper hexabromoplatinate film occurs when Cu²⁺ is reduced to Cu⁺. In the aqueous KBr solution, Pt^IVBr₆^2? is reduced electrochemically to Pt^IIBr₆^4?, and the Cu⁺ reacts with the Pt^IIBr₆^4? and Pt^IVBr₆^2?species. The electrocatalytic oxidation properties of dopamine, NADH, and S₂O₃^2? were determined using the copper(II) hexabromoplatinate films. The electrocatalytic reaction of dopamine with a copper(II) hexabromoplatinate film was investigated using the rotating ring-disk electrode method.     

The Effect of Argon and Nitrogen Ion Implantation on Nickel-Titanium Rotary Instruments

IntroductionThis qualitative study investigated the effect of N₂⁺ and Ar⁺ ion implantation on morphologic alterations and fatigue resistance in Pro Taper S1 NiTi (Dentsply-Maillefer, Ballaigues, Switzerland) rotary instruments.MethodsInstruments were divided into three groups: N₂⁺ implanted, Ar⁺ implanted, and unmodified control group. All instruments were used to prepare five curved canals in epoxy resin blocks with brushing motion. The instruments were examined in a scanning electron microscope (SEM) before use, after first use, and after the fifth use. A more demanding cyclic fatigue test was undertaken, submitting the instruments to 15-second periods of continuous rotation inside the curved canals without a brushing motion. Crack formation was analyzed with the SEM, and the number of 15-second periods required to fracture each instrument was recorded.ResultsNo significant morphologic alterations were observed in the instruments after the preparation of five canals. Crack density was similar in all groups. In the subsequent cyclic fatigue test, instruments implanted with nitrogen performed worse than those implanted with argon and the control group. Fracture faces show differences in the fracture modes.ConclusionsAr⁺ implantation improved the performance of S1 files moderately, whereas nitrogen ion–implanted files performed worse in the fatigue test. A reduction in file performance seems to be caused by nitrogen diffusion in the grain boundaries, instead of the desired improvement caused by titanium nitride formation.