钛的氧化行为对钛瓷结合力的影响

目的:观察钛的氧化行为对钛瓷结合力的影响。方法:铸造28mm×3mm×0.5mm的纯钛试件24个,喷砂、清洗后分为4组,每组6个,第1组不进行预氧化处理,第2、3、4组分别在750、800、900℃温度下,在烤瓷炉内进行预氧化处理5min。于每个金属试件中份8mm×3mm处,依次熔附Noritake TI-22瓷系统的黏结剂、遮色瓷、牙本质瓷,瓷层总厚度1mm。在拉伸试验机上采用三点弯曲法测试金瓷分离时的加载值。使用薄层X线衍射仪观察4组试件未附瓷的钛表面氧化膜中氧化物的种类。结果:不预氧化、750、800、900℃预氧化试件的金瓷分别加载(N)测试结果为10.33、9.98、5.53、3.37。不预氧化试件表面氧化膜中的氧化物全部是Ti6O;750、800、900℃试件的氧化膜中的氧化物为Ti6O和TiO2,900℃试件氧化膜中的TiO2的量明显增加。结论:随着氧化温度的升高,氧化膜中TiO2含量明显增加,钛瓷结合力显著下降,说明钛的高温氧化行为对钛瓷结合力有不利的影响。     

钛表面载锌微纳米拓扑结构修饰对成骨细胞行为的影响及其抗菌性能初探

目的制备载锌微纳米拓扑结构修饰的钛表面并探究其对成骨细胞行为的影响及其抗菌性能。方法通过氢氟酸酸蚀、碱热处理、硫酸锌水浴热处理,在纯钛表面制备两种载锌微纳米拓扑结构(15、60 min处理组)。以大颗粒喷砂酸蚀处理(SLA)钛表面为对照组、两种载锌微纳米拓扑结构修饰的钛表面为实验组,观察分析不同钛表面的微形貌和表面元素组成;将MC3T3-E1成骨细胞接种于各组试件表面,研究不同钛表面对成骨细胞行为的影响;将金黄色葡萄球菌接种于各组试件表面,研究不同钛表面的抗菌性能。结果在纯钛表面制备形成两种形貌均一的微纳米网络拓扑结构,均含有微量锌元素。较之SLA钛表面,两种载锌微纳米拓扑结构修饰的钛表面能明显上调MC3T3-E1成骨细胞的粘附铺展、增殖和成骨相关蛋白表达,并具有显著的抗菌性能,15 min处理组性能更优。结论载锌微纳米拓扑结构修饰的钛表面能有效促进成骨细胞的粘附、增殖和分化,且具有良好的抗菌性能。     

口腔含氟环境对钛表面氧化膜特性及其腐蚀行为的影响

目的 研究口腔含氟环境对钛表面氧化膜特性及其腐蚀行为的影响。方法 将纯钛试件浸泡于不同氟浓度的人工唾液中,以无氟人工唾液为对照组。收集浸泡7 d的试件与浸泡液,采用X射线光电子能谱(XPS)分析钛表面氧化膜组成;采用电化学阻抗谱(EIS)检测各组人工唾液中纯钛试件的腐蚀行为特征;采用电感耦合-等离子体发射光谱仪(ICP-OES)检测各组浸泡液中的钛离子释放量。结果 XPS广谱分析显示,钛表面的钛和氧元素含量随氟浓度的增加而逐渐降低,氟元素含量则相应增加;XPS高像素谱分析显示,钛表面的二氧化钛含量随氟浓度的增加而逐渐降低。EIS测试获得的奈奎斯特图(Nyquist)、波特相位图以及等效电路拟合数据显示,钛表面氧化膜的腐蚀阻抗随着氟浓度的增加而逐渐减小,钛腐蚀行为逐渐增强。ICP-OES检测发现,随着氟浓度的增加,钛离子释放量显著增加。结论 口腔含氟环境能破坏钛表面氧化膜,加速钛腐蚀行为,进而引发钛离子释放,且该效应随氟浓度的增加而加剧。     

牙科粘结剂对纯钛耐腐蚀性能的影响

目的 探讨临床常用的牙科粘结剂对纯钛材料耐腐蚀性能的影响。方法 用常用牙科粘结剂玻璃离子（GC）和聚羧酸锌水门汀（PC）粘结钛片,将试件浸泡于人工唾液中8周后,进行电化学阻抗谱和极化曲线检测。结果 电化学阻抗谱显示GC组试件的阻抗弧明显小于其余两组,相同频率（中低频区）下的阻抗值最小,相位角最大值及所处频率范围也最小。等效电路图拟合结果显示：GC组电容值明显大于其余两组（P＜0.05）;阻抗值由小到大为：GC组＜PC组＜对照组（CC）（P＜0.05）。极化曲线检测显示,各组极化电阻由小到大为：GC组＜PC组＜CC组（P＜0.05）;GC组的自腐蚀电流密度及自腐蚀电位的绝对值均明显大于其余两组（P＜0.05）。 结论 玻璃离子粘结剂的使用会降低纯钛的耐腐蚀性能,聚羧酸锌粘结剂对纯钛耐腐蚀性能影响较小。     

亲水性纯钛表面对成骨细胞黏附行为的影响

目的:体外研究亲水性喷砂酸蚀钛表面对成骨细胞黏附、铺展行为和黏着斑激酶(FAK)表达的影响.方法:钛片表面分别采用大颗粒喷砂酸蚀表面处理(sandblasted,large-grit,acid-etched,SLA)及亲水性化学活化大颗粒喷砂酸蚀表面处理(chemically-modified hydrophilic SLA,modSLA),在其表面接种人成骨细胞,对细胞黏附率、细胞铺展情况以及黏着斑激酶(FAK)的表达进行检测.应用SAS6.0软件包对数据进行统计学分析.结果:成骨细胞在modSLA表面的早期黏附率(1h、3h)显著高于SLA表面(P<0.05);接种3h后,modSLA表面的成骨细胞呈现更多的肌动蛋白结构和明显的成骨细胞骨架结构,细胞铺展更加明显,modSLA组细胞形状因子均值显著低于SLA组(P<0.05);免疫荧光分析显示,6h modSLA表面细胞内FAK的荧光强度高于SLA组(P<0.05).结论:亲水性化学活化大颗粒喷砂酸蚀处理钛表面较大颗粒喷砂酸蚀处理钛表面能显著增强成骨细胞在材料表面的贴附,促进细胞骨架沿一定方向伸展,促进黏着斑激酶(FAK)的表达,从而增强细胞的黏附力.     

钛表面微形貌影响成骨细胞行为及其分子机制的研究进展

钛具有骨整合特性,被认为是最适合的口腔种植材料。然而钛作为一种惰性金属,缺乏足够的生物活性。为了获得更快更好的骨结合,学者们通过各种表面改性技术改变钛表面微形貌,提高其生物活性,增强成骨能力。而对于钛表面改性促进骨结合的内部分子机制,国内外学者已进行大量研究。本文针对钛表面微形貌影响成骨细胞行为及其分子机制的研究进展作一综述。     

等离子渗氮对纯钛耐腐蚀性能影响的研究

目的：模拟口腔环境,研究在不同pH值（pH=6.8,pH=5.5）的人工唾液中,等离子渗氮对纯钛的电化学腐蚀行为的影响。方法：用Tafel曲线法,在不同pH值人工唾液中测定等离子渗氮对纯钛的自腐蚀电阻、自腐蚀电流密度、自腐蚀电位,并与对照组未等离子渗氮的纯钛进行比较分析。应用扫描电子显微镜（SEM）观察试件表面形貌变化。结果：在同一pH值的人工唾液中,等离子渗氮后纯钛的自腐蚀电阻、自腐蚀电流密度和自腐蚀电位与对照组比较均有显著性差异（P〈0.05）,pH值降低,纯钛自腐蚀电流密度增大,自腐蚀电阻、自腐蚀电位降低。SEM观察表明,pH=5.5时纯钛表面腐蚀现象更严重。结论：等离子渗氮后纯钛的耐腐蚀性能得到提高,pH值下降,耐腐蚀性能降低。     

负压对钛与树脂粘接剂粘接性能的影响

目的 本研究旨在探讨负压对不同粗糙度钛与树脂粘接剂粘接性能的影响。方法 铸造钛片（1×10×10）mm抛光后随机分为4组（n=50）。1组（对照组）：只作抛光处理;2、3和4组用110μm氧化铝分别在0.2 MPa、0.3 MPa和0.4 MPa的压力下喷砂。扫描电镜观察钛表面形貌并测量粗糙度。随机将每组分为2个亚组：常压（A）组和负压（S）组。A组常规用Panavia F树脂粘接剂粘接钛与树脂柱;S组在钛表面涂布Panavia F粘接剂后,在-0.1 MPa的负压箱内放置20 s,然后粘接树脂柱。每组随机选取一试件纵切,电镜观察粘接界面。将半数试件进行冷热循环（10000次）,对冷热循环前后的粘接试件进行剪切强度测试并分析断裂模式。采用双因素方差分析和Tukey LSD对数据进行统计分析。结果 随着喷砂压力的增加,钛表面粗糙度显著增加（P<0.05）。冷热循环前后,S组的剪切强度均显著高于A组（P<0.05）, S3组的剪切强度最高（P<0.05）。S组混合断裂的比例明显增加（P<0.05）。扫描电镜显示,与A组相比,S组试件与粘接剂结合更紧密。结论 负压能显...     

热处理温度对牙科铸造纯钛拉伸性能的影响

目的:观察不同的热处理温度对牙科纯钛铸造后力学拉伸性能的影响.方法:在6种热处理温度下,对牙用纯钛铸件的抗拉强度、屈服强度和延伸率3种力学指标进行测试;同时采用金相显微镜和扫描电镜观察铸件的显微组织结构及断口形貌.结果:当退火温度为650、700、750℃时,与对照组相比,铸件的抗拉强度、屈服强度和延伸率均有所提高;700℃处理组的抗拉强度、屈服强度和延伸率均为最高.显微组织结构显示对照组和热处理组中均可见晶粒粗大的β转变组织,700℃热处理组中晶粒明显细化,形态相对规则,并有等轴化趋势.断口扫描电镜分析显示700℃热处理组呈现明显的韧性断裂特征,韧窝大而深.结论:通过热处理可以提高牙科铸造纯钛的力学性能,当热处理温度为700℃时铸件的拉伸性能最佳.     

Interface effects on mechanical properties of particle-reinforced composites.

OBJECTIVES: Effective bonding between the filler and matrix components typically improves the mechanical properties of polymer composites containing inorganic fillers. The aim of this study was to test the hypothesis that composite flexural modulus, flexure strength, and toughness are directly proportional to filler-matrix interfacial shear strength. METHODS: The resin matrix component of the experimental composite consisted of a 60:40 blend of BisGMA:TEGDMA. Two levels of photoinitiator components were used: 0.15, and 0.5%. Raman spectroscopy was used to determine degree of cure, and thermogravimetry (TGA) was used to quantify the degree of silane, rubber, or polymer attachment to silica and glass particles. Filler-matrix interfacial shear strengths were measured using a microbond test. Composites containing glass particles with various surface treatments were prepared and the modulus, flexure strength, and fracture toughness of these materials obtained using standard methods. Mechanical properties were measured on dry and soaked specimens. RESULTS: The interfacial strength was greatest for the 5% MPS treated silica, and it increased for polymers prepared with 0.5% initiator compared with 0.15% initiator concentrations. For the mechanical properties measured, the authors found that: (1) the flexural modulus was independent of the type of filler surface treatment, though flexural strength and toughness were highest for the silanated glass; (2) rubber at the interface, whether bonded to the filler and matrix or not, did not improve toughness; (3) less grafting of resin to silanated filler particles was observed when the initiator concentration decreased. SIGNIFICANCE: These findings suggest that increasing the strength of the bond between filler and matrix will not result in improvements in the mechanical properties of particulate-reinforced composites in contrast to fiber-reinforced composites. Also, contraction stresses in the 0.5 vs 0.15% initiator concentration composites may be responsible for increases in interfacial shear strengths, moduli, and flexural strengths.     

Irradiance effects on the mechanical properties of universal hybrid and flowable hybrid resin composites.

OBJECTIVES: A potential problem with high-intensity lights might be failure of polymer chains to grow and cross-link in a desired fashion, thereby affecting the structure and properties of the polymers formed. The purpose of this study was to evaluate mechanical properties of resin composites polymerized using four different light-curing units. METHODS: A conventional quartz-tungsten-halogen (QTH) light, a soft-start light, an argon-ion laser, and a plasma-arc curing light were used to polymerize disk-shaped (9.0mm diameter x 1.0 mm high) and cylinder-shaped (4mm diameter x 8 mm high) specimens of a universal hybrid and a flowable hybrid composite. Biaxial flexure strength, fracture toughness, hardness, compressive strength, and diametral tensile strength were determined for each composite. RESULTS: The use of the plasma-arc curing light, a high-intensity light, resulted in significantly lower hardness for the universal hybrid composite compared with the hardness obtained using the conventional QTH and the soft-start units. Hardness was the only mechanical property that was adversely affected by the use of a high-intensity light. SIGNIFICANCE: High-intensity lights might affect some resin composite mechanical properties, but this effect cannot be generalized to all resin composites and all properties.     

The effects of two monofunctional diluent monomers and two photoinitiator systems on the properties of UDMA-based composites

PURPOSE: To compare the effects of two types of monofunctional co-monomers and two types of photoinitiator systems on the properties of urethane dimethacrylate (UDMA) based dental restorative composites. METHODS: The resin blends consisted of UDMA and a diluent co-monomer at a molar ratio of 9:1. The diluent comonomers were neo-decyl vinyl ester (Neo 10) or n-hexyl methacrylate (HMA). The photoinitiator system consisted of a bis-acyl phosphine oxide (BAPO) or camphorquinone plus ethyl 4-(dimethylamino)benzoate (CQ/4E). Each initiator system was utilized at 1% or 2% by mass of the resin blend. These resin blends were mixed by hand with silanized zirconia glass (85.7% by mass) to make the various composites. Flexural strength (FS) specimens, made from these pastes by visible light photopolymerization, were tested to failure after 24 hours water storage. Mercury dilatometry was used to evaluate the shrinkage, and the degree of double bond conversion was evaluated using near infrared spectroscopy (NIR). The first hypothesis tested was that use of Neo 10 in a UDMA composite would not have an effect on properties compared to the methacrylate HMA. The second hypothesis tested was that the BAPO initiator would not have an effect on the properties of a UDMA-based composite compared to the CQ/4E initiator. RESULTS: The hypotheses were tested at alpha = 0.05 and beta = 0.20. The major finding was that the lower level (1% by mass) of BAPO resulted in lower FS, lower conversion and lower shrinkage (rejecting the hypothesis that there was no difference due to initiator used) than composites formulated with the higher level of this initiator or either level of the CQ/4E initiator system, regardless of the comonomer used. The effects of two comonomers used were not differentiated in this study with respect to the properties examined (accepting the hypothesis that there was no difference due to diluent monomer).     

Rheological properties of hyaluronic acid and its effects on salivary enzymes and candida

Oral Diseases (2010) 16 , 382–387 Objective: To investigate the viscosity and wettability of hyaluronic acid (HA), its effects on lysozyme and peroxidase activities, and its candidacidal activity. Materials and methods: Human whole saliva, HA, hen egg‐white lysozyme (HEWL), and bovine lactoperoxidase (bLPO) were used. Viscosity was measured with a cone‐and‐plate digital viscometer, while wettability was determined by measuring the contact angle. Lysozyme activity was determined by the turbidimetric method. Peroxidase activity was determined with NbsSCN assay. Candidacidal activity was determined by comparing colony forming units. Results: The viscosity of HA solutions was proportional to its concentration, with 0.05 mg ml^?1 of HA in distilled water or 0.5 mg ml^?1 in simulated salivary buffer displaying similar viscosity values to stimulated whole saliva. The contact angle of HA solutions showed no significant differences according to the tested materials and tested HA concentrations. Contact angles of HA solutions on acrylic resin were higher than those of human saliva. HA did not affect lysozyme or peroxidase activities of whole saliva as well as HEWL or bLPO activities. HA also showed no candidacidal activity. Conclusions: The viscoelastic properties of HA compared with human saliva were objectively confirmed, indicating a vital role for HA in the development of effective salivary substitutes.     

Stannous fluoride and its effects on oral microbial adhesive properties in vitro

The effect of sodium and stannous fluoride compounds on the coherence of Streptococcus mutans was examined. Both commercial and reagent grade preparations were tested on S. mutans, strain 6715. Test fluoride aliquots at various concentrations were added to sucrose suspensions of S. mutans at a starting microbial suspensions equivalent to 25% transmission as read in a spectrophotometer. Test samples were rotated at 35 degrees, 80 rpm in an incubated orbital shaker. Analysis at 560 nm at various time periods, was performed to determine increases in %T as a function of aggregate formation. SnF2 preparations routinely inhibited coherence at concentrations as low as .001%, whereas NaF showed no effects on microbial cell-to-cell coherence.     

Effect of filler content and size on properties of composites

Two series of dental composites, along with the unfilled resin matrix, were examined to determine the effects of filler level and size on selected properties. Both series were prepared by incorporating a silanated barium borosilicate filler into a visible-light-activated polyphenylene polymethacrylate resin matrix. One series had a filler particle size of 2 microns, with filler levels of 20, 40, 45, 50, and 53% (vol). The second series contained a 15-microns filler in amounts of 20, 40, 50, 60, and 65% (vol). Tests conducted included: depth of cure as evaluated by hardness, water sorption, compressive strength, stress-strain behavior under slow compression, toothbrush abrasion, and wear by hydroxyapatite. Analysis of the data indicated that increased filler levels resulted in increased hardness, compressive strength and stiffness, and decreased water sorption. Also, there was a slight trend toward improved depth of cure. Incorporation of the 2-microns filler decreased the abrasion resistance of the resins to toothbrushing as compared with the unfilled resin, while addition of the 15-microns filler improved resistance. All filled resins exhibited a significant improvement in resistance to wear by hydroxyapatite as compared with the unfilled resin. There was a trend for increased wear with increased filler level. The particle size of the filler appeared to have a moderate influence on the properties. When compared with 15-microns filled resins of the same filler levels, the 2-micron filled series appeared to have inferior properties in terms of depth of cure, compressive strength, water sorption, and resistance to toothbrush abrasion. Properties which were less affected by particle size were hardness, stiffness, and wear resistance to hydroxyapatite.     

A urethane-based multimethacrylate mixture and its use in dental composites with combined high-performance properties

Objectives

To synthesize and characterize different molar weight urethane multimethacrylates with a single stage (one-pot) procedure. To prepare and characterize the properties of related composites.

Methods

Two methacrylate precursors were initially synthesized. Then, these precursors and the multimethacrylate system formed by their coupling were characterized by FTIR and ¹H NMR. The final product was used as a matrix (with TEGDMA and SiO₂ silanized microparticles) in the preparation of composites and their physical and mechanical properties were compared to those of a bis-GMA-based resin. Water sorption and solubility measurements of the composites were also performed.

Results

FTIR and NMR suggested that the proposed synthesis route yields a mixture of mainly urethane-di, -tri, and tetramethacrylates. The composites presented low polymerization shrinkage (e.g. 1.88 ± 0.08% for a resin with 70% of SiO₂) and high flexural strength (e.g. 124.74 ± 9.68 MPa for a resin with 65% of SiO₂) when compared to the bis-GMA based resin and other composites found to date. Water sorption and solubility results show that the composites were deemed compliant with ISO 4049 requirements.

Significance

The mixture containing different molar weight of urethane multimethacrylates showed to be an excellent substitute for bis-GMA, achieving an equilibrium of properties (unlike reports elsewhere which show the enhancement of some parameters in detriment to others) and composites with low polymerization shrinkage, suitable microhardness and degree of conversion, and up to standard water sorption/solubility and flexural strength.     

Physical properties of different composites

The purpose of this study was to determine the flexural strength (FS), flexural modulus (FM), depth of cure (DC), polymerization shrinkage (PS), and microhardness (VH) of the following composites: Two packable composites--Filtek P-60 and Solitaire 2; One ion-releasing composite--riston AT; and Two hybrid composites--Charisma and Filtek Z-250. Data of the different tests conducted were obtained as follows: FS and FM data were determined with a universal-testing machine; Polymerization shrinkage was determined using the apparatus of Watts and Cash; Depth of cure was measured with a micrometer (Mitotuyo, UK); and Microhardness was measured with a Shimadzu Microhardness tester (500 g, 15 seconds). All data of the different tests were statistically analyzed by one-way variance analysis (ANOVA), which yielded the following results: Filtek Z-250 showed the statistically highest flexural strength and modulus values. Solitaire 2 exhibited the highest shrinkage, while the volumetric shrinkage results of Filtek Z-250 and Filtek P-60 ranked the lowest. For depth of cure, there were no statistically significant differences among all materials tested (p<0.05). Microhardness results revealed the following tendency: Filtek Z-250 = Filtek P-60 > Ariston AT = Solitaire 2 = Charisma.