纳米二氧化硅含量对硼酸铝晶须-二氧化硅熔附体填料复合树脂弯曲性能的影响

目的研究正硅酸乙酯（TEOS）水解所得纳米二氧化硅（SiO2）含量对硼酸铝晶须（AlBw）与SiO2熔附体填料复合树脂弯曲性能的影响。方法采用TEOS溶胶－凝胶法制得纳米SiO2,按不同比例通过高温烧结使其熔附于AlBw表面,制作试样并测试其弯曲强度和弯曲弹性模量;利用透射电镜（TEM）观察高温处理过程对晶须表面形态的影响以及不同比例的熔附体形貌。结果AlBw-SiO2熔附体复合填料可显著提高牙科复合树脂的弯曲性能;AlBw和SiO2的质量比为3∶1时牙科复合树脂的弯曲强度达（130.29±8.38）MPa。结论TEOS溶胶－凝胶法水解所得的纳米SiO2含量可改善AlBw-SiO2熔附体填料复合树脂的弯曲性能。     

不同晶须及晶须用量对复合树脂力学性能的影响

目的：比较碳化硅晶须（SiCw）、硼酸铝晶须（ABw）、氧化锌晶须（ZnOw）增强复合树脂的弯曲性能，筛选最优配方。方法：测定复合树脂的弯曲强度和弯曲弹性模量：结果：β-SiCw熔附SiO2纳米粒子（β-SiCw／SiO2）、ABw熔附SiO2纳米粒子（ABw／SiO2）、ZnOw（四针状）均可以提高复合树脂的弯曲性能。本实验条件下复合树脂弯曲性能的最佳方案是：填料为ABw／SiO2，用量为60％时。结论：每一种晶须填料均可以提高复合树脂的弯曲强度和弯曲弹性模量，提高的程度与填料的用量相关。     

晶须熔附条件对晶须增强复合树脂性能的影响

目的：探讨不同熔附条件对新型牙科复合树脂弯曲性能的影响。方法：将自制的以硼酸铝晶须（ABw）和二氧化硅（SiO2）为主要成分的新型牙科复合树脂混合填料在不同熔附条件下制作试样并测试其弯曲强度和弯曲弹性模量;利用透射电镜（TEM）观察高温处理过程对晶须表面形态的影响。结果：ABw-SiO2熔附体复合填料可显著提高牙科复合树脂的弯曲性能;高温处理过程并未破坏ABw表面形态;熔附温度和时间为900℃、30 min时新型牙科复合树脂的弯曲强度达（151.90±8.89）MPa。结论：不同熔附条件改善了新型牙科复合树脂的弯曲性能。     

晶须-颗粒复合体对光固化复合树脂力学性能的影响

目的 研究硼酸铝晶须-二氧化硅颗粒(ABw-SiO2)复合体对光固化牙科复合树脂弯曲性能的影响.方法 以ABw和SiO2比例、正硅酸乙酯(TEOS)用量、硅烷偶联剂用量和填料复合体用量作为实验因素,设计L9(3)4正交试验,制作试件并测试其弯曲强度和弯曲弹性模量;利用扫描电镜观察熔附体形貌.并对弯曲性能最优组与最差组试件行断面扫描.以未加填料的基质组作为阴性对照,Z100(A2色)为阳性对照.结果 最优组弯曲强度达(123.14±17.37)MPa,与基质组差异有统计学意义.与Z100(A2)复合树脂间差异无统计学意义;弯曲弹性模量为(8.75±0.459)GPa.结论 正交试验因素对光固化牙科树脂的弯曲性能有显著影响;ABw-SiO2填料复合体可以显著提高光固化牙科树脂的弯曲性能.     

SiO2粒径分布对牙科复合树脂性能影响

目的研究SiO2粒径分布对牙科复合树脂无机填料的填充量和物理机械性能的影响。方法采用经硅烷表面修饰的气相法纳米SiO2(NS)和微米SiO2(MS),通过调整两者相对质量比,与双酚A双甲氧基缩水甘油酯牙科树脂单体共混,制备了一系列牙科复合树脂M50N20,M55N15,M58N12,M60N10,M63N07,研究了不同SiO2粒径分布对无机填料的填充量,以及复合树脂维氏硬度、三点弯曲强度和断面形貌的影响。结果复合树脂中填料的填充量取决于无机填料的分布及比表面大小,当MS/NS=58/12时,复合树脂的无机填料填充量达到84wt%。M58N12表现出最高的三点弯曲强度(153.2MPa)以及维氏硬度(102.3MPa)。复合树脂断面的SEM形貌分析表明,纳米SiO2与复合树脂基体有较好的粘合作用。结论复合树脂中SiO2粒径分布对物理机械性能以及无机填料的填充量有较显著的影响。     

氧化锌晶须增韧复合树脂的制备及机械性能的研究

目的:考察含氧化锌晶须复合填料对牙科复合树脂机械性能的影响。方法:采用机械共混法制备含氧化锌晶须、纳米二氧化硅填料复合树脂,SEM观察其表面形貌和分散情况,并考察表面处理的氧化锌晶须复合填料对复合树脂的挠曲强度、压缩强度和挠曲弹性模量的影响。结果:氧化锌晶须复合填料添加比为70%时复合树脂的综合力学性能最好,其挠曲强度、压缩强度和挠曲弹性模量分别为(87.16±2.86)MPa、(156.61±7.62)MPa和(2.32±0.17)GPa。结论:氧化锌晶须复合填料的加入能改善牙科复合树脂的机械性能,满足临床使用要求。     

固化工艺对晶须熔附颗粒复合树脂性能的影响

目的研究固化工艺对硼酸铝晶须熔附SiO_2颗粒(ABw-SiO_2)复合树脂性能的影响。方法根据胺活化剂(DHET)在复合树脂中的质量百分数,分为0.2%,0.3%和0.4%3个实验组,光固化型作为对照组,分别制作ABw-SiO_2复合体牙科复合树脂试件,检测试件弯曲强度和弯曲弹性模量;傅立叶变换红外光谱仪(FTIR)测试树脂的双键转化率。结果3组双固化ABw-SiO_2颗粒复合树脂弯曲性能差异无显著性。双固化型ABw-SiO_2颗粒复合树脂双键转化率为(62.23±1.43)%,光固化型为(55.96±1.86)%。结论双固化型ABw-SiO_2复合树脂的双键转化率高于光固化型树脂。     

含长链烷基季铵盐的纳米抗菌无机填料的合成及其在牙科复合树脂中的应用研究

目的 设计合成新型的含长链烷基季铵盐的纳米抗菌无机填料,以赋予牙科复合树脂更优良的抗菌性能。方法 在分子设计和筛选的基础上,制备了长链烷基季铵盐修饰的纳米抗菌二氧化硅填料,并对填料的抗菌性能进行评价。为进一步提高抗菌填料与树脂的结合力,采用硅烷偶联剂对抗菌填料表面进行了处理,并用红外光谱法对其结构特征进行分析;然后将新型纳米抗菌无机填料加入牙科复合树脂中,观察其在复合树脂基体中的分散情况,同时与商品化的Tetric N-Ceram纳米瓷化复合树脂进行对比;并以变异链球菌为对象,研究复合树脂的抗菌性能。结果 长链烷基季铵盐成功接枝到纳米二氧化硅颗粒表面;新型纳米抗菌无机填料的抗菌性能优于含短链烷基季铵盐的抗菌无机填料;偶联处理后的纳米抗菌无机填料在树脂基体中分散均匀,与树脂结合紧密,与Tetric N-Ceram纳米瓷化复合树脂类似;改性后的复合树脂抗菌性能良好。结论 含长链烷基季铵盐的纳米抗菌无机填料抗菌性能良好,经过表面偶联处理后可以很好地与牙科复合树脂共混,提高了牙科复合树脂的抗菌性能。     

牙科纳米氧化铝复合树脂的制备与性能研究

目的 制备一种新型的光固化纳米氧化铝复合树脂,探讨其用于口腔临床的可行性。方法 以双酚A双甲基丙烯酸缩水甘油酯(Bis-GMA)为树脂基质,甲基丙烯酸羟乙酯(HEMA)为活性稀释剂,添加纳米氧化铝填料对树脂基质进行增强增韧改性,制备一种新型牙科纳米氧化铝复合树脂,并表征其固化程度、弯曲强度、硬度、断面形貌、耐磨性、吸水性与水溶解性。结果 添加纳米氧化铝能提高复合树脂材料的刚性和硬度,当添加量达到3wt%时,复合树脂的力学性能、吸水和溶解性能均为最优。结论 复合树脂中加入一定比例的纳米氧化铝可达到增韧和耐磨的效果,该研究为开发新型牙科复合树脂提供了理论和实验基础。     

纳米增韧牙科复合树脂的研究

目的：研究纳米二氧化锆、纳米金刚石为功能填料加入到以钡玻璃粉为主填料的光固化牙科复合树脂中,观察树脂挠曲强度的变化.方法：采用双酚A-甲基丙烯酸缩水甘油酯（Bis-GMA）和二甲基丙烯酸三甘醇酯（TEGDMA）为树脂基质,钡玻璃粉（BG）为主填料,选择纳米二氧化锆,纳米金刚石为功能填料,采用原位聚合法生成光固化牙科树脂,万能材料试验机测试其挠曲强度.结果：纳米二氧化锆和纳米金刚石之间不存在交互效应.不同浓度纳米二氧化锆之间有显著差异,不含纳米二氧化锆的树脂挠曲强度显著高于含5%纳米二氧化锆树脂的挠曲强度.不同浓度纳米金刚石之间有显著差异,含0.2%纳米金刚石的树脂挠曲强度显著高于含0.1%纳米金刚石树脂的挠曲强度.结论：含5%纳米二氧化锆、0.2%纳米金刚石的复合树脂颜色美观,其挠曲强度能达到相应的国家标准及ISO标准,能满足临床需要.     

Effects of whisker-to-silica ratio on the reinforcement of dental resin composites with silica-fused whiskers

Resin composites need to be strengthened to improve their performance in large stress-bearing restorations. This study aimed to reinforce composites with whiskers and to investigate the effects of the whisker:silica ratio. It was hypothesized that changing the whisker-silica ratio would affect the whisker-matrix bonding and the filler's distribution, and hence alter the composite properties. Silica particles and whiskers were mixed at various whisker:silica mass ratios, thermally fused, and combined with a dental resin at filler mass fractions of 0-65%. Whisker:silica ratio and filler level had significant effects on composite properties. At 60% filler level, the silica composite (whisker:silica = 0:1) had a flexural strength (mean +/- SD; n = 6) of 104 +/- 21 MPa; that at a whisker:silica ratio of 1:0 was 74 +/- 36 MPa. However, that of the silica-fused whisker composite (whisker:silica = 5:1) was 210 +/- 14 MPa, compared with 109 +/- 23 MPa and 114 +/- 18 MPa of two prosthetic controls. Mixing silica with whiskers minimized whisker entanglement, improved filler distribution in the matrix, and facilitated whisker silanization and bonding to the matrix, thus resulting in substantially stronger composites.     

Dental composite resins containing silica-fused ceramic single-crystalline whiskers with various filler levels.

Currently available direct-filling composite resins are susceptible to fracture and hence are not recommended for use in large stress-bearing posterior restorations involving cusps. The glass fillers in composites provide only limited reinforcement because of the brittleness and low strength of glass. The aim of the present study was to use ceramic single-crystalline whiskers as fillers to reinforce composites, and to investigate the effect of whisker filler level on composite properties. Silica particles were fused onto the whiskers to facilitate silanization and to roughen the whiskers, thereby improving retention in the matrix. The composite flexural strength, elastic modulus, hardness, and degree of polymerization conversion were measured as a function of whisker filler mass fraction, which ranged from 0% to 70%. Selected composites were polished simulating clinical procedures, and the surface roughness was measured with profilometry. The whisker composite with a filler mass fraction of 55% had a flexural strength (mean +/- SD; n = 6) of 196+/-10 MPa, significantly higher than 83+/-14 MPa of a microfill and 120+/-16 MPa of a hybrid composite control (family confidence coefficient = 0.95; Tukey's multiple comparison). The composite modulus and hardness increased monotonically with filler level. The flexural strength first increased, then plateaued with increasing filler level. The degree of conversion decreased with increasing filler level. The whisker composite had a polished surface roughness similar to that of a conventional hybrid composite (p>0.1; Student's t). To conclude, ceramic whisker reinforcement can significantly improve the mechanical properties of composite resins; the whisker filler level plays a key role in determining composite properties; and the reinforcement mechanisms appear to be crack pinning by whiskers and friction from whisker pullout resisting crack propagation.     

Effects of silane coupling agent amount on mechanical properties and hydrolytic durability of composite resin after hot water storage

The purpose of this study was to evaluate the effects of the silane coupling agent amount on the flexural properties and hydrolytic durability on an experimental composite resin for understanding the optimum amount of silanation. A spherical filler was silanated with 7 different amounts of gamma-MPTS, 0, 0.17, 0.34, 0.66, 1.36, 2.72 and 5.45 mass%. Photopolymerized experimental composite resins were made from a 70/30 mass% of UDMA/TEGDMA and a 65 mass% of different silanated amounts of filler. Bar-shaped specimens were prepared for a 3-point bending test in 37 degrees C water after 1-day water storage at 37 degrees C and after an additional 1, 7, and 28 days hot water storage in Soxhlet's extractor. The flexural strength and flexural modulus of unsilanated filler dramatically decreased after 28 days hot water storage while those of silanated filler showed a slight change. These results suggested that the silanated amount on the silica filler is not sensitive for flexural properties and hydrolytic stability of composite resin.     

Mechanical properties of dental resin/composite containing urchin-like hydroxyapatite

ObjectivesTo investigate the reinforcing effect of urchin-like hydroxyapatite (UHA) in bisphenol A glycidyl methacrylate (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) dental resin (without silica nanoparticles) and dental composites (with silica nanoparticles), and explore the effect of HA filler morphologies and loadings on the mechanical properties.MethodsUHA was synthesized by a facile method of microwave irradiation and studied by X-ray diffraction (XRD), scanning electron microscope (SEM), and thermogravimetric analysis (TGA). Mechanical properties of the dental resin composites containing silanized UHA were tested by a universal mechanical testing machine. Analysis of variance was used for the statistical analysis of the acquired data. The fracture morphologies of tested composites were observed by SEM. Composites with silanized irregular particulate hydroxyapatite (IPHA) and hydroxyapatite whisker (HW) were prepared for comparative studies.ResultsImpregnation of lower loadings (5 wt% and 10 wt%) of silanized UHA into dental resin (without silica nanoparticles) substantially improved the mechanical properties; higher UHA loadings (20 wt% and 30 wt%) of impregnation continuously improved the flexural modulus and microhardness, while the strength would no longer be increased. Compared with silanized IPHA and HW, silanized UHA consisting of rods extending radially from center were embedded into the matrix closely and well dispersed in the composite, increasing filler-matrix interfacial contact area and combination. At higher filler loadings, UHA interlaced together tightly without affecting the mobility of monomer inside, which might bear higher loads during fracture of the composite, leading to higher strengths than those of dental resins with IPHA and HW. Besides, impregnation of silanized UHA into dental composites (with silica nanoparticles) significantly improved the strength and modulus.SignificanceUHA could serve as novel reinforcing HA filler to improve the mechanical properties of dental resin and dental composite.     

Effects of different whiskers on the reinforcement of dental resin composites.

OBJECTIVE: Whiskers were recently used to reinforce dental composites to extend their use to large stress-bearing restorations. The aim of this study was to investigate the effects of different types of whiskers on composite properties. METHODS: Silicon nitride and silicon carbide whiskers were each mixed with silica particles at whisker/silica mass ratios of 0:1, 1:5, 1:2, 1:1, 2:1, 5:1, and 1:0, and thermally treated. The composite was heat-cured at 140 degrees C. Strength and fracture toughness were measured in flexure, while elastic modulus and hardness were measured with nano-indentation. RESULTS: Both whisker type and whisker/silica ratio had significant effects on composite properties (two-way ANOVA; p<0.001). Silicon nitride whiskers increased the composite strength and toughness more than did silicon carbide. Silicon carbide whiskers increased the modulus and hardness more than silicon nitride did. The silicon nitride whisker composite reached a strength (mean+/-SD; n=6) of 246+/-33 MPa at whisker/silica of 1:1, while the silicon carbide whisker composite reached 210+/-14 MPa at 5:1. Both were significantly higher than 114+/-18 MPa of a prosthetic control and 109+/-23 MPa of an inlay/onlay control (Tukey's multiple comparison test; family confidence coefficient=0.95). Fracture toughness and work-of-fracture were also increased by a factor of two. Higher whisker/silica ratio reduced the composite brittleness to 1/3 that of the inlay/onlay control. SIGNIFICANCE: Whisker type and whisker/silica ratio are key microstructural parameters that determine the composite properties. Reinforcement with silica-fused whiskers results in novel dental composites that possess substantially higher strength and fracture toughness, and lower brittleness than the non-whisker control composites.     

BisGMA/TEGDMA dental composite containing high aspect-ratio hydroxyapatite nanofibers

Objectives

The objectives of this study are to investigate the properties of high aspect-ratio hydroxyapatite (HAP) nanofibers and the reinforcing effect of such fibers on bisphenol A glycidyl methacrylate (BisGMA)/triethylene glycol dimethacrylate (TEGDMA) dental resins (without silica microparticle filler) and dental composites (with silica microparticle filler) with various mass fractions (loading rates).

Methods

HAP nanofibers were synthesized using a wet-chemical method and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and thermal gravimetric analysis (TGA). Biaxial flexural strength (BFS) of the HAP nanofibers reinforced dental resins without any microsized filler and dental composites with silica microparticle filler was tested and analysis of variance (ANOVA) was used for the statistically analysis of acquired data. The morphology of fracture surface of tested dental composite samples was examined by SEM.

Results

The HAP nanofibers with aspect-ratios of 600 to 800 can be successfully fabricated with a simple wet-chemical method in aqueous solution. Impregnation of small mass fractions of the HAP nanofibers (5 wt% or 10 wt%) into the BisGMA/TEGDMA dental resins or impregnation of small mass fractions of the HAP nanofibers (2 wt% or 3 wt%) into the dental composites can substantially improve the biaxial flexural strength of the resulting dental resins and composites. A percolation threshold of HAP nanofibers, beyond which more nanofibers will no longer further increase the mechanical properties of dental composites containing HAP nanofibers, was observed for the dental composites with or without silica microparticle filler. Our mechanical testing and fractographic analysis indicated that the relatively good dispersion of HAP nanofibers at low mass fraction is the key reason for the significantly improved biaxial flexural strength, while higher mass fraction of HAP nanofibers tends to lead to bundles that cannot effectively reinforce the dental resins or composites and may even serve as defects and thus degrade the resulting dental resin and composite mechanical properties.

Significance

The incorporation of small mass fraction of HAP nanofibers with good dispersion can improve the mechanical property of dental resins and dental composites.     

Dynamic covalent chemistry (DCC) in dental restorative materials: Implementation of a DCC-based adaptive interface (AI) at the resin–filler interface for improved performance

ObjectiveDental restorative composites have been extensively studied with a goal to improve material performance. However, stress induced microcracks from polymerization shrinkage, thermal and other stresses along with the low fracture toughness of methacrylate-based composites remain significant problems. Herein, the study focuses on applying a dynamic covalent chemistry (DCC)-based adaptive interface to conventional BisGMA/TEGDMA (70:30) dental resins by coupling moieties capable of thiol–thioester (TTE) DCC to the resin–filler interface as a means to induce interfacial stress relaxation and promote interfacial healing.MethodsSilica nanoparticles (SNP) are functionalized with TTE-functionalized silanes to covalently bond the interface to the network while simultaneously facilitating relaxation of the filler–matrix interface via DCC. The functionalized particles were incorporated into the otherwise static conventional BisGMA/TEGDMA (70:30) dental resins. The role of interfacial bond exchange to enhance dental composite performance in response to shrinkage and other stresses, flexural modulus and toughness was investigated. Shrinkage stress was monitored with a tensometer coupled with FTIR spectroscopy. Flexural modulus/strength and flexural toughness were characterized in three-point bending on a universal testing machine.ResultsA reduction of 30% in shrinkage stress was achieved when interfacial TTE bond exchange was activated while not only maintaining but also enhancing mechanical properties of the composite. These enhancements include a 60% increase in Young’s modulus, 33% increase in flexural strength and 35% increase in the toughness, relative to composites unable to undergo DCC but otherwise identical in composition. Furthermore, by combining interfacial DCC with resin-based DCC, an 80% reduction of shrinkage-induced stress is observed in a thiol–ene system “equipped” with both types of DCC mechanisms relative to the composite without DCC in either the resin or at the resin–filler interface.SignificanceThis behavior highlights the advantages of utilizing the DCC at the resin–filler interface as a stress-relieving mechanism that is compatible with current and future developments in the field of dental restorative materials, nearly independent of the type of resin improvements and types that will be used, as it can dramatically enhance their mechanical performance by reducing both polymerization and mechanically applied stresses throughout the composite lifetime.     

硅烷偶联剂用量对硼酸铝晶须增强树脂挠曲强度的影响

目的:评价硅烷偶联剂用量对硼酸铝晶须增强树脂挠曲强度的影响。方法:使用0%、1%、2%、3%、4%质量分数的Z-6030对硼酸铝晶须进行表面处理;将处理过的晶须和树脂基质按一定的配方合成5组热固化型复合树脂,每组6个试件,在120℃的烘箱内固化1 h后,按ISO-4049标准进行三点弯曲测试。每组随机选1个试件,进行断面扫描电镜观察。采用SAS 9.2软件包对结果进行均数间两两比较。结果:硅烷偶联剂用量为2%质量分数时,增强树脂的挠曲强度（117.93±11.9）MPa最高,与其余4组差异显著。结论:硅烷偶联剂的用量对晶须的增强效果有显著影响,过多或过少均会降低复合树脂的挠曲强度。