纳米金刚石填料对光固化窝沟封闭剂黏结剪切强度和表面显微硬度的影响

目的：观察纳米金刚石填料对窝沟封闭剂黏结剪切强度和表面显微硬度的影响，并比较其与气相二氧化硅之间的差别。方法：按不同比例将纳米金刚石添加到窝沟封闭剂中，检测其黏结剪切强度、表面显微硬度。结果：添加纳米金刚石后窝沟封闭剂的表面显微硬度明显提高，黏结剪切强度不受影响。添加5、10、20、40g／L的纳米金刚石比添加20g／L气相二氧化硅能获得更高的黏结剪切强度和表面显微硬度。结论：适当比例的纳米金刚石填料可以提高窝沟封闭剂的机械性能。     

纳米金刚石填料对复合树脂耐磨性能及挠曲强度的影响

目的观察纳米金刚石填料对复合树脂耐磨性能、挠曲强度的影响,探索纳米金刚石填料的最佳比例。方法按不同比例将纳米金刚石添加到复合树脂中,检测其磨耗率、挠曲强度。结果添加比例为0.005%、1.000%组磨耗率、挠曲强度无明显变化。添加比例在0.020%～0.600%之间耐磨性能、挠曲强度明显提高,比例为0.600%时耐磨性能提高最为明显,添加比例为0.300%时挠曲强度提高最为明显。结论适当比例的纳米金刚石填料可以提高复合树脂的耐磨性能和挠曲强度。     

纳米金刚石填料对光固化窝沟封闭剂渗透性的影响

目的：观察纳米金刚石填料对光固化窝沟封闭剂渗透性的影响，并与气相二氧化硅作比较。方法：在光固化窝沟封闭剂中加入10、20g／L的纳米金刚石和20g／L的气相二氧化硅，检测其渗透性的变化，并对黏结界面作形态学观察。结果：添加10、20g／L的纳米金刚石后，窝沟封闭剂的渗透性不受影响，而添加20g／L的气相二氧化硅后渗透性显著降低，形态学观察见树脂突形成不良。结论：适当比例的纳米金刚石填料对窝沟封闭剂的渗诱件无明显影响．效果优于气相二氧化硅。     

自制桩核树脂机械性能的比较研究

目的对比3种自制桩核树脂与3种双固化进口桩核树脂的机械性能。方法将纳米SiO2与玻璃粉作为填料,以3种比例分散于不同基质中,组1：SiO2填料直径为50nto,基质添加BisEMA6;组2：SiO：填料直径为12nm和50nm,基质添加BisEMA6;组3：SiO2填料直径为12nm和50nm,基质添加BisEMA。测定比较3组自制桩核树脂和3种双固化进口桩核树脂的挠曲强度、抗压强度、断裂面微观结构。结果自制组2、3的挠曲强度与3组双固化进口树脂无显著差异（P〉0．05）,抗压强度高于后者（P〈0．05）,断裂面微观结构与后者相似;自制组1挠曲强度、抗压强度较自制组2、3低（P〈0．05）,断裂面微观结构不同。结论添加BisEMA、BisEMA6的基质分别与含有12nmSiO：的填料自行配制的纳米桩核树脂,挠曲强度达到进口树脂水平,抗压强度高于进口树脂水平。     

纳米复合树脂牙与普通树脂牙显微硬度的对比研究

目的目前临床上常用的普通树脂牙、纳米树脂牙和自研纳米人工牙显微硬度的对比分析研究。方法用动态超显微硬度仪对试件进行显微硬度测试。结果经动态超显微硬度仪测试，目前临床常用的几种复合树脂牙的雏氏硬度分别是：427．67Mpa、469．67Mpa、706．33Mpa、666．33Mpa（P〈0．05），我们研制的纳米树脂牙硬度为577．67Mpa。结论研制的人工牙显微硬度优于普通树脂牙，但与塑钢牙、纳米牙相比，还存在一定差距。     

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。     

纳米金刚石改性义齿粘附剂的粘接性能

目的:观察纳米金刚石作为改性功能填料加入到高分子树脂类义齿粘附剂中,对义齿粘附剂粘接性能的影响。方法:以不同比例配方的纳米金刚石作为功能填料,加入到义齿粘附剂中,观察其粘接抗张强度的变化,同时优选出纳米金刚石的最佳配方产物,浸泡在人工唾液后粘接性能的改变。结果:添加比例为0.05wt%、0.1wt%,义齿粘附剂的粘接抗张强度均明显提高,添加比例为0.1wt%时提高最为明显;纳米金刚石偶联剂改性后反而降低粘附剂强度;0.1wt%组浸泡人工唾液20min粘接抗张强度提高最明显。结论:适当比例的纳米金刚石能增加义齿粘附剂的粘接抗张强度,浸泡唾液一定时间后能改善其粘接性能。     

纳米填料复合树脂抛光后表面粗糙度及微结构的比较

目的评价纳米填料复合树脂抛光后表面粗糙度及微结构。方法4种纳米填料复合树脂制备成7mm×7mm试件,在一致的条件下抛光后测定表面粗糙度,并与同样条件下抛光后的微填料复合树脂Z250比较。使用扫描电镜（SEM）及原子力显微镜（AFM）观察表面性状。结果纳米填料复合树脂表面粗糙度较混合微填料树脂Z250低（P〈0．01）,前者中Z350和Grandio较Ceram．XDuo和Majestv低（P〈0．05）。SEM观察结果显示,与混合微填料树脂Z250比较,纳米填料复合树脂表面质地均匀．填料颗粒脱落造成的凹坑小而少。AFM下可见纳米填料复合树脂高出基准平面的颗粒或低于基准平面的凹坑的平均高度较混合微填料树脂Z250小（P〈0．01）;在纳米填料复合树脂中Z350和Grandio较Ceram-XDuo和Majesty小（P〈0．05）。结论纳米填料复合树脂较微填料复合树脂具有更光滑均质的微表面和更低的表面粗糙度．纳米填料复合树脂中Z350和Grandio具有更光滑均质的微表面．     

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.     

纳米SiO2对笼形低聚硅倍半氧烷复合树脂硬度和耐摩擦性的影响

目的测定加入不同比例纳米SiO2后,笼形低聚硅倍半氧烷（polyhedral oligomeric silsesquioxane,POSS）复合树脂的硬度和耐摩擦性,探索纳米SiO2含量的最佳比例。方法将硅烷偶联剂KH-550表面改性的纳米SiO2加入POSS复合树脂中,置入标准摸具内光固化60s,完成试件制作。根据SiO2占POSS复合树脂质量分数不同,将实验组分为0.5%组、1%组、1.5%组、2%组,不加SiO2的POSS复合树脂设为空白对照组,测定每组复合树脂在相同最大载荷下的硬度及划痕深度。结果统计学分析结果表明,1%组和1.5%组复合树脂的硬度显著增加（P〈0.05）,1.5%组增加更为明显。1.5%组复合树脂的划痕深度显著减小（P〈0.05）,即耐摩擦性显著增强。结论添加适当比例的纳米SiO2可以提高POSS复合树脂的机械性能。     

POSS填料对复合树脂弯曲强度和抗压强度的影响

目的：比较POSS复合树脂和三种临床常用复合树脂/聚合体弯曲强度和抗压强度,为POSS复合树脂的临床应用提供参考依据。方法：采用Zwick电子万能试验机分别测试试样的弯曲强度和抗压强度,以l.0mm/min的加载速度垂直加压直至试样破坏,记录破坏时的载荷,测试结果用SPSS16.0软件进行多样本均数方差分析（F检验）和SNK-q检验。结果：弯曲强度测试结果：FiltekTM Z250组最高,与其他三组间均有统计学差异;BeautifilII组好于POSS组和SureFil组（P〈0.05）;POSS组与SureFil组间无显著性差异（P〉0.05）。抗压强度测试结果：FiltekTM Z250组最高,与其他三组间均有统计学差异;SureFil组好于POSS组和BeautifilII组（P〈0.05）;POSS组和BeautifilII组间无显著性差异（P〉0.05）。结论：POSS复合树脂的弯曲强度和抗压强度可以满足临床应用需要。     

The effects of eugenol and epoxy-resin on the strength of a hybrid composite resin

The compatibility of different dental materials (root canal sealer and composite core build-up restoratives) is an important factor for a successful restoration. The aim of this in vitro study was to determine the effects on compressive and diametral tensile strength of a classical chemical cure composite resin (Henry Schein Composite Anterior-Posterior dental restorative) when in contact with either eugenol or an epoxy-resin (EZ-Fill) in a variety of situations: (a) eugenol or epoxy-resin added during mixing of a composite resin before curing; (b) vapor exposure to cured samples; and (c) specimens placed directly in eugenol or epoxy-resin (after curing). Compressive strengths and diametral tensile strengths were tested for each group. Only the addition of eugenol during mixing with the composite resin (directly before curing) resulted in specimens that were unable to be tested, because they did not achieve a full cure or hardness. For all other groups, there were no significant differences with respect to either compressive strength (p = 0.17) or diametral tensile strength (p = 0.39). Group 1 (mixed directly with eugenol) was found to be statistically different from groups 2 through 7.     

AE characteristics during compression test of high-copper amalgams and visible light-cured composite resins

Differences in environmental strength of high-copper amalgams and photo-cured composite resins for posterior after storage in deionized water at 37 degrees C for 1 year were evaluated by examining compressive strength and acoustic emission (AE) characteristics. The results were as follows: Microfailure in amalgams and composite resins was detected from the onset of stress and their microfailures toward catastrophic failure occurred at 70 to 90% of their ultimate strength. One-year compressive strength for amalgam decreased to 80 to 98% of its 24-hour compressive strength and that for composite resin to 65 to 75%.     

Analysis of strength properties of light-cured resin composites.

OBJECTIVES: To determine and correlate the compressive and tensile strengths of resin composites, to scale their failure probability and to analyze their failure mode under combined state of stresses. METHODS: Ten brands of composites were tested for compressive and diametral tensile strengths. A recently introduced device for testing of pure shear stresses was modified to adapt to smaller specimens. Uniformity of pure shear stress distribution in the significant section was verified by a photoelastic model. Loading specimens in pure shear up to failure determined their mode of fracture under combined state of stresses. RESULTS: Diametral tensile strength yielded values that were 20% of their respective compressive strength. Multiple comparison test indicated that strength properties of the tensile strength test were much more sensitive in predicting differences between resin composites when compared to a compressive strength test. Pertac (Espe) had the highest compressive strength, Graft LC (GC) and Z-100 (3M) had the highest diametral tensile strength. No correlation was found between tensile and compressive strengths. The Weibull modulus disclosed differences in the liability of the materials to fracture. When combined state of stresses were applied through the pure shear test, failure of each specimen occurred at the principal tensile planes. SIGNIFICANCE: Compressive strength cannot predict the ability of the resin composite to withstand tensile stresses. The importance of compressive strength is limited as failure of a brittle material occurs in tension.     

In Vitro Evaluation of Five Core Materials

PURPOSE: This in vitro study determined the fracture strength of five core materials supported by two different endodontic dowels. Diametral tensile strength and microhardness of the three resin composite core materials used in this study were also tested. MATERIAL AND METHODS: The fracture strength study used one lanthanide-reinforced flowable resin composite (Ti-Core Auto E), one titanium- and lanthanide-reinforced composite (Ti-Core), one lanthanide-reinforced composite (Ti-Core Natural), and two metal-reinforced glass ionomer core materials (Ketac Silver and GC Miracle Mix). Two types of dowels were used: a multitiered, split-shank threaded dowel with a flange (#1 Flexi-Flange) and one without a flange design (#1 Flexi-Post). The specimens were divided into ten groups. Each tooth/dowel and core specimen was placed in a special jig at 45 degrees and subjected to a load by a universal testing machine. The diametral tensile strength and the microhardness of the three resin composite core materials were measured by a universal testing machine and Barcol hardness tester, respectively. All test groups contained ten specimens. RESULTS: The fracture strength value of the resin composite core materials was significantly larger ( p < 0.0001) than those for the metal-reinforced glass-ionomer core materials. Analysis of variance (ANOVA) also showed that the Flexi-Flange dowel interacted with Ti-Core and Ti-Core Auto E to significantly ( p < 0.0013) increase the fracture strength relative to the Flexi-Post. One-way ANOVA revealed that there were no significant differences between them in terms of diametral tensile strength. The Barcol hardness values of the composite core materials were statistically different ( p < 0.0001), with the Ti-Core the highest, followed by Ti-Core Natural, then Ti-Core Auto E. CONCLUSIONS: Resin composite core material performed better than glass ionomer material in this in vitro study. The flowable composite core material performed about the same in terms of fracture strength and diametral tensile strength compared with nonflowable composites. Combined with certain core materials, the flange design increased the fracture strength of the tooth/dowel and core combination.     

Effect of retention grooves on fracture strength of Class 2 composite resin and amalgam restorations

The effect of approximal retention grooves on fracture strengths of class 2 composite resin and amalgam restorations was tested in vitro. Results indicated that retention grooves significantly improved (P less than 0.05) the compressive strength of amalgam restorations (38.6% stronger). For posterior composite resin restorations, there was no significant difference in mean compressive strength of restorations in preparations with and without retention grooves.     

Mechanical properties of compomer restorative materials.

The purpose of this study was to measure the compressive strength, flexural strength, microhardness, and surface roughness of three compomers (Compoglass, Dyract, and Hytac) and compare the values to the ones obtained for a resin-modified glass-ionomer cement (Vitremer) and a resin composite (Z100). All materials were handled according to the manufacturers' instructions. There was a significant difference (P < 0.01) among Vitremer, Hytac and Z100 composite with regard to yield strength. Vitremer values were lower than for Hytac, which were lower than for Z100. The yield strength values for Compoglass and Dyract were significantly lower than for Hytac and Z100 composite and significantly higher than for Vitremer (P < 0.01). There was no significant difference in the strain at yield among Vitremer, Hytac, and Z100, but their values were significantly higher than for Compoglass and Dyract (P < 0.01). The flexural strength data displayed a significant difference between Vitremer and Hytac (P < 0.05). Z100 was significantly stronger than the other products tested. The values of strain at break for Vitremer, Hytac, and Z100 were significantly lower than for Compoglass and Dyract (P < 0.01). The compressive strength results showed significantly higher values for Dyract, Compoglass, and Hytac than for Vitremer (P < 0.01). Z100 displayed higher values than the other products tested (P < 0.01). Hytac strength was significantly higher than for Dyract (P < 0.01). The microhardness of Compoglass and Dyract was not significantly different (P < 0.05). Hytac displayed microhardness values higher than for Vitremer, Compoglass, and Dyract (P < 0.01). However, all products tested showed values significantly lower than for Z100 (P < 0.01). The surface roughness values for Compoglass, Dyract, Hytac, and Z100 were not significantly different. Vitremer displayed a significantly higher value than Dyract, Hytac, and Z100 (P < 0.05).