Effect of Saliva Contamination on Shear Bond Strength of Orthodontic Brackets When Using a Self-Etch Primer

The effect of saliva contamination on the shear bond strength of orthodontic brackets, at various stages of the bonding procedure using a new self-etch primer was studied. The samples were divided into 4 groups according to 4 different enamel surface conditions: Group A: dry; Group B: saliva contamination before priming; Group C: saliva contamination after priming, and Group D: saliva contamination before and after priming. Stainless steel brackets were bonded in each test group with a light-cured composite resin (TransbondXT 3M). The shear bond strength was determined in the first 30 min after bonding. The analysis of variance indicated that the shear bond strengths of the 4 groups were significantly different (F=11.89, P<0.05). Tukey HSD tests indicated that contamination both before and after the application of the acid-etch primer resulted in a significantly lower (=4.6±1.7 MPa) shear bond strength than either the control group (=8.8±1.9 MPa) or the groups where contamination occurred either before (=7.9±2.0 MPa) or after (=6.9±1.5 MPa) the application of the primer. It was concluded that the new acid-etch primer could maintain adequate shear bond strength if contamination occurred either before or after the application of the primer. On the other hand, contamination both before and after the application of the primer could significantly reduce the shear bond strength of orthodontic brackets.

Influence of holding time on microstructure and shear strength of Mg alloy/steel joint diffusion bonded with Zn-5Al interlayer

The diffusion bonding of AZ31B Mg alloy and Q235 steel was investigated with a Zn-5Al alloy as interlayer and under different holding time ranging from 3 to 1 200 s. The microstructure and phase compositions of bonded joints were characterized by scanning electron microscopy( SEM),energy dispersive spectrometer( EDS) and X-ray diffraction( XRD)methods. The shear strength of Mg alloy/steel joints was measured by tensile tester. It was found that the microstructure of bonded joints evolved dramatically along with the prolongation of holding time. Under the holding time of 3 s,the main part of joint was composed of MgZn_2 phase and dispersed Al-rich solid solution particles. When increased the holding time more than 60 s,the excessive solution of AZ31B into the interfacial reaction area led to the formation of coarse phase and eutectic microstructure,and also the complex Fe-Al and Mg-Al-Zn IMCs at transition layer closed to Q235 steel side. According to the tensile testing characterizations,the joints obtained under holding time of 3 s exhibited the best shear strength of 84 MPa,and the fracture occurred at the intermediary part of joint where the flexible Al-rich solid solution particles could help to impede the microcrack propagations. With prolonging the holding time to 600 s,the shear strength of joints was deteriorated enormously and the fracture position was shifted to the transition layer part closed to Q235 steel.

Isotropic shear bond strength behavior of superficial bovine dentin: A pilot study

The aim of this pilot study was to evaluate the shear bond strength of superficial bovine incisor dentin in different crown regions. Bonding was performed to the incisal, middle and cervical thirds of superficial bovine coronal dentin (n = 20) with a two-step etch-and-rinse adhesive (Optibond Solo Plus) and resin composite (Z100). Shear bond strength was evaluated at 24 h and failure modes of representative specimens wereobserved with FE-SEM. Non-parametric Kruskal-Wallis test with a significance level of 0.05 was used for data analysis. Mean shear bond strength values for the incisal, middle, and cervical thirds were 36.9 (3.1), 42.6 (2.6), and 37.1 (2.1) respectively with no significant differences evidenced between the crown thirds (p = 0.19). Observation of the failure mode of representative specimens demonstrated that specimens with high bond strength values exhibited predominantly mixed-type failures whereas low strength specimens exhibited adhesive failures between the dentin and adhesive. The absence of significant differences in shear bond strength between crown thirds indicate that, regardless of tubule orientation, any crown region can be used when superficial bovine incisor dentin is used for shear bond strength testing.

Shear bond strengths between alumina-toughened zirconia cores and veneering ceramics and their susceptibility to aging

Objective:To evaluate the shear bond strength(SBS) between alumina-toughened zirconia (ATZ) cores and veneering ceramics,investigate the effect of aging in artificial saliva on SBS and compare it with that of yttria-stabilized tetragonal zirconia polycrystals(Y-TZP).Methods:Bars of ATZ and Y-TZP were layered with veneering ceramics in accordance to the recommendation of the manufacturer.Half of each group(n = 10) was aged at 134℃.(under 2 bar pressure) in an autoclave for 48 h.Subsequently,all specimens were subjected to shear force in a universal testing machine.The interface and fractured surface of the specimens were evaluated using scanning electron microscopy and X-ray energy dispersive spectroscopy.Results:The initial mean SBS values in MPa±SD were 28.9±8.0 for ATZ and 26.2±7.6 for Y-TZP.After aging,the mean SBS values for ATZ and Y-TZP were 22.9±4.9 MPa and 22.8±6.9 MPa,respectively.Neither the differences between the SBS values of the ATZ and Y-TZP groups nor the influence of aging on all groups were statistically significant.Conclusions:The SBS between the ATZ core and the veneering ceramics was not affected by aging.The SBS of ATZ to veneering ceramics was not significantly different compared with that of Y-TZP.

Comparison of Two Methods of Chlorhexidine Application of Shear Bond Strength Degradation between Composite Resin and Dentin

Background: Chlorhexidine could have effect on shear bond strength of composite resin-dentin. Objective: The purpose of this study is to compare two methods of chlorhexidine application of shear bond strength degradation between composite resin and dentin. Methods: Thirty samples of dentin were taken from the crown of premolars and then divided into three groups (n = 10). Group 1 were applied bonding without chlorhexidine, group 2 were applied with liquid chlorhexidine and followed by bonding, group 3 were applied bonding which contains chlorhexidine. Each group was divided into two sub-groups (n = 5): the group with and without 10% NaOCl immersion for one hour. Then, 4 samples in each sub-group were used to measure shear bond strength using Universal Testing Machine, and 1 sample was examined with Scanning Electron Microscope (SEM). Data were analyzed using SPSS 17 by Mann-Whitney and Kruskal Wallis test. Results: The highest mean shear bond strength without 10% NaOCl immersion was in group 1, while the highest mean with 10% NaOCl immersion was in group 3. Significant differences occurred between the groups 1 and 2, groups 2 and 3. Conclusion: Method of using bonding contains chlorhexidine can increase and inhibit degradation shear bond strength between composite resin and dentin.

The Shear Bond Strengths of Composite Bonded to Dentine Following Treatment with Two Dentine Occluding Desensitizing Toothpastes

Aim: This study determined whether prior brushing with desensitizing toothpastes (Sensodyne Rapid Relief and Colgate Pro-Relief) affected the shear bond strengths of composite to dentine surfaces after appropriate use of two different dentine bonding agents (SingleBond and PQ-1). Materials and Methods: Sixty caries free molar teeth were cleaned, disinfected and embedded in individual cylinders of polymethylmethracyrlate. The occulsal surfaces were flattened to expose dentine and finished down with 600 grit silicone carbide paper. The teeth were randomly divided into six groups of 10 teeth each. Two groups served as control where dentine surfaces were brushed with pumice slurry. Of the remaining 4 groups, 2 groups were brushed with Sensodyne Rapid Relief and 2 groups brushed with Colgate Pro-Relief. The dentine surfaces were brushed to simulate 2 weeks of twice-daily toothpaste use. The specimens in each of the control groups and experimental groups were subjected to dentine bonding procedures (Single Bond or PQ-1), and application of hybrid composite resin (Z-250) according to the manufacturer’s instructions. A universal material testing machine, with a cross head speed of 0.05 mm/min was used to determine shear bond strengths. Results: Mean shear bond strengths ranged from 5.71 MPa (Colgate pretreatment, composite bonded with Single Bond) to 9.07 MPa (Sensodyne pretreatment, composite bonded with Single Bond). Results showed neither of the main effects, of toothpaste type or bonding agent were significant (p > 0.05) but their interaction was (F = 4.25, p = 0.02). Post hoc analysis showed that teeth brushed with the Sensodyne group, treated with the unfilled dentine bonding agent had a significantly higher bond strength than those treated with the filled dentine bonding agent. Conclusion: The desensitizing toothpastes that use the mechanism of occlusion of open dentinal tubules in the preliminary management of tooth sensitivity should not have an adverse effect on future restorative treatment modalities.

Full-scale pullout tests of rock anchors in a limestone quarry focusing on bond failure at the anchor-grout and grout-rock interfaces

Rock anchors are a common safety measure for stabilising large-scale infrastructure,such as bridge towers,retaining walls,rock slopes and windmills.There are four principal failure modes for rock anchors:(a)tensile failure of the steel anchor,(b)anchor-grout interface failure,(c)grout-rock interface failure,and(d)rock mass uplift.Field tests were performed in a limestone quarry.These tests were designed to test failure modes B and C through pullout.In the tests of failure mode B,the shear stress on the anchor-grout interface is the largest at the top of the grout column and attenuates towards the distal end for small loads.The shear stress becomes uniformly distributed when the applied load is approximately 50%of the ultimate pullout load.The anchors designed to test failure mode C were installed with an endplate and had a higher toughness than the straight bar anchors.The shear stress on the grout-rock interface is the largest at the endplate and attenuates upward before slip starts along the interface.When the ultimate pullout load is reached,and the grout column starts to slip,the shear stress is approximately constant.The bond shear strength on the anchor-grout interface was approximately 20%of the uniaxial compressive strength of the grout,and the bond strength of the grout-rock interface was around 5%for that of the grout.The grout-rock interface is likely determined by whichever is weaker,the grout or the rock.

Impact of Dentinal Tubule Orientation on Dentin Bond Strength

This study aimed to determine the impact of dentinal tubule orientation on dentin bond strength to provide a reference for clinical cavity preparation in resin-bonded restoration. Patients aged 13-16 years were selected, including 18 males and 21 females. Forty-eight human maxillary first premolars from orthodontic extractions were chosen to prepare the test models with the dentinal tubule orientations perpendicular and parallel to the bonding substrate. The test models in the vertical and parallel groups were divided into three groups： total-etching with 20% phosphoric acid, total-etching with 35% phosphoric acid and self-etching, with the dentinal tubule surfaces bonded with composite resin blocks in each group. After the standard test models of dentinal tubule-composite resin blocks were placed in distilled water and stored at 37℃ for 24 h, shearing tests were performed using a universal material testing machine at a crosshead speed of 0.5 mm/min. The bond strength values in the vertical group were 19.33＋1.59 MPa for the 20% phosphoric acid group, 21.39±2.34 MPa for the 35% phosphoric acid group, and 16.88±1.54 MPa for the self-etching group. The bond strength values in the parallel group were 24.53±1.99 MPa for the 20% phosphoric acid group, 25.16＋2.88 MPa for the 35% phosphoric acid group, and 20.83±1.99 for the self-etching group. After using same total-etching adhesive, the shear bond strength of the parallel group was higher than that of the vertical group, and the difference was statistically significant （P〈0.05）. Regardless of vertical group or parallel group, the difference in the bond strength value between the total-etching groups and the self-etching group was statistically significant （P〈0.05）. It was concluded that the dentin bonding substrate which was parallel to the direction of the dentin tubule achieved an improved bond strength; the total-etching adhesives achieved higher bond strengths in dentin bond than the self-etching adhesives.

Bond Strength of Orthodontic Bracket Cement Using a Bleaching Light for Curing

Aim: To investigate the bond strengths achieved by using a Bleaching Curing Light (BCL) to polymerize orthodontic bonding cement. Material and Methods: 160 anterior bovine teeth were used to form 20 average sized human dental arches, and distributed into 2 groups according to which light curing method used: Group 1: BCL for 40 seconds, or Group 2: LED for 10 seconds. After storage in a controlled environment, Shear Bond Strength (SBS) and Adhesive Remnant Index (ARI) were determined. Results: Group 1 showed significantly lower SBS in the most posterior (first molar) position of the dental arch, (Group 1: 0.7 ± 1.0 MPa, Group 2: 2.9 ± 1.7 MPa, p Conclusion: Simultaneous full-arch curing of orthodontic bracket cement using a BCL is clinically acceptable in all but the most posterior locations along the dental arch.

不同清洁方法对高透氧化锆粘接强度和表面润湿性的影响

目的:研究不同清洁方法对唾液污染的高透氧化锆与自粘接树脂水门汀间剪切粘接强度和表面润湿性的影响。方法:制备80个高透氧化锆试件,随机分为5组(n=16),即对照组(无污染处理)、75%乙醇组、喷砂组、清洁剂组和大气压冷等离子体处理组等。测量表面接触角,测试剪切粘接强度,观察断裂模式。采用SPSS 26.0软件包对数据进行统计学分析。结果:大气压冷等离子体组的接触角最小(P<0.05);喷砂组、清洁剂组及大气压冷等离子体组的剪切粘接强度与对照组相比,无统计学差异(P>0.05),但均显著大于75%乙醇组(P<0.05);大气压冷等离子体组混合断裂模式增多。结论:喷砂、清洁剂及大气压冷等离子体清洁唾液污染的高透氧化锆,可获得与未被唾液污染前相当的粘接强度;大气压冷等离子体可显著提高高透氧化锆的表面润湿性。

两种复合树脂与牙本质剪切粘接强度的比较

目的在离体牙牙本质上涂布粘接剂后分别予以声波技术充填Sonicfill树脂及分层充填P60树脂,评估应用两种复合树脂与牙本质的剪切粘接强度。方法选择因牙周病拔除的磨牙40颗,制成40个牙本质试件,随机分为2组。A组为Sonicfill树脂组,B组为P60树脂组。每组涂布粘接剂后,A组采用声波技术充填树脂,B组采用分层技术充填树脂。经过循环温度为5℃及55℃的冷热循环疲劳试验,每个循环为3 min,共循环500次后,测试2组的剪切粘接强度(Shear Bond Strength,SBS)。结果A组的SBS为(10.32±1.13)MPa,B组的SBS为(8.43±0.98)MPa,两者差别有统计学意义(P<0.05)。结论运用声波技术的Sonicfill树脂充填体相比采用分层充填的P60树脂拥有更高的剪切粘接强度。因此,在修复过程中使用声波充填技术不亚于传统分层充填树脂,且临床操作时间更短。

胶粘剂粘度对CR/玻纤布复合胶布粘接性能的影响

针对氯丁橡胶和玻纤布的复合胶布,研究了胶粘剂粘度对复合胶布层间粘合强度和拉伸剪切强度的影响,并进行了分析。结果表明,随着胶粘剂粘度的逐渐降低,复合胶布的层间粘合强度和拉伸剪切强度先提高后降低,当胶粘剂流出时间为40~35 s时达到峰值。复合胶布的层间粘合试样破坏界面SEM显示,不同胶粘剂粘度试样的破坏界面呈现明显的差异。随着胶粘剂粘度的降低,6层复合胶布与金属轮之间的粘合强度同样呈现先提高后降低的现象,与复合胶布的层间粘合强度和拉伸剪切强度变化趋势一致。

新旧混凝土结合面剪切强度参数分析和计算研究

新旧混凝土结合面的抗剪强度是装配式混凝土结构和混凝土结构加固等领域重点关注的问题.基于搜集、整理的新旧混凝土结合面(以下简称结合面)的剪切试验数据库(含439个试件),对GB 50010―2010、ACI 318―19、Eurocode 2、PCI7th四个规范所给结合面抗剪建议计算式进行对比分析.结果表明:在各参数的影响下,ACI结果的保证率表现最好,而Eurocode 2计算强度的拟合效果最好;在结合面宽度达到300~400 mm时,GB 50010―2010的表现最好,但安全富余均较低,相对误差最大达到9倍.对数据库进行参数分析,发现结合面剪切强度τ_(exp)存在尺寸效应,与结合面的沿剪切方向尺寸关联较大;且τ_(exp)与夹紧力ρfy有较好的相关性.基于分析结果,根据叠加计算理论,对计算式提出建议和修正:分析引入尺寸效应系数β;同时修正了摩擦系数μ;应用了数据库拟合的销栓力分段函数,极大值为6.6 MPa.经对比验算证明,修正计算式在有无插筋及各种粗糙度情况下的误差最小,拟合效果最好,可为工程应用提供参考.

超高性能混凝土-石材界面黏结性能试验研究

超高性能混凝土(UHPC)加固修复既有石结构中,UHPC与石材之间优异的黏结性能是保证加固效果的关键。因此,为探究UHPC-石材界面的黏结性能,通过劈裂抗拉试验和双L型剪切试验,考察不同界面处理方式对UHPC-石材界面黏结性能的影响。结果表明,UHPC-石材界面破坏模式主要分为三种,其中发生模式C破坏(石材UHPC破坏)时界面黏结强度最大。界面键槽处理方式能显著提高UHPC-石材界面黏结强度、界面剪切刚度,且在改变破坏形态的同时有效提升试件的延性,当键槽深度为20 mm时,试件表现出较好的界面黏结性能。另外,试件剪切荷载-位移曲线包含滑移前阶段和滑移后阶段,凿毛试件在滑移后阶段没有经历塑性变形。相同界面处理方式下,UHPC-石材的界面抗剪强度与界面劈裂抗拉强度呈正相关关系。

树脂黏度对碳纤维与环氧树脂浸润性及界面结合性能的影响

碳纤维与环氧树脂基体形成良好的界面结合是发挥复合材料基本性能的保障,考察3种国产T700级碳纤维,研究树脂黏度对碳纤维浸润性以及界面结合性能的影响。结果表明:由室温升到60℃,树脂体系黏度从1401.9mPa·s降低到102.77mPa·s,碳纤维与树脂的接触角减小,浸润能力增强,从而提高复合材料的界面结合强度,在60℃下制备的复合材料层间剪切强度提高了17.44%。同时纤维表面的沟槽结构能够加强物理机械互锁作用,加强复合材料的界面结合强度。

层状陶瓷与镍扩散连接接头微观组织及性能

采用扩散连接方式对Ni与Ti_(3)AlC_(2)陶瓷进行连接,为了对Ni与Ti_(3)AlC_(2)的反应层进行详细分析,利用SEM、TEM对接头的微观组织进行研究,了解Ni扩散机制及接头形成机理.结果表明,在扩散连接过程中,Ni元素向原始Ti_(3)AlC_(2)陶瓷组织的扩散优先沿着晶界及相界面进行,在此处Ni会发生明显的富集,由于Ni与Ti_(3)AlC_(2)陶瓷有较好的化学相容性,因此两者之间能够发生化学反应形成扩散连接接头,随着保温时间的延长,Ni的扩散更加充分,因此形成较为连续的Ni的扩散层.在扩散连接温度为900℃,保温时间为60 min时,Ni与Ti_(3)AlC_(2)陶瓷扩散连接接头的典型界面组织为Ni/Ni_(3)(Al,Ti)+AlNi_(2)Ti+TiC/Ti_(3)AlC_(2)陶瓷,随着扩散连接温度升高,接头抗剪强度表现为先增后减,当扩散连接温度为900℃,保温时间60 min,Ni/Ti_(3)AlC_(2)陶瓷接头具有最优的力学性能,抗剪强度可达94.4 MPa.

固位钉对All-Bond2粘结强度的影响

目的 探讨固位钉对All-Bond 2粘结强度的影响。方法 应用All-Bond 2为粘结剂 ,将 15个离体牙随机分为 3组 ,测试加金属固位钉前后光敏复合树脂粘结离体牙表面的剪切粘结力 ,分析固位钉的作用。结果 实验I组 (不加固位钉 )的剪切粘结力为 2 5 .87+ 5 .10Kgf;实验II组和实验III组是将固位钉攻入牙本质内 ,深度分别为 2mm和 3mm ,其剪切粘结力分别为 :2 5 .77+ 3 .72Kgf及 2 6 .2 6 + 3.14Kgf。经统计学处理 ,三组间无显著性差异。结论 复合树脂与牙齿间的粘结强度与加或不加固位钉无相关性 ;

居住建筑节能系统外保温层PUR板的剪切粘接强度研究

为解决国内外墙外保温发展存在的问题,简述了居住建筑常用节能保温改造方式,梳理了外保温层起鼓、产生裂缝和脱落的原因,重点设计了建筑外墙外保温层PUR板(聚氨酯板)的剪切粘接强度测试试验,采用PUR板、胶粘剂和混凝土砖块制备外保温层,探究粘接界面缺陷面积和缺陷位置这2个因素对外保温层剪切粘接强度的影响。试验结果表明,粘接缺陷面积占比变大,试件剪切粘接强度会偏低,缺陷面积超过60%时,产生的影响更加严重;缺陷位置靠前,试件的剪切粘接强度偏低,缺陷位置不对称,也会直接影响外保温层的粘接强度。

5种流体树脂与牙釉质粘接性能的对比研究

目的通过比较Beautifil Flow Plus F00、FiltekTM Z350 XT、SDR、Tetric®N-Flows、Constic 5种流体树脂与牙釉质的粘接性能,为流体树脂的临床选择提供参考。方法选择因正畸拔除的成人离体前磨牙50颗,将离体牙随机分为5组(n=10),分别为F00组、Z350组、SDR组、Tetric组、Constic组,每组之间互为平行对照组。每颗离体牙颊侧中1/3磨除厚度为0.5 mm牙釉质,以直径为3 mm的圆形形态作为粘接面,每种树脂制作直径和长度均为3 mm圆柱形树脂试件10个,与预备好的牙釉质面进行粘接,自凝树脂进行包埋。将试件进行3000次冷热循环交替实验和37℃恒温水浴24 h实验后,进行剪切强度测试,记录数据;切断的粘接界面在扫描电镜下观察。结果F00组的剪切强度为(18.39±2.93)MPa、Z350组的剪切强度(11.03±1.55)MPa、SDR组的剪切强度为(12.77±1.55)MPa、Tetric组的剪切强度为(15.25±1.88)MPa、Constic组的剪切强度为(12.79±2.78)MPa,对所得数据进行ANOVA检验和SNK检验后得出,F00组的剪切强度显著高于其他4组(Z350组、SDR组、Tetric组、Constic组)(P<0.05);Tetric组的剪切强度显著高于其余3组(Z350组、SDR组、Constic组)(P<0.05);Z350组、SDR组、Constic组3组之间的剪切强度没有显著性差异(P>0.05)。结论5种流体树脂中Beautifil Flow Plus F00流体树脂粘接性能最高,Tetric®N-Flow流体树脂次之,FiltekTM Z350 XT、SDR、Constic这3种流体树脂粘接性能较低。

工艺参数对5A90铝锂合金扩散连接质量的影响规律

采用金相显微镜、扫描电镜和真空热压烧结炉等设备探究了5A90铝锂合金的扩散连接工艺。结果表明,在扩散连接过程中,随着温度的升高和保温时间的延长,试样中白色强化相增多,空洞减少,焊合度明显提高。剪切强度随扩散连接温度的提高而降低,随保温时间的减少而降低,进而使连接强度降低;这主要是由于扩散温度及保温时间对原子扩散过程产生影响。试样界面15μm的粗糙度避免了氧化铝薄膜的过厚,并保证了扩散连接时接头处的局部接触,使氧化膜破裂,得到最佳接头质量。典型参数下的断裂发生在母材中,以穿晶断裂为主要断裂形式,证明了5A90铝锂合金扩散连接接头的可靠性。通过对比分析,得到扩散连接最佳工艺参数为:连接温度540℃、保温2.5 h、表面粗糙度15μm。