不同粘结剂对瓷-牙本质粘结剪切强度的研究

目的：观察比较不同树脂粘结剂对IPS Empress 2全瓷基底粘结剪切强度的效果。方法：选择无龋坏的人磨牙24个,随机分为4组,每组6个。第1组用RelyX Veneer进行粘结。第2组用RelyX unicem进行粘结。第3组用RelyX ARC进行粘结。第4组用Variolink 2进行粘结。所有样本在37°C蒸馏水中储存24h后,进行测试,记录剪切强度值,用SPSS11.0对结果进行单因素方差分析,并在光学显微镜下观察粘结破坏情况。结果：RelyX Veneer、RelyX ARC、Variolink 2的剪切强度显著高于RelyX unicem的剪切强度（P〈0.05）,破坏界面多发生在牙本质与粘结剂之间。结论：RelyX Veneer、RelyX ARC、Variolink 2都可以用于IPS Empress 2全瓷系统的粘结。     

人工老化对全瓷贴面树脂粘结剂颜色稳定性的影响

目的研究人工老化对全瓷贴面树脂粘结剂颜色的影响。方法用VITABLOCS MARK-Ⅱ制作厚度为1 mm的试件40个,随机分为4组(n=10)。分别采用Superbond C&B化学固化粘结剂、VariolinkⅡ双重固化粘结剂、RelyX Veneer光固化粘结剂和Filtek Z350 Flow流动复合树脂进行粘结,4种粘结剂颜色均为A3。在黑暗环境下保持24 h后用色度计测量色度值。再将各组试件置于紫外光老化实验箱中进行老化后再次测量其色度值,比较4种树脂粘结剂的颜色稳定性。选定ΔE<3为临床可接受范围。结果 Superbond C&B、VariolinkⅡ、RelyX Veneer和Filtek Z350 Flow粘结剂的ΔE分别为2.32±0.21,2.50±0.29,0.68±0.24和0.79±0.20。其中Superbond C&B和VariolinkⅡ的ΔE高于其他组(P<0.05)。Superbond C&B和VariolinkⅡ之间,RelyX Veneer和Filtek Z350 Flow之间无显著性差异(P>0.05)。结论 4种树脂粘结剂在人工老化后均出现不同程度的颜色变化,但这种颜色改变程度在临床美学要求范围内。RelyX Veneer和Filtek Z350 Flow树脂具有较好的颜色稳定性。     

不同粘接剂对二氧化锆桩固位力的影响

目的探讨不同粘接剂对二氧化锆桩与根管内牙本质粘接强度的影响。方法将60颗完整无龋坏的离体上颌中切牙自釉牙骨质界处截断牙冠,根管桩道预备,制作二氧化锆桩核。60颗牙随机分为6组,分别用磷酸锌水门汀、聚羧酸锌水门汀、玻璃离子水门汀i、Bond加LuxaCore双固化树脂、RelyX Unicem树脂、32%磷酸加ESPE RelyX Unicem树脂粘固二氧化锆桩核。万能力学试验机进行推出测试,记录粘接强度,并对数据行统计学分析。结果 32%磷酸加ESPE RelyX Unicem树脂组、ESPE RelyX Unicem树脂组i、Bond加Luxa Core树脂组、聚羧酸锌水门汀组、玻璃离子水门汀组、磷酸锌水门汀组的二氧化锆桩粘接强度分别为（15.06±1.80）MPa、（11.57±1.33）MPa（、10.42±1.24）MPa（、7.30±1.05）MPa（、6.99±0.87）MPa（、3.97±0.95）MPa,固位力依次降低。其中32%磷酸加ESPE RelyX Unicem树脂组的固位力显著高于其他组,两两比较差异均有统计学意义（P〈0.05）;ESPE RelyX Unicem树脂组与Luxa Core树脂组之间（P=0.590）,聚羧酸锌组和玻璃离子组之间（P=0.490）的差异均无统计学意义;磷酸锌水门汀的粘接强度最低,与其它组比较差异均有统计学意义（P〈0.05）。结论临床粘固二氧化锆桩,树脂类粘接剂固位力较强,自粘接系统加用酸蚀技术可以显著提高二氧化锆桩在根管内的粘接强度。     

2种贴面材料在不同粘接系统下粘接强度的对比研究

目的:比较2种不同贴面材料与3种不同的瓷贴面粘接系统粘接后的粘接强度。方法:应用3种不同的瓷贴面粘接系统(Panavia F、Variolink Veneer、RelyX Veneer),将经过相同处理的离体牙和2种不同的贴面材料(IPS e.max铸瓷和CERAM-AGE聚合瓷)粘接,每组中随机选取一半试件(n=8)37℃水浴24 h,另一半(n=8)冷热循环5 000次后测试其剪切强度,电镜下观察断裂模式。结果:IPS e.max铸瓷组和CERAMAGE聚合瓷组中Variolink Veneer粘接系统在37℃水浴24 h后或5 000次冷热循环后都表现出了最高的粘接强度(P<0.05),所有试件在经过5 000次冷热循环后的粘接强度除Panavia F组外都有明显下降。结论:对于IPS e.max铸瓷和CERAMAGE聚合瓷,Variolink Veneer粘接系统的粘接强度高于Panavia F和RelyXVeneer粘接系统。     

不同核材料与二氧化锆陶瓷树脂粘接耐久性的研究

目的 研究不同类型核材料与二氧化锆陶瓷树脂间的粘接强度及耐久性。方法 二氧化锆陶瓷盘经研磨后通过2种自粘接型树脂水门汀（Clearfil SA Luting和RelyX U100）与不同核材料包括流动型复合树脂核材料、充填型复合树脂、钴铬合金以及牙本质进行粘接,组成个8实验组。每个实验组再分成2个亚组,分别接受0、10 000次冷热循环后进行剪切粘接强度测试。结果 核材料、树脂水门汀材料及老化条件均会对粘接强度产生明显影响（P<0.001）。冷热循环后,只有Clearfil SA Luting与钴铬合金的粘接强度没有明显降低（P>0.05）,并高于其余各核材料组（P<0.05）;Clearfil SA Luting与钴铬合金、流动型复合树脂核材料及充填型复合树脂间的粘接强度均明显高于RelyX U100相对应的粘接强度（P<0.05）,而Clearfil SA Luting和RelyX U100与牙本质间的粘接强度的差异无统计学意义（P>0.05）。结论 不同类型核材料和树脂水门汀材料能够对二氧化锆陶瓷树脂粘接耐久性产生明显影响。     

不同表面处理方法对纳米复合陶瓷与树脂水门汀粘接强度的影响

目的 评估不同表面处理对纳米复合陶瓷与树脂水门汀剪切粘接强度的影响。方法 将纳米复合陶瓷用计算机辅助设计/计算机辅助制作（CAD/CAM）技术切割成大小为10 mm×10 mm×3 mm的试件150块,并根据表面处理方法不同将试件按随机数字表的方法随机分为5组（n=30）：对照组、喷砂组、喷砂+硅烷组、酸蚀组和酸蚀+硅烷组。各组试件经过相应表面处理后,使用Single Bond Universal通用粘接剂+RelyX ^TM Ultimate Cliker ^TM树脂水门汀将树脂试件粘接于纳米复合陶瓷试件上,37 ℃蒸馏水中水浴24 h和30 d,万能试验机进行剪切粘接强度测试。结果 不同表面处理方法、不同的水浴时间都会影响到剪切粘接强度。喷砂+硅烷组的剪切粘接强度最大,与其他各组间差异均具有统计学意义（P<0.05）;对照组和酸蚀组间差异无统计学意义,但两组与其他组间差异具有统计学意义（P<0.05）;喷砂组和酸蚀+硅烷组之间差异无统计学意义（P>0.05）,但两组与其他组间差异具有统计学意义（P<0.05）。结论 喷砂、喷砂+硅烷、酸蚀+硅烷对纳米复合陶瓷表面处理,均可提高其与树脂水门汀的剪切粘接强度,喷砂+硅烷处理后剪切粘接强度最佳。     

多乐氟预防碳酸饮料对乳牙釉质脱矿的体外研究

目的:证实多乐氟能预防碳酸饮料对乳牙牙釉质的脱矿作用。方法:将72个乳牙釉质块随机分成4组,每组18块。人工唾液为对照组(A);可乐碳酸饮料浸泡组(B);多乐氟处理后可乐浸泡组(C);氟化泡沫处理后可乐浸泡组(D)。A组试件不作处理,B组试件浸泡于可乐中30 min,取出后用去离子水冲洗干净放置约4 min,再次浸泡于可乐中30 min,如此循环直至12 h。实验C、D组釉质块分别浸在多乐氟、氟化泡沫涂抹4 min后,后续处理同B组。上述处理后试件分别用扫描电镜、能谱分析仪检测釉质表面的形态变化及Ca²⁺、P³⁺含量( 重量百分比)。结果:对A组相比,可乐浸泡可致乳牙釉质表面脱矿;氟化物处理后可降低釉质表面的脱矿程度,并使晶体颗粒体积变大,其表面Ga²⁺、P³⁺含量的降低程度也低于B组,差异有统计学意义(P<0.05)。结论:多乐氟可抑制乳牙釉质在碳酸饮料中的脱矿,效果较好,并能促进其再矿化。     

冷热循环后4种双固化树脂粘结剂与根管内牙本质粘结性能的对照研究

目的:评价冷热循环前后4种双固化树脂粘结剂与根管内牙本质的粘结性能。方法:40颗健康上前牙随机分为8组。根管预备后选用4种树脂粘结剂(Clearfil DC Core Automix,Calibra esthetic resin cement,DMG LUX-ACORE Smartmix Dual,3M ESPE RelyXTM Unicem)分别粘结直径1.2mm纤维桩。将20颗牙沿垂直牙根长轴方向片切成厚度为1mm的薄片,用万能力学试验机进行微推出测试,体视显微镜观察断裂方式。对粘结强度及断裂类型进行统计学分析。另外20颗牙进行冷热循环处理10000次,放置24h后按同样步骤测试。结果:冷热循环前后粘结强度测试结果分别为:Clearfil DC Core Automix(8.9540±2.85955,7.1212±2.34645)MPa,Calibra esthetic resin cement(6.2314±1.83828,5.4596±1.99693)MPa,DMG LUXACORE Smartmix Dual(7.3410±2.27467,6.4844±1.99055)MPa,3M ESPE RelyXtm Unicem(7.8400±2.37045,6.9804±2.23403)MPa,冷热循环前后各组之间差异有显著性(P<0.05),冷热循环前后断裂方式均为粘结面型断裂为主。结论:4种双固化树脂粘结剂与根管内牙本质粘结强度差异显著。     

四种双固化树脂粘结剂与根管牙本质间微渗漏的研究

目的评价冷热循环对4种双固化树脂粘结剂与根管牙本质间微渗漏的影响。方法20颗健康上前牙随机分为4组。根管预备后选用4种粘结树脂及其配套粘结剂（Clearfil DC Core Automix,Calibra esthetic resincement,DMG LUXACORE Smartmix Dual,3M ESPE RelyX^TM Unicem）分别粘结直径1．2mm树脂纤维桩,并用此4种材料分别做树脂核。将试件冷热循环处理10000次（温度设定为4℃／60℃,浸泡时间30s,传递时间20s）后,用0．5％碱性品红溶液染色24h。将试件连续纵向剖开为四部分,体视显微镜下观察各剖面的微渗漏情况,并用Kmskal-WaillisH非参数检验进行统计分析。结果各种树脂粘结剂均存在微渗漏现象,各种粘结剂之间的微漏程度有显著性差异（P〈0．05）。结论冷热循环后4种双固化树脂粘结剂粘结纤维桩与根管牙本质之间均存在微渗漏现象,使用Clearfd DC Core Automix作为粘结树脂的试件微渗漏程度最轻。     

光纤激光蚀刻对氧化锆陶瓷性能影响的研究

目的:通过比较喷砂和不同功率光纤激光蚀刻处理对氧化锆陶瓷抗弯曲强度和剪切粘结强度的影响,探讨光纤激光蚀刻氧化锆陶瓷的可行性,为光纤激光蚀刻应用于临床提供参考。方法:将结晶后的氧化锆试件随机分为5组(n=10),处理如下:A组为空白对照组,B组为氧化铝颗粒喷砂组,C-E组分别为功率为2、4、6 W光纤激光处理组。测定各组试件的三点抗弯曲强度并观察其处理面的显微形貌。再将各组试件处理面与双固化复合树脂 Multilink N粘固,37 ℃恒温水浴24 h后测试剪切粘结强度。采用方差分析和LSD多重检验进行比较(α=0.05)。结果:各组试件的抗弯强度无统计学差异。A组与E组的粘结强度无明显差异;而与其余3组间的粘结强度差异均有统计学意义(P<0.005)。喷砂组和光纤激光蚀刻组两两比较显示,B、C、D 3组间的粘结强度无明显差异,E组的粘结强度低于B、C、D 3组(P<0.05)。结论:采用合适激光功率的光纤激光蚀刻技术能增强氧化锆陶瓷与复合树脂间的粘结强度,且对氧化锆自身的抗弯曲强度无明显影响,可以作为临床上氧化锆陶瓷表面处理的一种方法。     

Comparison of the effect of storage media on shear punch strength of resin luting cements

Objectives

To measure the shear punch strength of eight resin-containing luting cements before and after immersion in acidic solution and ethanol at different temperatures (37° C and 60 °C). Method: Specimens were prepared from six resin luting cements; Set (SDI), Panavia F (Kuraray), RelyX Veneer (3M/ESPE), VarioloinkII (Ivoclar), Maxcem (Kerr), Nexus2 (Kerr) and two Resin-modified glass-ionomer luting cements (RM-GICs); GC Fuji Plus (GC Corporation), RelyX Luting 2 (3 M/ESPE). For each material a total of 114 disc-shaped specimens were prepared. Six specimens were immersed in distilled water for 24 h at 37 °C, polished and subjected to baseline measurement for shear punch strength. The remaining 108 specimens were randomly divided into 18 groups of six, and immersed in three solutions; distilled water, 0.01 mol/L lactic acid, and 50% ethanol at 37 °C or 60 °C, for 1 week, 1 month or 3 months. Specimens were washed, dried and tested for final shear punch strength.

Results

Values were material and solution dependent. Values of Nexus 2 and Rely X Veneer are the highest, and Rely X Luting 2 the lowest. Ethanol and lactic acid specimens showed significantly lower values compared with the distilled water specimens. Conclusion: The shear punch strengths of the resin-containing luting cements were affected by time and storage solution. While some of the resin luting cements had significantly higher values compared to that of the RM-GICs, there were no significant differences between the RM-GICs and resin cements such as Panavia F and Set.     

Flexural Strength, Elastic Modulus, and pH Profile of Self-etch Resin Luting Cements

Purpose: To determine the flexural strength, modulus of elasticity, and 24‐hour pH profile of three self‐etching resin luting cements and to obtain comparative data for representative conventional resin and resin‐modified glass ionomer luting cements. Materials and Methods: Three self‐etching resin luting cements [RelyX Unicem (3M ESPE), Maxcem (Kerr), Embrace Wetbond (Pulpdent)] were tested and compared with two conventional resin cements [RelyX ARC (3M ESPE), Linkmax (GC)] plus two resin‐modified glass ionomer luting cements [Fuji Plus (GC), RelyX Luting Plus (3M ESPE)]. Flexural strength and modulus of elasticity were determined using bar‐shaped specimens (2 × 2 × 25 mm³) at 24 hours, using an Instron universal testing machine. Setting pH was measured using a flat‐surface pH electrode at 0, 2, 5, 15, and 30 minutes and 1, 2, 4, 6, and 24 hours after mixing. Testing was performed under both dual‐cured and self‐cured conditions for all dual‐cure cements. Data analysis included ANOVA and Tukey's test (p < 0.05). Results: The self‐etching cements showed similar flexural strength to the conventional resin cements, except for Embrace Wetbond self‐cured, which was considerably lower. Modulus of elasticity results were both higher and lower than for conventional resin cements. All photopolymerized conventional and self‐etch dual‐cure cements showed markedly higher flexural strength and modulus than when solely self‐cured. The resin‐modified glass ionomer cements were characterized by lower flexural strength and elastic modulus. Self‐etching resin cements showed lower initial pH (2.0 to 2.4) than conventional resin cements (4.8 to 5.2) and a wide range of final pH values (3.9 to 7.3) at 24 hours. One self‐etching cement (Unicem) revealed a unique pH profile characterized by a more rapid rise in pH to neutrality both when dual‐cured (15 minutes) and when auto‐cured (1 hour). Conclusions: The self‐etching resin cements evaluated in this study displayed disparate properties and cannot be considered a homogeneous group. Flexural strength properties were most uniform and were similar to those of the conventional resin cements, whereas moduli of elasticity showed greater variation. Setting pH profiles differed, depending on the brand and mode of cure, even within the same category of luting cement. All cements with dual‐cure capability, both conventional and self‐etch, showed significantly superior properties when photopolymerized.     

Bonding of resin composite luting cements to zirconium oxide by two air-particle abrasion methods

OBJECTIVE: This study evaluated the shear bond strength of two resin composite luting cements to zirconium oxide ceramic substrate using two air-particle abrasion methods. METHODS: Two resin composite cements, RelyX Unicem (3M ESPE) and Panavia F (Kuraray), each with an acidic composition, were used in combination with a zirconium oxide (DCS Dental AG) substrate containing Al2O3 and SiO2 (Rocatec system, 3M ESPE) and two air-particle abrasion methods. The shear bond strength of the resin composite cement to the substrate was tested after the samples were either water-stored for one week or thermocycled following 24 hours of water storage. RESULTS: The RelyX Unicem resin composite cement specimens with the Rocatec treatment (20.9 +/- 4.6 Mpa and 20.1 +/- 4.2 MPa, respectively, n = 12) demonstrated the highest shear bond strength. Alternatively, the lowest values were obtained for the Panavia F resin cement samples, with Al2O3 air-particle abrasion in both storage conditions, water storage for one week (17.7 +/- 8.9MPa) or thermocycling after 24 hours of water storage (16.3 +/- 4.9 MPa). Neither storage condition or particle abrasion system significantly affected shear bond strengths (ANOVA, p > 0.05). CONCLUSION: It was concluded that two different surface conditioning methods and storage conditions did not significantly affect the bonding properties of Panavia F and RelyX Unicem resin composite luting cements to Zirconia.     

Cervical microleakage in MOD restorations: in vitro comparison of indirect and direct composite

This study compared microleakage between indirect composite inlays and direct composite restorations. Forty-eight standard inlay MOD cavities, with cervical margins located either in enamel or dentin, were prepared in extracted human third molars. The specimens were randomly divided into 3 groups (n=16). In the control group, the cavities were restored with the composite Filtek Z250 (3M ESPE). For the experimental groups, indirect restorations were made with the Artglass (Heraeus-Kulzer) or Belleglass HP (Kerr Laboratories) systems and cemented with the dual curing cement RelyX ARC (3M ESPE). The adhesive system Single Bond (3M ESPE) was applied on all groups. The specimens were submitted to thermolcycling, coated with nail varnish, then immersed in 2% basic fuchsine aqueous solution for 24 hours. The teeth were then sectioned and leakage scores were evaluated (40x), based on a standard ranking. Data were submitted to statistical analysis (Mann-Whitney and Kruskal-Wallis tests) with a 95% confidence level. No statistical difference was found between substrates (p=0.595), and the materials performed similarly in dentin (p=0.482). Direct restorations showed higher leakage than indirect restorations at the enamel margins (p=0.004). Within the limitations of this experimental design, overall leakage was similar between both substrates, while the indirect systems provided a better sealing than direct composites only in enamel.     

Influence of previous provisional cementation on the bond strength between two definitive resin-based luting and dentin bonding agents and human dentin

This study evaluated the effect of two different types of provisional luting agents (RelyX Temp E, eugenol-based; RelyX Temp NE, eugenol-free) on the shear bond strengths between human dentin and two different resin-based luting systems (RelyXARC-Single Bond and Duo Link-One Step) after cementation with two different techniques (dual bonding and conventional technique). One hundred human molars were trimmed parallel to the original long axis, to expose flat dentin surfaces, and were divided into three groups. After related surface treatments for each specimen, the resin-based luting agent was applied in a silicone cylindrical mold (3.5 x 4 mm), placed on the bonding-agent-treated dentin surfaces and polymerized. In the control group (n = 20), the specimens were further divided into two groups (n = 10), and two different resin-based luting systems were immediately applied following the manufacturer's protocols: RelyX ARC-Single Bond (Group I C) and Duo Link-One Step (Group II C). In the provisionalization group (n = 40), the specimens were further divided into four subgroups of 10 specimens each (Group I N, I E and Group II N, II E). In Groups I N and II N, eugenol-free (RelyX NE), and in groups I E and II E, eugenol-based (RelyX E) provisional luting agents (PLA), were applied on the dentin surface. The dentin surfaces were cleaned with a flour-free pumice, and the resin-based luting systems RelyX ARC (Group I N and E) and Duo Link (Group II N and E) were applied. In the Dual bonding groups (n = 40), the specimens were divided into four subgroups of 10 specimens each (Group I ND, ED and Group II ND, ED). The specimens were treated with Single Bond (Groups I ND and ED) or One Step (Groups II ND and ED). After the dentin bonding agent treatment, RelyX Temp NE was applied to Groups I ND and II ND, and RelyX Temp E was applied to Groups I ED and II ED. The dentin surfaces were then cleaned as described in the provisionalization group, and the resin-based luting systems were applied: RelyX ARC-Single Bond (Group I ND and ED) and Duo Link-One Step (Group II ND and ED). After 1,000 thermal cycles between 5 degrees C and 55 degrees C, shear bond testing was conducted at a crosshead speed of 0.5 mm/minutes. One-way ANOVA, followed by a post hoc Tukey test (alpha = 0.05) was done. The dentin-resin-based luting system interfaces were evaluated under a scanning electron microscope. There was a significant reduction in the mean shear bond strength values of groups subjected to the provisionalization compared to the control and dual bonding technique groups (p < 0.05). The composition of provisional luting did not create a significant difference with regard to reducing shear bond strength values (p > 0.05). With regard to resin based luting systems, the shear bond strength values of the double-bond technique groups were not significantly different from the controls (p > 0.05).     

Effect of surface preparation on bond strength of resin luting cements to dentin

This study examined the effects of using two different burs for dentin surface preparation on the microtensile bond strength (microTBS) of three resin luting cements. Flat, deep dentin surfaces from 45 extracted human third molars were divided into three groups (n = 15) according to bur type: (i) diamond bur and (ii) tungsten carbide bur. The controls were abraded with #600-grit SiC paper. Both burs operated in a high-speed handpiece under water-cooling. Composite blocks were luted onto the dentin using one of three cements: RelyX ARC (ARC, 3M ESPE), Panavia F2.0 (PF, Kuraray) and RelyX Unicem (UN, 3M ESPE) following the manufacturers' instructions. For ARC, the dentin surface was treated with 32% phosphoric acid. The bonded specimens were stored at 37 degrees C for 24 hours and sectioned into 0.9 x 0.9 mm beams for microTBS testing. The data were analyzed using the two-way ANOVA and Student-Newman-Keuls tests. Representative fractured beams from each group were prepared for fractographic analysis under SEM. Two-way ANOVA revealed that the effects of "dentin surface preparation" and "luting cement" were statistically significant (p < 0.001); however, the interaction of these two factors was not significant (p > 0.05). ARC showed no significant difference in microTBS among the three differently prepared dentin surfaces. The microTBS of PF and UN was significantly lower when bonding to dentin prepared with a diamond bur (p < 0.05), compared to the control. For Panavia F2.0, higher bond strengths were achieved on the dentin surface prepared with a tungsten carbide bur. Proper bur selection is essential to optimizing the dentin adhesion of self-etch resin luting cements.     

Bonding effectiveness of adhesive luting agents to enamel and dentin.

OBJECTIVES: The bonding effectiveness of five adhesive luting agents to enamel and dentin using different application procedures was determined using a micro-tensile bond strength protocol (microTBS). METHODS: Enamel/dentin surfaces of human third molars were flattened using a high-speed diamond bur. Composite resin blocks (Paradigm, 3M ESPE) were luted using either Linkmax (LM; GC), Nexus 2 (NX; Kerr), Panavia F (PN; Kuraray), RelyX Unicem (UN; 3M ESPE) or Variolink II (VL; Ivoclar-Vivadent), strictly following manufacturers' instructions. For some luting agents, modified application procedures were also tested, resulting in four other experimental groups: Prompt L-Pop+RelyX Unicem (PLP+UN; 3M ESPE), Scotchbond Etchant+RelyX Unicem (SE+UN; 3M ESPE), Optibond Solo Plus Activator+Nexus 2 (ACT+NX; Kerr) and K-Etchant gel+Panavia-F (KE+P; Kuraray). The experimental groups were classified according to the adhesive approach in self-adhesive (UN), etch-and-rinse (ACT+NX, NX, KE+P, SE+UN and VL when bonded to enamel) and self-etch adhesive luting agents (LM, PLP+UN, PN and VL when bonded to dentin). The specimens were stored for 24h in distilled water at 37 degrees C prior to microTBS testing. The Kruskal-Wallis test was used to determine pairwise statistical differences (p<0.05) in microTBS between the experimental groups. RESULTS: When bonded to enamel, ACT+NX (15 MPa) and UN (19.6 MPa) scored significantly lower than VL (49.3 MPa), LM (49.2 MPa), PN (35.4 MPa) and SE+UN (35.2 MPa), while PLP+UN (23.5 MPa) showed a significantly lower microTBS than VL (49.3 MPa) and LM (49.2 MPa). No significant differences were noticed between VL (49.3 MPa), LM (49.2 MPa), NX (37.9 MPa), KE+PN (38.8 MPa), PN (35.4 MPa) and SE+UN (35.2 MPa). Regarding the bonding effectiveness to dentin, all luting agents bonded equally effectively (UN: 15.9 MPa; LM: 15.4 MPa; PN: 17.5 MPa; NX: 22.3 MPa), except VL (1.1 MPa), SE+UN (5.9 MPa) and ACT+NX (13.2 MPa). VL revealed an exceptionally high number of pre-testing failures, most likely due to a combined effect of not having cured the adhesive separately and an insufficiently light-cured luting agent. SIGNIFICANCE: Following a correct application procedure, the etch-and-rinse, self-etch and self-adhesive luting agents are equally effective in bonding to enamel and dentin. Several factors negatively influenced bond strength such as bonding RelyX Unicem to enamel without prior phosphoric acid etching; no separate light-curing of a light-polymerizable adhesive prior to cementation, use of a light-polymerizing adhesive converted into a dual-polymerizing adhesive, and use of a dual-cure luting agent with a low auto-polymerizable potential.     

In vitro study of mean loads and modes of failure of all-ceramic crowns cemented with light-cured or dual-cured luting cement, after 1 and 30 d of storage

This study compared the mean loads and modes of failure of teeth restored with all-ceramic crowns (ACCs) cemented with dual-cured (RelyX ARC; 3M ESPE) or light-cured (RelyX Veneer; 3M ESPE) luting cements. Clinically, there are advantages of light-cured cements over the recommended dual-cured cements, namely increased working time, improved handling, colour stability, and a homogenous mix. Forty, sound, extracted, human, premolar teeth underwent a standardized preparation for ACCs. IPS Empress (Ivoclar-Vivadent) crowns of standard dimensions were fabricated and 20 were cemented with each cement. The crowns were stored for 1 or 30 d in water and subjected to a compressive load to failure at 0.017 mm s⁻¹. There were no significant differences in loads at failure, between each cement group, at each storage period, and there were no significant differences in loads at failure, for each cement, at 1 and 30 d of storage. There were also no significant differences in modes of failure between each cement group. Before recommending light-cured cement as an alternative to dual-cured cement for the cementation of all-ceramic crowns, further research is required to establish the depth of ceramic at which light-cured lutes fail to polymerize completely.     

Reliability of fiber post bonding to root canal dentin after simulated clinical function in vitro

The aim of this study was to investigate the effect of thermomechanical loading (TML) on the bond strength of fiber posts luted with three different resin cements. Sixty-six extracted human anterior teeth were endodontically treated and restored with fiber posts (RelyX Fiber Posts, 3M ESPE) using three commercially available resin cements and three corresponding core build-up materials (n=22 each): Panavia F 2.0/Clearfil DC Core Automix (Kuraray), Variolink II/Multicore Flow (Ivoclar Vivadent), and RelyX Unicem/Filtek Z250 (3M ESPE). Twelve specimens of each group received all-ceramic crowns and were subjected to TML. The other 10 specimens were stored in saline solution for 24 hours. The roots were sectioned and bond strength was measured using a push-out test. Adhesive interfaces of two specimens of each group subjected to TML were analyzed using field emission scanning electron microscopy (FESEM). Bond strengths of fiber posts were significantly affected by the type of resin cement (p<0.0005) and TML (p<0.0005; two-way analysis of variance). TML significantly reduced bond strengths for all materials ((6.0 (6.2) MPa)) compared with initial bond strengths ((14.9 (10.4) MPa)). RelyX Unicem resulted in significantly higher bond strengths before ((18.3 (10.3) MPa)) and after TML ((9.8 (7.5) MPa)) compared with the other materials (p<0.0005; Tukey HSD). Using FESEM, Variolink II and Panavia F demonstrated a hybrid layer partly detached from the underlying resin cement, whereas no hybrid layer was observed for RelyX Unicem. The decrease in bond strength after TML suggests that retention of fiber posts may be reduced after clinical function. Therefore, endodontically treated teeth that are restored using fiber posts may benefit from additional reinforcement via coronal restorations using adequate ferrules and/or adhesive techniques.     

Micromechanical properties of veneer luting resins after curing through ceramics

The aim of this study was to assess the performance of light-cured luting resin after curing under the ceramic restoration in comparison to dual-cured luting resin, by evaluating the micromechanical properties. Two hundred seventy thin luting composite films of ca. 170 μm in thickness were prepared by using two light-cured luting resins (Variolink Veneer, Ivoclar Vivadent; RelyX Veneer, 3M ESPE) and a dual-cured luting resin (Variolink II, Ivoclar Vivadent). The composites were cured by using a LED-unit (Bluephase?, Ivoclar Vivadent) with three different curing times (10, 20, and 30 s) under two ceramics (IPS e.max Press, Ivoclar Vivadent; IPS Empress? CAD, Ivoclar Vivadent) of different thicknesses (0, 0.75, and 2 mm). Forty-five groups were included, each containing six thin films. The samples were stored after curing for 24 h at 37°C by maintaining moisture conditions with distilled water. Micromechanical properties of the composites were measured with an automatic microhardness indenter (Fisherscope H100C, Germany). For each sample, ten indentations were made, thus totalizing 60 measurements per group. Micromechanical properties of the luting resins were statistically analyzed (SPSS 17.0). Significant differences were observed between the micromechanical properties of the luting resins (p < 0.05). Variolink II showed the highest values in modulus of elasticity (E = 11 ± 0.5)* and Vickers hardness (HV = 48.2 ± 3.2)* and the lowest values in creep (Cr = 4.3 ± 0.1)* and elastic–plastic deformation (We/Wtot = 38.6 ± 0.7)* followed by RelyX Veneer (E = 6.9 ± 0.3, HV = 33 ± 2.5, Cr = 4.6 ± 0.2, We/Wtot = 41.8 ± 1.0)* and Variolink Veneer (E = 4.4 ± 0.4, HV = 20.1 ± 2.6, Cr = 5 ± 0.2, We/Wtot = 43.7 ± 1.3)*. Dual-cured luting resin expressed higher values in the micro-mechanical properties compared to the light-cured luting resins. The effect of luting resin type on the micromechanical properties of the luting resins was higher than the effect of curing time, ceramic type and ceramic thickness respectively (*The values of reference without ceramics for 30 s curing time).