卤素和LED光固化灯照射复合树脂的机械强度比较

目的探讨3M2500型卤素光固化灯和3M FreeLight型LED光固化灯对光固化复合树脂机械强度及固化深度的影响。方法用WD-5A型电子拉力试验机、DUH-W201S型动态超显微硬度计2种仪器,通过测试比较卤素光固化灯和LED光固化灯照射Tetric ceram HB(Vivadent)A2色光固化复合树脂后其挠曲强度、压缩强度、表面硬度、固化深度的差异,从而比较3M2500型卤素光固化灯和3M FreeLight型LED光固化灯的性能。结果卤素光固化灯照射Tetric ceram HB复合树脂40s,LED光固化灯照射Tetric ceram HB10s,前者固化深度平均可达3.98mm,后者固化深度平均可达2.136mm,两者均可完全固化2mm,LED光固化灯固化树脂深度低于卤素光固化灯;表面硬度DHT115平均值分别为73.292MPa和39.668MPa,统计学分析95%水平有差别(P<0.05),LED灯对应的树脂硬度低于卤素灯;压缩强度平均值分别为242.1MPa和287.7MPa,统计学分析95%水平无明显差别(P>0.05);挠曲强度平均值分别为88.9MPa和97.0MPa,统计学分析95%水平无明显差别(P>0.05)。结论LED灯照射Tetric ceram HB复合树脂10s能达到卤素灯照射Tetric ceram HB复合树脂40s的聚合水平,适合于口腔临床应用。     

不同温度及不同光固化灯对光固化复合树脂硬度的影响

目的:探讨不同温度处理后的光固化复合树脂用卤素光固化灯和第2代LED光固化灯照射后复合树脂硬度的差别.方法:设5℃(冷藏)、23℃(常温)、40℃(加热)3种不同温度处理光固化复合树脂Clearfil AP-X.再分别用卤素光固化灯Translux CL和LED灯Elipar FreeLight2照射,采用显微维氏硬度计测量树脂试件表面和底部的硬度.结果采用SPSS 17.0软件包进行方差分析.结果:40℃加热处理后的树脂试件表面和底部的硬度值均较其他2种温度处理后的树脂硬度值增高(P＜0.01).3种温度处理后.LED灯照射树脂试件表面和底部硬度值比卤素灯照射后的硬度值高(P＜0.01).结论:树脂试件使用前预加热处理,可以增强树脂的硬度;第2代LED灯的固化效率优于卤素灯.     

光源距离对6种LED固化灯光强度衰减的影响

目的:评估6种LED固化灯光照射强度随光源距离的增加出现衰减的程度。方法:选择6种LED光固化灯:配置标准光导棒的Bluephase、Bluephase C8和Elipar S10,配置聚光透镜的Ascent PX,配置涡轮光导棒的Demi和Ti-Lite GT-1500。使用光强测量仪在距光源0、1、2、3、4、5 mm测量光固化灯的光照射强度,每一距离测量10次,并计算光强度平均值及相应的光强度衰减率。结果:6种固化灯初始光强度分别为859 m W/cm2(Bluephase C8)、1 121 m W/cm2(Bluephase)、1 133 m W/cm2(Elipar S10)、1 300 m W/cm2(Ascent PX)、1 497 m W/cm2(Demi)和1 192 m W/cm2(Ti-Lite)。除Ascent PX的1~3 mm光源距离外,光源距离每增加1 mm,6种固化灯的光照射强度均出现显著降低(P<0.05)。距离光源5 mm时,只有Bluephase、Elipar S10和Ascent PX的光强度超过了400 m W/cm2,光强度衰减率分别为56.7%、58.7%、53.8%,明显低于Bluephase C8(66%)、Demi(78.8%)和Ti-Lite(>72.2%)。结论:临床中应尽可能选用高强度LED固化灯并延长照射时间以弥补光源距离增加所造成的光强度衰减,建议选择配置标准光导棒或聚光透镜的高强度LED光固化灯。     

不同粘接系统及不同类型LED光固化灯对新型氧化锆材料与牙本质粘接强度影响的比较研究

目的　应用不同粘接系统及不同类型LED光固化灯对新型氧化锆材料与牙本质进行粘接后,比较其剪切强度的大小,为新材料修复体的临床适应证及粘接系统、固化灯的选择提供依据。方法　按统一标准选择60颗离体上颌切牙制作研究模型,预备桩道,CAD/CAM扫描制作“玉瓷”氧化锆桩核,随机分成6组,分别采用3种粘接系统（Panavia F、Multilink N、NX3-Nexus）及2种型号的LED灯（普通型、VALO型）进行粘接和固化,然后将模型水平切割成1.0 mm的薄片,进行薄片推出实验。采用SPSS17.0统计软件分析比较各组剪切强度大小。结果　使用普通型LED灯固化的Panavia F的剪切强度优于Multilink N和NX3-Nexus（P＜0.05）;使用VALO型LED灯固化的Panavia F也比其他两种粘接系统的剪切强度高（P＜0.05）。同种粘接系统使用普通型和VALO型LED灯固化的剪切强度差异均无统计学意义（P＞0.05）。结论　不同型号的LED灯固化后,Panavia F的粘接强度均优于Multilink N和NX3-Nexus;使用VALO型LED灯固化后的粘接强度与普通型LED灯的无显著差异,但可大幅度减少椅旁操作时间。     

两种新型光固化灯与传统卤素灯照射复合树脂固化效果的比较

目的 探讨新型光固化灯Starlight S型LED光固化灯、DNX-TW-518型等离子弧光灯与传统的卤素光固化灯对Z100(3M,America)光固化复合树脂的固化深度和表面硬度的影响.方法 根据ISO 4049:2000标准.分别用两种新型光固化灯与传统卤素灯在标准条件下照射同一种复合树脂.检测其各自的固化深度和硬度.测试结果用SPSS软件进行方差分析和Dunnett-t检验,α=0.05.结果 卤素先固化灯照射Z100复合树脂40s组的平均固化深度可达3.760mm.高于LED光固化灯照射10s组的平均固化深彪.285mm(P<0.05);略高于LED光固化灯照射208组的平均固化深度3.693mm,但两者之同比较差别无统计学意义(P>0.05).等离子弧光灯照射3s组、5s组的平均固化深度分剐为1.984mm、2.575mm,均小于卤素灯照射40s组(P<0.05).而等离子孤光灯照射10s组的平均固化深度为4.387mm.高于卤素灯照射40s组(P灯20S组(55.309±4.472)GPa(P0.05).结论 不同光固化灯照射光敏复合树脂在相同条件下的固化深度和表面硬度不同.两种新型光固化灯田化复合树脂的潜力与卤素灯相似甚至有些方面胜于卤素灯.适合于口腔临床应用.     

2种薄膜对LED光固化灯光照强度的影响

目的 通过检测2种光固化灯分别在裸机、套保鲜膜和套一次性薄膜套情况下,不同距离的光照射强度和衰减程度,比较2种薄膜对光固化灯光照强度的影响.方法 选择3M ESPE EliparTM S10和赛特力牙椅配套miniLed 2种光固化灯,使用光强检测仪器在垂直照射0 mm、3 mm、6 mm的情况下,分别检测裸机、套保鲜膜、套一次性薄膜套的光照强度,每一组检测10次,并计算光照强度的平均值和光照强度的衰减率.结果 3M ESPE EliparTM S10和赛特力牙椅配套miniLed的裸机光照强度分别为1082.4 mW/cm2和1541.7 mW/cm2.使用保鲜膜和薄膜套后,2种光固化灯的光照强度都有所衰减,保鲜膜的衰减率分别为1.36％和2.88％,薄膜套的衰减率分别为3.24％和11.53％.随着光照距离的增加,光照强度衰减分别为38.84％和45.71％.2种光固化灯薄膜套组的衰减程度均大于保鲜膜,距离6 mm时光照强度均低于1000 mW/cm2.结论 临床光固化灯使用保护套后光照强度会有所下降,近距离基本不影响树脂固化.当光照距离增加到6 mm时可能会影响树脂的固化深度.     

两种光固化模式对窝沟封闭材料封闭效果的影响

目的 分别在光固化灯(VALO?Cordless)超高功率和常规功率两种固化模式下研究窝沟封闭材料的封闭效果,比较微渗漏程度和操作时间的差异,为临床提供参考.方法 收集符合纳入标准的青少年磨牙及前磨牙,共计80颗,窝沟封闭剂分别是:A组和B组采用自酸蚀粘接剂(3M ESPE Single Bond Universal)与流动树脂(3M ESPE FiltekTM Z350 XT)联合应用,C组和D组采用自酸蚀自粘接流体树脂(DMG-Constic),固化模式分别为A组和C组采取常规光固化;B组和D组采取超能量光固化.所有标本在0.1％罗丹明B荧光染液中浸泡24 h后进行编号、切割,在激光共聚焦显微镜镜下观察4组试样的封闭剂与牙釉质本质界之间的渗漏程度,记录微渗漏值进行统计学分析.结果(1)4组试样的微渗漏深度值分别为:A组(375.08±32.4)μm,B组(340.04±35.99)μm,C组(306.71±13.56)μm,D组(265.27±24.69)μm;(2)A组、C组、D组的操作时间大于B组,在相同光固化模式及相同粘接技术条件下,各组之间的操作时间的差异有统计学意义(P<0.05),不同光固化模式和不同树脂在操作时间上有交互作用;A组、B组、C组的微渗漏值大于D组,且在相同光固化模式及相同粘接技术条件下,各组之间的微渗漏值存在差异(P<0.05),不同光固化模式和不同树脂在微渗漏程度上没有交互作用.结论 在超能量光固化模式下,虽然使用自酸蚀粘接剂联合流动树脂进行窝沟封闭使用的时间最少,但使用自酸蚀自粘接流体树脂进行操作能有效地减小微渗漏,提高治疗效果,值得临床推广应用.     

饵激光预备及光固化灯超强功率模式对树脂微渗漏的影响

目的研究饵激光备洞和光固化灯超强功率模式对树脂充填微渗漏的影响。方法将40颗离体后牙随机平均分成4组进行备洞和充填固化。A组:高速涡轮机加安福士椅旁LED灯(550 m W/cm2,20 s);B组:高速涡轮机加VALO光固化灯(超强功率模式3 200 m W/cm2,3 s);C组:铒激光加安福士椅旁LED灯;D组:铒激光加VALO光固化灯。所有样本制备V类洞并行树脂充填后置于37℃生理盐水中24 h,冷热循环后亚甲基蓝溶液染色,在低速切割机下颊舌向切开,体式显微镜下观察剖面微渗漏情况,计分,统计。结果所有样本的龈壁微渗漏与牙合壁相比较更高,A组微渗漏程度较B、C组低,有统计学差异(P<0.05)。D组微渗漏最大,与其他各组有统计学差异(P<0.05)。结论铒激光备洞和光固化灯超级功率模式都会增加树脂充填微渗漏的发生。     

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光固化复合树脂通过光聚合进行固化,已有多种光固化灯用于口腔材料的光固化。随着发光二极管（LED）技术的迅速发展,LED光固化灯已逐渐成为多数临床应用的标准设备。本文就LED光固化灯的物理学特性、口腔临床应用发展、导光管及其消毒作一综述,分析未来发展趋势,为其在口腔临床应用提供参考依据。     

不同颜色与厚度的2种玻璃陶瓷修复体对光固化灯透射光学性能的影响

目的：研究不同种类、颜色与厚度玻璃陶瓷修复体对口腔常用光固化灯的透射玻璃陶瓷后透射光光学性能的改变。方法：用CAD/CAM技术制作二硅酸锂基玻璃陶瓷和白榴石增强型玻璃陶瓷圆片试件,每种玻璃陶瓷选择颜色为A2和A3,共分为4组。每组制作厚度为0.5~4.0mm的圆片共8个,总计32个。收集2台全新LED光固化灯,用光谱辐照度计和光功率计（积分球标定精度）测量2台光固化灯3种功率模式下的中心波长和光强,以及透射玻璃陶瓷圆片后透射光的中心波长和光强。采用SPSS 25.0软件包对数据进行统计学分析。结果：不同光固化灯功率模式、玻璃陶瓷不同类型、颜色的透射光中心波长有显著差异（P<0.05）;不同光固化灯功率模式、玻璃陶瓷不同类型、颜色、厚度的透射光光强有差异（P<0.05）。结论：光固化灯的功率模式,玻璃陶瓷的类型和颜色对透射光的中心波长有影响,玻璃陶瓷的厚度对透射光的中心波长无影响。光固化灯的功率模式,玻璃陶瓷的类型、颜色、厚度对透射光的光强有影响;其中,玻璃陶瓷厚度对透射光的光强衰减影响最显著。     

Analysis of the degree of conversion of LED and halogen lights using micro-Raman spectroscopy

This study determined the degree of conversion of two LED (light-emitting diodes) (Elipar FreeLight [FL], 3M ESPE; GC e-Light [EL], GC), a high intensity (Elipar TriLight [TL], 3M ESPE) and a very high intensity (Astralis 10 [AS], Ivoclar Vivadent) halogen light. The degree of conversion of these lights was compared to a conventional halogen light (Max [MX] (control), Dentsply-Caulk). Ten different light curing regimens, including pulse (EL1), continuous (FL1, EL2, TL1), turbo (EL3, AS1) and soft-start (FL2, EL4, TL2) modes of various lights were also investigated. Composite specimens of dimensions 3 x 3 x 2 mm were cured with the 10 different light curing regimens investigated. Micro-Raman spectroscopy was used to determine the degree of conversion at the top and bottom surfaces of a composite restorative (Z100, [3M ESPE]) at 60 minutes post-light polymerization. Five specimens were made for each cure mode. The results were analyzed using ANOVA/Scheffe's post-hoc test and Independent Samples t-tests at significance level 0.05. The degree of conversion ranged from 55.98 +/- 2.50 to 59.00 +/- 2.76% for the top surface and 51.90 +/- 3.36 to 57.28 +/- 1.56% for the bottom surface. No significant difference in degree of conversion was observed for the 10 light curing regimens when compared to MX (control). The curing efficiency of LED lights was comparable to halogen lights regardless of curing modes.     

Post-gel shrinkage with different modes of LED and halogen light curing units

This study compared the post-gel shrinkage of two LED (light-emitting diodes) lights (Elipar FreeLight [FL], 3M ESPE; GC e-Light [EL], GC), a high intensity (Elipar TriLight [TL], 3M ESPE) and a very high intensity (Astralis 10 [AS], Ivoclar Vivadent) halogen light to a conventional (Max [MX] (control), Dentsply-Caulk) halogen light. Ten light curing regimens were investigated. These included continuous (FL1, EL2, MX, TL1 and AS1), soft-start (FL2, EL4, TL2), pulse activation (EL1) and turbo (EL3) modes. A strain-monitoring device and test configuration was used to measure the linear polymerization shrinkage of a composite restorative (Z100, [3M ESPE]) during and post-light polymerization up to 60 minutes when cured with the different modes. Five specimens were made for each cure mode. Results were analyzed using ANOVA/Scheffe's post-hoc test and independent sample t-tests at significance level 0.05. Shrinkage associated with the various modes of EL was significantly lower than MX immediately after light polymerization and at one-minute post-light polymerization. No significant difference between MX and the various lights/cure modes was observed at 10, 30 and 60-minutes post-light polymerization. At all time intervals, post-gel shrinkage associated with continuous light curing mode was significantly higher than the soft-start light curing mode for FL and TL.     

Effects of curing lights on human gingival epithelial cell proliferation

BackgroundLight-emitting diode (LED) and quartz-tungsten-halogen (QTH) curing lights are used commonly in clinics. The aim of this study was to assess the effect of these lights on the proliferation of human gingival epithelial cells.MethodsSmulow-Glickman (S-G) cells were exposed to a VALO LED (Ultradent) or an XL3000 QTH (3M ESPE) light at 1 millimeter or 6 mm distance for 18, 39, 60, and 120 seconds. Untreated and Triton X-100 treated cells were used as controls. At 24, 48, and 72 hours after light exposure, cell proliferation was evaluated via a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.ResultsThe authors first evaluated the performances of these 2 lights. Both LED and QTH lights generated heat. The LED light generated less heat than the QTH light and could save approximately two-thirds of the curing time. When used for 18 seconds at a 6 mm distance, the LED light did not inhibit the proliferation of S-G cells. However, if the exposure time was longer (for example, 39, 60, or 120 seconds), the LED light inhibited cell proliferation. The inhibitory effect increased when the exposure time was increased to 39, 60, or 120 seconds. The QTH light did not inhibit S-G cell proliferation if the exposure time was less than 120 seconds.ConclusionsProlonged exposure to a blue curing light (both LED and QTH) inhibits the proliferation of gingival epithelial cells and may cause damages to oral soft tissues.Practical ImplicationsIn dental practices, a balance should be struck in consideration of curing time not only to cure the composites completely but also to minimize unnecessarily prolonged light exposure.     

Depth of cure and surface microhardness of composite resin cured with blue LED curing lights.

OBJECTIVES: This study examined the depth of cure and surface microhardness of Filtek Z250 composite resin (3M-Espe) (shades B1, A3, and C4) when cured with three commercially available light emitting diode (LED) curing lights [E-light (GC), Elipar Freelight (3M-ESPE), 475H (RF Lab Systems)], compared with a high intensity quartz tungsten halogen (HQTH) light (Kerr Demetron Optilux 501) and a conventional quartz tungsten halogen (QTH) lamp (Sirona S1 dental unit). METHODS: The effects of light source and resin shade were evaluated as independent variables. Depth of cure after 40 s of exposure was determined using the ISO 4049:2000 method, and Vickers hardness determined at 1.0 mm intervals. RESULTS: HQTH and QTH lamps gave the greatest depth of cure. The three LED lights showed similar performances across all parameters, and each unit exceeded the ISO standard for depth of cure except GC ELight for shade B1. In terms of shade, LED lights gave greater curing depths with A3 shade, while QTH and HQTH lights gave greater curing depths with C4 shade. Hardness at the resin surface was not significantly different between LED and conventional curing lights, however, below the surface, hardness reduced more rapidly for the LED lights, especially at depths beyond 3 mm. SIGNIFICANCE: Since the performance of the three LED lights meets the ISO standard for depth of cure, these systems appear suitable for routine clinical application for resin curing.     

Effect of two light-emitting diode (LED) and one halogen curing light on the microleakage of Class V flowable composite restorations

AIM: The disadvantages of light cured composite resin materials with respect to microleakage are predominantly a result of polymerization shrinkage upon curing. It has been shown curing methods play a significant role in polymerization shrinkage of light-cured composite resins. The purpose of this study was to investigate the effect of light-emitting diode (LED) light curing units (LCUs) compared with a halogen LCU on microleakage of three different flowable composites using self-etch adhesives. METHODS AND MATERIALS: A total of 63 extracted human premolars were prepared with standardized Class V cavity preparations on the buccal and lingual surfaces of each tooth. The occlusal margin of the cavities was located on the enamel and the gingival margin was on dentin. Teeth were randomly assigned to three groups of 21 teeth each as follows: Group 1: Adper Prompt L-Pop + Filtek Flow (3M ESPE); Group 2: AdheSE + Tetric Flow (Ivoclar, Vivadent); and Group 3: Clearfil Protect Bond + Clearfil Protect Liner F (Kuraray Medical Inc.). All the groups were subdivided into three groups according to the curing lights used (n=7). Two LED LCUs, Elipar FreeLight and Elipar FreeLight 2 (3M ESPE), and one halogen-based LCU, Hilux Expert (Benlioglu ), were used. All teeth were then immersed in 0.5% basic fuchsin dye solution for 24 hours after thermocycling (500 cycles; between 5 degrees C to 55 degrees C). The teeth then were longitudinally sectioned and observed under a stereomicroscope (40X magnification) by two examiners. The degree of dye penetration was recorded separately for enamel and dentin. Data were analyzed with the Kruskal-Wallis and Mann-Whitney tests with the Bonferroni correction. RESULTS: No statistically significant differences in microleakage were observed between groups either on enamel or dentin (p>0.05). CONCLUSION: With the limitation of this in vitro study, the differences in microleakage between LCUs used were not statistically significantly different. Elipar Free Light 2 reduces curing time which can be considered as an advantage.     

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??Objective??The new type of zirconia materials and dentin was bonded with different adhesive systems??using different types of LED curing lights. By comparing the shear strength??to provide certain theoretical reference for the choice of clinical indications??adhesives systems and curing lights of the new type of restoration. Methods??According to the unified standard??maxillary incisors in vitro were selected as experimental samples. Prepared and scanned post space??new type of zirconia post was made by CAD/CAM. Randomly divided into 6 groups??post was respectively bonded using 3 kinds of adhesive systems ??Panavia F??Multilink N??NX3-Nexus?? and 2 kinds of LED lights ??ordinary ??VALO??. Then the samples were horizontally cut into a 1 mm slice. The slices were released in the universal mechanical test machine??the shear strength of each group was analyzed by SPSS 17.0. Results????The shear strength of Panavia F was better than that of Multilink N and NX3-Nexus??using the ordinary LED curing light ??P < 0.05??. Panavia F also had higher shear strength than the other two adhesive systems, using VALO LED curing light ??P < 0.05??. There was no significant difference in shear strength between the ordinary and VALO light??using the same adhesive systems ??P > 0.05??. Conclusion????The adhesion strength of Panavia F is better than those of Multilink N and NX3-Nexus??using different types of LED curing lights. There is no significant difference in adhesion strength between VALO and ordinary LED curing light??the VALO LED curing light can significantly reduced the operating time by the side of the chair.     

Influence of curing methods and materials on the marginal seal of class V composite restorations in vitro

The study tests the hypothesis that soft-start irradiation improves, whereas, high intensity irradiation compromises the margin quality and marginal seal of Class V resin based composite [RBC] restorations. Box-shaped Class V cavities were prepared in extracted, human third molars with cervical margins located apical to the CEJ. Cavities were restored using a multi-step bonding agent (Optibond FL, Kerr), a thin layer of flowable resin composite and two increments of fine hybrid resin composite (Filtek Flow/Filtek Z250, 3M ESPE; Revolution f2/Herculite XRV, Kerr). Light irradiation was performed using either the standard (40 seconds) or the soft-start mode (40 seconds with exponential increase) of a quartz tungsten halogen or an LED curing light (Elipar Trilight, Elipar Freelight, 3M ESPE); for high intensity irradiation, a Plasma Are curing unit was used with three irradiations of three seconds (Apollo 95E, DMDS). After 30 days of water storage and thermal cycling (n = 2500, 5-55 degrees C), margin quality was assessed in the SEM using the replica technique and marginal seal was evaluated using dye penetration (AgNO3 50%). Few differences were observed between the light curing protocols. However, less leakage was observed in the case of the lower shrinking RBC Filtek Z250.     

Hardness of a bleaching-shade resin composite polymerized with different light-curing sources

The microhardness of a bleaching-shade resin composite polymerized with different light-curing units was evaluated. Composite samples (3M ESPE Filtek Supreme) were applied to brass rings (2 mm in thickness, 5 mm in diameter). Three commercial LED lights were used to polymerize the specimens and the results were compared to those of a conventional halogen light. The light sources used in the present study were: Demetron Optilux 401 (QTH), 3M ESPE Elipar FreeLight (LED 1); Kerr L.E. Demetron I (LED 2), and ColtoluxLED lights (LED 3). The microhardness of the top and bottom surfaces was assessed with a digital Vickers hardness-measuring instrument, under load. At the bottom surface, no significant difference among the light sources was observed (two-way ANOVA). At the top surface, the QTH light source presented significantly higher hardness values compared to the values observed when LED 1 and LED 3 were used. There were no significant differences between the QTH and LED 2 light sources. Significantly higher hardness values were also found at the top surface when compared to the values observed at the bottom surface. The power density of the polymerization light sources seemed to be responsible for the observed resin composite hardness, not their irradiance.     

Polymerization efficiency of different photocuring units through ceramic discs

This study compared the ability of a variety of light sources and exposure modes to polymerize a dual-cured resin composite through ceramic discs of different thicknesses by depth of cure and Vickers microhardness (VHN). Ceramic specimens (360) (Empress 2 [Ivoclar Vivadent], color 300, diameter 4 mm, height 1 or 2 mm) were prepared and inserted into steel molds according to ISO 4049, after which a dual-cured composite resin luting material (Variolink II [Ivoclar Vivadent]) with and without self-curing catalyst was placed. The light curing units used were either a conventional halogen curing unit (Elipar TriLight [3M/ESPE] for 40 seconds), a high-power halogen curing unit (Astralis 10 [Ivoclar Vivadent] for 20 seconds), a plasma arc curing unit (Aurys [Degré K] for 10 seconds or 20 seconds) or different light emitting diode (LED) curing units (Elipar FreeLight I [3M/ESPE] for 40 seconds, Elipar FreeLight II [3M/ESPE] for 20 seconds, LuxOmax [Akeda] for 40 seconds, e-Light [GC] for 12 seconds or 40 seconds). Depth of cure under the ceramic discs was assessed according to ISO 4049, and VHN at 0.5 and 1.0 mm distance from the ceramic disc bottom was determined (ISO 6507-1). Medians and the 25th and 75th percentiles were determined for each group (n=10), and statistical analysis was performed using the Mann-Whitney-U-test (p < or = 0.05). The results showed that increasing ceramic disc thickness had a negative effect on the curing depth and hardness of all light curing units, with hardness decreasing dramatically under the 2-mm thick discs using LuxOmax, e-Light (12 seconds) or Aurys (10 seconds or 20 seconds). The use of a self-curing catalyst is recommended over the light-curable portion only, because it produced an equivalent or greater hardness and depth of cure with all light polymerization modes.