光固化复合树脂固化深度的逐步回归分析

目的:分析不同处理因素对光固化复合树脂固化深度的影响,探讨各因素对固化深度的影响程度.方法:采用多因素不同水平析因实验设计,共制备192例试件.所得试件经Planmeca曲面断层机扫描,并测量其固化深度.所有实验数据采用SPSS 11.5软件包进行t检验、多元逐步回归.结果:不同光源、不同投照距离、不同光照时间之间的差异具有统计学意义(P＜0.01);多元逐步回归分析表明,3个因素与固化深度存在显著的线性相关关系(P＜0.01).结论:3个因素均可影响光固化复合树脂的固化深度,以光照时间对固化深度的影响最大,且三者之间存在交互作用.     

影响光固化复合树脂固化深度的有关因素探讨

目的:探讨不同树脂、不同光固化灯、不同投照距离、不同投照时间等因素对光固化复合树脂固化深度的影响。方法:制备底面直径4mm,高6mm的圆柱形试件模具,采用多因素不同水平的析因实验设计,共制备192例试件。用Planmeca曲面断层机扫描试件,并测量其固化深度。实验数据采用SPSS11.5软件包进行方差分析。结果:4种处理因素自身不同水平比较,差异具有统计学意义(P<0.01),且4个因素之间存在交互作用(P<0.01)。结论:2种光固化灯、2种树脂、4个投照距离、4个投照时间对光固化深度均有影响。对每种因素的优化,必将对固化深度产生叠加效果。     

The effectiveness of cure of LED and halogen curing lights at varying cavity depths

This study compared the effectiveness of cure of two LED (light-emitting diodes) lights (Elipar FreeLight [FL], 3M-ESPE and GC e-Light [EL], GC) to conventional (Max [MX] (control), Dentsply-Caulk), high intensity (Elipar TriLight [TL], 3M-ESPE) and very high intensity (Astralis 10 [AS], Ivoclar Vivadent) halogen lights at varying cavity depths. Ten light curing regimens were investigated. They include: FL1-400 mW/cm2 [40 seconds], FL2-0-400 mW/cm2 [12 seconds] --> 400 mW/cm2 [28 seconds], EL1-750 mW/cm2 [10 pulses x 2 seconds], EL2-350 mW/cm2 [40 seconds], EL3-600 mW/cm2 [20 seconds], EL4-0-600 mW/cm2 [20 seconds] --> 600 mW/cm2 [20 seconds], TL1-800 mW/cm2 [40 seconds], TL2-100-800 mW/cm2 [15 seconds] --> 800 mW/cm2 [25 seconds], AS1-1200 mW/cm2 [10 seconds], MX-400 mW/cm2 [40 seconds]. The effectiveness of cure of the different modes was determined by measuring the top and bottom surface hardness (KHN) of 2-mm, 3-mm and 4-mm thick composite (Z100, [3M-ESPE]) specimens using a digital microhardness tester (n = 5, load = 500 g; dwell time = 15 seconds). Results were analyzed using ANOVA/Scheffe's post-hoc test and Independent Samples t-Test (p < 0.05). For all lights, effectiveness of cure was found to decrease with increased cavity depths. The mean hardness ratio for all curing lights at a depth of 2 mm was found to be greater than 0.80 (the accepted minimum standard). At 3 mm, all halogen lights produced a hardness ratio greater than 0.80 but some LED light regimens did not; and at a depth of 4 mm, the mean hardness ratio observed with all curing lights was less than 0.80. Significant differences in top and bottom KHN values were observed among different curing regimens for the same light and between LED and halogen lights. While curing with most modes of EL resulted in significantly lower top and bottom KHN values than the control (MX) at all depths, the standard mode of FL resulted in significantly higher top and bottom KHN at a depth of 3 mm and 4 mm. The depth of composite cure with LED LCUs was, therefore, product and mode dependent.     

Composite cure and shrinkage associated with high intensity curing light

This study investigated the effectiveness of cure and post-gel shrinkage of three visible light-cured composite resins (In Ten-S [IT], Ivoclar Vivadent; Z100 [ZO], 3M-ESPE; Tetric Ceram [TC], Ivoclar Vivadent) when polymerized with a very high intensity (1296 +/- 2 mW/cm2) halogen light (Astralis 10, Ivoclar Vivadent) for 10 seconds. Irradiation with a conventional (494 +/- 3 mW/cm2) halogen light (Spectrum, Dentsply) for 40 seconds was used for comparison. The effectiveness of cure was assessed by computing the hardness gradient between the top and bottom surfaces of 2-mm composite specimens after curing. A strain-monitoring device was used to measure the linear polymerization shrinkage associated with the various composites and curing lights. A sample size of five was used for both experiments. Data was analyzed using ANOVA/Scheffe's post-hoc and Independent Samples t-tests at significance level 0.05. Results showed that the effect of the curing method on the effectiveness of cure and shrinkage was material-dependent. Polymerization of IT and TC with Spectrum for 40 seconds resulted in significantly more effective cure than polymerization with Astralis for 10 seconds. Polymerization of ZO with Spectrum for 40 seconds resulted in significantly more shrinkage than polymerization with Astralis for 10 seconds. In view of the substantial time saving, using high intensity lights may be a viable method to polymerize composites.     

Thermal changes and cure depths associated with a high intensity light activation unit

OBJECTIVES: The objectives of this study were to evaluate the thermal emission and curing characteristics of a high intensity halogen light (Astralis 10-Ivoclar Vivadent, Schaan. Leichtenstein) alone and on curing a conventional and a fast-curing micro-hybrid composite. METHODS: A bead thermistor was placed in the base of a standard model cavity. The cavity was irradiated using the light unit whilst empty, and when filled with either composite. Temperature rises were recorded using the light in four different output modes. Further samples were prepared to assess depth of cure via a digital penetrometer, light transmission using a computer-based radiometer, and microhardness with a Wallace hardness tester. RESULTS: Mean peak temperature rises recorded during polymerisation of the composites ranged from 6.9 degrees C for the product InTen-S cured with the Adhesive programme (Adh) to 11.0 degrees C for the product Tetric Ceram HB cured with the High Power (HI P) programme. A significantly greater depth of cure was obtained for InTen-S in line with the greater light transmission obtained for this material. DISCUSSION: The very high thermal emission characteristics reported in a recently published investigation for this light unit were not confirmed. CONCLUSIONS: As the extent of thermal trauma that can be tolerated by the dental pulp is unknown consideration should be given to the choice of light activation unit and curing programme when polymerising light activated resin based restorations in deep cavities close to the pulp.     

Optical power outputs,spectra and dental composite depths of cure,obtained with blue light emitting diode (LED) and halogen light curing units (LCUs)

OBJECTIVE: To test the hypothesis that a prototype LED light curing unit, (LCU), a commercial LED LCU and a halogen LCU achieve similar cure depths, using two shades of a camphorquinone photoinitiated dental composite. To measure the LCUs' outputs and the frequency of the LED LCU's pulsed light, using a blue LED array as a photodetector. DESIGN: Cure depth and light output characterisation to compare the LCUs. SETTING: An in vitro laboratory study conducted in the UK. MATERIALS AND METHODS: The LCUs cured A2 and A4 composite shades. A penetrometer measured the depth of cure. Analysis was by one-way ANOVA, two-way univariate ANOVA and Fisher's LSD test with a 95% confidence interval. A power meter and spectrograph characterised the LCUs' emissions. A blue LED array measured the pulsed light frequency from an LED LCU. RESULTS: Statistically significant different LCU irradiances (119 mW/cm2 to 851 mW/cm2) and cure depths (3.90 mm SD +/- 0.08 to 6.68 mm SD +/- 0.07) were achieved. Composite shade affected cure depth. A blue LED array detected pulsed light at 12 Hz from the commercial LED LCU. CONCLUSIONS: The prototype LED LCU achieved a greater or equal depth of cure when compared with the commercial LCUs. LEDs may have a potential in dentistry for light detection as well as emission.     

3种光固化灯照射不同颜色复合树脂的固化深度比较

目的探讨LED光固化灯与传统卤素灯对不同颜色复合树脂的固化深度的影响。方法选取FiltekTMZ350和Premisa两种树脂,FiltekTMZ350组选取A1B,A2B,A3B 3种颜色,Premisa组选取A1E,A2E,A3E 3种颜色,自制实验模具,将树脂填入模具。每种颜色树脂制作60例试件,分为3组,每组20例,分别用2种新型LED光固化灯Demi LED和Bluephase20i与传统卤素灯ALC-50在标准条件下照射试件,检测固化深度。结果 Demi LED光照10 s、Bluephase20i光照10 s树脂的固化深度均达到3 mm,与传统的卤素光固化灯ALC-50光照40 s有显著差异,但前两者之间无显著差异。Premisa树脂中2种LED照射组A1E,A2E和A3E 3种颜色之间固化深度有统计学差异。结论在相同条件下,Demi LED和Bluephase20i照射10 s树脂固化深度大于传统卤素灯ALC-50照射同一树脂40 s,适合临床应用。树脂颜色的加深对树脂固化深度有影响。     

Effects of various light curing methods on the leachability of uncured substances and hardness of a composite resin

The purpose of this study was to evaluate the effect of the various light curing units (plasma arc, halogen and light-emitting diodes) and irradiation methods (one-step, two-step and pulse) using different light energy densities on the leachability of unreacted monomers (Bis-GMA and UDMA) and the surface hardness of a composite resin (Z250, 3M). Leachability of the specimens immersed for 7 days in ethanol was analysed by HPLC. Vicker's hardness number (VHN) was measured immediately after curing (IC) and after immersion in ethanol for 7 days. Various irradiation methods with three curing units resulted in differences in the amount of leached monomers and VHN of IC when light energy density was lower than 17.0 J cm(-2) (P = 0.05). However, regardless of curing units and irradiation methods, these results were not different when the time or light energy density increased. When similar light energy density was irradiated (15.6-17.7 J cm(-2)), the efficiency of irradiation methods was different by the following order: one-step > or = two-step > pulse. These results suggest that the amount of leached monomers and VHN were influenced by forming polymer structure in activation and initiation stages of polymerization process with different light source energies and curing times.     

Comparison of light transmittance in different thicknesses of zirconia under various light curing units

PURPOSE

The objective of this study was to compare the light transmittance of zirconia in different thicknesses using various light curing units.

MATERIALS AND METHODS

A total of 21 disc-shaped zirconia specimens (5 mm in diameter) in different thicknesses (0.3, 0.5 and 0.8 mm) were prepared. The light transmittance of the specimens under three different light-curing units (quartz tungsten halogen, light-emitting diodes and plasma arc) was compared by using a hand-held radiometer. Statistical significance was determined using two-way ANOVA (α=.05).

RESULTS

ANOVA revealed that thickness of zirconia and light curing unit had significant effects on light transmittance (P<.001).

CONCLUSION

Greater thickness of zirconia results in lower light transmittance. Light-emitting diodes light-curing units might be considered as effective as Plasma arc light-curing units or more effective than Quartz-tungsten-halogen light-curing units for polymerization of the resin-based materials.     

Temperature rise during adhesive and resin composite polymerization with various light curing sources

This study evaluated the temperature rise in two different adhesive (Clearfil SE Bond [CSEB] and EBS-Multi [EBSM]) and composite systems (Clearfil AP-X [CAPX,] Pertac II [PII]) by the same manufacturer when illuminated by four different light sources: Light-emitting diode (LED), Plasma arc curing (PAC), high intensity quartz tungsten halogen (HQTH) and quartz tungsten halogen (QTH). Forty dentin disks were prepared from extracted premolars. These dentin disks were placed in apparatus developed to measure temperature rise. Temperature rise during photopolymerization of adhesive resin and resin composite was then measured. The mean values of temperature increases for adhesive and resin composites did not differ significantly (p=0.769). The highest temperature rise was observed during photopolymerization of EBSM with PAC (5.16 degrees C) and HQTH (4.28 degrees C), respectively. Temperature rise values produced by QTH (1.27 degrees C - 2.83 degrees C for adhesive resin; 1.86 degrees C - 2.85 degrees C for resin composite) for both adhesive and resin composites were significantly lower than those induced by PAC and HQTH (p<0.05). However, these values were significantly higher than those produced by LED (1.16 degrees C - 2.08 degrees C for adhesive resin; 1.13 degrees C - 2.59 degrees C for resin composite). Light sources with high energy output (PAC and HQTH) caused significantly higher temperature rise than sources with low energy output (QTH and LED). However, in this study, no temperature rises beneath 1-mm dentin disk exceed the critical 5.6 degrees C value for pulpal health.     

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.     

The influence of various light curing units on the cytotoxicity of dental adhesives

ObjectivesThe objective of this study was to test the hypothesis that various light curing units (LCUs) have an influence on the cytotoxic action of adhesive systems.MethodsSamples of the dental adhesives (Syntac^®, iBondTM, Clearfil? Protect Bond, Prime & Bond? NT, Adper? Prompt? L-Pop?) were prepared in microwell plates, making use of the LCUs Voco Polofil Lux (VPL), EMS Swiss Master Light^® (SML) and the LED prototype developed by the IMT of Jena University. To obtain extracts, the samples were topped with cell culture medium, which was changed daily on the 1st to 7th days and then on the 14th, 21st and 28th day, and stored for further use at ?20 °C. Human gingival fibroblasts (HGFs) were cultivated in the extract-containing medium for 48 h. The viability of the HGFs was determined by the neutral red (NR) uptake test. The statistical test was performed by one-way ANOVA according to Bonferroni.ResultsDuring the first few days, reduction of the viability rates of the HGFs by 85–90% were observed in all adhesives. A rise up to a plateau phase was observed at different times depending on the materials. The influence of the LCUs on the cytotoxic action of the dental adhesives was clearly evident for the adhesives Syntac^® and Clearfil? Protect Bond. In case of the Syntac^® extracts, cytotoxicity after polymerization with the VPL was statistically significant reduced compared to the other LCUs used (p < 0.001). A comparison between all the adhesives used proved that Adper? Prompt? L-Pop? and Prime & Bond NT^® had the lowest overall cytotoxicities.SignificanceIn practice, one should use combinations of dental adhesive and LCU in which the material has the least toxic influences.     

Effect of distance from curing light tip to restoration surface on depth of cure of composite resin

AIMS: While light-activating composite resins, the light tip may not always be close to the surface of the restoration. This may be intentional in an attempt to create a ramp cure. The aim of this study was to determine the effect of a range of separation distances between the light tip and the restoration surface on the depth of composite cure for different types of light-curing units with a broad range of outputs. METHODS: Three halogen light units, one plasma arc-curing (PAC) light unit and two light-emitting diode (LED) curing lights in clinical use were tested, and a total of 570 restorations cured in a two-part human tooth model at separations ranging from 0 to 15 mm. The tooth was disassembled and depth of cure determined using the scrape test ISO 4049. Light intensity was also measured at each separation distance for each light. RESULTS: The depth of cure was generally found to decrease as the separation distance increased for all lights at the various cure times. However, the effect of increasing the separation distance was less than anticipated. The depth of cure was also related to the light output. CONCLUSIONS: Depth of composite cure was directly related to intensity and duration of light exposure and inversely related to distance of the light source from the surface for halogen and plasma lights. However, the effect of increasing the separation distance up to 15 mm was less than expected. Altering the separation distance in order to modify the polymerisation characteristics is unlikely to be effective.     

Influence of different light curing units on the cytotoxicity of various dental composites.

OBJECTIVES: To evaluate the dependence of the toxicity of various dental composites on the use of high- and low-power light curing units (LCUs). METHODS: The composites Filtek Z 250, Durafill VS, Solitaire 2 and Grandio were polymerized using different light densities from three LCUs, namely Heliolux II, Swiss Master Light (SML) and a prototype LED. The toxicity of polymerized samples was tested by exposing them to the cell culture medium up to 28 days. The extracts of the composites were collected daily and used for incubation in human gingival fibroblasts cultures. RESULTS: Slow, low-intensity curing using the LED or the Heliolux II showed similar characteristics for all four composites, regarding the cell viability rate of human gingival fibroblasts. After 1 day of storage suboptimal results could be observed for the SML/Durafill and optimal results for SML/Grandio combination (approximately 100% cell viability). In addition, the composite Solitaire the SML yielded significantly better results than the other LCUs (cell viability, p < or = 0.001: SML 60.5%, Heliolux 44.5%, LED 44.2%). Furthermore, the combination of the SML with Z 250 composite showed, after the first day and up to day 28, statistically significantly higher cell viability rates than the combination with the LED or Heliolux II. SIGNIFICANCE: This study shows that the combination of a high power LCU with some composites positively influences the HGF cell viability effected by the investigated composite extracts. Moreover, there is further indication that a reduction of composite toxicity is possible if the curing mode is adapted to the used composite.