• Restorative Dentistry and Endodontics
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• v.18 no.1
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• pp.215-226
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• 1993

Color stability of tooth colored restorative resins is an important factor, particularly in anterior teeth restoration. The purpose of this study was to evaluate the color stability and opacity change of several light curing composite resins. Specimens of eight composite resins(Prisma AP. H., Brilliant Enamel, Charisma, Durafil, Helio Progress, Herculite XR, P-50 and Silux Plus) were divided into two groups : In Group 1, the specimens were polymerized by visible light curing unit for 60 seconds on both sides and in Group 2, the post-cured specimens were heat tempered by light/heat curing unit for 45 units(about 18 min.). All specimens were stored in distilled water at $60^{\circ}C$ for 30 days. The color characteristics($L^*,a^*,b^*$) and opacity of the specimens before and after immersion were measured by spectrocolorimetry and the total color difference(${\Delta}E^*$) and opacity change (${\Delta}Y%$) were computed. The results obtained were as follows : 1. SP and APH in both groups, DF, HP and HXR in Group 1 showed ${\Delta}E^*$-value above 2.0. 2. DF, HP, SP and HXR in Group 1 showed higher ${\Delta}E^*$-value than in Group 2, but the others had no significant difference. 3. The opacity of CH and HXR in Group 1, and of CH and BE in Group 2 decreased after immersion, while that of the others increased. 4. Opacity change of BE, P50 and HXR was significantly different between Group 1 and 2. These results suggest that color change in the post-cure heat tempered specimens by light/heat curing unit was smaller than that of the specimens polymerized by visible light curing unit. No clinically detectable opacity changes were noted for any materials in either goup.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.2
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• pp.273-279
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• 2004

Recently, newly developed single high-intensity LED curing lights for composite resins are claimed to have a higher intensity than previous LED curing lights and to results in optimal properties and short curing time. The purpose of this study was to determine the curing effectiveness of the curing units and to evaluate the relationship between the degree of polymerization and distance from curing light tip end to resin surface. One composite resin was tested(Filtek Z250). Thin film specimens were cured with a LED curing unit(Elipar Freelight 2, 10s), Plasma Arc curing unit(Flipo, 6s), Halogen curing light(XL3000, 20s) at four curing light tip to the resin surface(0mm, 2mm, 4mm, 6mm). Degree of conversion of composite resins were determined by a Fourier Transform Infrared Spectrometer(FTIR). From the present study, the following results were obtained. 1. In all curing units, relative light intensity was significantly decreased according to the increase of distance of light tip to the resin surface(p<0.05). LED curing units showed a higher percentile decrease in intensity than other curing units. 2. In all curing units, degree of conversion was decreased as increase of the distance but no statistically significant difference(p>0.05) except between 4mm and 6mm(p<0.05). 3. When comparing degree of conversion of light curing units at each distance(0mm, 2mm, 4mm, 6mm), LED curing light had a higher degree of conversion than plasma arc and halogen curing lights at 0, 2, 4mm(p<0.05). At 6mm, there was a no significant difference among the curing units(p>0.05).

• The Journal of the Korean dental association
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• v.57 no.3
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• pp.175-184
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• 2019

Increasing the aesthetic needs of patients and decreasing the use of amalgam had led to increased demand for dental resin composite. Thereby, light curing unit (LCU) has become an essential equipment in dental clinic. To ensure long-term prognosis of photopolymerized materials, LCU should have a uniform and consistent radiant output and an emission spectrum that includes the active wavelength range of photoinitiators. In addition, when the correct use and thorough maintenance and repair of LCU are performed, the higher success rate of restoration using photopolymerization materials will be achieved.

• Restorative Dentistry and Endodontics
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• v.26 no.5
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• pp.387-392
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• 2001

When cavity floor is near the pulp, polymerization of light-activated restorations results in temperature increase. This temperature increase cause by both the exothermic reaction process and the energy absorbed during irradiation. Therefore instating base is required. Most frequently used insulating base is glass ionmer. The purpose of this study was to evaluate intrapulpal temperature changes of glass ionomer according to various curing intensity and curing time. Caries and restoration-free mandibular molars extracted within three months were prepared Class I cavity of 3$\times$6mm with high speed handpiece. 1mm depth of dentin was evaluated with micrometer in mesial and distal pulp horns. Pulp chambers were filled with 37.0$\pm$0.1$^{\circ}C$ water to CEJ. Chromium-alumina thermocouple was placed in pulp horn for evaluating of temperature changes. glass ionomer material was placed in 2mm. total curing time was 40s: continuous 40s, intermittent 20s, intermittent 10s. Glass ionomer material was cured with 300mW/$\textrm{cm}^2$, 550mW/$\textrm{cm}^2$ light curing unit. The results were as follows : 1. Temperature in pulp increased as curing unit power is increased. 2. Temperature in pulp more increased continuous emission than intermittent emission.

• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.4
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• pp.245-251
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• 2017

Since light curing composite resin was introduced in the 1960s, light curing process has been considered as an essential process. Herein, various light sources became available for the process. Quartz-tungsten-halogen (QTH) light curing units (LCUs) dominated the market until the 1990s, before the LED LCUs started replacing them in the 2000s. The LED, developed approximately 50 years ago, came into use in the dentistry field from the late 1990s, and the LED LCUs, with the 2000s. Since then, the LED LCUs have gone through many advancements to its current fourth generation. In accordance to such advancements of the LED light curing unit, the majority of light curing unit used today are LED LCUs. As much as its usage has increased, it is necessary that dental clinicians understand the characteristics of the device. The objective of this review report is to provide the history of the scientific development and describe the characteristics of the LED LCUs.

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.4
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• pp.623-631
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• 2007

Effect of Soft-start curing on the contraction stress of composite resin restoration polymerized with LED and plasma curing unit The purpose of this study was to evaluate the influence of soft-start light curing on contraction stress and hardness of composite resin. Composite resin (Filtek $Z-250^{TM}$, 3M ESPE, USA) was cured using the one-step continuous curing method with three difference light sources ; conventional halogen light ($XL3000^{TM}$, 3M ESPE, USA) cure for 40 seconds at $400 mw/cm^2$, LED light (Elipar Freelight $2^{TM}$, 3M-ESPE, USA) cure for 20 seconds at $800\;mW/cm^2$ a and plasma arc light ($Flipo^{TM}$, LOKKI, France) cure for 12 seconds at $1300 mW/cm^2$. For the soft-start curing method ; LED light (Elipar Freelight $2^{TM}$, 3M-ESPE, USA) cure exponential increase with 5 seconds followed by 17 seconds at $800\;mW/cm^2$ and plasma arc light ($Flipo^{TM}$, LOKKI, France) cure 2 seconds light exposure at $650\;mW/cm^2$ followed by 11 seconds at $1300\;mW/cm^2$. The strain guage method was used for determination of polymerization contraction. Measurements were recorded at each 2 second for the total of 800 seconds including the periods of light application. Obtained data were analyzed statically using Repeated measures ANOVA, One way ANOVA, and Tukey test. The results of present study can be summarized as follows: 1. Composite resin restoration showed transient expansion just after irradiation of curing light. Contraction stress was increased rapidly at the early phase of polymerization and reduced slowly as time elapsed (P<0.05). 2. Contraction stress was not revealed significant difference between Halogen curing light groups and LED and Plasma Light curing with soft-start group (P>0.05). 3. LED and Plasma Light curing with soft-start showed lower contraction stress than the one-step continuous light curing (P<0.05).

• Restorative Dentistry and Endodontics
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• v.22 no.1
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• pp.254-266
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• 1997

This study was to know the usefulness of argon laser for composite resin, to prove the polymerized effect of heat treatment of composite resin inlay and to get the curing method for optimal physical properties of composite resin inlay. In this study we used four light curing units and one heat curing unit: Visilux $II^{TM}$, a visible light gun: $SPECTRUM^{TM}$, an argon laser: Unilux AC$^{(R)}$ and Astorn XL$^{(R)}$, visible light curing unit: CRC-$100^{TM}$ for heat treatment. Compared to a control group, we divided the experemental groups into five as follows: Control group: Light curing(Visilux $II^{TM}$) Experimental group 1 : Light curing(Visilux $II^{TM}$) + Light curing(Unilux AC$^{(R)}$) Experimental group 2: Light curing(Visilux $II^{TM}$) + Light curing(Astron XL$^{(R)}$) + Heat treatment(CRC-$100^{TM}$) Experimental group 3 : Laser curing($SPECTRUM^{TM}$) Experimental group 4 : Laser curing($SPECTRUM^{TM}$) + Light curing(Unilux AC$^{(R)}$) Experimental group 5 : Laser curing($SPECTRUM^{TM}$) + Light curing(Astron XL$^{(R)}$) + Heat treatment (CRC-$100^{TM}$) According to the above classification, we made samples through the curing of Clearfil CR Inlay$^{(R)}$, which is a composite resin for inlay, in a separable cylindrical metal mold and polycarbonate plate. And then, we measured and compared the value of compressive strength, diametral tensile strength and the surface micro hardness of each sample. The results were as follows : 1. Among the experimental groups, group 5 showed the highest value of compressive strength, $157.50{\pm}10.24$ kgf and control group showed the lowest value of compressive strength, $103.93{\pm}21.93$ kgf. Control group showed significant difference with the experimental groups(p<0.001). Group 2 which was treated by the heat showed higher compressive strength than that of group 1 which was not, and there was significant difference between group 1 and group 2(p<0.001). Group 5 which was treated by heat showed higher compressive strength than group 4 which was not, and there was significant difference group 4 and group 5(p<0.001). 2. Among the experimental groups, group 5 showed the highest value of diametral tensile strength, $95.84{\pm}1.97$ kgf and control group showed the lowest value of diametral tensile strength, $81.80{\pm}2.17$ kgf. Control group which was cured by visible light showed higher diametral tensile strength than group 3 which was cured Argon Laser. Group 2 which was treated by heat showed higher compressive strength than that of group 1 which was not, and there was significant difference between group 1 and group 2(p<0.001). Group 5 which was treated by heat showed higher compressive strength than group 4 which was not, and there was a significant difference group 4 and group 5(p<0.001). 3. Among the experimental groups, group 5 showed the highest value of microhardness of top surface, $148.42{\pm}9.57$ kgf and control group showed the lowest value of microhardness, $111.43{\pm}7.63$ kgf. In the case of bottom surface, group 5 showed the highest value of $146.19{\pm}7.62$ kgf, and control group showed the lowest, $104.03{\pm}11.05$ kgf. Group 3 which was cured by Argon Laser showed higher diametral tensile strength than control group which was cured only with a visible light gun. Group 2 which was treated by heat showed higher compressive strength than that of group 1 which was not, and there was a significant difference between group 1 and group 2(p<0.001). Group 5 which was treated by heat showed higher compressive strength than group 4 which was not, and there was a significant difference group 4 and group 5(p<0.001). 4. According to the above results, we took a conclusion that argon laser can be used as a useful unit for curing the composite resin and heat treatment can improve the physical properties of the composite resin inlay.

• Journal of the korean academy of Pediatric Dentistry
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• v.41 no.2
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• pp.152-156
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• 2014

The purpose of this study is to compare efficiency of broad spectrum LEDs ($VALO^{(R)}$, Ultradent, USA) with conventional LED curing lights ($Elipar^{TM}$ Freelight 2, 3M ESPE, USA) using a microhardness test. The light curing units used were $VALO^{(R)}$ in three different modes and $Elipar^{TM}$ Freelight 2. The exposure time was used according to the manufacturer's instructions. After cured resin specimens were stored in physiological saline at $37^{\circ}C$ for 24 hours, microhardness was measured using Vickers microhardness tester. The microhardness of upper and lower sides of the specimens were analyzed separately by the ANOVA method (Analysis of Variance) with a significance level set at 5%. At upper side of resin specimens, an increased microhardness was observed in the broad spectrum LED curing light unit with a high power mode for 4 seconds and plasma emulation mode for 20 seconds (p < 0.05). However, at the lower side of resin specimens, there were no significant differences in microhardness between broad spectrum LED curing light unit and conventional LED curing light unit.

• Restorative Dentistry and Endodontics
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• v.14 no.1
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• pp.149-159
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• 1989

The purpose of this study was to assess the effects of wavelength and intensity of light curing units on the curing of composite resin. The wavelength and intensity of nine units were evaluated with Optical Multichannel Analyzer and Radiometer. Two-part split stainless steel mold with a cylindrical hole-3.0mm in diameter, 6.0mm in hgieht-was prepared. After placing a Mylar strip between two parts, 100 specimens were made by inserting each of four composite resins into the mold and irradiating for 20 seconds with five light units alternatively. The curing depths were measured by scraping method and evaluated by two-way ANOVA. And Vicker's hardness measurements were made on the longitudinally sectioned surface at 0.5mm interval. The results were as follows: 1. Visilux 2 showed a narrow spectral band within the effective wavelength in initiating polymerization and the highest intensity. Translux showed the diffuse spectrum of wavelength and the lower light intensity. 2. Visilux 2 showed the highest curing effect in any composite resin and then followed by Optilux, Efos 35, Heliomat and Translux. (p < 0.01) 3. Durafill showed the deepest curing depth in any light unit and then followed by Bisfil M, Silux and Heliosit. (p < 0.01). 4. Maximum hardness values showed 0.1mm and 0.5mm under top surface and then gradually decreased with depth.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.2
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• pp.245-253
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• 2003

The degree of conversion of cross-linked polymer has great importance in determining the physical and mechanical properties, and biocompatibility. Therefore, this study examined the comparison of light-cured composite resin polymerization of various light-curing systems composed of plasma arc, halogen, LED curing units and pluse-delay curing with FTIR. From this experiment, The following results were obtained : 1. From FTIR, the degree of conversion(DC) of composite resin was 34.52-49.31%, DC of composite resin used in Flipo was $39.36{\pm}1.22%$, CrediII $45.64{\pm}1.34%$, XL3000 $43.48{\pm}1.34%$, VIP(mode 4) $44.31{\pm}0.72%$, LUXOMAX $49.31{\pm}2.37%$, Elipar Freelight $44.51{\pm}0.62%$ and $34.52{\pm}0.85%$ in pulse-delay curing. 2. The degree of conversion of composite resin in each light-curing unit was highest DC of the LUXOMAX system, lowest DC of the pulse-delay curing. 3. Compared with other curing system, Flipo, LUXOMAX, and pulse-delay curing were significant difference(p<0.05). 4. In same curing method group, the differences of each light-curing unit were no significace in halogen(conventional) curing method(p>0.05), but significance in plasma arc curing and LED curing method(p<0.05).