• Restorative Dentistry and Endodontics
• /
• v.35 no.5
• /
• pp.353-358
• /
• 2010

Objectives: The purpose of this study was to measure the power density of light curing units transmitted through resin inlays fabricated with direct composite (Filtek Z350, Filtek Supreme XT) and indirect composite (Sinfony). Materials and Methods: A3 shade of Z350, A3B and A3E shades of Supreme XT, and A3, E3, and T1 shades of Sinfony were used to fabricate the resin inlays in 1.5 mm thickness. The power density of a halogen light curing unit (Optilux 360) and an LED light curing unit (Elipar S10) through the fabricated resin inlays was measured with a hand held dental radiometer (Cure Rite). To investigate the effect of each composite layer consisting the resin inlays on light transmission, resin specimens of each shade were fabricated in 0.5 mm thickness and power density was measured through the resin specimens. Results: The power density through the resin inlays was lowest with the Z350 A3, followed by Supreme XT A3B and A3E. The power density was highest with Sinfony A3, E3, and T1 (p < 0.05). The power density through 0.5 mm thick resin specimens was lowest with dentin shades, Sinfony A3, Z350 A3, Supreme XT A3B, followed by enamel shades, Supreme XT A3E and Sinfony E3. The power density was highest with translucent shade, Sinfony T1 (p < 0.05). Conclusions: Using indirect lab composites with dentin, enamel, and translucent shades rather than direct composites with one or two shades could be advantageous in transmitting curing lights through resin inlays.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.34 no.1
• /
• pp.62-72
• /
• 2007

The purpose of present study was to determine whether different kinds of curing lights can alter microtensile bond strength(MTBS) of class I cavity pulpal and axial wall specimens in primary molar. Thirty clean mandibular 2nd primary molar's occlusal enamel were removed and class I cavity, size of $2{\times}4{\times}2mm$ was prepared. Dentin bonding agent was applied according to manufacturer's manual. Each group was cured with Halogen Curing Unit, Plasma Curing Unit and LED Curing Unit. Composite resin was bulk filled and photo cured with same curing unit. MTBS specimens which size is $0.7{\times}0.7{\times}4mm$ were prepared with low speed saw. Specimens were coded by their curing lights and wall positions (Halogen - Axial wall group, Halogen - Pulpal wall group, Plasma - Axial wall group, Plasma - Pulpal wall group, LED - Axial wall group, LED - Pulpal walt group). MTBS were tested at 1 mm/min cross Head speed by Universal Testing Machine. Fractured surface and bonding surface was observed with SEM. T-test between axial and pulpal specimens in each curing lights, one-way ANOVA among different curing light specimens in each wall positions were done. Weibull distribution analysis was done. The results were as follows : Mean MTBS of pulpal wall specimens were significantly greater than that of axial wall specimens at each curing units(p<.05). There was no significant difference in the MTBS among three curing units at axial wall and pulpal wall. In Weibull distribution, pulpal wall specimens were more homogeneous than axial wall specimens.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.35 no.1
• /
• pp.18-29
• /
• 2008

The purpose of this study was to compare the polymerization shrinkage of several filling methods using strain gauges. In this study, a light-emitting diode(LED) curing unit(Elipar Freeligh2, 3M EPSE, USA) and plasma arc lamp(PAL) curing unit(Flipo, LOKKI, France) were used for curing, Filtek $Z350^{TM}$(3M EPSE, USA) composite resin was used for the cavity filling. Sixty permanent bicuspid teeth, that were extracted for orthodontic treatment, were studied. The cavities were prepared on the occlusal surface and were filled using the following methods : 1) bulk filling, 2) parallel filling, 3) oblique filling The strain was recorded on the buccal, lingual, mesial and distal surfaces and the strain values were computed into stress values. The shear bond strength of each filling method was tested using a Micro Universal Testing machine. The results can be summarized as follows: 1. In the strain changes, all LED and PAL curing groups showed an increase on the buccal surface and a slow decrease as time elapsed. 2. In the strain changes of the mesial and distal surfaces, the decreases and increases were shown repeatedly and reduced as time elapsed. 3. There were no significant statistical strain changes among filling methods in the LED or PAL curing groups. 4. There were significant statistical strain changes between the LED and PAL curing groups on the buccal surface(p<0.05). 5. From the shear bond strength results, in the LED curing group, filling method 3 showed lower surface stress than filling method 1 and 2(p<0.05). In the PAL curing group, there were no significant statistical strain changes between each filling method. 6. The surface stress of each group was lower than the shear bond strength.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.32 no.4
• /
• pp.634-643
• /
• 2005

The aim of this study is to evaluate the effects of blue light emitting diode (LED) Light Curing Units (FreeLight 2, L.E.Demetron I, Ultra-Lume 5) on the microhardness of three resin composites (Z250, Point 4, Dyract AP) and to determine their optimal curing time. Samples were made using acrylic molds $(2.0mm{\times}3mm)$ of each composite. All samples were prepared over a Mylar strip placed on a flat glass surface. After composite placement on the molds, the top surface was covered with another Mylar strip and a glass slab was gently pressed over it. The times of irradiation were as follows: Elipar TriLight, 40 s; Elipar FreeLight 2. L.E.Demetron I, and Ultra-Lume 5, 10s, 20s, 40s, respectively. Mean hardness values were calculated at the top and bottom for each group. ANOVA and Sheffe's test were used to evaluate the statistical significance of the results. Results showed that FreeLight 2, Ultra-Lume 5, and L.E.Demetron I were able to polymerize point 4 in 20 seconds to a degree equal to that of the halogen control at 40 seconds. FreeLight 2 and L.E.Demetron I were able to polymerize Z250 in 10 seconds to a degree equal to that of the halogen control at 20 seconds. FreeLight 2 and L.E.Demetron I were able to polymerize Dyract AP in 10 seconds to a degree equal to that of the halogen control at 40 seconds. The commercially available LED curing lights used in this study showed an adequate microhardness with less than half of the exposure time of a halogen curing unit.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.30 no.3
• /
• pp.431-438
• /
• 2003

This study investigates pulp chamber temperature rise during composite resin polymerization by plasma arc(Group III : Flipo 3 sec, Group IV : Flipo 5 sec) and LED curing units(Group V : Lux-O-Max, 40 sec) as well as conventional halogen lamp curing units(Group I : VIP mode3, 20 sec, Group II : VIP mode6, 20 sec). The results are as follows : 1. All of the investigated pulp chamber temperature rises are lower than the boundary temperature could result in irreversible damage to the pulpal tissue ($5.5^{\circ}C$). 2. In the group II, it is found the significantly higher pulp chamber temperature rise than any other groups(p<0.05). 3. In the group of composite resin light-cured with VIP, it is found the significantly higher pulp chamber temperature rise in the group II than group I(p<0.05). 4. In the group of composite resin light-cured with Flipo, it is found the significantly higher pulp chamber temperature rise in the group IV than group III (p<0.05). 5. In the case of comparing VIP and Flipo, group II is significantly higher pulp chamber temperature rise than group III, IV(p<0.05), and group IV is significantly higher pulp chamber temperature rise than group I(p<0.05), and it does not significantly differ between group I and III. 6. In the group of composite resin light-cured with Lux-O-Max, it is found the significantly lower pulp chamber temperature rise than any other groups (p<0.05).

• Restorative Dentistry and Endodontics
• /
• v.35 no.2
• /
• pp.125-133
• /
• 2010

Objectives: Rapid polymerization of overlying composite resin causes high polymerization shrinkage stress at the adhesive layer. In order to alleviate the shrinkage stress, increasing the light intensity over the first 5 seconds was suggested as an exponential curing mode by an LED light curing unit (Elipar FreeLight2, 3M ESPE). In this study, the effectiveness of the exponential curing mode on reducing stress was evaluated with measuring microtensile bond strength of three adhesives after the overlying composite resin was polymerized with either continuous or exponential curing mode. Methods: Scotchbond Multipurpose Plus (MP, 3M ESPE), Single Bond 2 (SB, 3M ESPE), and Adper Prompt (AP, 3M ESPE) were applied onto the flat occlusal dentin of extracted human molar. The overlying hybrid composite (Denfil, Vericom, Korea) was cured under one of two exposing modes of the curing unit. At 48h from bonding, microtensile bond strength was measured at a crosshead speed of 1.0 mm/min. The fractured surfaces were observed under FE-SEM. Results: There was no statistically significant difference in the microtensile bond strengths of each adhesive between curing methods (Two-way ANOVA, p > 0.05). The microtensile bond strengths of MP and SB were significantly higher than that of AP (p < 0.05). Mixed failures were observed in most of the fractured surfaces, and differences in the failure mode were not observed among groups. Conclusion: The exponential curing method had no beneficial effect on the microtensile dentin bond strengths of three adhesives compared to continuous curing method.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.33 no.4
• /
• pp.615-623
• /
• 2006

The purpose of this study was to evaluate the specificity, sensitivity, and diagnostic power of caries activity test using LED fluorescence. The subjects of this study were 55 children of $6{\sim}7$ years old. LED light were irradiated to labial or buccal surface of all teeth. Fluorescence from initial carious lesion of teeth illuminated by an LED light was observed through barrier filter and the number of teeth showing lesion, size and position of lesion were counted. Streptococcus mutans colony counting and dDfFtT rate test were also done and their correlation was compared. And then specificity, sensitivity, diagnostic power of optical caries activity test using LED light were evaluated. 1. There was positive $correlation({\gamma}=0.43)$ between LED fluorescence test and Streptococcus mutans count(P<0.05). 2. When visual examination was defined to standard testing method, the specificity, sensitivity, diagnostic power of LED fluorescence test were 100%, 76.1%, and 100%. 3. When dDfFtT rate was defined to standard testing method, the specificity, sensitivity, diagnostic power of LED fluorescence test were 88.9%, 47.8%, and 95.7%. 4. When S. mutans colony counting was defined to standard testing method, the specificity, sensitivity, diagnostic power of LED fluorescence test were 100%, 58.7%, and 100%. Considering the above results, optical caries activity test using LED light could be regarded as a practical method because of its close relationship with microbiological caries activity test.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.33 no.3
• /
• pp.438-446
• /
• 2006

The purpose of this study was to evaluate the microleakage of composite resin($Z250^{(R)}$) and compomer(Dyract AP) cured with various curing lights(Elipar $TriLight^{(R)}$, $Flipo^{(R)}$, and Elipar FreeLight $2^{(R)}$). Box-shaped class V cavities were prepared on the buccal and lingual surfaces of extracted human third molars. The sectioned specimens were evaluated for dye penetration and following results were obtained. 1. Regarding microleakage in the enamel margin with different curing light sources, there was no significant difference in Dyract AP whereas $Z250^{(R)}$ with $Flipo^{(R)}$ showed higher microleakage score than those of FreeLight $2^{(R)}$ or $TriLight^{(R)}$(p<0.05). 2. Regarding microleakage in the dentin margin with curing light sources, there were no significant differences in both Dyract AP and $Z250^{(R)}$(p>0.05). 3. Regarding microleakage in the enamel margin with filling materials. there were no significant differences in both filling materials with $Flipo^{(R)}$ whereas $Z250^{(R)}$ showed less microleakage than Dyract AP with FreeLight $2^{(R)}$ or $TriLight^{(R)}$ (p<0.05). 4. Regarding microleakage in the dentin margin with filling materials, there wer no significant differences in both filling materials with $TriLight^{(R)}$ whereas $Z250^{(R)}$ showed less microleakage than Dyract AP with FreeLight $2^{(R)}$ or $Flipo^{(R)}$ (p<0.05). 5. Enamel margin showed less microleakage than dentin margin when filled with Dyract AP and cured with $Flipo^{(R)}$ or FreeLight $2^{(R)}$ (p<0.05), but there were no statistically significant differences between the enamel and the dentin in the rest groups. This study suggested that $Z250^{(R)}$ showed lower microleakage score than Dyract AP. and that $Flipo^{(R)}$ showed higher microleakage score than FreeLight $2^{(R)}$ and $TriLight^{(R)}$ in the enamel margin filled with $Z250^{(R)}$.

• Polymer(Korea)
• /
• v.31 no.2
• /
• pp.117-122
• /
• 2007

In this work, the mechanical and electrical properties, and thermal stability of vapor-grown carbon nanofibers/polyimide (VGCNFs/PI) composite film synthesized by in-situ polymerization were investigated in terms of tensile properties, volume resistivity and thermogravimetric analysis (TGA), respectively. From the results, the addition of VGCNFs with a certain amount into polyimide led to obvious improvement in tensile strength. The volume resistivity of the films was decreased with increasing the VGCNFs content and the electrical percolation threshold appeared between 1 and 3 wt% of VGCNFs content, which was probably caused by the formation of interconnective structures among the VGCNFs in a composite system. The thermal stability of the film was higher than that of pure PI one. This result indicated that the crosslinking of VGCNFs/PI Composites was enhanced by well-distribution of YGCNFs in PI resin, resulting in the increase of the thermal stability of the resulting composites.

• Applied Chemistry for Engineering
• /
• v.21 no.4
• /
• pp.396-400
• /
• 2010

In this work, the adsorption behaviors of activated carbons (ACs) containing chelating functional groups were studied in $CO_2$ removal. The ACs were modified by pyrolysis of peroxide and glycidyl methacrylate graft polymerization in order to induce chelating functional groups, such as diethylenetriamine groups on the AC surfaces. The surface functional groups of the ACs were characterized by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The textural properties of the ACs were analyzed by $N_2$/77 K isotherms. Adsorption behaviors of the ACs were observed in the amounts of $CO_2$ adsorption. From the results, we found that the chelating functional groups on the AC surfaces led to enhance selectivity and chemisorption on $CO_2$ adsorption in spite of decreasing the physical adsorption properties.