• Restorative Dentistry and Endodontics
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• v.20 no.1
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• pp.129-141
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• 1995

Composite resin and glass-ionomer cement can be used for the purpose of repair of defective amalgam restoration. The purpose of this study was to evaluate of shear bond strength of esthetic restorative materials to dental amalgam. The materials used in this study were Photo Clearfil Bright(light curing composite resin), Clearfil F II(chemical curing composite resin), Fuji II LC(light curing glass-ionomer cement), Fuji II (chemical curing glass-ionomer cement), All-Bond 2(intermediary), and Scotchbond Multi-Purpose (intermediary). A total of 120 acrylic cylinders with amalgam were divided into 8 groups After amalgam condensation, all specimens were stored for 48 hours in water at $37^{\circ}C$ and tested with Instron universal testing machine between amalgam and composite resins and glass-ionomer cements. The data were analyzes statiscally by ANOVA and Duncan test. The following results obtained ; 1. The shear bond strength of bonded composite resin to amalgam was higher than bonded glass-ionomer cement(P<.001). 2. The group 4 had highest shear bond strength with 15.45kgf/$cm^2$ and the group 5 had lowest shear bond strenght with 3.26kgf/$cm^2$(P<.001). 3. In the group 3, 4, 5, 6, the group 3, 4 with All-Bond 2 had higher shear bond strength than the group 5, 6 with Scotch bond MP both in light-curing and in chemical curing. 4. Both in composite resin and glass-ionomer cement, chemical curing materials had higher shear bond stength than light curing materials(P<.001).

• 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).

• Restorative Dentistry and Endodontics
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• v.21 no.1
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• pp.360-365
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• 1996

The purpose of this study was to evaluate the changes in the degree of conversion on a composite resin surface following heat treatment and mylar strip finishing. The effects of the time interval between the light-curing and heat-curing process were also evaluated. The composite resin surface which had been covered with a coverglass showed a lower conversion rate than the surface from which a layer of $500{\mu}m$ was ground away. The composite resin surface was definitely affected by oxygen during the heat curing process when it had not been insulated. When the composite resins were heat cured after 3 days of storage following the light curing process, the increased in the degree of conversion through heatcuring was limited.

• Restorative Dentistry and Endodontics
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• v.20 no.2
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• pp.487-507
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• 1995

Composite resin repair requires strong bond strength between the new and old materials. The objective of the current study was to identify the optimal treatments for sufficient bond strengths. Bondings between same kinds of materials and cross bondings using chemical curing composites and light curing composites were tested. Surface treatments included the methods of sand-blasting, acid etching and coating of bonding agent. Seven kinds cases of combinations from three kinds of methods were experimented and compared with a control group of which surfaces were highly polished. Measurements of shear bond strength and observations of surface morphologic changes using a scanning electron microscope were done. Following conclusions were drawn : 1. The highest bond strength among composite resins were exhibited by the treatment of the sand-blasting and the coating of bonding agent. 2. Acid etched surfaces showed the lowest bond strength. Bond strengths obtained from experimental groups including acid etching were lower than those obtained from same kinds of experimental groups without acid etching. 3. Simple method of the coating of bonding agent produced the slightly increased bond strength on chemical curing composite and reduced bond strength on light curing composite. 4. Bonding surfaces of chemical curing composite resin showed slightly higher bond strengths than light curing composite resin, however significant differences were not confirmed statistically. 5. More significant irregular surfaces were created by sand-blasting method than acid etching method. 6. A principal component of fillers of both resins was silicon. Acid etching method produced the seperations and degradations of fillers, these were significant on light curing composite resins which containing barium fillers.

• Journal of Technologic Dentistry
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• v.29 no.2
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• pp.9-15
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• 2007

As the development of nanotechnology, the use of composite resins which containing nanofillers becomes popular. The purpose of this study was to test the degree of polymerization of nanofillercontaining composite resins. For the study, three different nanofiller-containing composite resins and two different light-curing units were used. To evaluate the degree of polymerization, the maximum polymerization shrinkage taking place during the light curing, and the microhardness, after the light curing, were measured. As results, two light-curing units exhibited a similar emission spectrum to that of the included photoinitiator, camphorquinone. The only difference between the light-curing units were the width of the emission spectrum. Three different composite resins showed different microhardness values. Among them, Grandio showed the greatest microhardness value. However, there was less microhardness difference on the top and bottom surfaces due to the difference of the light-curing units. The maximum polymerization shrinkage values were also similar in the tested specimens regardless of the difference of the light-curing units. However, Grandio showed the least polymerization shrinkage. According to the manufacturers' data, Grandio showed the highest filler content(vol%).

• Restorative Dentistry and Endodontics
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• v.16 no.1
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• pp.158-166
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• 1991

In order to investigate the cytotoxicity of composite resin in vitro, BALB / C mouse fibroblast were cultured in MEM in which silux, P-50, microrest, clearfil, amalgam and glass - ionomer, in shape of $2{\times}9mm$ circular disk. The experiments were- performed by cell count on 4 hours, 1, 3, 6 days and the composite resin groups, amalgam, glass - ionomer were compared. 1. On the sixth day, the cellular number of resin composite groups were remarkedly reduced, in contrast, the that of amalgam and glass - ionomer group continuously increased. 2. It was only on the 4 hours that the cellular number contained in amalgam were reduced, but increased thereafter, and the cellular number contained in glass - ionomer are greater than other groups. 3. In resin group, especially between self - curing resin and light - curing resin, there is no difference in cellular number statistically (p>0.05). 4. It was amalgam where the round cell without cellular process was found on the 4. hours and on the 6 th day the cell without cellular process was found numeroulsy in resin group whereas in amalgam and glass - ionomer, like control group was contained cell forming monolayer. These result suggested that the toxicity of the self - curing and light - curing resin greater than that of the amalgam and glass - ionomer.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.4
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• pp.593-599
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• 2003

The purposes of this study were to evaluate the microleakage of class V composite resin restorations utilizing the different curing lights, to assess the flowable resin, $Filtek^{TM}Flow$(3M Dental Products, USA) and composite resin, $Filtek^{TM}Z250$(3M Dental Products, USA) which need 20s curing time for halogen light could replace $Z100^{TM}$ Restorative(3M Dental Products, USA) for the microleakage, and to evaluate the effect of adhesive resin on marginal microleakage. Light curing units used in this study were conventional halogen light, XL3000(3M Dental Products, USA) and plasma arc light, Flipo(Lokki, France). Class V cavities were prepared and each cavity was filled with each composite resin. After being filled, the teeth were stored in distilled water, polished, thermocycled and soaked in 1% methylene blue solution. Following results were obtained from evaluation of the sectioned surface. 1. There was no statistically significant difference in microleakage of $Filtek^{TM}Flow$ and $Filk^{TM}Z250$ between two kinds of curing units(p>0.05). 2. Flowable resin, $Filtek^{TM}Flow$ showed more microleakage than Z100 and $Filtek^{TM}Z250$ regardless of curing units(p<0.05). 3. Adhesive resin reduced the microleakage of composite resin in both halogen light and plasma arc light(p<0.05).

• Journal of the korean academy of Pediatric Dentistry
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• v.25 no.4
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• pp.731-748
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• 1998

The purpose of this study was to test the hypothesis that the more thorough cure of lightactivated composite resin could be obtained if a new way of delivering the light source deep through the resin body is developed when compared to the conventional bulk cure or incremental cure. Using cylindrical resin blocks and natural teeth, various curing conditions were tested for their effects on the degree of microleakage and microhardness. Data were analyzed statistically using One-Way ANOVA and Scheff's Multiple Range test. The results of the present study were as follows: 1. The increment of reduction in microhardness with depth was shown to be higher in group I and II than in group II and V. 2. At the level of lower inner surface and the bottom surface, significantly lower microhardness values were obtained in group I and II when compared to group III, IV and V. Group IV showed the lowest value among three groups(III, IV, V) representing the only statistically significant difference from group V(p<05). 3. Differences between groups in the degree of microleakage detected were shown to be statistically significant (p<05) with the exception of group IV and V at both occlusal and gingival margins. 4. Based upon the above-mentioned results, commonly cited recommendation of incremental curing is strongly supported and the light-transmitting wedge insertion method can be considered as a effective and feasible clinical procedure for the better curing of composite resin. However, more studies under a variety of conditions should be completed before this method is applied actually to the clinical setting.

• 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).

• Restorative Dentistry and Endodontics
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• v.29 no.1
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• pp.58-67
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• 2004

The objectives of this study was to evaluate current visible light curing units regarding microhardness and microleakage. Fourty samples of composite resin(Z-250, 3M) were cured by different light curing units (Flipo, LOKKI; Credi II, 3M; XL 3000, 3M: Optilux 500, Demetron) in acrylic blocks. Microhardness was measured using a calibrated Vickers indenter on both top and bottom surfaces after 24 hours of storage in air at room temperature. Class V cavities were prepared on buccal and lingual surfaces of fourty extracted human molars. Each margin was on enamel and dentin/cementum. Composite resin(Z-250, 3M) was filled in cavities and cured by four different light curing units (Flipo, LOKKl; Credi II, 3M; XL 3000, 3M: Optilux 500, Demetron). The results of this syudy were as follows: Microhardness 1. Flipo showed low microhardness compared to Optilux 500, Credi II significantly in upper surface. Flipo didn't show a significant difference compared to XL 3000. 2. The microhardness resulting from curing with Flipo was lower than that of others on lower surfaces. Microleakage 1. Dentin margin showed significantly high dye penetration rate than enamel margin in all groups(p<0.05). 2. No significant differences were found on both enamel and dentin margin regarding curing units.