• Journal of the korean academy of Pediatric Dentistry
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• v.46 no.1
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• pp.1-9
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• 2019

The aim of this study was to compare the degree of conversion and polymerization shrinkage of low and high viscosity bulk-fill giomer-based and resin-based composites. Two bulk-fill giomer (Beautifil Bulk Restorative (BBR), Beautifil Bulk Flowable (BBF)), two bulk-fill (Tetric N-Ceram Bulk-fill (TBF), SureFil SDR flow (SDR)) and two conventional resin composites (Tetric N-Ceram (TN), Tetric N-flow (TF)) were selected for this study. The degree of conversion was measured by using Fourier transform infrared spectroscopy. Polymerization shrinkage was measured with the linometer. For all depth, BBR had the lowest degree of conversion and SDR had the highest. At 4 mm, the degree of conversion of low and high viscosity bulk-fill giomer resin composites was lower than that of bulk-fill resin composites (p < 0.05). At the depth between 2 mm and 4 mm, there were significant difference with TBF, TN and TF (p < 0.05), while no significant difference in the degree of conversion was measured for BBR, BBF and SDR. Polymerization shrinkage of six resin composites decreased in the following order: TF > SDR > BBF > TBF > TN and BBR (p < 0.05). Polymerization shrinkage of bulk-fill giomer resin composites was lower than that of bulk-fill resin composites (p < 0.05). From this study, it is found that the bulk-fill giomer resin composites and TBF were not sufficiently cured in 4 mm depth. The degree of conversion of low and high viscosity bulk-fill giomer resin composites was significantly lower than bulk-fill resin composites in both 2 mm and 4 mm depths. Therefore, such features of bulk-fill giomer resin composites should be carefully considered in clinical application.

• Journal of the korean academy of Pediatric Dentistry
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• v.43 no.4
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• pp.365-373
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• 2016

Composites are the most useful restorative material. However, composites have some disadvantages such as polymerization shrinkage, long working time, and susceptibility to water and contamination, which are stood out more especially when treating children. To solve these problems, bulk-fill composites have been developed. The aim of this study is to compare mechanical properties of bulk-fill and conventional composites. Bulk-fill composites (SureFil SDR flow (SDR), Tetric N-Ceram bulk fill (TBF)) and conventional composites (Filtek Z-350 (Z-350), Unifil Flow (UF), Unifil Loflo Plus (UL)) were used. The Vickers hardness tester was used to measure the microhardness of materials, and Fourier transform infrared spectroscopy was used to measure the degree of conversion. Polymerization shrinkage was measured by using a linometer. Flexural and compressive properties were measured by using the universal testing machine. Data were statistically analyzed by ANOVA and Scheffe's post hoc test. The level of significance was set to p < 0.05. Most conventional composites showed higher microhardness than bulk-fill composites. However, bulk-fill composites showed a higher top/bottom microhardness ratio than conventional composites. Bulk-fill composites showed a higher top/bottom degree of conversion ratio than conventional composites. The polymerization shrinkage was highest in UL and lowest in Z-350. The polymerization shrinkage of flowable composites was higher than that of non flowable composites. The compressive properties were highest in Z-350 and lowest in SDR and UL. In terms of flexural properties, Z-350 was the highest. However, none of the bulk-fill composites exhibited mechanical properties as good as those of conventional composites. Nonetheless, the ratio of microhardness and degree of conversion, which are important properties of bulk filling, were higher in bulk-fill composites. Therefore, the bulk-fill composites might be considered suitable restorative materials in pediatric dentistry.

• Journal of the korean academy of Pediatric Dentistry
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• v.42 no.4
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• pp.281-290
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• 2015

The aim of this study was to evaluate shear bond strength (SBS) of bulk-fill resin composites (RCs) to dentin and their micro-leakage. One high-viscosity bulk-fill RC and 2 low-viscosity bulk-fill RCs were compared with 1 conventional RC. 7thgenerationbondingagentswereused. In order to evaluate SBS values, 40 permanent molars were selected and divided into 4 groups. The bulk-fill RCs were applied in 4 mm thickness, whereas the conventional RC was applied in 2 mm thickness. In order to evaluate micro-leakage, class I cavities ($5{\times}2{\times}4mm$) were prepared in 32 permanent molars. The teeth were divided into 4 groups and restored with resin composites in an increment of 4 mm for the bulk-fill RC and in 2 horizontal increments of 2 mm for the conventional RC. The mean SBS value of conventional RC showed no statistically significant difference when compared with those of low-viscosity bulk-fill RCs. However, the mean SBS value of high-viscosity bulk-fill RC was significantly lower than that of conventional RC (p < 0.05). There were no statistically significant differences in micro-leakage between the 4 groups. For SBS and micro-leakage, the use of low-viscosity bulk-fill RCs might help clinicians simplify the procedure.

• Journal of the korean academy of Pediatric Dentistry
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• v.46 no.4
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• pp.353-361
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• 2019

The aim of this study was to evaluate the color stability of bulk-fill and conventional resin composites with respect to different storage media and thickness of composites. Filtek™ Z250 and Filtek™ Z350XT were evaluated as conventional resin composites. Filtek™ Bulk-fill Posterior Restorative and Tetric^® N-Ceram Bulk Fill were evaluated as bulk-fill resin composites. CIE L^*a^*b^* values of baseline were measured after 24 hours of storage in distilled water, and each resin composite group was divided into three subgroups and stored in distilled water, red wine, and coffee media respectively. Again after 1, 7 and 28 days of immersion, color changes (ΔE^*) were calculated using the CIE L^*a^*b^* values. The greatest ΔE^* was observed in red wine for all resin composites, and the mean color changes were ranked in the increasing order of distilled water, coffee, red wine. Filtek™ Z350XT exhibited the greatest color change in all media, followed by Filtek™ Bulk-fill Posterior Restorative. Filtek™ Z250 and Tetric^® N-Ceram Bulk Fill followed with similar mean color change values. According to the 2 different thicknesses of 2 mm and 4 mm of bulk-fill resin composites, there was no thickness-related difference on color changes.

• Journal of the korean academy of Pediatric Dentistry
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• v.44 no.4
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• pp.446-454
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• 2017

Recently, there have been many studies on bulk-fill resin composites. However, studies on the proper materials for pediatric patients are rare. The aim of this study was to compare the cavity wall adaptation of bulk-fill resin composites with conventional resin composite in class II cavities of primary molars using microcomputed tomography (micro-CT). Standardized class II slot cavities were prepared in 80 exfoliated primary molars and randomly divided into 4 groups. The control group was restored with conventional resin composite, Filtek Z-350 XT (FZ), and the three groups were restored with bulk-fill resin composites, Filtek bulk-fill posterior (FB), Tetric N-Ceram Bulk Fill (TNC), Filtek bulk-fill flowable (FBF). All specimens were thermocycled and then immersed in 50% silver nitrate ($AgNO_3$) solution. Micro-CT was used to measure the penetration volume of the total silver nitrate and the degree of cervical marginal leakage and the number, size, and position of the voids were evaluated. The results revealed that the volume of silver nitrate were significantly different between FB and FZ (p < 0.05). The results also revealed that the penetration length of silver nitrate FBF showed statistically lower than the FZ and FB (p < 0.05). There was no significant difference between the groups in number and size of voids. In conventional resin composite, most of the voids were present inside the restoration (83.3%), but the voids in the bulk-fill resin composites incidence were higher in the gingivoaxial angle. The cavity wall adaptation demonstrated in class II restorations of primary molar by new bulk fill resin composites was similar to conventional incremental technique. Bulk-fill resin composites might be an clinical option for a faster restoration in deciduous teeth.

• Journal of Dental Rehabilitation and Applied Science
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• v.32 no.3
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• pp.184-193
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• 2016

Purpose: To evaluate marginal leakage of bulk fill flowable composite resin filling with different curing time by using microcomputed tomography technology. Materials and Methods: 30 previously extracted human molars were randomly divided into 6 groups based upon restorative system and different curing time. Class II cavities (vertical slot cavities) were prepared. An individual metallic matrix was used to build up the proximal wall. The SonicFill or SureFil SDR flow was inserted into the preparation by using 1 bulk increment, followed by light polymerization for different curing times. The different exposure times were 20, 40, and 60 seconds. All specimens were submitted to 5,000 thermal cycles for artificial aging. Micro-CT scanning was performed by using SkyScan 1272. One evaluator assessed microleakage of silver nitrated solution at the resin-dentin interface. The 3D image of each leakage around the restoration was reconstructed with CT-Analyser V.1.14.4. The leakage was analyzed with the Mann-Whitney test. Results: Significant differences were observed between the light curing times, but no significant differences were found between the bulk fill composite resins. Increasing in the photoactivation time resulted in greater microleakage in all the experimental groups. Those subjected to 60 seconds of light curing showed higher microleakage means than those exposed for 20 seconds and 40 seconds. Conclusion: Increasing the photoactivation time is factor that may increase marginal microlekage of the bulk fill composite resins. Further, micro-CT can nondestructively detect leakage around the resin composite restoration in three dimensions.

• Journal of Dental Rehabilitation and Applied Science
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• v.31 no.4
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• pp.294-300
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• 2015

Purpose: The purpose of this study was to measure the color of low viscosity bulk-fill resin with a capping layer and to compare it with the color of microhybrid composite resin. Materials and Methods: A low viscosity bulk-fill resin (SDR) and microhybrid composite resin of shade A2 (A2) or A3 (A3) were fabricated to 4 mm thickness and light cured for 20 seconds. CIE $L^*a^*b^*$ values of the resin specimens were measured with a colorimeter. Then shade A2 and A3 microhybrid composite resin was capped over low viscosity bulk-fill resins in 2 mm thickness (SA2, SA3). The resin specimens were light cured for 20 seconds and the color was measured and analyzed (n = 10). Color differences (${\Delta}E$) between SA2 and A2, SA3 and A3 were also calculated. Results: $L^*$ value was highest in SDR followed by SA2 and SA3. $L^*$ value of A2 and A3 was the lowest. $a^*$ value was lowest in SDR followed by SA2 and SA3, and A2 and A3 was the highest. $b^*$ value was lowest in SDR followed by A2 and SA2, and A3 and SA3 was the highest. ${\Delta}E$ between A2 and SA2 (${\Delta}E=3.4$), and that between A3 and SA3 (${\Delta}E=3.1$) was lower than the perceptible color difference threshold of ${\Delta}E=3.7$. Conclusion: ${\Delta}E$ between low viscosity bulk-fill resin with a capping layer and microhybrid resin was lower than the perceptible color difference threshold.

• Journal of the korean academy of Pediatric Dentistry
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• v.43 no.4
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• pp.427-434
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• 2016

The aim of this study was to compare the mechanical properties of high viscosity bulk-fill resin composites, $Filtek^{TM}$ Bulk Fill Posterior Restorative (FBF) and $Tetric^{(R)}$ N-Ceram Bulk Fill (TBF), with conventional composite ($Filtek^{TM}$ Z-350 XT, Z-350). The Vickers hardness test which indicates the degree of conversion was performed and the dye penetration test was performed to measure the microleakage which indicates polymerization shrinkage amount. To minimize experimental error, the standardized 3D-printed molds and the bovine teeth were used. Obtained data were analyzed by the Kruskal-Wallis test and Mann-Whitney test with the confidence interval of 95%. In the microhardness test within 1 hour of polymerization, lower surface of FBF and TBF showed significantly lower value than that of Z-350 (p < 0.05). But after 24 hours, the microhardness of FBF had increased and showed no significant difference with Z-350 (p > 0.05). In top and 2 mm depth surface, mean microhardness values were in the following order: Z-350 > FBF > TBF (p < 0.05). The mean microleakage value of TBF was significantly lower than others (p < 0.05). For clinical application of bulk-fill resin composites, caution for applying masticatory forces during 24 hours after polymerization is advised and further studies to decrease microleakage should be conducted.

• The Journal of the Korean dental association
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• v.57 no.3
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• pp.162-168
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• 2019

Composite resin restorations in posterior teeth are increasing due to the aesthetic needs of patients and the development of materials. This trend will accelerate in line with domestic insurance policies. However, resin composites generate stresses due to their contraction during the polymerization process. To reduce the polymerization shrinkage stress of resin composites, incremental layering technique has been recommended for decades. This technique reduces stress at the cavity wall interface and allows a more efficient light curing of the material. Bulk-fill resin composites have been designed to simplify the restorative technique because they can be placed into cavities in a single increment of 4-5mm. The simplification of the operative procedures is desirable in clinical daily practice. In this context, bulk-fill resin composites are an attractive alternative for posterior restorations. However, a clearer understanding of the clinical performance of this relatively new class of materials in comparison to conventional resin composites is required. Based on previous studies, the aim of the current review was to present the clinical criteria for the use of bulk-fill composites in direct restorations of posterior teeth.

• Journal of Dental Rehabilitation and Applied Science
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• v.35 no.1
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• pp.1-10
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• 2019

Purpose: The aim of this study was to evaluate the influence of polishing methods on the color stability of composite resins. Materials and Methods: Two bulk-fill and four conventional resin composites were filled in cylindrical molds (6 mm diameter, 4 mm height) and light-cured. The specimens were stored in $34^{\circ}C$ distilled water for 24 h. Spectrophotometer was used to determine the color value according to the CIE $L^*a^*b^*$ color space. Each group was divided into three groups according to polishing methods (n = 5). Group 1 was control group (Mylar strip group), group 2 was polished with PoGo, and group 3 was polished with Sof-Lex Spiral wheels. Color evaluation was performed weekly for 4 weeks after immersion in $34^{\circ}C$ distilled water. The results were analyzed by generalized least squares method (P < 0.05). Results: Generalized least squares analysis revealed that Sof-Lex Spiral wheels group showed the significantly lower ${\Delta}E$ values compared to PoGo and control group (P < 0.05). The ${\Delta}E$ values of polished group showed the significantly lower than the ${\Delta}E$ values of unpolished group (P < 0.05). Regarding color changes of composite resins, there was no significant difference between the ${\Delta}E$ values of Filtek Z250 and Filtek Z350 XT Universal restorative in all time intervals (P < 0.05). Tetric N-Ceram Bulk Fill showed the significantly lower ${\Delta}E$ values compared to other composite resins in 1, 2, 3 weeks (P < 0.05). Conclusion: Within the limitations of this study, polishing methods influence the color stabilities of composite resins. The group polished with Sof-Lex Spiral Wheels showed more resistance to discoloration than group polished with PoGo.