• Proceedings of the KACD Conference
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• 2008.05a
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• pp.235-245
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• 2008

The aim of this study was to develop a method for measuring the slumping resistance of resin composites and to relate it to the rheological characteristics. Five commercial hybrid composites (Z100. Z250. DenFil, Tetric Ceram. ClearFil) and a nanofill composite (Z350) were used to make disc-shaped specimens of 2 mm thickness. An aluminum mold with square shaped cutting surface was pressed onto the composite discs to make standardized imprints. The imprints were light-cured either immediately (non-slumped) or after waiting for 3 minutes at $25^{\circ}C$ (slumped). White stone replicas were made and then scanned for topography using a laser 3-D profilometer. Slumping resistance index (SRI) was defined as the ratio of the groove depth of the slumped specimen to that of the non-slumped specimen. The pre-cure viscoelasticity of each composite was evaluated by an oscillatory shear test and normal stress was measured by a squeeze test using a rheometer. Flow test was also performed using a flow tester. Correlation analysis was performed to investigate the relationship between the viscoelastic properties and the SRI. SRI varied between the six materials (Z100 < DenFil < Z250 < ClearFil < Tetric Ceram < Z350). The SRI was strongly correlated with the viscous (loss) shear modulus G' but not with the loss tangent. Also. slumping resistance was more closely related to the resistance to shear flow than to the normal stress. Slumping tendency could be quantified using the imprint method and SRI. The index may be applicable to evaluate the clinical handling characteristics of composites.

• Journal of the korean academy of Pediatric Dentistry
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• v.46 no.3
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• pp.318-327
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• 2019

The purpose of this study was to identify which combination of zirconia crowns and cements is most similar in color to the maxillary primary incisors by varying the color of zirconia crowns, crown thickness, and shade of cements. Prefabricated zirconia crowns in 3 shades and crowns fabricated using 6 types of zirconia blocks were used in this study. These were filled with A2-shade or translucent-shade resin cement and the $L^*$, $a^*$, and $b^*$ values were calculated using a spectrophotometer. The color differences between the natural teeth and the zirconia crowns were assessed. The shade of the final restoration was more similar to that of the natural teeth using A2-shade than translucent-shade resin cement. Application of A2-shade cement to a 0.5-mm-thick crown fabricated from a smile series 2 zirconia block resulted in the color most similar to that of the natural teeth. A2-shade resin cement is recommended for zirconia crown restoration in anterior primary teeth compared to TR-shade resin cement for more esthetic restoration. Since restorations with Nu-smile zirconia crowns were not esthetically favorable in terms of shade, improvement of the shade characteristics of the product or development of a new kind of zirconia crown is required.

• Restorative Dentistry and Endodontics
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• v.28 no.6
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• pp.467-474
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• 2003

복합레진에 의한 구치부 2급 와동의 수복에서 치은부 변연이 법랑-백아 경계 하방에 위치하는 경우 복합레진의 중합 수축에 의한 응력은 변연부의 폐쇄능력을 저하시키고 이로인한 미세누출은 2차적인 우식이나 술후과민증을 일으켜 임상에서의 성공을 위협한다. 본 연구에서는 2급 와동에서 복합레진으로 수복하기 전에 치은 변연부를 중합수축에 의한 응력을 완화시킬 수 있는 것으로 알려진 몇가지 재료들을 중간층으로 먼저 충전한 후 충전용 복합레진으로 충전한 뒤 치은부 변연에서 이들 중간층과 치질 사이의 미세누출의 정도를 비교하였다. 20개의 발거된 구치의 근, 원심면에 각각 상자 모양의 2급 와동을 형성하고 40개의 와동을 무작위로 10개씩, 4개의군으로 나누었다. 1군은 중간층의 수복없이 Clearfil SE Bond과 Clearfil AP-X로 충전하였으며 2, 3 및 4군은 중간층으로 각각 Revolution, Dyract그리고 FujiII LG를 먼저 충전한 후 1군과 동일한 방법으로 복합레진을 충전하였다. 충전된 시편은 열순환후 2% methylene blue 용액에 12시간 침잠시킨 후 색소의 침투도를 stereomicroscope로 관찰하였으며 실험결과는 Kruskal-Wallis non-parametric independent analysis 및 Mann-Whitney U test로 통계분석하여 다음의 결론을 얻었다. 1. 레진강화형 글라스아이오노머를 중간층으로 먼저 수복하고 복합레진으로 충전한 경우에서 더 적은 미세누출을 보였다(p<0.05). 2. 유동성 레진과 콤포머를 중간층으로 수복한 경우와 복합레진만으로 수복한 경우는 미세누출에 있어서 유의한 차이를 나타내지 않았다(p>0.05).

• Journal of Industrial Technology
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• v.35
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• pp.35-39
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• 2015

One of the purposes of the study was to investigate and compare the physical properties(depth of light cure, degree of conversion, water absorption) of 4 kinds of composit resins prepared in this lab; Bis-GMA based, Bis-EMA based, Bis-GMA/UDMA based, and Bis-EMA/UDMA based composit. Another aim was to compare the physical properties of the composit resins with those of the commercialized products(Charmfil flow(Denkist), Quadrant flow(CAVEX)) in market. All of the composit resins and the commercialized products showed almost same values of the physical properties. It was found that all of the composit resins prepared in this lab satisfied the physical properties specified in ISO 4049.

• Journal of Industrial Technology
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• v.35
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• pp.31-34
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• 2015

The purpose of the study was to investigate the mechanical properties (diametral tensile strength, flexural strength, compressive strength, Vickers hardness) of 4 kinds of composit resins; Bis-GMA based composit, Bis-EMA based composit, Bis-GMA/UDMA based composit, and Bis-EMA/UDMA based composit, The composit resin based Bis-GMA showed stronger mechanical properties than Bis-EMA. It was found that the addition of UDMA to both Bis-GMA based composit and Bis-EMA based composit highly improved mechanical properties. However, the mechanical properties of the composit resins prepared in this study were lower than those of the commercialized products in market(Charmfil flow(Denkist), Quadrant flow(CAVEX)), since the composit resins prepared in this study has much lower inorganic filler content of 43wt% comparing with 50~70wt% inorganic filler content of the commercialized products.

• The korean journal of orthodontics
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• v.29 no.1 s.72
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• pp.107-112
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• 1999

As increasing number of adult patients, the esthetic orthodontic appliances are needed. They are tooth-colored or translucent ceramic and resin brackets. Although ceramic and resin bracket have good esthetics, there are some disadvantage such as frictions. Recently, metal-reinforced resin bracket(MRBB) were introduced. The purpose of this study is to find frictional force of MRRB, ceramic bracket and resin brackets. There is few study in frictional force about metal reinforced resin bracket(MRRB). This study used 4 orthodontic wire(.016 S-S, .0l6X.022 S-S, .016 $TMA^{\circledR}$, .0l7X.025 $TMA^{\circledR}$ and 5 brackets(one metal bracket, one ceramic bracket, one resin bracket, two MRRB). The following result is obtained using metal bracket(Ormco.Co., U.S.A), ceramic brackets($Crystalline^{\circledR}$), resin bracket( Clear Medium $Siamase^{\circledR}$). Following conclusions are obtained. 1. Ceramic and resin bracket have significantly more frictional forces than metal reinforced resin bracket and metal bracket. 2. There is no significant difference in frictional force according to the slot types of metal - reinforced resin brackets. 3. There is no significant difference in frictional force between metal reinforced resin bracket and metal bracket. 4.. Frictional force is decreased in S-S wire than TMA wire.

• Composites Research
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• v.25 no.6
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• pp.236-240
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• 2012

The purpose of this study was to investigate the feasibility on the detection of dental composite delamination using a lock-in thermography method. Amplitude and phase images of detected thermal signals were analyzed according to the lock-in frequencies. At a lock-in frequency of 0.05 Hz, the ligament thickness of 0.5 mm in the specimen exhibited the highest amplitude contrast between defective area and sound area. For ligament thicknesses of 1 mm and 1.5 mm, delamination detection was possible at 0.025 Hz and 0.01 Hz through the amplitude differences. At lock-in frequencies of 0.006 Hz and 0.01 Hz, ligament thickness 0.5 mm exhibited the highest phase contrast. For ligament thicknesses of 1 mm and 1.5 mm, the phase contrast exhibited possible detection of delamination at 0.006-0.1 Hz.

• The Journal of Korean Academy of Prosthodontics
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• v.52 no.2
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• pp.82-89
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• 2014

Purpose: The purpose of this study was to observe the change of viscoelastic properties of dental resin cements during polymerization. Materials and methods: Six commercially available resin cement materials (Clearfil SA luting, Panavia F 2.0, Zirconite, Variolink N, RelyX Unicem clicker, RelyX U200) were investigated in this study. A dynamic oscillation-time sweep test was performed with AR1500 stress controlled rheometer at $32^{\circ}C$. The changes in shear storage modulus (G'), shear loss modulus (G"), loss tangent (tan ${\delta}$) and displacement were measured for twenty minutes and repeated three times for each material. The data were analyzed using one-way ANOVA and Tukey's post hoc test (${\alpha}$=0.05). Results: After mixing, all materials demonstrated an increase in G' with time, reaching the plateau in the end. RelyX U200 demonstrated the highest G' value, while RelyX Unicem (clicker type) and Variolink N demonstrated the lowest G' value at the end of experimental time. Tan ${\delta}$was maintained at some level and reached the zero at the starting point where G' began to increase. The tan ${\delta}$and displacement of the tested materials showed similar pattern in the graph within change of time. The displacement of all 6 materials approached to zero within 6 minutes. Conclusion: Compared to other resin cements used in this study, RelyX U200 maintained plastic property for a longer period of time. When it completed the curing process, RelyX U200 had the highest stiffness. It is convenient for clinicians to cement multiple units of dental prostheses simultaneously.

• Composites Research
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• v.22 no.6
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• pp.45-51
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• 2009

The marginal integrity at the composite resin-tooth interface has been analyzed in real time through acoustic emission (AE) monitoring during the polymerization shrinkage of composite resin subjected to the light exposure. It was found that AE signals were generated by the polymerization shrinkage. Most AE hit events showed a blast type signal having the principal frequency band of 100-200kHz. Bad bonding states were indicated by many hit events in the initial curing period of 1 minute with high contraction rate. The quantity of hit events for the human molar dentin specimen was much less than that for the steel ring specimen but more than that for the PMMA ring specimen. The better the bonding state, the less the AE hit events. The AE characteristics were related with the tensile crack propagation occurring in the adhesive region between the composite resin and the ring substrate as well as the compressive behavior of the ring substrate, which could be used for a nondestructive characterization of the marginal disintegrative fracture of the dental restoration.

• Journal of Dental Rehabilitation and Applied Science
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• v.37 no.1
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• pp.16-22
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• 2021

Purpose: The purpose of this study is to investigate the effect of surface polishing and fabrication method on the flexural strength of temporary restorative resin. Materials and Methods: Each of four fabrication methods was used to make 30 temporary restorative resin specimens and the specimens were divided into two groups depending on whether they were polished by mechanical polishing. Specimens were stored in 37℃ thermostat for 24 hours. Flexural strength was measured using a universal testing machine (UTM). The data obtained through the experiment were analyzed with Two-way ANOVA, Tukey's HSD test and Paired t-test. Results: CAD/CAM milling group showed the highest flexural strength regardless of surface polishing. In decreasing order, the flexural strength of the other fabrication method group was as follows SLA 3D printing, DLP 3D printing, and Conventional method group. Conclusion: Surface polishing did not affect flexural strength of the temporary restorative resin (P > 0.05). However, there were statistically significant differences in flexural strength depending on fabrication method (P < 0.05).