• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.514-517
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• 2005

Microstereolithography(MSL) has evolved from the stereolithography technique, and is also based on a light-induced layer-stacking fabrication. Although integral MSL allows the manufacture of a complete layer by one irradiation only, there is a problem related with shape precision due to the light-intensity distribution of focused image. In this study, we developed the integral MSL apparatus using Digital Micromirror Device ($DMD^{TM})$, Texas Instruments) as dynamic pattern generator. It is composed of Xenon-Mecury lamp, optical devices, pattern generator, precision stage, controllers and the control program. Also, we have studied curing depth and width of photocurable resin according to the change of exposure energy.

• Restorative Dentistry and Endodontics
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• 제46권4호
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• pp.51.1-51.13
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• 2021

Objectives: This study aimed to evaluate the effect of improper positioning single-peak and multi-peak lights on color change, microhardness of bottom and top, and surface topography of bulk fill and incremental composites after artificial aging for 1 year. Materials and Methods: Bulk fill and incremental composites were cured using multi-peak and single-peak light-emitting diode (LED) following 4 clinical conditions: (1) optimal condition (no angulation or tip displacement), (2) tip-displacement (2 mm), (3) slight tip angulation (α = 20°) and (4) moderate tip angulation (α = 35°). After 1-year of water aging, the specimens were analyzed for color changes (ΔE), Vickers hardness, surface topography (Ra, Rt, and Rv), and scanning electron microscopy. Results: For samples cured by single-peak LED, the improper positioning significantly increases the color change compared to the optimal position regardless of the type of composite (p < 0.001). For multi-peak LED, the type of resin composite and the curing condition displayed a significant effect on ΔE (p < 0.001). For both LEDs, the Vickers hardness and bottom/top ratio of Vickers hardness were affected by the type of composite and the curing condition (p < 0.01). Conclusions: The bulk fill composite presented greater resistance to wear, higher color stability, and better microhardness than the incremental composite when subjected to improper curing. The multi-peak LED improves curing under improper conditions compared to single-peak LED. Prevention of errors when curing composites requires the attention of all personnel involved in the patient's care once the clinical relevance of the appropriate polymerization reflects on reliable long-term outcomes.

• 대한소아치과학회지
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• 제33권3호
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• pp.438-446
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• 2006

광중합 수복재의 중합시 발생되는 틈을 최소화하기 위해 최근 여러 가지 광중합기와 중합방법이 개발되고 있는데, 할로겐 광과 플라즈마광, LED광으로 광조사를 했을 때 미세누출을 비교하는 실험을 통해 임상에 적용해보고자 한다. 치아의 협설면에 5급와동을 형성하고, 광중합레진을 수복하여 광중합한 뒤 24시간 후 2% 메틸렌블루 용액에 담근 다음 치아를 협설로 절단하여 미세누출도를 평가하였다. 통계처리는 Kruskal-Wallis test와 Man-Whitney test를 사용하여 각 군의 유의성을 검정하였다. 법랑질에서 Dyract AP로 충전한 경우 광원에 따른 미세누출의 차이는 없었으나, $Z250^{(R)}$으로 충전한 경우에서는 $Flipo^{(R)}$가 FreeLight $2^{(R)}$혹은 $TriLight^{(R)}$보다 미세누출이 컸다. 충전재에 따른 법랑질 변연에서의 미세누출을 측정한 결과 LED광 혹은 할로겐 광중합시 복합레진이 컴포머에 비해 작은 미세누출을 보였으나, $Flipo^{(R)}$에서는 두 재료간의 차이가 없었다. 상아질변에서는 $Flipo^{(R)}$와 FreeLight $2^{(R)}$로 중합시 $Z250^{(R)}$이 Dyract AP보다 미세누출이 작았으나, $TriLight^{(R)}$에서는 두 재료간의 차이가 없었다. 이번 연구에서 $Z250^{(R)}$이 Dyract AP보다는 미세누출이 작았으며, $Z250^{(R)}$으로 충전한 경우 에나멜변연에서 $Flipo^{(R)}$가 FreeLight $2^{(R)}$나 $TriLight^{(R)}$보다 미세누출이 크다는 것을 알 수 있었다.

• 전기전자학회논문지
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• 제24권1호
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• pp.140-146
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• 2020

We investigated light extraction film based on polymer dispersed liquid crystal (PDLC) for application in organic light emitting diodes (OLEDs). At least 30 seconds of direct UV irradiation process for curing PDLC film on a bottom-emitting OLEDs was successfully achieved without damage on the intrinsic properties of the OLED. We demonstrated that high haze and transmittance can be tuned simultaneously by controlling the UV curing time. By adding PDLC as an external layer without any additional treatment, the light scattering and extraction is increased. Consequently, a PDLC scattering film with 89.8% and 59.9 of total transmittance and haze respectively, achieved about 16% of light intensity enhancement from integrating sphere measurement.

• The Journal of Advanced Prosthodontics
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• 제13권4호
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• pp.246-257
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• 2021

PURPOSE. This study aimed to investigate the Vickers Hardness Number (VHN) of light- and dual cured resin cements cured through monolithic zirconia specimens (VITA YZ) of various translucencies: translucent (T); high translucent (HT); super translucent (ST); and extra translucent (XT) at 0, 24, and 48 h after curing. MATERIALS AND METHODS. Four zirconia specimens from each translucency were prepared. Two light-cured resin cements (Variolink N LC; VL and RelyX Veneer; RL) and two dual-cured resin cements (Variolink N DC; VD and RelyX U200; RD) were used. The cement was mixed and loaded in a mold and cured for 20 s through the zirconia specimen. The upper surface of cements was tested for VHN using a microhardness tester at 0, 24, and 48 h after curing. The VHN were analyzed using two-way repeated, Brown-Forsythe ANOVA with Games Howell post-hoc analysis and independent t-tests (P < .05). RESULTS. All cements showed significantly higher VHN from 0 h to 24 h (P < .001). At 48 h, the VHN of light-cured cements were significantly lower when cured under the T groups than under XT groups (P = .001 in VL, P = .014 in RL). At each post curing time of each translucency, VD showed higher VHN than VL (P < .05), and RD also showed higher VHN than RL (P < .05). CONCLUSION. The translucency of zirconia has an effect on the VHN for light-cured resin cements, but has no effect on dual-cured resin cements. Dual-cured resin cement exhibited higher VHN than the light-cured resin cement from the same manufacturer. All resin cements showed significantly higher VHN from 0 h to 24 h.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.1155-1156
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• 2006

In this paper, we analyzed the effect of EVA Sheet Gel Content depending on curing condition for photovoltaic module. Gel Content was measured by manufacturing Glass/EVA Sheet/Back Sheet scheme at several curing temperature and curing time. And the surface analysis of EVA Sheet depending on process condition could be observed using SEM(Scanning Electron Microscope). Through this experiment, we could confirm that there are differences on Gel Content of EVA Sheet and surface configuration depending on curing temperature and curing time. To find out the optical characteristic dependency on curing condition, Class/EVA Sheet/Glass scheme was fabricated. The optical transmittance of EVA Sheet at visible wavelength was enhanced 5% when compared to Glass/Glass scheme. And the transmittance of $130^{\circ}C$/4min, $110^{\circ}C$/4min, $160^{\circ}C$/6min process condition was higher at ultraviolet wavelength range. These curing conditions could be regarded as the best process for suppression the discoloration speed of EVA Sheet under UV light.

• 대한치과기공학회지
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• 제42권4호
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• pp.341-347
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• 2020

Purpose: This study aimed to evaluate the effect of post-curing method on the flexural strength of provisional restorative resins produced by a digital light processing printer. Methods: A total of 20 specimens were produced, with a length of 64 mm, width of 10 mm, and thickness of 3.3 mm using a digital light processing printer. Two types of provisional restorative resins made with different post-curing methods were investigated and divided into conventional and vacuum groups. For the flexural strength test, each group was prepared by each method according to ISO 10477, and the flexural strength was measured with a universal testing machine. For statistical analysis, data were analyzed by independent t-test and Mann-Whitney U test. Results: The flexural strengths of the conventional and vacuum groups were 151.89 MPa and 131.94 MPa, respectively, showing a statistically significant difference (p<0.05). Conclusion: Within the limitation of this study, provisional restorative resins produced with vacuum demonstrated lower flexural strength than those produced with conventional postcuring method.

• 대한치과의료관리학회지
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• 제9권1호
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• pp.7-13
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• 2021

The present randomized controlled trial aimed to evaluate changes in occlusion of indirect restorations before and after attachment using resin cement according to universal adhesives. This study included patients who underwent indirect restoration treatment at the Yonsei University Dental Hospital between April and October 2016. Universal adhesives requiring light curing and those not requiring light curing were used in this study. Changes in occlusion before and after adhesion of the indirect restoration were evaluated using articulating paper and shimstock as well as through the discomfort felt by the patients. To analyze the differences between the universal adhesive, Fisher's exact tests were performed using SPSS ver. 22.0 software. Of the 39 cases of indirect restoration, 29 were included in the study. A change in occlusion after adhesion of the indirect restoration was observed in only one case of universal adhesive that required light curing. The patient felt that the occlusion increased after the attachment of the restoration, and it was observed that the occlusion point was different from that before attachment. However, the results of the analysis were not statistically significant. Based on the findings, the universal adhesives did not affect the occlusion before and after indirect adhesion restoration using RelyX Ultimate.

• 대한치과기공학회지
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• 제44권3호
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• pp.76-80
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• 2022

Purpose: The purpose of this study is to analyze the depth according to curing using photocurable resin for dental three-dimensional printing. Methods: A stainless mold with a height of 4 mm was prepared. Ultraviolet (UV) polymerization resin was injected into the mold. Photocuring was then performed for 5 minutes using a photopolymerizer, and the height was measured using a digital measuring instrument (first group). Second, light polymerization was also performed outside the mold for 5 minutes, and the height was measured using a digital measuring instrument. Third, light polymerization was further performed for 5 minutes, and the height was measured using a digital measuring instrument. Statistical analysis was performed with the Kruskal-Wallis test, which is a nonparametric test (α=0.05). Results: The third group had the largest measurement length, whereas the first group had the smallest. However, the difference between groups was not statistically significant (p>0.05). The color of the first group was different from that of the second and third groups. Conclusion: All of the 4-mm-thick photocured specimens had a curing reaction, but the part that was not directly irradiated with UV did not show its original color.

• Restorative Dentistry and Endodontics
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• 제16권1호
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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.