• 한국산업융합학회 논문집
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• 제26권4_2호
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• pp.629-637
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• 2023

This study aimed to evaluate the effect of post-curing equipment and time on the flexural strength of 3D printing resins produced by a liquid crystal display(LCD) printer. The three 3D printing resins(DENTCA Denture Teeth, DT; C&B 5.0 hybrid, CH; C&B Permanent A2, CP) were divided into four groups according to post-curing time(10 min and 30 min) and equipment with or without vacuum treatment. For the three-point flexural strength test and biaxial strength test were prepared by method according to ISO 10477, ISO 6872, respectively. Flexural strength was measured with universal testing machine. Comparison between post-curing time of each post-curing equipment was analyzed by independent sample t-test and Mann-Whitney U test(α=.05), and comparison between groups according to each 3D printing resin was performed by Kruskal-Wallis test and post-hoc by Bonferroni-Dunn test(α=.05). The flexural strength of the resin post-curing under vacuum was higher than that of the resin post-curing in air. In the comparison according to the post-curing time, in the case of the post-curing equipment without vacuum, the 30 minute curing time showed significantly higher flexural strength than the 10 minute curing time, except for the biaxial flexural strength of CH(P<.05). In the post-curing equipment with vacuum, the three-point flexural strength of all 3D printing resins(DT, CH, and CP) showed a higher value at 30 minute curing time than at 10 minute curing time.

• The Journal of Advanced Prosthodontics
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• 제13권2호
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• pp.89-99
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• 2021

PURPOSE. This study aimed to compare the accuracy (trueness and precision) of interim crowns fabricated using DLP (digital light processing) according to post-curing time. MATERIALS AND METHODS. A virtual stone study die of the upper right first molar was created using a dental laboratory scanner. After designing interim crowns on the virtual study die and saving them as Standard Triangulated Language files, 30 interim crowns were fabricated using a DLP-type 3D printer. Additively manufactured interim crowns were post-cured using three different time conditions-10-minute post-curing interim crown (10-MPCI), 20-minute post-curing interim crown (20-MPCI), and 30-minute post-curing interim crown (30-MPCI) (n = 10 per group). The scan data of the external and intaglio surfaces were overlapped with reference crown data, and trueness was measured using the best-fit alignment method. In the external and intaglio surface groups (n = 45 per group), precision was measured using a combination formula exclusive to scan data (10C2). Significant differences in accuracy (trueness and precision) data were analyzed using the Kruskal-Wallis H test, and post hoc analysis was performed using the Mann-Whitney U test with Bonferroni correction (α=.05). RESULTS. In the 10-MPCI, 20-MPCI, and 30-MPCI groups, there was a statistically significant difference in the accuracy of the external and intaglio surfaces (P<.05). On the external and intaglio surfaces, the root mean square (RMS) values of trueness and precision were the lowest in the 10-MPCI group. CONCLUSION. Interim crowns with 10-minute post-curing showed high accuracy.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 C
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• pp.944-946
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• 1999

The thermal stability of the post cured epoxy-polysiloxane IPN structure was observed by using DSC and TGA. As the post curing time increased the glass transition temperature increased and the secondary exothermic peak disappeared. The thermally decomposing activation energy calculated by using Kissinger expression was 225.6 kJ/mol. The thermal stability of the grafted IPN of epoxy and silicon compound depends on the composing ratio and post curing conditions of time and temperature.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 춘계학술대회 논문집
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• pp.227-230
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• 1998

The effects of post curing conditions on thermal properties of alumina filled epoxy resin system DGEBA/MDA/SN were investigated. As the post curing time increased at 15$0^{\circ}C$, the glass transition temperature increased from 121 to 124, slightly. As the heating rate increased, high thermal decomposing temperature (T$_{d}$) and most decomposing temperature (T$_{p}$) increased. For the case of post-cured system at 15$0^{\circ}C$ for 4 days showed lower values than virgin system. At the post curing condition the system must have been thermally degraded.ded.

• 한국기계가공학회지
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• 제17권2호
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• pp.47-53
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• 2018

Nowadays, additive manufacturing (AM) technology is a promising process to fabricate complex shaped devices applied in medical and dental services. Among the AM processes, a DLP (digital light processing) type 3D printing process has some advantages, such as high precision, relatively low cost, etc. In this work, we propose a simple method to fabricate precise dental models using a DLP 3D printer. After 3D printing, a part is commonly post-cured using secondary UV-curing equipment for complete polymerization. However, some shrinkage occurs during the post-curing process, so we adaptively control the UV-exposure time on each layer for over- or under-curing to change the local shape-size of a part in the DLP process. From the results, the shrinkage amounts in the post-curing process vary due to the UV-dose in 3D printing. We believe that the proposed method can be utilized to fabricate dental models precisely, even with a change of the 3D CAD model.

• 한국정밀공학회지
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• 제32권9호
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• pp.781-786
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• 2015

Recently, studies of 3D printing methods have been working in various applications. For example, the powder base method laminates the prints by using a binding or laser sintering method. However, the draw back of this method is that the post process is time consuming and does not allow for parts to be rapidly manufactured. The binding method requires the post process while the time required for the post process is longer than the manufacturing time. This paper proposes a UV curing binding method with an integrated piezo printing head system. The optimization of an arbitrary waveform generation for the control of a UV curable resin droplet was researched, in addition to developed optimized UV curing processes in multi nozzle ink jet heads.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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• pp.548-551
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• 1999

The cure characteristics of metal particle filled DGEBA/MDA/SN/ zeolite epoxy resin composite system for EMI shielding were investigated by dynamic DSC run method and FT-lR spectroscopy. As the heating rate increased, the peak temperature on dynamic DSC curve increased because of the rapid cure reaction. From the straight line of the Kissinger plot, the curing reaction activation energy and pre-exponential factor could be obtained. As the post-curing time at 15$0^{\circ}C$ increased, the glass increased the glass transition temperature or the thermal stability increased. When the post curing time is too long, the system filled with metallic Al particle can be thermally oxidized by the catalytic reaction of metal filler and the thermal stability of the composite for the EMI shielding application may be decreased.

• 한국구조물진단유지관리공학회 논문집
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• 제21권5호
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• pp.42-48
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• 2017

콘크리트 구조물이 화재 손상을 입을 경우 노출온도 및 지속시간에 따라 구조물의 심각한 성능 저하를 야기하며, 콘크리트의 재료 물성 저하를 수반한다. 화재 손상을 입은 콘크리트 구조물의 재사용여부 및 보수보강 판단을 위해서는 손상 직후 및 재양생 조건에 따른 주요 손상 부위의 면밀한 손상 평가가 필요하다. 본 연구에서는 재양생 조건에 따른 화재 손상을 입은 콘크리트의 재료물성 회복에 관한 실험적 연구를 수행하였다. 화재 손상을 입은 콘크리트 시편을 상대습도 및 재양생 기간을 달리한 재양생 조건을 적용하였으며, 충격공진기법을 도입하여 콘크리트 시편의 화재 손상 전후 및 재양생 이후의 동탄성계수를 측정하여 손상 정도를 평가하였다. 측정된 결과로부터 재양생 조건 중 높은 상대습도 조건에서 지배적으로 재료물성의 회복이 발생하였다. 추가적으로 콘크리트 시편의 동탄성계수 및 인장강도의 직접적인 비교 및 선형회귀분석을 수행하여 재양생 조건에 따른 영향을 분석하였으며, 이를 토대로 높은 습도 조건에서 동탄성계수의 회복이 인장강도에 비해 두드러지게 나타남을 확인하였다.

• Imaging Science in Dentistry
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• 제42권2호
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• pp.89-93
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• 2012

Purpose : Clinicians commonly encounter cases in which it is difficult to determine whether adjacent radiopacities are normal or pathologic. The ideal radiopacity of composite resin is equal to or higher than that of the same thickness of aluminum. We aimed to investigate the possible effects of different curing times on the post-24-hour radiopacity of composite resins on digital radiographs. Materials and Methods : One mm thick samples of Filtek P60 and Clearfil resin composites were prepared and cured with three regimens of continuous 400 mW/$cm^2$ irradiance for 10, 20 and 30 seconds. Along with a 12-step aluminum step wedge, digital radiographs were captured and the radiopacities were transformed to the equivalent aluminum thicknesses. Data were compared by a general linear model and repeated-measures of ANOVA. Results : Overall, the calculated equivalent aluminum thicknesses of composite resins were increased significantly by doubling and tripling the curing times (F(2,8)=8.94, p=0.002). Notably, Bonferroni post-hoc tests confirmed that the radiopacity of the cured Filtek P60 was significantly higher at 30 seconds compared with 10 seconds (p=0.04). Although the higher radiopacity was observed by increasing the time, other comparisons showed no statistical significance (p>0.05). Conclusion : These results supported the hypothesis that the radiopacity of resin composites might be related to the duration of light curing. In addition to the current standards for radiopacity of digital images, defining a standard protocol for curing of dental materials should be considered, and it is suggested that they should be added to the current requirements for dental material.

• The Journal of Advanced Prosthodontics
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• 제5권4호
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• pp.464-470
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• 2013

PURPOSE. The aim of this Fourier transform infrared (FTIR) spectroscopic study was to measure the degree of conversion (DC) of dual-cured resin cements light-irradiated through zirconia ceramic disks with different thicknesses using various light-curing methods. MATERIALS AND METHODS. Zirconia ceramic disks (KT12) with three different thicknesses (1.0, 2.0, and 4.0 mm) were prepared. The light transmittance of the disks was measured using ultraviolet visible near-infrared spectroscopy. Four different light-curing protocols were used by combining two curing light modes (Elipar TriLight (standard mode) and bluephase G2 (high power mode)) with light-exposure times of 40 and 120 seconds. The DCs of the two dual-cured resin cements (Duo-Link and Panavia F2.0) light-irradiated through the disks was analyzed at three time intervals (3, 7, and 10 minutes) by FTIR spectroscopy. The data was analyzed using repeated measures ANOVA (${\alpha}$=.05).Two-way ANOVA and Tukey post hoc test were used to analyze the 10 minute DC results. RESULTS. The 1.0 mm thick disk exhibited low light transmittance (<25%), and the transmittance decreased considerably with increasing disk thickness. All groups exhibited significantly higher 10 minute DC values than the 3 or 7 minute values (P<.05), but some exceptions were observed in Duo-Link. Two-way ANOVA revealed that the influence of the zirconia disk thickness on the 10 minute DC was dependent on the light-curing methods (P<.001). This finding was still valid even at 4.0 mm thickness, where substantial light attenuation took place. CONCLUSION. The curing of the dual-cured resin cements was affected significantly by the light-curing technique, even though the additional chemical polymerization mechanism worked effectively.