• Proceedings of the Korean Society of Computer Information Conference
• /
• 2019.07a
• /
• pp.315-316
• /
• 2019

전투복, 군용 천막 등에 사용되는 위장무늬는 군 작전 수행 시 주변 환경의 색상, 패턴을 모사하여 개인병사 및 무기체계의 위장 기능을 극대화하고, 이를 통해 아군의 생명과 시설피해를 최소화하기 위한 목적으로 사용된다. 특히 최근 들어 군의 작전환경과 임무가 복잡하고 다양해짐에 따라, 작전환경에 대한 데이터의 취득 및 정량적 분석을 통해 전장 환경에 최적화된 위장무늬 패턴 및 색상 추출에 대한 연구의 필요성이 증대되고 있다. 본 논문에서는 한반도 자연환경 영상에 대한 자기 조직화 지도(SOM, Self-organizing Map) 기반의 한반도 자연환경 대표 색상 군집화 연구 방법에 대해 서술한다. 이를 위해 한반도 내 위도를 고려한 장소에서 시간별, 계절별 자연환경 영상 수집을 진행하며, 수집된 영상 내 다수의 화소의 군집화를 위해 2차원 SOM을 활용한다. 영상 내 각 화소의 색상 값에 대한 SOM의 학습 시, RGB공간상의 색차/색상 인지 왜곡을 피하기 위하여 CIEDE2000 색차 식을 통해 군집화를 진행한다. 실험결과에서는 온라인상으로 수집한 여름 및 가을철 대표 색상 군집화 결과와, 현재까지 수집된 계절별 자연환경 사진 내 6억 7648개 화소에 대한 대표 색상 군집화 결과를 보여준다.

• The Journal of Advanced Prosthodontics
• /
• v.15 no.2
• /
• pp.93-100
• /
• 2023

PURPOSE. The aim of this study is to evaluate the effect of resin cement color, cement thickness, and thermocycling on the final color of monolithic lithium disilicate crowns. MATERIALS AND METHODS. A total of ninety prepared central incisors of typodont teeth were restored with lithium disilicate crowns which have different cement thicknesses (40 ㎛, 80 ㎛, and 120 ㎛) and cement shades (clear, yellow, and white). Color parameters of restorations were measured with a spectrophotometer in three different steps 1) before cementing 2) after cementing and 3) after thermocycling with 10000 cycles. Color differences (ΔE₀₀) were calculated with the CIEDE2000 formula and evaluated according to perceptibility (0.8) and acceptability (1.8) thresholds. The ΔE₀₀ data were analyzed by using two-way ANOVA before and after thermocycling (α = .05). RESULTS. There was no interaction between the cement shade and the cement thickness factors. After cementation, the mean ΔE₀₀ was under the perceptibility threshold in the group of 40 ㎛ cement thickness and clear cement while it was between the perceptibility and acceptability thresholds (0.8 < ΔE₀₀ < 1.8) for all other groups. After thermocycling, the ΔE₀₀ values were between the perceptibility and acceptability thresholds for all experimental groups. Although there were no significant differences among the groups, thermocycling increased the color difference values. CONCLUSION. The cementation of restorations with clear, yellow, and white resin cements resulted in color differences with uncemented restorations except for the group cemented with clear cement in 40 ㎛ cement thickness. All study groups revealed perceptible color change after thermocycling.

• Restorative Dentistry and Endodontics
• /
• v.48 no.4
• /
• pp.33.1-33.12
• /
• 2023

Objectives: This study aimed to evaluate the bleaching efficacy and hydrogen peroxide permeability in the pulp chamber by the at-home bleaching gel in protocols applied on different dental surfaces. Materials and Methods: Forty premolars were randomly into 4 groups: control group no bleaching, only application on the buccal surface (OB), only application on the lingual surface (OL) and application in buccal and lingual surfaces, simultaneously (BL). At-home bleaching gel (White Class 7.5%) was used for the procedure. The bleaching efficacy was evaluated with a digital spectrophotometer (color change in CIELAB [ΔE_ab] and CIEDE 2000 [ΔE₀₀] systems and Whitening Index for Dentistry [ΔWI_D]). The hydrogen peroxide permeability in the pulp chamber (㎍/mL) was assessed using UV-Vis spectrophotometry and data were analyzed for a 1-way analysis of variance and Tukey's test (α = 0.05). Results: All groups submitted to bleaching procedure showed bleaching efficacy when measured with ΔE_ab and ΔE₀₀ (p > 0.05). Therefore, when analyzed by ΔWI_D, a higher bleaching efficacy were observed for the application on the groups OB and BL (p = 0.00003). Similar hydrogen peroxide permeability was found in the pulp chambers of the teeth undergoing different protocols (p > 0.05). Conclusions: The application of bleaching gel exclusively on the OB is sufficient to achieve bleaching efficacy, when compared to BL. Although the OL protocol demonstrated lower bleaching efficacy based on the ΔWI_D values, it may still be of interest and relevant in certain clinical scenarios based on individual needs, requiring clinical trials to better understand its specificities.

• The Journal of Advanced Prosthodontics
• /
• v.16 no.2
• /
• pp.115-125
• /
• 2024

PURPOSE. The purpose of this in vitro study was to investigate the fracture resistance, surface hardness, and color stain of 3D printed, CAD-CAM milled, and conventional interim materials. MATERIALS AND METHODS. A total of 80 specimens were fabricated from auto polymerizing polymethyl methacrylate (PMMA), bis-acryl composite resin, CAD-CAM polymethyl methacrylate resin (milled), and 3D printed composite resin (printed) (n = 20). Forty of them were crown-shaped, on which fracture strength test was performed (n = 10). The others were disc-shaped specimens (10 mm × 2 mm) and divided into two groups for surface hardness and color stainability tests before and after thermal cycling in coffee solution (n = 10). Color parameters were measured with a spectrophotometer before and after each storage period, and color differences (CIEDE2000 [DE00]) were calculated. The distribution of variables was measured with the Kolmogorov Smirnov test, and one-way analysis of variance (ANOVA), Tukey HSD, Kruskal-Wallis, Mann-Whitney U tests were used in the analysis of quantitative independent data. Paired sample t-test was used in the analysis of dependent quantitative data (P < .05). RESULTS. The highest crown fracture resistance values were determined for the 3D printed composite resin (P < .05), and the lowest were observed in the bis-acryl composite resin (P < .05). Before and after thermal cycling, increase in mean hardness values were observed only in 3D printed composite resin (P < .05) and the highest ΔE₀₀ value were observed in PMMA resin for all materials (P < .05). CONCLUSION. 3D printing and CAD-CAM milled interim materials showed better fracture strength. After the coffee thermal cycle, the highest surface hardness value was again found in 3D printing and CAD-CAM milled interim samples and the color change of the bis-acryl resin-based samples and the additive production technique was higher than the PMMA resin and CAD-CAM milled resin samples.