• 대한치과기공학회지
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• 제31권1호
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• pp.23-36
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• 2009

The goal of esthetic restoration is to achieve morphologic, optical, and biologic acceptance. Creation of a natural looking ceramic restoration, which blends harmoniously with surrounding dentition, is not always achieved. A successful color match is an important aspect of any esthetic dental restoration. Since natural enamel has inherent translucency, it is important that ceramic restorations reproduce the translucency and color of the natural teeth. However, the final color match of porcelain crowns to adjacent natural dentition remains some problem. Difficulties related to color matching arise from the structural differences that exist between metal ceramic crowns and natural teeth, the limited range of available ceramic shades, inadequate shade guides, different types of metal alloys, repeated firing, the condensation technique, and varying compositions of ceramic materials. Many factors contribute to the esthetic success of dental restoration: optical properties such as color and its elements of hue, value, and chroma; translucency and opacity; light transmission and scattering; and metamerism and fluorescence. The purpose of this study was to determine the color changes of metal-ceramic system with different veneering porcelain powder after repeated firing. The objectives of this in vitro study were to measure the lightness($L^*$), chromaticity($a^*$), chromaticity($b^*$), chroma($C^*$), hue(h), reflectance(%), color difference(${\Delta}E$). The following conclusions were obtained: 1. An increase in the number of firings resulted in decrease in lightness($L^*$) but increase in chromacticity($a^*$) with all porcelain. After the second sintering resulted in decrease in chromacticity($b^*$) with opaque-dentin porcelain and dentin porcelain but in increase with enamel porcelain and translucency porcelain. And after the second sintering resulted in decrease in chroma($C^*$) with opaque-dentin porcelain and dentin porcelain, but on the whole side in decrease with enamel porcelain and translucency porcelain. 2. After the second firing, a increase in the number of firings resulted in decrease reflectance(%) in all wavelength. 3. There were noticeable color differences(${\Delta}E$) between first sintering and multiple firings(dentin porcelain: 5.29~8.15, opaque-dentin porcelain: 4.83~8.2, enamel porcelain: 8.93~13.15, translucency porcelain: 9.37~12.91), but the color difference(${\Delta}E$) after second sintering were down to 4.87 in all porcelain. 4. Given the NBS Criteria, a 'trace' was not found this study but a 'slight' was found 2-3, 3-5 in dentin porcelain, 2-3 in opaque-dentin porcelain, 3-5, 5-10 in enamel porcelain and translucency porcelain, a 'noticeable' was 2-5, 3-10, 5-10 in dentin porcelain and opaque-dentin porcelain, 2-3, 2-5, 3-10 in enamel porcelain 2-3, 3-10 in translucency porcelain, an 'appreciable' was 1-2, 1-3, 2-10 in dentin porcelain 1-2, 1-3, 2-10, 3-10 in opaque-dentin porcelain, 2-10 in enamel porcelain, 2-5, 2-10 in translucency porcelain, a 'much' was 1-5, 1-10 in dentin porcelain and opaque-dentin porcelain, 1-2, 1-3, 1-5 in enamel porcelain 1-2, 1-3, 1-5, 1-10 in translucency porcelain, a 'very much' was 1-10 in enamel porcelain.

• The Journal of Advanced Prosthodontics
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• 제8권3호
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• pp.181-186
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• 2016

PURPOSE. The opacity of zirconia is an esthetic disadvantage that hinders achieving natural and shade-matched restorations. The aim of this study was to evaluate the translucency of non-colored and colored framework zirconia and monolithic zirconia. MATERIALS AND METHODS. The three groups tested were: non-colored framework zirconia, colored framework zirconia with the A3 shade according to Vita Classic Scale, and monolithic zirconia (n=5). The specimens were fabricated in the dimensions of $15{\times}12{\times}0.5mm$. A spectrophotometer was used to measure the contrast ratio, which is indicative of translucency. Three measurements were made to obtain the contrast ratios of the materials over a white background ($L^*w$) and a black background ($L^*b$). The data were analyzed using the one-way analysis of variance and Tukey HSD tests. One specimen from each group was chosen for scanning electron microscope analysis. The determined areas of the SEM images were divided by the number of grains in order to calculate the mean grain size. RESULTS. Statistically significant differences were observed among all groups (P<.05). Non-colored zirconia had the highest translucency with a contrast ratio of 0.75, while monolithic zirconia had the lowest translucency with a contrast ratio of 0.8. The mean grain sizes of the non-colored, colored, and monolithic zirconia were 233, 256, and 361 nm, respectively. CONCLUSION. The translucency of the zirconia was affected by the coloring procedure and the grain size. Although monolithic zirconia may not be the best esthetic material for the anterior region, it may serve as an alternative in the posterior region for the bilayered zirconia restorations.

• 대한치과의사협회지
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• 제49권4호
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• pp.203-210
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• 2011

The aims of this study were to evaluate the adequate thickness of opaque resins for situations such as an oral black cavity and discolored tooth structure, as well as the translucency of each opaque material at various thicknesses. Six opaque-shade composite resins (Z-350 OA3, Amelogen Universal A2O, Esthet-X A2O, Esthet-X A4O, Charmfil UO and Aelite Universal OA3) were prepared in metal molds with a hole of 8 mm in diameter and various thicknesses (0.5mm, 1.0mm, 1.5mm, 2.0mm, 2.5mm, 3.0 mm and 4.0mm). Four backgrounds (white tile, black tile, C4 shade porcelain and opaque resin itself) were used to determine the translucency parameter (between black and white backgrounds). and to mimic a black oral cavity (between black and opaque resin backgrounds) and a discolored tooth structure (between C4 and opaque resin backgrounds). Color measurements were made by a colorimeter to determine the CIELAB values of each specimen with each background and to calculate the translucency parameter and ${\Delta}E^*$ value difference among the specimens on the backgrounds. The translucency parameter and ${\Delta}E^*$ obtained between black and opaque resin backgrounds decreased in similar pattern as thickness increased. A C4 background was masked by resin thicknesses of 0.5-1.0mm, while a black background required thicknesses of 1.0-2.0mm. Adequate knowledge about differences in the optical character like translucency of the materials used is essential, together with the accumulated experience of the individual clinician.

• The Journal of Advanced Prosthodontics
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• 제6권6호
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• pp.456-461
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• 2014

PURPOSE. Translucency and colour stability are two most important aspects for an aesthetic dental restoration. Glass ceramic restorations are popular amongst clinicians because of their superior aesthetic properties. In the last decade, zirconia has generated tremendous interest due to its favorable mechanical and biological properties. However, zirconia lacks the translucency that lithium disilicate materials possess and therefore has limitations in its use, especially in esthetically demanding situations. There has been a great thrust in research towards developing translucent zirconia materials for dental restorations. The objective of the study was to evaluate and compare the transmittance of a translucent variant of zirconia to lithium disilicate. MATERIALS AND METHODS. Two commercially available zirconia materials (conventional and high translucency) and 2 lithium disilicate materials (conventional and high translucency) with standardized dimensions were fabricated. Transmittance values were measured for all samples followed by a microstructural analysis using a finite element scanning electron microscope. One way analysis of variance combined with a Tukey-post hoc test was used to analyze the data obtained (P=.05). RESULTS. High translucency lithium disilicate showed highest transmittance of all materials studied, followed by conventional lithium disilicate, high translucency zirconia and conventional zirconia. The difference between all groups of materials was statistically significant. The transmittance of the different materials correlated to their microstructure analysis. CONCLUSION. Despite manufacturers' efforts to make zirconia significantly more translucent, the transmittance values of these materials still do not match conventional lithium disilicate. More research is required on zirconia towards making the material more translucent for its potential use as esthetic monolithic restoration.

• 구강회복응용과학지
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• 제37권3호
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• pp.111-122
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• 2021

목적: 5Y-ZP의 세가지 층 간 굽힘강도, 투과도를 비교하고 추가적인 소성이 미치는 영향을 연구하고자 하였다. 연구 재료 및 방법: 소결한 지르코니아 블록을 세가지 층에 따라 분리한 후 원형 디스크 시편을 제작하였다. 시편의 직경은 15.0 mm이며, 2축굽힘강도와 투과도를 측정하기 위한 시편의 두께는 각각 1.2 mm와 1.0 mm이다. 시편들을 추가적인 소성 횟수(0, 1, 3번)에 따라 세 군으로 분류한 후 추가적인 소성은 900℃ 이하의 온도에서 퍼니스를 사용하여 소성 횟수에 따라 시행하였다. 만능재료시험기와 자외선-가시광선 분광광도계를 사용하여 2축굽힘강도와 투과도를 측정하였다. 상의 변화를 관찰하기 위해 X선 회절 분석을 시행하였다. 측정값은 One-way ANOVA, Tukey HSD test를 통하여 분석하였다(α = 0.05). 결과: 층 간 2축굽힘강도는 유의한 차이가 없었지만(P > 0.05) 투과도는 유의한 차이가 있었다(P < 0.05). 절단 및 전이층은 1번의 추가적인 소성 후 굽힘강도가 유의하게 감소하였으며, 3번의 추가적인 소성 후에는 모든 층의 굽힘강도가 소성 전과 비교하여 유의하게 감소하였다. 몸체 층을 제외한 나머지 층들은 추가적인 소성 후에 투과도가 유의하게 감소하였다. 모든 그룹의 X선 회절 분석 결과는 유사하였다. 결론: 5Y-ZP의 세 층은 투과도의 차이만 존재하였다. 추가적인 소성은 각 층의 굽힘강도와 투과도에 다른 영향을 미쳤으나 상전이는 발견되지 않았다.

• 대한치과의사협회지
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• 제58권7호
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• pp.443-447
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• 2020

The esthetic properties of zirconia receive increasing attention as its demand and application escalates. Thus, it is crucial to investigate how zirconia is esthetically different from other dental ceramics. In this study, we evaluated the translucency of zirconia and suggest a method to increase its translucency. We examined the shade of zirconia and offer its distinguishing features. Finally, we analyzed monolithic zirconia restorations to propose esthetic considerations in clinics.

• The Journal of Advanced Prosthodontics
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• 제7권5호
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• pp.400-405
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• 2015

PURPOSE. The purpose of this study is to mix dental ceramic powder in varying ratios and evaluate the effect of the mixing ratio on color and translucency. MATERIALS AND METHODS. The ceramic powder of shade A3 of the same product was mixed with the shade A2 of three products: IPS e.max Ceram (Ivoclar Vivadent, Schaan, Liechtenstein), Vintage Halo (SHOFU Inc., Kyoto, Japan), and Ceramco 3 (Ceramco-Dentsply, Burlington, NJ, USA) in the following fixed ratios (0 wt%, 25 wt%, 50 wt%, 75 wt%, and 100 wt%) and then fired. A total of 150 specimen of ceramic fired were manufactured in a regular size (W: 8.5 mm, L: 10.5 mm, and H: 1.5 mm). For color and translucency, $L^*$, $a^*$, and $b^*$ were measured and Two-way analysis of variance (ANOVA) and One-way analysis of variance (ANOVA) were used for data analysis (${\alpha}$=0.05). RESULTS. The higher the mixing ratio was, $L^*$, $a^*$, and $b^*$ of IPS e.max Ceram were all increased, and $L^*$ of Vintage Halo was reduced and $a^*$ and $b^*$ were increased. $L^*$ and $a^*$ of Ceramco3 were reduced and $b^*$ of Ceramco3 was increased. Color difference (${\Delta}E^*ab$) was increased in all three products as the mixing ratio got higher. Increased mixing ratios resulted in decreased translucency parameter (TP) values for IPS e.max Ceram but increased TP values for Vintage Halo and Ceramco3. CONCLUSION. In this limited study, CIE $L^*$, $a^*$, and $b^*$ were influenced by the mixing ratio of the A3 powders and porcelain powder mixtures represented a various color and translucency.

• 대한화장품학회지
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• 제37권2호
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• pp.121-127
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• 2011

미백과 더불어 피부 칙칙함은 많은 여성들의 고민거리다. 칙칙함이란 피부의 붉은 기와 광택이 감소하고, 노란기는 증가하며 피부의 명도가 저하되어 보이는 상태를 말하며, 최근까지 피부 칙칙함의 경우, 일반적으로 피부색 측정을 통해 명도, 색 불균일성 등으로 많이 평가하였다. 명도는 $L^{*} \;a^{*}\; b^{*}$ 표색계(CIELAB color space system)의 $L^{*}$로 나타낸다. 하지만 $L^{*}$값은 칙칙함 중 하나의 현상, 명도를 측정한 지표일 뿐만 아니라 칙칙함(투명감)같은 인지효능과의 연계점을 찾기 힘든 단점이 있다. 이에 투명감이 높은 피부(칙칙하지 않은 피부)는 동일한 광세기가 피부로 입사하였을 때 피부 내부로부터 빛이 많이 돌아오는 피부이고 이는 확산 반사광(내부 반사광)이 큰 피부라는 피부 투명감 측정 방법에 따라 편광기술을 이용한 자사 제작의 이전 투명감 측정 기기와 측정의 용이성과 휴대성을 개선한 $Lumiscan^{TM}$이라 명명한 신규기기를 개발, 기존 투명감 측정기기와 신규기기로 20 ~ 30대 남성과 여성의 얼굴 피부 투명도를 측정하여 육안을 통한 투명감과 확산반사광 값의 관계를 통해 신규기기의 성능을 확인하고자 하였다. 이번 연구에서 육안 평가와 신규기기의 확산 반사광 값 사이에 단순 비교가 아닌 강한 상관성(R = 0.732, p < 0.01)이 있음을 확인할 수 있었으며 이전 자사개발 기기가 지닌 낮은 휴대성과 측정의 불편함을 개선한 $Lumiscan^{TM}$의 성능평가를 확인할 수 있었다.

• 대한치과기공학회지
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• 제44권4호
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• pp.118-125
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• 2022

Purpose: The color of dental zirconia is very important in terms of aesthetics. To reproduce the color tone, a colorant is applied to zirconia to express the color tone. I would like to point out that the color, brightness, and saturation of the colorant used to express the color A3 may vary depending on the manufacturer. Methods: Each zirconia block received a total of 25 circular specimens for the experiment. The zirconia specimen was then deposited by colorant type to reproduce the color tone. Color differences and translucency were measured using a spectrophotometer. To compare and analyze the zirconia color according to the type of colorant, one-way ANOVA was used. Results: For each type of zirconia colorant, there was no statistically significant difference in translucency or b^* (p>0.05). There was a statistical difference in L^* and a^* (p<0.05). Conclusion: The ΔE^*ab (D65) value is less than 5.5 or less, and the color difference is within an acceptable range.

• Restorative Dentistry and Endodontics
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• 제40권2호
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• pp.128-135
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• 2015

Objectives: This study evaluated the effects of the resin thickness on the microhardness and optical properties of bulk-fill resin composites. Materials and Methods: Four bulk-fill (Venus Bulk Fill, Heraeus Kulzer; SDR, Dentsply Caulk; Tetric N-Ceram Bulk Fill, Ivoclar vivadent; SonicFill, Kerr) and two regular resin composites (Charisma flow, Heraeus Kulzer; Tetric N-Ceram, Ivoclar vivadent) were used. Sixty acrylic cylindrical molds were prepared for each thickness (2, 3 and 4 mm). The molds were divided into six groups for resin composites. The microhardness was measured on the top and bottom surfaces, and the colors were measured using Commission Internationale d'Eclairage (CIE) $L^*a^*b^*$ system. Color differences according to the thickness and translucency parameters and the correlations between the microhardness and translucency parameter were analyzed. The microhardness and color differences were analyzed by ANOVA and Scheffe's post hoc test, and a student t-test, respectively. The level of significance was set to ${\alpha}=0.05$. Results: The microhardness decreased with increasing resin thickness. The bulk-fill resin composites showed a bottom/top hardness ratio of almost 80% or more in 4 mm thick specimens. The highest translucency parameter was observed in Venus Bulk Fill. All resin composites used in this study except for Venus Bulk Fill showed linear correlations between the microhardness and translucency parameter according to the thickness. Conclusions: Within the limitations of this study, the bulk-fill resin composites used in this study can be placed and cured properly in the 4 mm bulk.