• The Journal of Korean Academy of Prosthodontics
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• v.59 no.2
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• pp.190-200
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• 2021

Purpose. The aim of this study was to evaluate biaxial flexural strength and hardness of colored monolithic zirconia after dipping in different time intervals of coloring solution. Materials and Methods. Disk shaped specimens were prepared from monolithic zirconia (Eclipse V2.0, AMS, Gimpo, Korea). Four experimental groups were categorized (n = 12) due to coloring time (PU (0s); ST (8s); OV (1 min); PS (preshade)), to evaluate biaxial flexural strength and Vickers hardness. After fracture, X-ray diffraction analysis was performed using fractured specimens. Results were analyzed with one-way ANOVA test. Results. There was no significant difference between groups in the biaxial flexural strength test. However, in the Vickers hardness test, the group with standard dipping time (ST) showed significantly higher value than the group without dipping in coloring liquid (PU)(P=.038). Also, there was no significant difference in the rest of the groups (P>.05). As a result of X-ray diffraction analysis, specific peaks of tetragonal phase were shown and the volume of monoclinic phase fraction was lower than 25%. Conclusion. Although this study has several limitations, coloring liquids had no significant effect on biaxial flexural strength. Vickers hardness was significantly different between the group to which the coloring liquid was applied and the group to which the coloring solution was not applied, but there was no significant difference between the other groups. Also, the flexural strength of monolithic zirconia corresponds to Class 5 of the minimal flexural strength standard according to the use of dental ceramics.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.124-130
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• 2021

Dental prosthesis translucency importantly contributes to aesthetic outcomes. The purpose of this study was to investigate the effect of drying time and zirconia coloring agent type on translucency. For the experiment, 90 circular specimens were fabricated for each zirconia block. Then, zirconia specimens were treated with a coloring agent for 180 seconds and dried for 0 seconds (undried), 30 seconds (intermediate dry), or 30 minutes (complete dry). Then, a specimen was placed on a black standard tile or a white standard tile, and using a standard D65 light source reflected was measured using the light removal method. A total of three repeated measurements were obtained per specimen. One-way ANOVA was used to compare and analyze the relationship between zirconia translucency and drying time. Zirconia and coloring liquid types were significantly associated with translucency (P < 0.001). Although no significant difference was observed with respect to drying time (P > 0.922), zirconia in the completely dried (30 minutes) state was more translucent.

• The Journal of Korean Academy of Prosthodontics
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• v.60 no.3
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• pp.293-300
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• 2022

Various materials and restorative options have been introduced recently with growing interest in esthetic dental treatment in modern society. Zirconia is especially known for its biocompatibility as well as remarkable toughness and resistance to wear, but it is limited in its use for esthetically focused treatment in anterior region for its white opacity. Lately the development of different kinds of zirconium blocks, such as colored block, clear block, and multi-layered block, allowed more extensive use of zirconia as a treatment option. This report describes a case, in which a prosthetic crown maxillary anterior region was stained with a combination of various coloring liquids before sintering to reproduce natural-looking color scheme in final restoration. The case was reported as the utilization of coloring liquid on monolithic zirconia crown could achieve esthetically satisfying prosthesis for both dentist and patient.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.3
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• pp.312-319
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• 2009

Statement of problem: Delamination of veneering porcelain from underlying ceramic substructures has been reported for zirconia-ceramic restorations. Colored zirconia cores for esthetics have been reported that their bond strength with veneered porcelain is weaker compared to white zirconia cores. Purpose: This study aimed to investigate the shear bond strength by manufacturing the veneering porcelain on the colored zirconia core, using the layering technique and heat-pressing technique, and to evaluate the clinical stability by comparing the result of this with that of conventional metal ceramic system. Material and methods: A Metal ceramic (MC) system was tested as a control group. The tested systems were Katana zirconia with CZR (ZB) and Katana Zirconia with NobelRondo Press (ZP). Thirty specimens, 10 for each system and control, were fabricated. Specimen disks, 3 mm high and 12 mm diameter, were fabricated with the lost-wax technique (MC) and the CAD-CAM (ZB and ZP). MC and ZB specimens were prepared using opaque and dentin veneering ceramics, veneered, 3 mm high and 2.8 mm in diameter, over the cores. ZP specimens were prepared using heat pressing ingots, 3 mm high and 2.8mm in diameter. The shear bond strength test was performed in a Shear bond test machine. Load was applied at a cross-head speed of 0.50 mm/min until failure. Mean shear bond strengths (MPa) were analyzed with the One-way ANOVA. After the shear bond test, fracture surfaces were examined by SEM. Results: The mean shear bond strengths (SD) in MPa were MC control 29.14 (2.26); ZB 29.48 (2.30); and ZP 29.51 (2.32). The shear bond strengths of the tested systems were not significantly different (P > .05). All groups presented cohesive and adhesive failures, and showed predominance of cohesive failures in ceramic veneers. Conclusion: 1. The shear bond strengths of the tested groups were not significantly different from the control group (P >.05). 2. There was no significant different between the layering technique and the heat pressing technique in the veneering methods on the colored zirconia core. 3. All groups presented cohesive and adhesive failures, and showed predominance of cohesive failures in ceramic veneers.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.176-182
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• 2018

One of the most important factor of esthetic prosthesis is the color of the teeth. Zirconia is produced in the process of design, milling, coloring, drying, and sintering. The effect of the drying degree of zirconia colorant on the color tone is examined. For the experiment, a total of 45 zirconia specimens(15 for each) were fabricated by using cad/cam system. The zirconia specimens(L block(LAZOR), Z block(Zircos-E block posterior), A block(AlphaZ)) were then subjected to zirconia sintering in accordance with the manufacturer's instructions, using a chemical coloring agent to Non-drying(0sec), intermediate (10sec), and completely dried (10min) temperature holding times. The color tone was measured using a spectrophotometer. The results were analyzed with a One-way analysis of variance and the Tukey post-hoc test (${\alpha}=.05$) The $L^*$ values of L, A specimens, $a^*$ values of A specimens, and $b^*$ values of Z specimens were not statistically different according to the degree of drying (p>0.05), While the $L^*$ value of Z specimen, $a^*$ value of L, Z specimen, $b^*$ values of L, A specimens were statistically different according to the degree of drying(p <0.05). In conclusion, the drying of zirconia colourants improves zirconia brightness and increases the optical properties of the enamel.

• Korean Journal of Dental Materials
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• v.44 no.2
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• pp.171-178
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• 2017

The purpose of this study is to investigate the effect of number of times dipped in coloring liquid and sintering temperature on the flexural strength of zirconia ceramic. In this study, using a zirconia block having improved transparency, specimens with size of $25mm{\times}2mm{\times}1.5mm$ were fabricated. The zirconia ceramic specimens were divided into three groups according to the number of times dipped in coloring liquid by 0, 2 and 4 times, and dyed in the coloring liquid to give color to each specimen. Then, after sintering them at the final temperature of $1,450^{\circ}C$ and $1,600^{\circ}C$, flexural strength was measured using a universal testing machine (total 6 group, n=10 for each group). Also, a scanning electron microscopy (SEM) was performed to observe its microstructure, and the data obtained through the experiment were analyzed with two-way ANOVA. The results of the flexural strength analysis show that the highest value was measured $762.3{\pm}42.3MPa$ in EKL2 group, while the lowest value was $516.4{\pm}77.1MPa$ in EKH4 group. According to the results of the two-way ANOVAs, flexural strength was not related with interaction between sintering temperature and number of times dipped in coloring liquid ($R^2=0.737$). However, there were statistically significant differences in flexural strength depending on sintering temperature (P<0.001). The flexural strength of zirconia ceramics having improved transparency was dependent on sintering temperature. The number of times dipped in the coloring liquid did not affect flexural strength of the zirconia ceramic having improved transparency.

• Journal of Dental Rehabilitation and Applied Science
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• v.34 no.4
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• pp.306-316
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• 2018

Monolithic zirconia has been widely used in fixed partial dentures due to high strength and fracture toughness. Nevertheless, the usage of monolithic zirconia in anterior restoration was limited because of opacity. Recently, esthetic monolithic zirconia blocks are developed by improving translucency and using various shading systems. Manufacturer introduces 3M $Lava^{TM}$ Esthetic with increased cubic phase and fluorescent ingredients is more esthetic than previous monolithic zirconia. This case report describes favorable anterior restorations using translucent monolithic zirconia.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.8
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• pp.2150-2156
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• 2009

The effects of MgO and coloring agents on the physical properties and color of zirconia based ceramics with glass frit were studied. The addition of MgO was effective on the coloring of zirconia-20wt% glass frit system. Major factor on the coloring was turned out to be sintering temperature. Coloring agents was turned out to be more effective than the addition of MgO on the coloring of zirconia base ceramics. Specimen without glass frit showed drastic change in color, while specimen with 20wt% glass frit revealed a limited change in color. This means that the addition of glass frit suppresses the coloring of zirconia based ceramics. The effect of sintering temperature on coloring revealed little change in color.

• The Journal of Korean Academy of Prosthodontics
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• v.49 no.1
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• pp.73-79
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• 2011

Purpose: The aim of this study was to evaluate the effect of repeated firings on the color of zirconia restoration with different shading method. Materials and methods: Three different types of zirconia frameworks (adding metallic pigments to the initial zirconia powder before sintering (Group NM), dipping the milled frameworks in dissolved coloring agents (Group KI), or application of liner material to the sintered white frameworks (Group KW) were used to support A3 shade dentin porcelain. Repeated firings (3, 5, or 7) were performed, color differences among ceramic specimens were measured using a colorimeter. Repeated measurements analysis of variance (ANOVA) was used to analyze the data for significant difference. The Tukey Honestly Significant Different (HSD) test was used to perform multiple comparisons (${\alpha}$ = .05). Results: 1. $L^*a^*b^*$ values of the ceramic systems were affected by the number of firings (1, 3, 5 or 7 firings) (P < .001) and shading methods (P < .001). 2. As the number of firings increased, the $L^*$ (for all groups) and $a^*$ value (for KW and NM groups) decreased and the $b^*$ value(for all groups) increased. 3. The mean color differences caused by repeated firings were perceptible (${\Delta}E$ > 1) for group KW and KI fired after 3 times, except for group NM fired after 7 times. 4. In order of decreasing ${\Delta}E$ value fired after 7 times, the values were group KI(${\Delta}E$ = 2.26) > group KW (${\Delta}E$ = 1.47) > group NM (${\Delta}E$ = 1.08) (P < .001). Conclusion: Repeated firings influenced the color of the zirconium-oxide all-ceramic specimens with different shading methods.

• Journal of dental hygiene science
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• v.15 no.5
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• pp.577-584
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• 2015

The purpose of this study was to evaluate the effect of metal chloride infiltration treatment on color and strength changes of the yttria-stabilized tetragonal zirconia polycrystals (Y-TZP). Fifty disc specimens were prepared with a Y-TZP powder (ZPEX; Tosoh, Japan). Thirty different metal chloride solutions containing 0.03~0.08 wt% chromium and 0.03~0.07 wt% terbium ions were prepared. Presintered Y-TZP specimens were soaked in metal chloride coloring liquids for 3 minutes and sintered in air at $1,450^{\circ}C$ for 2 hours. The color of the specimens was measured with spectrophotometer and color difference (${\Delta}E^*$) was obtained based on the CIE $L^*$, $a^*$, $b^*$ color coordinate values. To evaluate the effect of metal chloride infiltration strength changes, the biaxial flexural test was performed at crosshead speed 0.5 mm/min. Colors of the sintered Y-TZP showed the colors of Vita shade guide A1, A2 and A3 with the infiltration of chromium and terbium chloride solutions. Density of the sintered Y-TZP increased by the infiltration of chromium and terbium chloride solutions. Bi-axial flexural strength of the sintered Y-TZP did not show statistically significant differences by the infiltration of chromium and terbium chloride solutions (p>0.05). Chromium and terbium chloride did not affect the crystal phase of zirconia, and all specimens showed tetragonal phase. Accordingly, this study suggests that chromium and terbium chlorides can make colored zirconia while adding in a liquid form. The color of colored zirconia differ from that of vita shade guide but it can use all ceramic restoration as substructure in dental clinic.