• The Journal of Advanced Prosthodontics
• /
• v.6 no.2
• /
• pp.71-78
• /
• 2014

PURPOSE. The objective of this study was to evaluate the clinical acceptability of all-ceramic crowns fabricated by the digital veneering method vis-$\grave{a}$-vis the traditional method. MATERIALS AND METHODS. Zirconia specimens manufactures by two different manufacturing method, conventional vs digital veneering, with three different thickness (0.3 mm, 0.5 mm, 0.7 mm) were prepared for analysis. Color measurement was performed using a spectrophotometer for the prepared specimens. The differences in shade in relation to the build-up method were calculated by quantifying ${\Delta}E^*$ (mean color difference), with the use of color difference equations representing the distance from the measured values $L^*$, $a^*$, and $b^*$, to the three-dimensional space of two colors. Two-way analysis of variance (ANOVA) combined with a Tukey multiple-range test was used to analyze the data (${\alpha}$=0.05). RESULTS. In comparing means and standard deviations of $L^*$, $a^*$*, and $b^*$ color values there was no significant difference by the manufacturing method and zirconia core thickness according to a two-way ANOVA. The color differences between two manufacturing methods were in a clinically acceptable range less than or equal to 3.7 in all the specimens. CONCLUSION. Based on the results of this study, a carefully consideration is necessary while selecting upper porcelain materials, even if it is performed on a small scale. However, because the color reproducibility of the digital veneering system was within the clinically acceptable range when comparing with conventional layering system, it was possible to estimate the possibility of successful aesthetic prostheses in the latest technology.

• The Journal of Advanced Prosthodontics
• /
• v.9 no.5
• /
• pp.394-401
• /
• 2017

PURPOSE. The purpose of this study was to compare the optical properties of pre-colored dental monolithic zirconia ceramics of various thicknesses sintered in a microwave and those in a conventional furnace. MATERIALS AND METHODS. A2-shade of pre-colored monolithic zirconia ceramic specimens ($22.0mm{\times}22.0mm$) in 3 thickness groups of 0.5, 1.0, and 1.5 mm were divided into 2 subgroups according to the sintering methods (n=9): microwave and conventional sintering. A spectrophotometer was used to obtain CIELab color coordinates, and translucency parameters and CIEDE2000 color differences (${\Delta}E_{00}$) were measured. The relative amount of monoclinic phase ($X_m$) was estimated with x-ray diffraction. The surface topography was analyzed by atomic force microscope and scanning electron microscope. Statistical analyses were conducted with two-way ANOVA (${\alpha}=.05$). RESULTS. There were small interaction effects on CIE $L^*$, $a^*$, and TP between sintering method and thickness (P<.001): $L^*$ (partial eta squared ${{\eta}_p}^2=0.115$), $a^*$ (${{\eta}_p}^2=0.136$), and TP (${{\eta}_p}^2=0.206$), although higher $b^*$ values were noted for microwave sintering regardless of thickness. Color differences between two sintering methods ranged from 0.52 to 0.96 ${\Delta}E_{00}$ units. The $X_m$ values ranged from 7.03% to 9.89% for conventional sintering, and from 7.31% to 9.17% for microwave sintering. The microwave-sintered specimen demonstrated a smoother surface and a more uniform grain structure compared to the conventionally-sintered specimen. CONCLUSION. With reduced processing time, microwave-sintered pre-colored dental monolithic zirconia ceramics can exhibit similar color perception and translucency to those by conventional sintering.

• Journal of Technologic Dentistry
• /
• v.41 no.3
• /
• pp.195-201
• /
• 2019

Purpose: This study was investigated the effect of multilayer zirconia block type and sintering method on fracture strength, micro structure and color of zirconia copings. Methods: Three kinds of multi-layered zirconia blocks were used to identify the effects of the kinds of multi-layered zirconia blocks and sintering methods on fracture strength and color reproducibility of zirconia copings. 60 Zirconia copings were fabricated and fracture strength, micro structure and color reproducibility were compared and evaluated. Results: In all the blocks, the CS group, which refers to the general sintering method had higher fracture strength of zirconia copings than the MS group that refers to the microwave sintering method(MCS/MMS; 2,107.5N/1,930.4N, DCS/DMS; 917.0N/879.1N, UCS/UMS; 2,256.9/2,050.7N). In relation to CIE $L^*$, $a^*$, $b^*$ values of zirconia copings depending on the kinds of multi-layered zirconia blocks and sintering methods, the MS group using the microwave sintering method had lower brightness and chroma than the CS group using the general sintering method. Conclusion: In all the blocks, the CS group(general sintering) had higher fracture strength of zirconia copings than the MS group(microwave sintering). In relation to CIE $L^*$, $a^*$, $b^*$ values of zirconia copings depending on the kinds of multilayered zirconia blocks and sintering methods, the MS group using the microwave sintering method had lower brightness and chroma than the CS group using the general sintering method.

• Imaging Science in Dentistry
• /
• v.41 no.1
• /
• pp.11-16
• /
• 2011

Purpose : The aim of this study was to evaluate the effect of liquid crystal display (LCD) monitor type and observer experience on the diagnostic performance in soft-copy interpretations of maxillary sinus inflammatory lesions on panoramic radiographs. Materials and Methods : Ninety maxillary sinuses on panoramic images were grouped into negative and positive groups according to the presence of inflammatory lesions, using CT for confirmation. Monochrome and color LCDs were used. Six observers participated and ROC analysis was performed to evaluate the diagnostic performance. The reading time, fatigue score, and inter-/intra-observer agreements were assessed. Results : The interpretation of maxillary sinus inflammatory lesions was affected by the LCD monitor type used and by the experience of the observer. The reading time was not significantly different, however the fatigue score was significantly different between two LCD monitors. Inter-observer agreement was relatively good in experienced observers, while the intra-observer agreement for all observers was good with monochrome LCD but not with color LCD. Conclusion : The less experienced observers showed lowered diagnostic ability with a general color LCD.

• Journal of Korean Dental Science
• /
• v.8 no.2
• /
• pp.49-56
• /
• 2015

Purpose: The effect of accelerated aging on color stability of various dual-cured self-adhesive resin cements were evaluated in this study. Materials and Methods: Color stability was examined using three different brands of dual-cured self-adhesive resin cements: G-CEM LinkAce (GC America), MaxCem Elite (Kerr), and PermaCem 2.0 (DMG) with the equivalent color shade. Each resin cement was filled with Teflon mold which has 6 mm diameter and 2 mm thickness. Each specimen was light cured for 20 seconds using light emitting diode (LED) light curing unit. In order to evaluate the effect of accelerated aging on color stability, color parameters (Commission Internationale de l'Eclairage, CIE $L^*$, $a^*$, $b^*$) and color differences (${\Delta}E^*$) were measured at three times: immediately, after 24 hours, and after thermocycling. The $L^*$, $a^*$, $b^*$ values were analyzed using Friedman test and ${\Delta}E^*$ values on the effect of 24 hours and accelerated aging were analyzed using t-test. These values were compared with the limit value of color difference (${\Delta}E^*=3.7$) for dental restoration. One-way ANOVA and Scheff's test (P<0.05) were performed to analyze each ${\Delta}E^*$ values between cements at each test period. Result: There was statistically significant difference in comparison of color specification ($L^*$, $a^*$, $b^*$) values after accelerated aging except $L^*$ value of G-CEM LinkAce (P<0.05). After 24 hours, color difference (${\Delta}E^*$) values were ranged from 2.47 to 3.48 and $L^*$ values decreased and $b^*$ values increased in all types of cement and MaxCem Elite had high color stability (P<0.05). After thermocycling, color change's tendency of cement was varied and color difference (${\Delta}E^*$) values were ranged from 0.82 to 2.87 and G-CEM LinkAce had high color stability (P<0.05). Conclusion: Color stability of dual-cured self-adhesive resin cements after accelerated aging was evaluated and statistically significant color changes occurred within clinically acceptable range.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.31 no.2
• /
• pp.96-103
• /
• 2015

Purpose: The purpose of this study was to spectrophotometrically evaluate the influence of porcelain layer thickness and substructure. Materials and Methods: Four groups of porcelain specimens (metal and ceramic substructure) was prepared for analysis. Color parameters were measured with spectrophotometer and color difference (${\Delta}E*$) were calculated. T-test and one-way ANOVA test were used to find out significant difference and Tukey test was used to identify where the difference ware. Results: Increasing the thickness of porcelain decreased values (P < 0.05). Increasing the thickness of porcelain on ceramic substructure decreased the $a^*$ (P < 0.05) but, the $b^*$ were not statistically different. Total color difference (${\Delta}E*$) were below 1 when the difference of porcelain thickness were 0.5 mm. Conclusion: The thickness of porcelain are the factor effecting on color. This study will help the color are controlled by changing the thickness of porcelain clinically.

• The Journal of the Korean dental association
• /
• v.52 no.9
• /
• pp.541-549
• /
• 2014

The restorative treatment using titanium implants has become a standard procedures in everyday clinical practice. However, there are several concerns about the use of titanium as a materials. Above all, the grayish metal color provokes esthetic problems when the soft tissue around the implants is not optimal. Recently, zirconia has been emerging as an alternative to titanium due to its white color and superior physicochemical properties. In this paper, the current findings about zirconia implants was reviewed based on the results from animal and clinical experiments. In addition, the immediate implantation protocols using the natural tooth form zirconia implants was introduced as a novel procedures and future perspectives were discussed.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.60 no.6
• /
• pp.1183-1189
• /
• 2011

In this study, we propose the unsupervised image segmentation algorithm to estimate dental plaque accumulations on digital imaging with methylene blue disclosed plaque. With this aim, RGB color plane is mapped into HSI coordinates and the circular histogram of Hue is reconstructed by applying Otsu's threshold level. The histogram distribution on Saturation features is also analyzed by maximizing the variance between a plaque candidate and non-plaque one. The dental plaque regions are resolved by applying the composite decision logics based on the threshold level of Hue and Saturation.

• The Journal of Advanced Prosthodontics
• /
• v.12 no.2
• /
• pp.55-60
• /
• 2020

PURPOSE. The aim was to evaluate the effect of four acidic beverages on the roughness (Ra) and color change (ΔE_ab) of two brands of artificial teeth and a heat-polymerized acrylic resin (HPAR) for use in a prosthetic base. MATERIALS AND METHODS. All materials were divided into 5 groups, according to the used acidic beverage (artificial saliva - control, red wine, orange juice, coke-based, and lemon juice-based soft drink). The immersion process was divided into two stages: T1 - immersion in the acidic solutions for 10 minutes for 14 days; T2 - after T1, the samples were immersed in grape juice for 14 days. The Ra of the samples was evaluated in a rugosimeter and the ΔE_ab in a spectrophotometer, before and after the immersions. The analysis of variance of one (ΔE_ab) and two factors (Ra) and Tukey were performed (α=.05). RESULTS. There was a statistical difference for roughness after immersion (T1) for Trilux and Tritone teeth, regardless of the acid solution. For Trilux teeth, all acid solutions increased Ra (P<.05). For Tritone teeth, only the coke-based soft drink did not statistically change Ra. Grape juice (T2) altered Ra only of artificial teeth (P<.05). The color was changed for all materials, after T1 and T2. CONCLUSION. In general, the acidic solutions changed the Ra and ΔE_ab of HPAR and artificial teeth after T1. The grape juice altered the roughness only of the artificial teeth, promoting a clinically acceptable color change in the materials.

• Journal of Technologic Dentistry
• /
• v.33 no.3
• /
• pp.203-210
• /
• 2011

Purpose: The purpose of this study was to compare color correspondence of different sizes of Vita Mark II$^{(R)}$ and TriLuxe$^{(R)}$ Feldspar blocks. Methods: The three commercially available shades(1M2, 2M2, 3M2) of Mark II & TriLuxe blocks for the CEREC$^{(R)}$ CAD/CAM system were examined. For each of three colors, three different sizes were tested, 5 blocks each. The measurements were made using a spectrophotometer equipped with an integrating sphere using the CIE $L^*$, $a^*$, $b^*$ colorimetric system. Results: The $L^*$, $a^*$, $b^*$ value of Vita Mark II$^{(R)}$ ceramic block showed significantly higher than TriLuxe$^{(R)}$ ceramic block(p<0.05). In comparing the Vita Mark II$^{(R)}$ specimen of the three different shade, color differences between materials(${\Delta}E^*$) showed the lowest value of 2.09, and the highest was 2.24. ${\Delta}E^*$ values of the materials of Vita Mark II$^{(R)}$ were higher than 2. As the size of ceramic block differed, the color correspondence of Vita Mark II$^{(R)}$ showed statistically significant difference but, this result is clinically acceptable. Conclusion: All the different sizes of the different shades of Vita TriLuxe$^{(R)}$ blocks for the CEREC$^{(R)}$ system showed the high degree of color correspondence necessary in industrially prefabricated CAD/CAM blocks. The results of the present study suggested that it would be necessary to establish the reproducible and constant color specification system for an esthetic restoration.