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PubMed2005

Color formulation and reproduction of opaque dental ceramic.

OBJECTIVES: The purpose of this study was to determine the validity and accuracy of mixing opaque feldspathic dental ceramic to obtain specific shades using two methods: (1) Concentration Additivity of Optical Parameters (CALAB) and (2) Concentration Additivity of Kubelka-Munk Optical Coefficients (CAK/S). METHODS: A total of 25 opaque feldspathic dental ceramic specimens were fabricated by mixing six different pure shades in different concentrations. The reflectance spectra were measured and the actual CIELAB L*, a* and b* coordinates were obtained for the 25 specimens. The CALAB and CAK/S methods were used to predict the L*, a* and b* values with reference to the concentrations of the pure shades. Correlation analysis was carried out between the actual and predicted L*, a* and b* values for both methods. The color differences (DeltaE*) between actual and predicted L*, a* and b* values were also calculated and analyzed using repeated measures ANOVA. RESULTS: Pearson's correlation coefficients between predicted and actual values for both methods were greater than 0.98. The mean DeltaE*s were 0.24 (0.11) for CALAB method and 0.21 (0.11) for the CAK/S method. The repeated measures ANOVA revealed a statistically significant difference (P=0.0213) between the mean DeltaE*s from the two methods. SIGNIFICANCE: Both methods produced mean DeltaE*s between the actual and predicted methods that were below the threshold of human perceptibility. The simpler CALAB method can be used to determine the opaque ceramic mixture for specific shades with accuracy.

Aluminum Silicates↗
PubMed1999

Color stability of heat-polymerized and autopolymerized soft denture liners.

STATEMENT OF PROBLEM: The physical and mechanical properties of soft denture liners are influenced by a number of factors. Aging is one factor that has an effect on the characteristics of polymers. The resistance of denture liners to aging can potentially influence the color stability of these liners. PURPOSE: This study attempted to determine the color stability of soft liners by subjecting them to an in vitro accelerated aging test. MATERIAL AND METHODS: Two autopolymerizing and 3 heat polymerizing commercially available soft denture lining materials were tested. Seven sample disks were made of each material according to manufacturers' instructions. Color measurements were recorded before and after the accelerated aging process. Color changes (DeltaE) were calculated by measuring tristimulus values at several wavelengths in the visual spectrum with the use of Commission International de l'Eclairge Lab (CIE-LAB) uniform color scale. RESULTS: Kruskall-Wallis variance analysis and Mann-Whitney U-Wilcoxon rank sum W tests were performed for statistical comparison of the DeltaE values. Ufigel P and Simpa liner materials showed significantly greater color changes than the other tested materials. There were no significant differences in color change among Ufigel L-Molloplast B, Ufigel L-Flexor, and Molloplast B-Flexor liner materials. However, a significant difference in color change was found between Ufigel P and Simpa liners. CONCLUSION: Heat-polymerized soft liners were more color stable than autopolymerized soft liners. No significant differences were found among heat polymerized materials; however, significant differences in color change were found between the 2 autopolymerized liners.

Analysis of Variance↗
PubMed2005

The use of digital imaging for colour matching and communication in restorative dentistry.

OBJECTIVE: To develop a shade matching method based on digital imaging and to compare observers' ability using this method with the conventional one set against a spectrophotometric 'gold standard'. METHODS: Two Vita Lumin shade guides were used in this study, nine shades being selected from the first Vita Lumin shade guide, A2, A3, A3.5, B2, B3, B4, C1, C2 and C3. A second shade guide was used to match the selected shades. A Nikon Coolpix 990 digital camera with Nikon SB21B ring flash was used to record the digital images of the shade tabs of the two shade guides and the images were processed using Adobe Photoshop software. A total of 27 samples (three replicates of each shade of the nine tabs selected) were matched with a digital shade guide prepared from the digital images of the second shade guide by 10 observers on a computer screen (computerised matching method). The 10 observers also matched the same shade tabs using the conventional matching method simulated in a phantom head. In addition, colour values were obtained from the digital images using Adobe Photoshop and quantified according to an internationally recognised scale as CIELAB colour values, L*,a*,b*. The relationship of the digitally derived CIELAB values to the CIELAB values obtained using a reflectance spectrophotometer was investigated. RESULTS: The cross tabulation statistical analysis showed a statistically significant difference (p<0.001) between the conventional method and the computer method with a 43% and 61.1% correct match respectively. There was also a statistically significant difference between observers in both methods (p<0.001 and p<0.04 for the conventional and computer methods respectively). A statistically significant high correlation of the CIELAB colour values were found between both colour measurement methods (p<0.001). CONCLUSION: The observers' shade matching performance was significantly better with the computer method compared with the conventional one. There was a large variation in the observers' matching ability. The digital camera can be used as a means of colour measurements in the dental clinic.

Color↗
PubMed1996

Effect of firing on the color stability of a light-cured ceramic stain.

PURPOSE: This study evaluated the color stability of four stains of a light-cured porcelain stain system between the light-cured and fired stages. MATERIALS AND METHODS: Thirty-six ceramometal discs 20 mm in diameter and 2 mm in thickness were cast to provide the substrate on which Ceramco II porcelain was applied. The porcelain was polished to a uniform thickness of 2 mm, and the samples were divided into four groups and assigned a color (yellow, orange, green, or blue). Orbit LC stain was applied in a thin layer and light-cured for 40 seconds. After light-curing, three color readings were made with a Minolta Chroma Meter II. The porcelain discs were then fired in a porcelain oven and three color measurements were again made. The pre- and postfired Commission Internationale de I'Eclairage L*a*b* values were recorded and the color difference (delta E) was calculated for each specimen. The clinical significance for the computed delta E ratings was completed according to previously modified criteria. RESULTS: The results show that the mean delta E between the light-cured and fired stages of Orbit LC are clinically acceptable. No statistically significant differences (p < .05) were observed between any of the four groups. CONCLUSIONS: A light-cured porcelain stain system was evaluated for color stability between light-cured and fired stages. Within the conditions of this study, the following conclusions can be made: (1) There was no clinically significant color difference between light-cured and fired stages for the stain colors evaluated; and (2) the final color of the restorations altered with light-cured stains can be predicted before firing.

Analysis of Variance↗
PubMed1997

Construction of a custom-shaded interim denture using visible-light-cured resin.

A patient treatment is presented to demonstrate a technique using visible-light-cured (VLC) resin to create a characterized denture base for an interim denture. This indication for characterization is routinely seen with African-Americans with dark-pigmented gingiva. Using a combination of blue VLC tray resin and pink VLC denture base resin, the mixture achieves a darker-colored denture base. This technique was used for the fabrication of an interim denture for a patient who required an immediate interim denture. The prosthesis was worn during the healing phase and allowed the patient to function while the definitive prosthesis was being fabricated.

Adult↗
PubMed2004

Accelerated aging effects on color and translucency of bleaching-shade composites.

PURPOSE: This study was performed to evaluate the influence of accelerated aging on the color and translucency parameter (TP) of bleaching-shade resin composites. MATERIALS AND METHODS: Thirty-three bleaching shades and two control conventional shades of microhybrid (MH) and microfill (MF) resin composite specimens (n = 5) were aged in an accelerated aging chamber set to standard CAM 180 cycles. One side of each specimen was evaluated for surface color and TP changes compared with baseline in increments of 150 kJ/m2 for intervals up to 450 kJ/m2 using a spectrophotometer. A deltaE* > or = 3.7 was considered to be a poor match, and the total TP range was divided into three equal parts representing low, medium, and high translucency. Data were analyzed with analysis of variance. RESULTS: Compared to the baseline, deltaL*, deltaa*, deltab*, and deltaE* ranges at 450 kJ/m2 were -0.8 to 5.0, -0.6 to 1.2, -8.3 to 0.0, and 0.7 to 8.6 for MH and 0.2 to 1.3, 0.1 to 1.3, -2.5 to 1.1, and 1.7 to 2.7 for MF composites. Scheffé's S intervals (p = .05) for comparisons of deltaL*, deltaa*, deltab*, and deltaE* values of MH composites between baseline and 450 kJ/m2 were 1.6, 0.6, 1.7, and 1.5, respectively. Corresponding Tukey-Kramer intervals for MF composites were 0.7, 0.3, 0.6, and 0.6, respectively. TP values at baseline ranged from 0.9 to 4.3 for MH and from 1.4 to 2.2 for MF composites, whereas deltaTP for baseline minus 450 kJ/m2 ranged from -1.1 to 1.7 for MH and from -0.1 to 0.3 for MF composites. Scheffé's S interval (p = .05) for comparisons of deltaTP values of MH composites for baseline minus 450 kJ/m2 was 1.0. Corresponding Tukey-Kramer interval for MF composites was 0.4. CONCLUSIONS: Aging-dependent color changes at 450 kJ/m2 were above the limit that indicated a poor match for 18/26 MH, while corresponding values for microfills were within acceptable range. Accelerated aging generally caused decreases in L* (specimens became darker) and a* values (specimens became redder), while b* values increased (specimens became more chromatic) for both MH and MF composites. TP was relatively stable during aging for both MH and MF composites.

Color↗
PubMedDate not supplied

A simple screening test for color matching in dentistry.

This study compared a simple and readily available shade guide color-matching test with the general industry standard test for color discrimination. This study indicates that a simple screening test for color defective vision and color discrimination skills in dentistry can be performed by matching two Vita-Lumin shade guides. Those dental office personnel who score a low number of matches in the Vita test (that is, seven or fewer correct matches) should have additional color discrimination testing and refer shade matching to other personnel with higher scores.

Adult↗
PubMed2004

Effect of individual shades on reliability and validity of observers in colour matching.

The effect of individual shades in shade guides, on the reliability and validity of measurements in a colour matching process is very important. Observer's agreement on shades and sensitivity/specificity of shades, can give us an estimate of shade's effect on observer's reliability and validity. In the present study, a group of 16 students, matched 15 shades of a Kulzer's guide and 10 human incisors to Kulzer's and/or Vita's shade tabs, in 4 different tests. The results showed shades I, B10, C40, A35 and A10 were those with the highest reliability and validity values. In conclusion, a) the matching process with shades of different materials was not accurate enough, b) some shades produce a more reliable and valid match than others and c) teeth are matched with relative difficulty.

Color↗
PubMedDate not supplied

Effect of toothbrushing on the material loss, roughness, and color of intrinsically and extrinsically stained porcelain used in metal-ceramic restorations: an in vitro study.

PURPOSE: Because of abrasion by toothbrushing, dental materials in the oral cavity are subjected to substance loss to a different extent depending on the hardness of the material. This study investigated the color-change effect of substance loss and change of roughness resulting from toothbrushing of internally and externally stained metal ceramic. MATERIALS AND METHODS: Metal-ceramic specimens 15 mm in diameter and 2 mm thick were made. Blue colorant suspension was applied over the enamel porcelain (enamel-stained), in the body porcelain (dentin-stained), and over the opaque porcelain (opaque-stained). One group was not stained. Each group was made up of seven samples. All specimens were brushed in an experimental device. Material loss, roughness measurements, and spectrophotometric evaluations were made before and after brushing. Overall color change, chroma change, and value change were calculated with the use of the CIE-LAB uniform color scale. RESULTS: Significant substance loss as a result of brushing was observed. No significant differences between chroma changes, between value changes of different groups, or between overall color changes of dentin- and enamel-stained groups were found. The difference between overall color changes of opaque-dentin and opaque-enamel stained groups was statistically significant. CONCLUSION: Staining should be done as deeply as possible to obtain durable color appearance.

Dental Porcelain↗
PubMed2006

Interactions of pigments and opacifiers on color stability of MDX4-4210/type A maxillofacial elastomers subjected to artificial aging.

STATEMENT OF PROBLEM: The color instability and degradation of maxillofacial elastomers limit the function and cosmetic quality of facial prostheses. PURPOSE: The purpose of this study was to measure the interactions of oil pigments plus dry earth opacifiers at 5%, 10%, and 15% by volume in stabilizing the color of MDX4-4210/type A silicone elastomers before and after artificial aging. MATERIAL AND METHODS: In the first part of the study, each of 5 opacifiers (Georgia kaolin powder neutral, kaolin powder calcined, Artskin white, dry pigment titanium (Ti) white, or Ti white artists' oil color) at 10% concentrations were combined with each of 5 oil pigment types (no pigment, cadmium-barium red deep, yellow ochre, burnt sienna, or a mixture of the 3 pigments), for a total of 25 experimental groups of elastomers. In the second part of the study, 50 experimental groups of elastomers were made by combining 1 of 5 opacifiers at 5% and 15% concentrations with 1 of 5 oil pigments as in Part 1. Five specimens of each elastomer were tested, for a total of 375 specimens. In each part of the study, all specimens were aged in an artificial aging chamber. CIE L*a*b* values were measured by a spectrophotometer. The color differences (DeltaE*) were subjected to repeated-measures analysis of variance. Mean values were compared by Tukey-Kramer intervals (alpha = .05). RESULTS: In Part 1, when the opacifiers were tested at 10% concentration, Ti white oil color had the most color change, and dry pigment Ti white had the least; all other opacifiers were not significantly different from each other. In Part 2, at 5%, Ti white oil color had the most color change; all other opacifiers were not significantly different from the others. At 15%, Ti white oil color again had the most color change, followed by Artskin white, kaolin powder calcined, and Georgia kaolin; Ti white dry earth pigment had the least color change. Overall, 5% Artskin white had less color change than the 15%, whereas 15% dry pigment Ti white had less color change than the 5% (P < .001). The 5% and 15% of other opacifiers were not significantly different. CONCLUSIONS: At all 3 concentrations, oil pigments mixed with opacifiers helped protect the MDX4-4210/type A silicone elastomer from color degradation over time. Dry pigment Ti white remained the most color stable over time, followed by the pigments mixed with kaolin powder calcined, Georgia kaolin, Artskin white, and Ti white artists' oil color.

Barium Sulfate↗
PubMed2004

Optical and color stabilities of paint-on resins for shade modification of restorative resins.

The purpose of this study was to examine the optical and color stabilities of the paint-on resin used for shade modification of restorative resins. Three shades of paint-on resin and two crown and bridge resins were used. The light transmittance characteristics of the materials during accelerated aging tests such as water immersion, toothbrush abrasion, ultraviolet (UV) light irradiation, and staining tests were measured. Discolorations of materials resulting from tests were also determined. There were no significant effects of water immersion, toothbrush abrasion and UV light irradiation on the light transmittance and visible color change of paint-on resins, whereas the staining tests significantly decreased the light transmittance and increased color change of the translucent shades of materials. Our results indicate that the paint-on resins exhibit stable optical properties and color appearance, which are at least as good as the crown and bridge resins.

Acrylic Resins↗
PubMed2004

Color stability of acrylic resin adhesives with different initiation modes.

The purpose of this study was to evaluate the color stability of two acrylic resin adhesives with different activation systems: a benzoyl peroxide (BPO)-amine redox system and a tri-n-butylborane (TBB) derivative system. The colorimetric values of the two resins in different shades (Clear and Ivory) were determined (n=5) 24 hours after polymerization as a baseline using the L*a*b* system of the Commission Internationale de l'Eclairage (CIE). The specimens were thereafter immersed in distilled water, and the color difference (deltaE*) values were calculated. After 24 weeks, the TBB-initiated material showed a significantly (p<0.05) lower color change than the BPO-amine-initiated material. The deltaE* values for the BPO-amine-initiated materials were 6.9 for Clear and 15.8 for Ivory, whereas those for the TBB-initiated materials were 1.3 and 1.8 respectively. Thus, it was concluded that the TBB-initiated material had superior color stability to that of the BPO-amine-initiated material.

Acrylic Resins↗
PubMed1996

Light transmission of composite luting resins.

The final color of all-ceramic restorations is dependent on the surrounding structures and on the ceramic itself. The degree that the layer of the composite luting agent contributes to this final color formation can only be estimated. Based on general optical physics, this paper reports on transmissivity of some commercially available composite luting resins and discusses how these theoretical results apply to clinical situations.

Color↗
PubMed1999

[Color comparison of VITA shade guide and metal ceramic restoration].

OBJECTIVE: To understand color distribution of Vita shade guide and metal ceramic restoration and make Vita shade guide more reasonable in clinical applying. METHODS: The international standard CIE1976L*a*b* color system and Minolta CR-100 spectrocolorimeter were selected to measure and compare the characteristics of the shade guide and metal ceramic restoration. RESULTS: Color differences were noted between the shade guide and ceramic restorations. The value of metal ceramic restoration was brighter than that of VITA shade guide tab. There was different chroma between metal ceramic restoration and Vita shade guide. Metal ceramic restorations were yellower and redder. But no saturation differences were found between ceramic restorations and D2, D3 tabs. CONCLUSION: During clinical color-matching of metal ceramic porcelains, it is suggested that a VITA shape guide tab with lower brightness and paler color than that of adjacent teeth should be selected.

Colorimetry↗