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At least 199 records · Page 11Linked to original sources
PubMed1994

Comparison of the color stability of ten new-generation composites: an in vitro study.

OBJECTIVES: The aim of this in vitro study was to evaluate the color stability of modern light-cured composites when subjected to various physico-chemical and staining conditions. METHODS: Ten brands were evaluated including hybrids, microfine hybrids and microfilled composites. Some universal shade samples underwent only staining tests, while others were subjected to one of the following experimental conditions: thermocycling, postcuring, polishing or a 1 wk immersion in saline, prior to staining. The coloring solutions used for the staining tests were: coffee, E 110 food dye, vinegar and erythrosin. A colorimetric evaluation according to the CIE L*a*b* system was performed after experimental periods of 1 and 3 wk. RESULTS: Erythrosin caused the greatest color change for the composites tested. A reduced susceptibility to staining was observed where surfaces had been polished. Low water sorption, a high filler-resin ratio, reduced particle size and hardness, and an optimal filler-matrix coupling system were related to improved composite resistance to discoloration. SIGNIFICANCE: Resistance of modern composites to discolorations still depends on their structure and manipulation.

Absorption↗
PubMed2000

Physical properties of a silicone prosthetic elastomer stored in simulated skin secretions.

STATEMENT OF PROBLEM: Facial prostheses worn over an extended time are exposed to various environmental factors, including sebaceous oils (sebum) and perspiration. PURPOSE: This study investigated the physical properties of tensile strength and modulus, elongation, tear strength, hardness, weight, and color change, of a silicone facial elastomer after immersion for 6 months in simulated sebum and perspiration at 37 degrees C. MATERIAL AND METHODS: Specimens made of Episil silicone elastomer were immersed in simulated alkaline or acidic perspiration as well as in sebum. Tensile and tear tests were conducted according to ISO specifications no. 37 and 39, respectively, in a Monsanto testing machine. Shore A hardness measurements were run according to ASTM D 2240. Weight changes were followed at 5, 15, 30, and 180 days, and color changes were determined in the CIE LAB system using a tristimulus colorimeter. RESULTS: An improvement of mechanical properties for specimens immersed in acidic perspiration was attributed to facilitation of the propagation of cross-linking reaction during aging of the silicone samples. Some weight increase was observed for the specimens immersed into the aqueous solution, whereas for those immersed in sebum, weight loss was recorded, probably because of extraction of some compounds. In this latter case, the color change was lower than that corresponding to simulated perspiration. CONCLUSION: The silicone specimens aged for a period, which simulates 1.5 years of clinical service, showed minimal changes with respect to the properties studied.

Absorption↗
PubMed2004

The influence of some different factors on the accuracy of shade selection.

The purpose of this study was to elucidate some of the factors on which accurate shade taking depends. Custom shade tabs (0.5, 1.0 and 1.5 mm porcelain thickness) were fabricated from selected Vita and Shofu porcelains. Four main factors were investigated, namely, the difference between the two types of porcelain used, the effect of light quality, the effect of porcelain thickness and the experience of the observer. The chi-square test for independence at a probability level of P <0.05 was used to analyse the results. The results indicated that in ideal light there was no difference between the two porcelains (P=0.58). The experienced observers proved better than the novice observers in ideal light conditions (P=0.003). Thickness was also significant in the overall results (P=0.0001), in that thicker samples gave more accurate results. The results indicate that in adverse light, there was an overall difference between the two porcelains (P=0.046), but no difference between the experienced and novice observers. The thickness made no difference to the experienced or the novice observer in adverse light. These results indicate that the most influential factor on shade taking was the light quality (P <0.0001); better results were obtained overall for the ideal light situation. In ideal light thicker samples gave better results (P=0.0001).

Clinical Competence↗
PubMed2000

A method for evaluating color stability of light-cured composite resins using an experimental filter.

The purpose of this study was to investigate a method for evaluating color stability of light-cured composite resins using an experimental filter that simulates human enamel. The light transmission coefficients and their spectral distributions from 400 to 600 nm of twelve enamel specimens were measured. The experimental filter was designed so that its light transmittance characteristics were similar to those of enamel. Color stability tests for ten shades of two light-cured composite resins, which were irradiated directly and indirectly through the experimental filter with a light source, were performed. Despite different irradiation procedures, most materials exhibited significant color changes in the color stability test. Although the differences were small, the group of specimens irradiated indirectly through the filter showed significantly higher color differences in comparison with those irradiated directly. Our results indicate that the light attenuating effect of enamel affects the color stability of light-cured composite resins.

Color↗
PubMed1999

Shade matching and communication in conjunction with segmental porcelain buildup.

To the majority of patients, the aesthetic appearance of a restoration is often as important as its biological compatibility and function. While technological advancements have significantly improved the procedures and biomaterials utilized to fabricate ceramic restorations, the definitive result must address these increasing aesthetic expectations. A means of properly matching a crown restoration with the surrounding natural dentition is therefore critical. This article discusses shade communication between the members of the restorative team as well as ceramic layering techniques that can be utilized to achieve enhanced aesthetic results.

Adult↗
PubMed2002

Effect of opacifiers on color stability of pigmented maxillofacial silicone A-2186 subjected to artificial aging.

PURPOSE: This study was designed to determine the effect of opacifiers used at different ratios on the color stability of pigmented A-2186 silicone maxillofacial elastomers and to evaluate the color spectrophotometrically before and after artificial aging. MATERIALS AND METHODS: Sixty experimental groups of elastomers were made using various concentrations (5%, 10%, and 15%) of 4 opacifiers (Georgia kaolin powder neutral, kaolin powder calcined, Artskin white, and dry pigment titanium white) with 1 of 5 dry earth cosmetic pigment groups (no pigment [control], red, yellow ochre, burnt sienna, and a mixture of all pigments). Five specimens of each elastomer were tested, for a total of 300 specimens. All specimens were placed in an aging chamber and artificially aged by exposure to light, water spray, fluctuating temperatures, and humidity. CIE L*a*b* values were measured by spectrophotometer. The color differences (Delta E*) at various exposure energies (150, 300, and 450 kJ/m(2)) were subjected to 4-way analysis of variance with repeated measures (super ANOVA). Mean values were compared with Tukey-Kramer intervals calculated at the 0.05 significance level. RESULTS: The trained human eye can detect color changes (Delta E*) greater than 1.0. Adding all pigments to any of the kaolin groups did not protect silicone A-2186 from color degradation over time. Mixing red pigment in all groups at all times drastically increased DeltaE* values ranging from 0.1 to 1.3 up to 16.6 to 49.6. Yellow ochre had an effect only with 10% and 15% concentrations of kaolin powder calcined, increasing the value of Delta E* to greater than 1.0. Burnt sienna had an effect only with a 15% concentration of kaolin powder calcined, increasing the value of Delta E* at 300 and 450 kJ/m(2) to greater than 11.0. At the 5% concentration, kaolin powder calcined had the smallest color changes, followed by, in order, dry pigment titanium white, Artskin white, and Georgia kaolin. At the 10% concentration, Artskin white had the smallest color changes, followed by, in order, dry pigment titanium white, kaolin powder calcined, and Georgia kaolin. At the 15% concentration, Artskin white again had the smallest color changes, followed by, in order, dry pigment titanium white, Georgia kaolin, and the kaolin powder calcined. The smallest color changes in each kaolin group were at the 10% concentration for Artskin white, dry pigment titanium white, and kaolin powder calcined and at the 5% concentration for Georgia kaolin. CONCLUSIONS: Mixing dry earth cosmetic pigments with opacifiers did not protect silicone A-2186 from color degradation over time, especially in the case of red pigment. The group in which pigments were mixed with 10% Artskin white had the smallest color changes over time, followed by, in order, the groups in which pigments were mixed with 10% dry pigment titanium white, 10% kaolin powder calcined, and 5% Georgia kaolin. Red pigment had a significant effect on all opacifiers, especially Georgia kaolin and kaolin powder calcined. Yellow ochre and burnt sienna had an effect only on 15% kaolin powder calcined. Among all the pigment groups tested, yellow ochre remained the most color stable over time.

Analysis of Variance↗
PubMed2004

Shading Vita In-ceram YZ substructures: influence on value and chroma, part II.

In this study, the influence of differently shaded substructures made of Y-TZP from different manufacturers (without, with 0.5 mm or 1.0 mm ceramic veneer with Vita VM9 Base Dentin) on the lightness, the saturation, and the color shade (= value, chroma, and hue) was measured and assessed with a spectral photometer (Easy Shade, Vita) on a clinical case in the mouth and on models of different color. Shading substructures made of Y-TZP facilitated adaptation to the basic shade and reduced the layer thickness of the veneer ceramic required to achieve the desired color. This should be done in the future as a matter of routine. In this way, tooth substance can be better conserved when preparing the teeth, and the esthetic result is not diminished. The material used for the production of the working models (plaster or plastic) should be tooth colored and in terms of lightness--analogous to the shading of the substructure--in order to facilitate clinical color measurement and quality control in the laboratory.

Aluminum Oxide↗
PubMed2006

[Effect of three kinds of rare earth oxides on chromaticity and mechanical properties of zirconia ceramic].

OBJECTIVE: To evaluate the colouration of zirconia ceramic by adding three kinds of rare earth oxides. The influence of the pigments concentration on the mechanical properties and the microstructure was also analyzed. METHODS: Added different concentrations of CeO(2), Er(2)O(3) and Pr(6)O(11) in tetragonal zirconia poly crystals stabilized with 3 mol% yttria (3Y-T2P) powder, compacted at 200 MPa using cold isostatic pressure, and sintered to 1 400 degrees C. The heating rate was 150 degrees C/h and the dwelling time was 2 hours. The chromaticity of sintered bodies was measured with chroma meter. The relative density, hardness, flexure strength and fracture toughness were investigated as well. The phase stability of the colorized and pure zirconia was evaluated by X-ray diffraction (XRD) using an automated diffractometer. The microstructures of the specimens were evaluated by scanning electron microscope (SEM). RESULTS: Several kinds of color achieved by the different pigments praseodym oxide, cerium oxide and erbium oxide were presented in the CIELab system. The a* value increased with the added amount of Er(2)O(3), while b* value rose with the increasing amount of CeO(2) and Pr(6)O(11). However, three pigments failed to decrease L* value and the sintered body appeared too bright. Adding three pigments influenced flexure strength of zirconia ceramic significantly, but had little influence on the hardness and fracture toughness. Microscopy revealed the relationship between the porosity and shapes of grains was correlated to strength of the diphase ceramics. No additional phase could be detected by XRD, except t-ZrO(2) in all colorized samples after sintering at 1 400 degrees C for 120 min. CONCLUSIONS: Zirconia ceramic can be colorized by CeO(2), Er(2)O(3), and Pr(6)O(11). Pigments even in a small amount influence the mechanical properties of the colorized zirconia material, which necessitates further investigation.

Coloring Agents↗
PubMedDate not supplied

Effect of dissolution on color of extrinsic porcelain colorants.

The effect of in vitro dissolution in acidulated phosphate-fluoride gel on the color of metal ceramic samples having surface metal oxide colorants was determined. Three different colorants were applied using two techniques at two different firing temperatures. The color difference was most apparent when the colorant and glaze were combined with only one firing cycle. All colorants increased in value, but changes in color difference were most evident with the blue colorant. It was concluded that dissolution in acidulated phosphate-fluoride gel does affect the color of extrinsic metallic oxide colorants.

Acidulated Phosphate Fluoride↗
PubMedDate not supplied

Porcelain laminate veneers for discolored teeth using complementary colors.

Porcelain laminate veneers are affected by the color of prepared abutment teeth, so that if these teeth are discolored they may cause problems in a restoration. This paper describes how complementary color theory is applied to resolve this situation and provide a more esthetic restoration. Tooth discoloration is classified into four base colors: orange, brown, blue-purple, and reddish gray, and a shade selection technique and a veneer fabrication technique are presented.

Color↗
PubMedDate not supplied

Color stability of low-fusing porcelains for titanium.

The resistance to staining of two low-fusing porcelains (Procera and Duceratin) for use with titanium and one conventional feldspathic porcelain (Vita VMK 68) were examined visually according to a protocol similar to the ADA Specification No. 69. The color deviation was also quantified using a colorimeter. Forty samples of each product were prepared using manufacturer's instructions and the samples divided into two groups of 20. The samples of one group were immersed in methylene blue, and the control group in distilled water. Of the twenty samples from each group, ten were ground to remove the glaze. The color values for each sample were recorded prior to and after immersion in the staining medium. The color deviation value, Delta E, for each sample was calculated. Visually discernible stain was present on the unglazed samples of all three porcelain products immersed in methylene blue. No stain was visually detectable on the glazed samples or the unglazed samples immersed in distilled water for all three porcelain products. The objective evaluation confirmed that the unglazed porcelain products had statistically higher color deviation after immersion in methylene blue.

American Dental Association↗
PubMedDate not supplied

Opacity and color changes of tooth-colored restorative materials.

Internal opacity and color changes of several esthetic direct restorative materials were determined using an accelerated test proposed by Asmussen (1981). Five chemically cured composites, seven light-cured composites, and three resin-modified glass-ionomer cements were placed in acrylic rings. After curing, they were left at 37 degrees C for 1 week before baseline measurement, and then stored in 60 degrees C distilled water up to 4 weeks. Color change was determined by a color analyzer, and contrast ratio representing opacity was calculated. All chemically cured composites tested discolored to dark yellow or dark brown after 4 weeks. Opacity decreased for two macrofilled composites. Light-cured composites discolored slightly, but their opacity change was negligible. All resin-modified glass-ionomer cements tested showed an abrupt decrease of opacity at the initial stage, with accompanying darkening of the materials. Opacity decrease was found to be a factor of discoloration for some tooth-colored restorative materials, and might be caused by a refractive index change of the matrix phase of the materials.

Analysis of Variance↗
PubMed1998

In vivo color stability of resin composite veneers and acrylic resin teeth in removable partial dentures.

OBJECTIVE: The color stability of laboratory-made composite veneers was compared to that of artificial resin teeth under in vivo conditions. METHOD AND MATERIALS: Veneers and resin teeth of removable partial dentures were measured colorimetrically with reflection spectrophotometry; the color changes were characterized in the Commission Internationale d'Eclairage L*a*b* color space. The color was first determined 24 hours after manufacture and again after 6, 12, and 18 months at incisal, cervical, and centrofacial tooth positions. The denture teeth and veneers were measured, cleaned to eliminate the influence of surface discoloration, and measured again at every recall. The food consumption and tooth cleaning habits of the patients were taken into account. RESULTS: In all groups the maximum color changes from the baseline measurement were delta L* = 2.1, delta a* = 0.4, and delta b* = 1.8. The changes in the delta E* values were between 1.0 and 2.5 units. Despite polishing, the delta E* values increased by approximately 0.2 to 0.3 units in relation to the previous measurement with increased wearing time. External discolorations were eliminated by polishing, depending on the type of material; the maximum color change because of polishing was between 0.8 and 2.0 units for delta E*. The resin teeth showed no significant changes in the delta E* values. CONCLUSION: After a wearing period of 18 months, the discolorations of the tested materials were clinically acceptable. The artificial resin teeth showed statistically smaller color changes than did the veneering materials.

Color↗
PubMed1998

Pigments and their application in maxillofacial elastomers: a literature review.

PURPOSE: This literature review provides information about pigments used for facial and somatoprostheses. MATERIAL: This information includes common pigment and index names and numbers, lightfastness categories, chemical type and class, and the chemical formulas of the common pigments used in maxillofacial prosthetics. CONCLUSION: It can be deduced from this review that the pigments used with silicone elastomers do exhibit a color change, and that a color change is to be expected.

Humans↗
PubMed1996

Porcelain veneer color blending.

Matching the color of porcelain veneers to existing teeth has proved to be a challenge for the restorative dentist. The resulting color of a veneer depends upon several factors. This paper reviews a technique for making a test veneer to predict with accuracy the color of the result.

Dental Porcelain↗