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.     

Influence of pigment and opacifier on dimensional stability and detail reproduction of maxillofacial silicone elastomer

We evaluated the influence of chemical disinfection and accelerated aging on the dimensional stability and detail reproduction of a silicone elastomer containing an opacifier and/or a pigment. A total of 120 samples were fabricated from Silastic MDX 4-4210 silicone and divided into groups (n = 10) according to pigment and/or opacifier (ceramic powder and/or barium sulfate) and disinfectant solution (neutral soap, Efferdent, or 4% chlorhexidine). The specimens were disinfected 3 times per week during 60 days and then subjected to accelerated aging for 1008 hours. Dimensional stability and detail reproduction tests were performed after specimens' fabrication (baseline) and chemical disinfection and periodically during accelerated aging (252, 504, and 1008 hours). The results were analyzed using 3-way repeated-measures analysis of variance and the Tukey Honestly Significant Difference test (a = 0.05). All groups exhibited dimensional changes over time. The disinfectant, pigment, and time (P < 0.0001) affected the dimensional stability of silicone. Statistically significant dimensional differences were not observed between the tested groups. Accelerated aging influenced the dimensional stability of the samples. All groups scored 2 in the detail reproduction tests, which represents the full reproduction of 3 test grooves with accurate angles. Incorporation of opacifier and/or pigment alters the dimensional stability of silicones used in facial prosthetics but seems to have no influence on detail reproduction. Accelerated aging is responsible for most of the dimensional changes in Silastic MDX4 4210, but all dimensional changes measured in this study remained within the limits of stability necessary for this application.     

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.     

臭氧老化对SY-1硅橡胶色彩稳定性的影响

目的 :了解臭氧老化对内着色SY 1硅橡胶色彩稳定性的影响 ,以便为选用适宜的硅橡胶着色颜料提供理论依据。方法 :SY 1硅橡胶按所加色料不同分为 4组 (对照组、水粉颜料土黄色、油画颜料土黄色、无机盐类颜料中铬黄 ) ,按国家标准对其进行臭氧老化并测定老化前后L 、a 、b 值 ,据此计算△E值。结果 :经臭氧老化 72h ,对照组△E为 0 .5 5± 0 .11;水粉土黄组△E为 3 .5 5± 0 .0 9;油画土黄组△E为 1.40± 0 .11;中铬黄组△E为 1.5 7± 0 .0 7。结论 :SY 1硅橡胶在臭氧老化条件下 ,油画类颜料与无机盐类颜料色彩稳定性优于水粉颜料。     

热固化下油画颜料着色硅橡胶的色度稳定性研究

目的:对热固化条件下的油画颜料耐热性能和化学稳定性进行评价.方法:测定80℃热固化,固化时间90 min与室温固化23℃,固化时间24 h两组油画颜料着色的硅橡胶试样的色度值(Lab),并计算试样间的色差值(△E).结果:热固化试样的色度值为:61.1,12.3,10.8;对照组为:60.9,12.1,10.7;两者之间的色差为AE=0.3.结论:油画颜料着色硅橡胶在热固化过程中具有良好的色度稳定性.油画颜料可以作为适宜的赝复配色颜料.     

Stain removal from a pigmented silicone maxillofacial elastomer

The removal of environmental stains from a pigmented maxillofacial elastomer was carried out by solvent extraction under network swelling. Silastic 44210 was pigmented with 11 maxillofacial pigments prior to staining. Samples were stained with lipstick, methylene blue, and disclosing solution. These stains were then removed by solvent extraction with 1,1,1-trichloroethane. Color parameter measurements both before and after staining and after solvent extraction demonstrated the effectiveness of removing these stains by solvent extraction while causing little or no change in the color of the pigmented samples.     

Evaluation of some mechanical properties of a new silicone elastomer for maxillofacial prostheses after addition of intrinsic pigments

Objective

The approximate life span of a silicone maxillofacial prosthesis is as short as 1.5–2?years of clinical service, then a new prosthesis should be fabricated. The most common reason for re-making the prosthesis is silicone mechanical properties degradation. The aim of this study was to assess some mechanical properties of VST-30 silicone for maxillofacial prostheses after addition of intrinsic pigments.

Change in color of a maxillofacial prosthetic silicone elastomer,following investment in molds of different materials

Purpose:

In the authors’ experience, the color of silicone elastomer following polymerization in molds made of gypsum products is slightly different from the color that was matched in the presence of the patient, before the silicone is packed. It is hypothesized that the investing materials and separating media have an effect on the color during the polymerization process of the silicone.

Materials and Methods:

This study compares and evaluates the change in color of silicone elastomer packed in three commonly used investing materials - Dental stone (white color), dental stone (green color), and die stone (orange color); coated with three different separating media – Alginate-based medium, soap solution and a resin-based die hardening material. Pigmented silicone samples of dimensions 1.5 cm × 2 cm × 0.5 cm were made from the elastomer in the above-mentioned mold materials using combinations of the mentioned separating media. These served as test group samples. Control group samples were made by packing a mix of the same pigmented elastomer in stainless steel molds. The L*, a*, b* values of the test and control group samples were determined using a spectrophotometer. The change in color (Delta E) was calculated between the control and test groups.

Results:

The mean L, a, b values for the control group were, 31.8, 26.2, and 36.3, respectively. Average values of change in color (Delta E) for samples packed utilizing alginate-based medium, die hardener, and soap solution, respectively in white dental stone (2.70, 2.74, and 2.88), green dental stone (2.19, 2.23, 2.42), and orange die stone (3.19, 2.72, 2.80) were tabulated.

Conclusion:

Among the investing materials studied, die stone showed the most color change (3.19), which was statistically significant. Among the separating media, die hardener showed the least color change (2.23). The best combination of an investing material and separating media as per this investigation is a dental stone (green) and alginate-based separating medium.     

染色剂对SY-1硅橡胶色彩稳定性影响的研究

目的 测试SY-1硅橡胶在多种外源性染色剂中的颜色稳定性。方法 将SY-1硅橡胶试件浸泡在几种常见的染色试剂中，应用美能达CS-321便携式色差仪分别测试出浸泡前和浸泡后1、2、3、4周的色度值，利用色差公式计算出试件的色差值，并与国外同类产品MDX4—4210进行对照。结果 不同外源性染色剂对硅橡胶有不同的影响。随着染色时间的延长，不同染色剂对硅橡胶的染色程度不同。结论 硅橡胶的色彩稳定性与外源性着色剂的种类，作用时间及自身特性相关。SY-1硅橡胶的色彩稳定性与MDX4—4210基本接近。     

Mechanical properties and bonding of maxillofacial silicone elastomer mixed with nano-sized anti-microbials

ObjectivesThe antibacterial efficacy of silicone is improved by impregnating it with antimicrobials such as chlorohexidine and zinc oxide. The purpose of this study was to examine mechanical properties and bonding of maxillofacial silicone elastomer mixed with Zinc Oxide nanoparticles (ZnO-NP), and Chlorohexidine Diacetate Salt (CHX) at three different concentrations (1 %, 3 %, and 5 %).MethodsSpecimens of a silicone elastomer (M511) were prepared and divided into 7 groups. Group 1 was control of no additive. Groups 2–4 included silicone elastomer mixed with ZnO-NP (surface area = 67 m²/g) at 3 different concentrations (by weight %); 1 %, 3 % and 5 %. Groups 5–7 included silicone elastomer mixed with CHX at the same concentrations. Tear and tensile strengths, elongation percentage, modulus of elasticity, and shear bond strength to primed acrylic resin surfaces were evaluated. Data was analyzed with 1-way ANOVA, Bonferroni, and Dunnett’s T3 post-hoc tests (P < 0.05).ResultsThere was significant effect of the additives on the tensile strength, elongation percentage, tear strength, and shear bond strength (P < 0.05). Shear bond strengths ranged from 0.55 to 0.96 MPa. Silicone elastomer mixed with CHX (5 %) resulted in the highest shear bond strength (P < 0.05). Non-linear regressions between tensile strength and ZnO and CHX additives were 0.95 and 0.96 respectively.SignificanceAll additives reduced the tensile strength of the silicone. However, CHX at 5 % optimized shear bond strength and thus is proposed in order to fabricate maxillofacial prostheses of sufficient mechanical properties, bonding and antimicrobial activity.     

Accelerated color change in a maxillofacial elastomer with and without pigmentation

STATEMENT OF PROBLEM: Maxillofacial prostheses require frequent replacement because the elastomer and its color additives undergo changes. PURPOSE: This study attempted to determine whether predictable color changes occur when 3 pigments are individually incorporated into a specific silicone elastomer. MATERIAL AND METHODS: The materials included an RTV elastomer; 1 natural inorganic pigment, burnt sienna; and 2 synthetic organic pigments, Hansa yellow and alizarin red. Eight test groups of 10 polymerized specimens were established. Groups 1 and 2, acting as the control, involved only the elastomer. Groups 3 and 4 were composed of elastomer and burnt sienna. Groups 5 and 6 consisted of elastomer and Hansa yellow. Groups 7 and 8 comprised elastomer and alizarin red. Odd-numbered groups were assigned to a test site in Miami, Fla., whereas the even numbered groups went to Phoenix, Ariz. Specimens weathered in Miami and Phoenix received sunlight exposures of 1305.7 MJ/m2 and 1310.2 MJ/m2, respectively, over time. Before and after weathering, the L* a* b* color parameter (DeltaE*) of each specimen was determined spectrophotometrically. RESULTS: Mean color changes that occurred in Arizona were larger than those produced in Florida. Specifically, these differences ranged from 0.4 (alizarin red groups) to 2.36 units for the 2 unpigmented control groups. Other differences showed significance for the unpigmented (P=.001), burnt sienna (P=.006), and Hansa yellow groups (P=.001). CONCLUSION: Outdoor weathering tests in which documented ASTM methods were used provided a valid baseline for future research on color changes in maxillofacial prostheses.     

Color stability of thermochromic pigment in maxillofacial silicone

PURPOSE

Maxillofacial silicone elastomer is usually colored intrinsically with color pigments to match skin colors. The purpose of this study was to investigate the color stability of a maxillofacial silicone elastomer, colored with a thermochromic, color changing pigment.

MATERIALS AND METHODS

Disc-shaped maxillofacial silicone specimens were prepared and divided into 3 groups: a conventionally colored control group, one group additionally colored with 0.2 wt% thermochromic pigment , and one group with 0.6 wt% thermochromic pigment. Half of the surface of each specimen was covered with an aluminium foil. All of the specimens were exposed to UV radiation in 6 hour cycles over 46 days. In between the UV exposures, half of the specimens were stored in darkness, at room temperature, and the other half was stored in an incubator, at a humidity of 97% and a temperature of +37℃. Color measurements were made with a spectrophotometer and registered according to the CIELAB L^*a^*b^* color model system. The changes in L^*, a^* and b^* values during artificial aging were statistically analyzed by using paired samples t-test and repeated measures ANOVA. P-values <.05 were considered as statistically significant.

RESULTS

The UV exposure resulted in visually noticeable and statistically significant color changes in the L^*, a^* and b^* values in both of the test groups containing thermochromic pigment. Storage in the incubator lead to statistically significant color changes in the a^* and b^* values of the specimens containing thermochromic pigment, compared to those stored at room temperature.

CONCLUSION

The specimens containing thermochromic pigment were very sensitive to UV radiation, and the thermochromic pigment is not suitable, as such, to be used in maxillofacial prostheses.