J Adv Prosthodont.  2013 May;5(2):75-83. 10.4047/jap.2013.5.2.75.

Color stability of thermochromic pigment in maxillofacial silicone

• Kantola R
• Lassila LV
• Tolvanen M
• Valittu PK

• KMID: 2284744
• DOI: http://doi.org/10.4047/jap.2013.5.2.75

Abstract

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 +37degrees C. 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.

Keyword

Maxillofacial silicone; Thermochromic pigment; Color stability

MeSH Terms

Aging
Darkness
Humidity
Incubators
Maxillofacial Prosthesis
Silicone Elastomers
Skin
Silicone Elastomers

Figure

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  Fig. 1 The division of specimens into groups prior to exposure to artificial aging. Each group consisted of 12 specimens, half of the surface was wrapped with aluminium foil to protect the surface from UV irradiation.

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  Fig. 2 A: Color change in L*, a* and b* values after exposure to UV irradiation, B: The overall color change of the specimens, ΔE, after exposure to UV irradiation.

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  Fig. 3 Comparison of the color value a* (red chroma) of the specimens at day 1 and day 38 of the study.

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  Fig. 4 The color change of the UV exposed specimens after 46 days.

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