Use of thermochromic pigment in maxillofacial silicone elastomer.
BACKGROUND
Silicone elastomers are used to fabricate external maxillofacial prostheses and are colored to match the adjacent facial skin. In cold winter weather, in certain individuals, the color of the skin changes toward red, which leads to a color difference between the prostheses and the surrounding tissue.


OBJECTIVE
The purpose of this study was to study the use of a thermochromic, color-changing pigment in a maxillofacial silicone elastomer to mimic the color change of the skin in cold weather. An additional aim was to compare different pigment concentrations.


METHODS
The maxillofacial silicone elastomer was colored with an intrinsic coloring technique to match fair skin. The skin-colored silicone was divided into 3 groups: fair skin color, fair skin color to which was added 0.2 wt% thermochromic pigment, and fair skin color with 0.6 wt% thermochromic pigment. Disk-shaped, 7 × 35 mm specimens (n=12 per group) were prepared and color measurements were made with a spectrophotometer at room temperature and after storage in a freezer. Differences and changes in color were calculated according to the CIELAB-system, and changes in the values of the L*, a*, and b* color coordinates were analyzed with general linear modeling for repeated measures.


RESULTS
When the color of the specimens at room temperature was compared with the color after storage in a freezer, the color change of both thermochromic pigment groups was statistically significant (P<.001) for L * and a* values and for b* values in the 0.6 wt% group. The color change of the control group (ΔE 0.95) was not visually noticeable. The change toward redness after freezer storage appeared natural in the specimens with 0.2 wt% thermochromic pigment (ΔE 2.66). The color change of the specimens with 0.6 wt% thermochromic pigment was too noticeable for clinical use (ΔE 16.81).


CONCLUSIONS
A concentration of 0.2 wt% thermochromic pigment led to a slight visual color change toward red of the silicone elastomer after freezer storage, while a concentration of 0.6 wt% thermochromic pigment led to a more noticeable color change.
Chief Prosthodontist, Department of Oral and Maxillofacial Diseases, Vaasa Central Hospital, Vaasa, Finland. Electronic address: rosita.kantola@vshp.fi.
Rosita M
RM
Kantola
Hemmo
H
Kurunmäki
Pekka K
PK
Vallittu
Lippo V J
LV
Lassila
D001672:Biocompatible Materials / Q000737:chemistry; D003080:Cold Temperature; D003116:Color; D004396:Coloring Agents / Q000737:chemistry*; D004129:Dimethylpolysiloxanes / Q000737:chemistry; D005615:Freezing; D006801:Humans; D008422:Materials Testing; D008447:Maxillofacial Prosthesis; D017797:Prosthesis Coloring; D011474:Prosthesis Design; D012826:Silicone Elastomers / Q000737:chemistry*; D012880:Skin Pigmentation; D013053:Spectrophotometry; D013696:Temperature
D001672:Biocompatible Materials; D004396:Coloring Agents; D004129:Dimethylpolysiloxanes; C020964:MDX 4-4210; D012826:Silicone Elastomers