Influence of pigments and opacifiers on color stability of silicone maxillofacial elastomer☆

Abstract 

Objectives

To determine the effects of opacifiers and silicone pigments on the color stability of silicone A-2000 maxillofacial prosthetic elastomers subjected to artificial aging.

Methods

Seventy-five groups (n=5) were made by various combinations (5%, 10%, and 15%) of four dry earth opacifiers (Georgia kaolin, Gk; calcined kaolin, Ck; Artskin white, Aw; titanium white dry pigment, Td); and 1 silicone pigment white (Sw) with one of 5 silicone pigments (no pigment (control), red (Pr), yellow (Py), burnt sienna (Po), and a mixture of Pr+Py+Po). A reflection spectrophotometer was used for color measurements. Color differences (ΔE*) between baseline and after an energy exposure of 450kJ/m² in an artificial aging chamber were calculated. A ΔE*=3.0 was used as 50:50% acceptability threshold in result interpretation, while ΔE*=1.1 was used as 50:50% perceptibility threshold. Means were compared by Fisher's PLSD intervals at the 0.05 level of significance. Color differences after aging were subjected to three-way analysis of variance.

Results

Yellow ochre mixed with all opacifiers at all intervals had increased ΔE* values significantly from 0.7–2.1 up to 3.8–10.3. When mixed groups were considered, at 5%, Gk exhibited the smallest color changes, followed by Td<Aw=Sw<Ck, respectively. At 10%, Aw<Td<Gk<Sw=Ck. At 15%, Td<Aw<Gk=Sw<Ck (< indicates p<0.0001 and = indicates p>0.05). The smallest color differences, observed for opacifier groups, were recorded for Gk at 5%, and Td and Aw at 10% and 15%. Overall, 15% Td exhibited the smallest, whereas 5% Ck exhibited the most pronounced color change after artificial aging. All ΔE* values were below the 50:50% acceptability threshold, indicating acceptable color stability. Color differences for 10% and 15% of Aw and Td were below 50:50% perceptibility thresholds, indicating excellent color stability.

Conclusion

Silicone pigments mixed with 10% and 15% Artskin white and titanium white dry pigment opacifiers protected silicone A-2000 from color degradation over time. Yellow silicone pigment significantly affected color stability of all opacifiers especially silicone pigment white and calcined kaolin.

Keywords: Color stability, Silicone A-2000, Maxillofacial prosthetics, Silicone elastomer, Facial prosthesis, Color differences (ΔE*), Artificial aging