Color Stability of Facial Silicone Prosthetic Elastomers after Artificial Weathering

Abstract

Background: External prostheses exhibit an unwanted color change over time. Color deterioration of prosthetic elastomers affects the life expectancy of facial prostheses in a service environment. The effect of different pigmentation and irradiation duration on color stability of four silicone elastomers after artificial weathering was investigated in this study.

Methods: The materials used included four different pigmented industrially synthesized RTV (room temperature vulcanizing) silicones. The materials chosen in this study were representative silicone prosthetics that are widely used in the last decade in maxillofacial prostheses. Artificial weathering was performed in a weatherometer of total radiant energy 1.35 W/m² (UVA - UVB). The samples were exposed in eight different periods (8, 24, 48, 72, 96, 120, 144, 168 hours). L, a, b readings were obtained before and after weathering from a spectrophotometer to define color changes. Color changes were calculated from the following equation: ΔE = (ΔL² + Δa² + Δb²)½. The data were subjected to two-way analysis of variance at a significance level of α = 0.05. Also, simple mathematical models were developed for color changes.

Results: The results showed that color changes depend on irradiation time and initial color of samples. Episil Europe 1 and Episil Africa 3 were identified as the most stable materials since their color changes were not eye detectable. Contrary to materials Episil Europe 2, 3 that showed significant color changes.

Conclusion: Artificial weathering caused significant, eye detectable, but yet still clinically acceptable color changes in the examined prosthetic silicone elastomers due to deterioration that occurs through irradiation.

Keywords: Color, degradation, elastomers, prostheses, silicones