Color stability of silicone maxillofacial elastomers subjected to artificial aging

Realistic coloration and color stability of maxillofacial prostheses are important cosmetic features for patients. Objectives: To measure the effects of different types of extrinsic coloring (EC) techniques on color stability of various silicone maxillofacial elastomers (silicone). Methods: Eight experimental groups of elastomers (N=18/group, total=144 specimens) were made using various combinations of 4 different silicone (MDX4-4210/Type A [MDX], A-2186F, A-2000, A-2006)) with 5 functional intrinsic pigment [FIP] colors (no pigment and white [controls], red, yellow, blue, or a mixture of white+red+yellow+blue) and 6 EC techniques (Type A/oil pigment [A/OP], A-2186F/FIP, A-2186F or A-2000 or A-2006/extrinsic pigment [EP]/Trichlorethane [T], and A/EP/T). Silicone FIP white was added at 5% for intrinsic coloring (IC) and 10% for EC by volume. Amount of EC pigment were 8 times stronger than IC. The baseline color readings were done on both sides of the specimen to measure effects of color degradation of both EC and IC (N=288). Specimens were artificially aged in an aging chamber. CIE L* a* b* values were measured by spectrophotometer. Color differences (ΔE*) at 150 kJ/m² were subjected to 3-way ANOVA. Means were compared by Fisher's PLSD intervals at the 0.05 level of significance. Results: CIELAB perceptibility and acceptability on 50%-50% color difference thresholds of colored maxillofacial elastomer specimens were 1.1 and 3.0, respectively. Mean ΔE* value of all mixed groups for IC and EC were below 1.5 and 1.7, respectively, where IC of A-2000, A-2006, A-2186F with A-2186F/FP/T and EC of A-2186F and A-2006 with A/EP/T were below 1.1. A-2186F, A-2000, and A-2006 with EC=A/EP/T were more color stable compared to EP=A-2186F/EP/T, A-2000/EP/T, or A-2006/EP/T, respectively (p<0.001). Conclusion: All silicone elastomers and IC and EC techniques tested showed acceptable color stability after artificial aging at 150 kJ/m². The study was supported by NIH grant T32DE015355.