PURPOSE:
The purpose of this study was to investigate the influence of certain defined variables on color and opacity of silicone elastomers for maxillofacial prostheses.

MATERIALS AND METHODS:
Three condensation-type and five addition-type silicone elastomers were tested for their changes in color and opacity as a result of aging. The specimens were aged under a xenon light source, dry or wet, and in darkness, also dry (control specimens) or wet. The aging times were 24, 96, 168, 336, 504, 840, 1176, and 1512 hours. The changes in appearance were measured with a spectrophotometer.

RESULTS:
The condensation-type polymers increased in opacity in an aqueous environment, while the addition-type polymers, as a group, showed the smallest color changes. Although the addition-type polymers generally had a higher filler content than the condensation types, they had a lower opacity. However, because of their higher viscosity, the condensation-type polymers offer better possibilities for intrinsic coloring of the prosthesis.

CONCLUSION:
Under the experimental conditions studied, significant differences between the silicone elastomers regarding color and opacity changes were demonstrated. However, for a proper choice of material in a given case, these factors have to be related to biologic and mechanical properties of the material.

Reference
Changes in appearance of silicone elastomers for maxillofacial prostheses as a result of aging.
Hulterstöm AK, Ruyter IE
Int J Prosthodont. 1999 Nov-Dec; 12(6): 498-504