Ultraviolet radiation-induced color shifts occurring in oil-pigmented maxillofacial elastomers

Abstract

Statement of problem. Oil-based pigments are added to a maxillofacial prosthesis either as base colorants present within the elastomer or as surface tints that are painted on with an adhesive. Color stability of the pigments and pigmented prosthetic materials on exposure to ultraviolet radiation are unknown. Purpose. This study measured ΔE* color changes caused by ultraviolet radiation for materials colored with 5 oil pigments, applied either as base colorants (intrinsic) or surface tints (extrinsic) to a silicone elastomer. Material and methods. One of 5 oil pigments was added to polydimethyl siloxane disks to serve as a base colorant (0.2 weight percent present throughout a 2 mm thick disk) or as a concentrated surface tint (2.0 weight percent concentrated in upper 0.3 mm thickness). Pigmented disks, along with pigment-only and elastomer-only control disks, were exposed to ultraviolet radiation for 400, 600 and 1800 hours. ΔE* color changes were measured at baseline and for each time interval. Results. Control samples underwent minimum color changes after 1800 hours (ΔE*≤2.0), whereas samples containing oil pigments as base colorants demonstrated a wide range of susceptibility to ultraviolet radiation, with the greatest changes occurring for pigments cadmium red, cadmium yellow, and yellow ochre (7.1≤ΔE*≤9.4). Elastomers coated with the same oil pigments as concentrated surface tints demonstrated significantly lower color shifting after 1800 hours of radiation exposure (maximum ΔE* =4.2, P ≤.05). Conclusion. Customizing a prosthesis with an oil-pigmented surface tint may reduce the incidence of color change, provided a sufficient amount of pigment is present. (J Prosthet Dent 1999;82:441-6.)