title: Effect of opacifiers and UV absorbers on pigmented maxillofacial silicone elastomer, part 1: color stability after artificial aging.
abstract: BACKGROUND
  Much dissatisfaction with the color instability and reduced lifetime of extraoral maxillofacial prostheses due to degradation has been reported.
  
  
  OBJECTIVE
  The purpose of this study was to compare the effect of a UV mineral-based light protecting agent (LP) on the color stability of pigmented maxillofacial silicone elastomer MDX-4210/Type A after artificial aging to 2 widely used opacifiers.
  
  
  METHODS
  Forty-five groups were established (n=225 total). Three different types of opacifiers (LP, titanium white dry pigment [TW], or silicone intrinsic white [SW]) were added to silicone MDX-4210/type A at 3 concentrations (5%, 10%, or 15%) and subsequently combined with each of 5 colors (no pigments [control], red, blue, yellow, or mixed pigments). Artists' oil pigment was used with LP and TW, while intrinsic silicone pigment was used to color SW. Before and after an energy exposure of 450 kJ/m(2), CIE L*a*b* values were measured with a spectrophotometer. The CIELAB 50:50% perceptibility (ΔE*=1.1) and acceptability threshold (ΔE*=3.0) were used to interpret color changes (ΔE*). Color differences after aging were subjected to 3-way ANOVA. Means were compared by the Fisher PLSD intervals at α=.05.
  
  
  RESULTS
  The ΔE* values of all groups were below the acceptability threshold of ΔE*=3.0, except for the control group of SW at 10%, which showed the greatest color change (ΔE*=3.1). When mixed pigment groups were considered, at 5% concentration, LP showed the smallest color change, followed by SW and TW (P<.05); at 10%, no significant differences among the 3 opacifiers were noted (P>.05); at 15%, LP showed the smallest color change, followed by TW and SW (P<.05).
  
  
  CONCLUSIONS
  All 3 opacifiers at all concentrations protected pigmented silicone MDX4-4210/Type A from color degradation. The LP group showed the smallest color changes.
authors.affiliation: Department of Prosthodontics, School of Stomatology, Fourth Military Medical University, Xi'an, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Han
authors.forename: John M
authors.initials: JM
authors.lastname: Powers
authors.forename: Sudarat
authors.initials: S
authors.lastname: Kiat-Amnuay
mesh_terms: D020099:Coated Materials, Biocompatible; D003116:Color; D003124:Colorimetry; D008422:Materials Testing; D008447:Maxillofacial Prosthesis; D017797:Prosthesis Coloring; D012826:Silicone Elastomers; D013473:Sunscreening Agents; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D020099:Coated Materials, Biocompatible; D012826:Silicone Elastomers; D013473:Sunscreening Agents