title: Influence of pigments and opacifiers on color stability of silicone maxillofacial elastomer.
abstract: OBJECTIVE
  To determine the effects of opacifiers and silicone pigments on the color stability of silicone A-2000 maxillofacial prosthetic elastomers subjected to artificial aging.
  
  
  METHODS
  Seventy-five groups (n=5) were made by various combinations (5%, 10%, and 15%) of four dry earth opacifiers (Georgia kaolin, Gk; calcined kaolin, Ck; Artskin white, Aw; titanium white dry pigment, Td); and 1 silicone pigment white (Sw) with one of 5 silicone pigments (no pigment (control), red (Pr), yellow (Py), burnt sienna (Po), and a mixture of Pr+Py+Po). A reflection spectrophotometer was used for color measurements. Color differences (DeltaE*) between baseline and after an energy exposure of 450kJ/m(2) in an artificial aging chamber were calculated. A DeltaE*=3.0 was used as 50:50% acceptability threshold in result interpretation, while DeltaE*=1.1 was used as 50:50% perceptibility threshold. Means were compared by Fisher's PLSD intervals at the 0.05 level of significance. Color differences after aging were subjected to three-way analysis of variance.
  
  
  RESULTS
  Yellow ochre mixed with all opacifiers at all intervals had increased DeltaE* values significantly from 0.7-2.1 up to 3.8-10.3. When mixed groups were considered, at 5%, Gk exhibited the smallest color changes, followed by Td<Aw=Sw<Ck, respectively. At 10%, Aw<Td<Gk<Sw=Ck. At 15%, Td<Aw<Gk=Sw<Ck (< indicates p<0.0001 and = indicates p>0.05). The smallest color differences, observed for opacifier groups, were recorded for Gk at 5%, and Td and Aw at 10% and 15%. Overall, 15% Td exhibited the smallest, whereas 5% Ck exhibited the most pronounced color change after artificial aging. All DeltaE* values were below the 50:50% acceptability threshold, indicating acceptable color stability. Color differences for 10% and 15% of Aw and Td were below 50:50% perceptibility thresholds, indicating excellent color stability.
  
  
  CONCLUSIONS
  Silicone pigments mixed with 10% and 15% Artskin white and titanium white dry pigment opacifiers protected silicone A-2000 from color degradation over time. Yellow silicone pigment significantly affected color stability of all opacifiers especially silicone pigment white and calcined kaolin.
authors.affiliation: Department of Restorative Dentistry and Biomaterials, University of Texas Dental Branch at Houston, Houston, TX 77030, USA. sudarat.kiat-amnuay@uth.tmc.edu
authors.forename: Sudarat
authors.initials: S
authors.lastname: Kiat-amnuay
authors.forename: Meghan
authors.initials: M
authors.lastname: Beerbower
authors.forename: John M
authors.initials: JM
authors.lastname: Powers
authors.forename: Rade D
authors.initials: RD
authors.lastname: Paravina
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry*; D003116:Color; D004396:Coloring Agents / Q000737:chemistry*; D006801:Humans; D008447:Maxillofacial Prosthesis; D017797:Prosthesis Coloring / Q000379:methods*; D012828:Silicones / Q000737:chemistry*; D013053:Spectrophotometry; D013997:Time Factors
chemical_list: D001672:Biocompatible Materials; D004396:Coloring Agents; D012828:Silicones