title: In vitro evaluation of color change in maxillofacial elastomer through the use of an ultraviolet light absorber and a hindered amine light stabilizer.
abstract: BACKGROUND
  External prostheses composed of silicone elastomers exhibit an unwanted color change over time.
  
  
  OBJECTIVE
  This study evaluated color stability when an ultraviolet light absorber and hindered amine light stabilizer were mixed in the maxillofacial elastomer containing either organic or inorganic pigments.
  
  
  METHODS
  The materials used were an RTV silicone elastomer, 1 natural inorganic dry-earth pigment (burnt sienna) and 2 synthesized organic pigments (hansa yellow and alizarin red), ultraviolet light absorber (UVA) and hindered amine light stabilizer (HALS). Specimens (n=160) were fabricated in a custom mold and randomly assigned and exposed to weathering sites in Miami and Phoenix for approximately 3 months. Eight test groups (2 of each 4 material types with or without additives) of 10 specimens each were assigned to each site. L*, a*, b* readings were obtained before and after weathering from a spectrocolorimeter. Nonpigmented elastomers served as the control. Three-factor ANOVA was conducted to examine interaction effects between weathering sites, specimen type, and the presence of additive (alpha=.05). Overall color change (Delta E) and change in color coordinates (Delta L*, Delta a*, Delta b*) of specimen groups with and without additive were analyzed with independent sample t tests.
  
  
  RESULTS
  In specimen groups with the additives (UVA and HALS), color change decreased significantly (P<.05) in burnt sienna and hansa yellow in Phoenix and in the control and hansa yellow in Miami. Additives did not affect color change in the alizarin red group.
  
  
  CONCLUSIONS
  UVA and HALS were shown to be effective in retarding color change in some circumstances.
authors.affiliation: Department of Restorative Dentistry, Division of Proshodontics, College of Dentistry, University of Tennessee, Memphis, 38163, USA.
authors.forename: Ngoc H
authors.initials: NH
authors.lastname: Tran
authors.forename: Mark
authors.initials: M
authors.lastname: Scarbecz
authors.forename: John J
authors.initials: JJ
authors.lastname: Gary
mesh_terms: D000042:Absorption; D000588:Amines / Q000737:chemistry; D000704:Analysis of Variance; D000880:Anthraquinones / Q000737:chemistry / Q000528:radiation effects; D001672:Biocompatible Materials / Q000737:chemistry* / Q000528:radiation effects; D003124:Colorimetry; D003652:Decanoic Acids / Q000737:chemistry / Q000528:radiation effects; D006801:Humans; D008422:Materials Testing; D008447:Maxillofacial Prosthesis; D010860:Pigments, Biological / Q000737:chemistry / Q000528:radiation effects; D010880:Piperidines / Q000737:chemistry / Q000528:radiation effects; D017797:Prosthesis Coloring; D012826:Silicone Elastomers / Q000737:chemistry* / Q000528:radiation effects; D013053:Spectrophotometry; D014230:Triazoles / Q000737:chemistry / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D000588:Amines; D000880:Anthraquinones; D001672:Biocompatible Materials; D003652:Decanoic Acids; D010860:Pigments, Biological; D010880:Piperidines; D012826:Silicone Elastomers; D014230:Triazoles; C016151:tinuvin; C083752:Tinuvin 770; C010078:alizarin