title: Color stability of pigmented maxillofacial silicone elastomer: effects of nano-oxides as opacifiers.
abstract: OBJECTIVE
  This study evaluated the effects of nano-oxides on the color stability of pigmented silicone A-2186 maxillofacial prosthetic elastomers before and after artificial aging.
  
  
  METHODS
  Each of three widely used UV-shielding nano-sized particle oxides (TiO(2), ZnO, CeO(2)), based on recent survey of the industry at 1%, 2%, 2.5% concentrations were combined with each of five intrinsic silicone pigment types (no pigments, red, yellow, blue, and a mixture of the three pigments). Silicone A-2186 without nano-oxides or pigments served as control, for a total of 46 experimental groups of elastomers. In each group of the study, all specimens were aged in an artificial aging chamber for an energy exposure of 450kJ/m(2). CIE L*a*b* values were measured by a spectrophotometer. The 50:50% perceptibility (ΔE*=1.1) and acceptability threshold (ΔE*=3.0) were used in interpretation of recorded color differences. Color differences after aging were subjected to three-way analysis of variance. Means were compared by Fisher's PLSD intervals at the 0.05 level of significance.
  
  
  RESULTS
  Yellow pigments mixed with all three nano-oxides at all intervals increased ΔE* values significantly from 3.7 up to 8.4. When mixed pigment groups were considered, TiO(2) at 2%, and 2.5% exhibited the smallest color changes, followed by ZnO and CeO(2), respectively (p<0.001). At 1%, CeO(2) exhibited the smallest color changes, followed by TiO(2) and ZnO, respectively (p<0.001). The smallest color differences, observed for nano-oxides groups, were recorded for CeO(2) at 1%, and TiO(2) at 2% and 2.5%. When the nano-oxides were tested at all concentrations, CeO(2) groups overall had the most color changes, and TiO(2) groups had the least. All ΔE* values of the mixed pigment groups were below the 50:50% acceptability threshold (ΔE*=1.2-2.3, below 3.0) except 2% CeO(2) (ΔE*=4.2).
  
  
  CONCLUSIONS
  1% nano-CeO(2) and 2% and 2.5% nano-TiO(2) used as opacifiers for silicone A-2186 maxillofacial prostheses with mixed pigments exhibited the least color changes when subjected to artificial aging at 450kJ/m(2). Yellow silicone pigment mixed with all three nano-oxides significantly affected color stability of A-2186 silicone elastomer.
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: Yimin
authors.initials: Y
authors.lastname: Zhao
authors.forename: Chao
authors.initials: C
authors.lastname: Xie
authors.forename: John M
authors.initials: JM
authors.lastname: Powers
authors.forename: Sudarat
authors.initials: S
authors.lastname: Kiat-amnuay
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry / Q000528:radiation effects*; D002563:Cerium / Q000737:chemistry / Q000528:radiation effects; D003116:Color; D004396:Coloring Agents / Q000737:chemistry / Q000528:radiation effects*; D004129:Dimethylpolysiloxanes / Q000737:chemistry / Q000528:radiation effects; D020724:Elastomers / Q000737:chemistry / Q000528:radiation effects; D006801:Humans; D008447:Maxillofacial Prosthesis; D053758:Nanoparticles / Q000737:chemistry / Q000528:radiation effects*; D055620:Optical Phenomena; D010087:Oxides / Q000737:chemistry / Q000528:radiation effects*; D017797:Prosthesis Coloring / Q000379:methods*; D012828:Silicones / Q000737:chemistry / Q000528:radiation effects; D014025:Titanium / Q000737:chemistry / Q000528:radiation effects; D014466:Ultraviolet Rays; D015034:Zinc Oxide / Q000737:chemistry / Q000528:radiation effects
chemical_list: C076788:A 2186; D001672:Biocompatible Materials; D004396:Coloring Agents; D004129:Dimethylpolysiloxanes; D020724:Elastomers; D010087:Oxides; D012828:Silicones; C009495:titanium dioxide; D002563:Cerium; C030583:ceric oxide; D014025:Titanium; D015034:Zinc Oxide