title: Color stability of thermochromic pigment in maxillofacial silicone.
abstract: OBJECTIVE
  Maxillofacial silicone elastomer is usually colored intrinsically with color pigments to match skin colors. The purpose of this study was to investigate the color stability of a maxillofacial silicone elastomer, colored with a thermochromic, color changing pigment.
  
  
  METHODS
  Disc-shaped maxillofacial silicone specimens were prepared and divided into 3 groups: a conventionally colored control group, one group additionally colored with 0.2 wt% thermochromic pigment , and one group with 0.6 wt% thermochromic pigment. Half of the surface of each specimen was covered with an aluminium foil. All of the specimens were exposed to UV radiation in 6 hour cycles over 46 days. In between the UV exposures, half of the specimens were stored in darkness, at room temperature, and the other half was stored in an incubator, at a humidity of 97% and a temperature of +37℃. Color measurements were made with a spectrophotometer and registered according to the CIELAB L(*)a(*)b(*) color model system. The changes in L(*), a(*) and b(*) values during artificial aging were statistically analyzed by using paired samples t-test and repeated measures ANOVA. P-values <.05 were considered as statistically significant.
  
  
  RESULTS
  The UV exposure resulted in visually noticeable and statistically significant color changes in the L(*), a(*) and b(*) values in both of the test groups containing thermochromic pigment. Storage in the incubator lead to statistically significant color changes in the a(*) and b(*) values of the specimens containing thermochromic pigment, compared to those stored at room temperature.
  
  
  CONCLUSIONS
  The specimens containing thermochromic pigment were very sensitive to UV radiation, and the thermochromic pigment is not suitable, as such, to be used in maxillofacial prostheses.
authors.affiliation: Vaasa Central Hospital, Vaasa, Finland. ; University of Turku, Institute of Dentistry, Department of Biomaterials Science and Turku Biomaterials Centre - TCBC, Turku, Finland.
authors.forename: Rosita
authors.initials: R
authors.lastname: Kantola
authors.forename: Lippo V J
authors.initials: LV
authors.lastname: Lassila
authors.forename: Mimmi
authors.initials: M
authors.lastname: Tolvanen
authors.forename: Pekka K
authors.initials: PK
authors.lastname: Valittu
keywords: Color stability; Maxillofacial silicone; Thermochromic pigment