title: Mechanisms of goniochromism relevant to restorative dentistry.
abstract: OBJECTIVE
  This study aims to determine the effects of multiple translucent layers, the alignment of composite structures, and specular reflecting backings as goniochromatic mechanisms relevant to dentistry.
  
  
  METHODS
  Rectangular composite specimens were filled with very short E-glass fibers (120 microm length, 16 microm diameter). The fibers were oriented random, perpendicular, and parallel to the surface normal using an electric field. A Minolta CS-100 colorimeter was used to measure the color at various angles of samples with various filler alignments, translucent sublayers, and specular reflecting backings.
  
  
  RESULTS
  All three investigated mechanisms were proven to have a goniochromatic effect. Filler alignment perpendicular to the surface made the composites more transmissive and reduced the dependence of lightness on observation angle. Backing composites with a pigmented sublayer caused the color of the sublayer to be more apparent when the observation angle is perpendicular to the surface. The specular reflection of a gold backing was only partially diffused by the specimen.
  
  
  CONCLUSIONS
  The determination of the effects of these goniochromatic mechanisms is relevant to dentistry, because teeth are naturally aligned composites composed of multiple translucent layers. Therefore, understanding these goniochromatic effects is important to recreating them in restorative materials. Also, gold backings were previously found to give restoratives a more vital appearance, and this perceived vitality may be related to goniochromism.
authors.affiliation: Department of Chemical Engineering, University of Louisiana at Lafayette, P.O. Box 44130, Lafayette, LA 70504-4130, USA. wchirdon@louisiana.edu
authors.forename: William M
authors.initials: WM
authors.lastname: Chirdon
authors.forename: William J
authors.initials: WJ
authors.lastname: O'Brien
authors.forename: Richard E
authors.initials: RE
authors.lastname: Robertson
mesh_terms: D003116:Color; D003188:Composite Resins / Q000737:chemistry; D003793:Dental Restoration, Permanent; D005898:Glass; D008689:Methacrylates; D055620:Optical Phenomena; D012542:Scattering, Radiation
chemical_list: D003188:Composite Resins; D008689:Methacrylates; C009753:fiberglass