Mechanisms of goniochromism relevant to restorative dentistry.
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.
Chirdon
William M
WM
Department of Chemical Engineering, University of Louisiana at Lafayette, P.O. Box 44130, Lafayette, LA 70504-4130, USA. wchirdon@louisiana.edu
O'Brien
William J
WJ
Robertson
Richard E
RE
D003116:Color; D003188:Composite Resins / Q000737:chemistry; D003793:Dental Restoration, Permanent; D005898:Glass; D008689:Methacrylates; D055620:Optical Phenomena; D012542:Scattering, Radiation
D003188:Composite Resins; D008689:Methacrylates; C009753:fiberglass