Confirmation of theoretical colour predictions for layering dental composite materials.
OBJECTIVE
The aim of this study is to confirm the theoretical colour predictions for single and double layers of dental composite materials on an opaque backing.


METHODS
Single and double layers of composite resins were fabricated, placed in optical contact with a grey backing and measured for spectral radiance. The spectral reflectance and colour were directly determined. Absorption and scattering coefficients as previously reported, the measured thickness of the single layers and the effective reflectance of the grey backing were utilized to theoretically predict the reflectance of the single layer using corrected Kubelka-Munk reflectance theory. For double layers the predicted effective reflectance of the single layer was used as the reflectance of the backing of the second layer and the thickness of the second layer was used to predict the reflectance of the double layer. Colour differences, using both the CIELAB and CIEDE2000 formulae, measured the discrepancy between each directly determined colour and its corresponding theoretical colour.


RESULTS
The colour difference discrepancies generally ranged around the perceptibility threshold but were consistently below the respective acceptability threshold.


CONCLUSIONS
This theory can predict the colour of layers of composite resin within acceptability limits and generally also within perceptibility limits.


CONCLUSIONS
This theory could therefore be incorporated into computer-based optical measuring instruments that can automate the shade selections for layers of a more opaque first layer under a more translucent second layer for those clinical situations where an underlying background colour and a desirable final colour can be measured.
The Ohio State University, College of Dentistry, Division of Restorative, Prosthetic and Primary Care Dentistry, Columbus, OH, USA.
Sarah S
SS
Mikhail
The Ohio State University, College of Dentistry, Division of Restorative, Prosthetic and Primary Care Dentistry, Columbus, OH, USA. Electronic address: Johnston.5@osu.edu.
William M
WM
Johnston
D000465:Algorithms; D003116:Color; D003188:Composite Resins / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D005544:Forecasting; D006801:Humans; D008027:Light; D008422:Materials Testing; D012542:Scattering, Radiation; D013499:Surface Properties
D003188:Composite Resins; D003764:Dental Materials; C539358:Herculite Ultra
Colour; Dental composite material; Layering; Reflectance theory