IADR Abstract Archives
Colour Measurement of Shade Guide In Vitro and In Vivo
Objectives: To investigate colour differences of shade guide tabs measured under in vitro and in vivo conditions using digital imaging techniques.
Methods: Tabs from a VITA 3D-MASTER shade guide (n=29) were measured by a custom-built tooth imaging system. Images of the shade guide tabs were individually captured in vitro against a black background. In vivo images were captured against a background of an open mouth of healthy volunteers, with the shade guide tab positioned between the upper and lower anterior teeth. The lighting and the measurement geometry were controlled to be consistent throughout the study. The imaging system was calibrated with colour checker charts and a graphic-user-interface (GUI) was used to grab the region of interest on the shade guide tabs in the captured images. RGB values were converted into CIELAB values by the camera calibration model. Colour difference values (ΔE*ab and ΔE2000) of each shade guide tab were calculated between the in vitro and in vivo conditions.
Results: The mean colour differences and standard error values of the shade guide under in vitro and in vivo conditions are shown below. All the shade tabs measured with the oral cavity background were found to be lighter, redder and less yellow than those measured in vitro. The differences are significant for all L*a*b* values (p<0.05, Student’s t-test). The average colour difference values for both ΔE formulae were between 2-3 units.
Conclusions: Shade guide colours were measured under in vitro and in vivo conditions and the colours were found to be significantly different between the two conditions.
Methods: Tabs from a VITA 3D-MASTER shade guide (n=29) were measured by a custom-built tooth imaging system. Images of the shade guide tabs were individually captured in vitro against a black background. In vivo images were captured against a background of an open mouth of healthy volunteers, with the shade guide tab positioned between the upper and lower anterior teeth. The lighting and the measurement geometry were controlled to be consistent throughout the study. The imaging system was calibrated with colour checker charts and a graphic-user-interface (GUI) was used to grab the region of interest on the shade guide tabs in the captured images. RGB values were converted into CIELAB values by the camera calibration model. Colour difference values (ΔE*ab and ΔE2000) of each shade guide tab were calculated between the in vitro and in vivo conditions.
Results: The mean colour differences and standard error values of the shade guide under in vitro and in vivo conditions are shown below. All the shade tabs measured with the oral cavity background were found to be lighter, redder and less yellow than those measured in vitro. The differences are significant for all L*a*b* values (p<0.05, Student’s t-test). The average colour difference values for both ΔE formulae were between 2-3 units.
Conclusions: Shade guide colours were measured under in vitro and in vivo conditions and the colours were found to be significantly different between the two conditions.