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|Title: ||The colour measurement of ceramic samples using a commercial colour measuring device and a laboratory spectrophotometer|
|Authors: ||Stevenson, Brian|
|Supervisor(s): ||Ibbetson, Richard|
|Issue Date: ||2009|
|Publisher: ||The University of Edinburgh|
|Abstract: ||The selection of shade for a porcelain crown is a subjective process and mode of
fabrication is known to have an effect.
This investigation sought to determine the accuracy of a commercially-available
shade-matching device (IdentaColor II) when used to measure the colour of
proprietary, custom-made all-ceramic and custom-made metal-ceramic samples of
shades B1, A3 and D4 under different calibration and lighting conditions as well as
over time. The findings from the first part of the study led to an investigation of the
influence of fabrication technique on the colour co-ordinates recorded for the ceramic
samples measured previously. Colour measurements were made using a laboratory
spectrophotometer, Spectraflash SF600 and were used as a comparator for the
IdentaColor II. The reproducibility of these colour measurements was also assessed.
The fabrication variables investigated were shade, thickness of ceramic, type of
ceramic sample, number of firing cycles, operator, and method of condensation. An
attempt was made to determine the correlation between fabrication technique,
porosity and colour co-ordinates.
The results indicated that IdentaColor II used a measurement system for colour
values that conformed to no known standard which made validation difficult.
Differences in the colour values were found between different calibration and lighting
conditions and over time but these differences were clinically inconsequential. The
results from IdentaColor II were reproducible but with limitations: the colours
recorded were generally lighter than the chosen standard, there was a
preponderance of “A” shades and the device never recorded the intended shade of a
sample. The limitations of the colour scale used by IdentaColor II made its further
investigation difficult and comparisons with colour-reference standards impossible.
The results for the samples which had been measured by IdentaColor II and
Spectraflash SF600 were different: (1) the colour scales used by the two devices
were different, (2) the scale used by IdentaColor II had a larger range, (3) the
measurements from Spectraflash SF600 were more consistent both within each data
set and over time and (4) the trends in the recorded colour co-ordinates when the
ceramic thickness increased were different. The colour co-ordinates (C.I.E. L*a*b*)
from Spectraflash SF600 for samples ostensibly of the same shade of ceramic were
affected by the mode of fabrication which in turn influenced porosity. The colour coordinates
generally decreased as the ceramic thickness of metal-ceramic samples of
shades B1, A3 and D4 increased and as the amount of pre-sintered slurry
condensation increased of metal-ceramic tabs of shades B1 and A3. Metal-ceramic
tabs were a closer colour match to the shade tabs than all-ceramic samples of the
|Appears in Collections:||School of Clinical Sciences thesis and dissertation collection|
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