The selection of shade for a porcelain crown is a subjective process and mode ofudfabrication is known to have an effect.udThis investigation sought to determine the accuracy of a commercially-availableudshade-matching device (IdentaColor II) when used to measure the colour ofudproprietary, custom-made all-ceramic and custom-made metal-ceramic samples ofudshades B1, A3 and D4 under different calibration and lighting conditions as well asudover time. The findings from the first part of the study led to an investigation of theudinfluence of fabrication technique on the colour co-ordinates recorded for the ceramicudsamples measured previously. Colour measurements were made using a laboratoryudspectrophotometer, Spectraflash SF600 and were used as a comparator for theudIdentaColor II. The reproducibility of these colour measurements was also assessed.udThe fabrication variables investigated were shade, thickness of ceramic, type ofudceramic sample, number of firing cycles, operator, and method of condensation. Anudattempt was made to determine the correlation between fabrication technique,udporosity and colour co-ordinates.udThe results indicated that IdentaColor II used a measurement system for colourudvalues that conformed to no known standard which made validation difficult.udDifferences in the colour values were found between different calibration and lightingudconditions and over time but these differences were clinically inconsequential. Theudresults from IdentaColor II were reproducible but with limitations: the coloursudrecorded were generally lighter than the chosen standard, there was audpreponderance of “A” shades and the device never recorded the intended shade of audsample. The limitations of the colour scale used by IdentaColor II made its furtherudinvestigation difficult and comparisons with colour-reference standards impossible.udThe results for the samples which had been measured by IdentaColor II andudvudSpectraflash SF600 were different: (1) the colour scales used by the two devicesudwere different, (2) the scale used by IdentaColor II had a larger range, (3) theudmeasurements from Spectraflash SF600 were more consistent both within each dataudset and over time and (4) the trends in the recorded colour co-ordinates when theudceramic thickness increased were different. The colour co-ordinates (C.I.E. L*a*b*)udfrom Spectraflash SF600 for samples ostensibly of the same shade of ceramic wereudaffected by the mode of fabrication which in turn influenced porosity. The colour coordinatesudgenerally decreased as the ceramic thickness of metal-ceramic samples ofudshades B1, A3 and D4 increased and as the amount of pre-sintered slurryudcondensation increased of metal-ceramic tabs of shades B1 and A3. Metal-ceramicudtabs were a closer colour match to the shade tabs than all-ceramic samples of theudsame thickness.
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