Colour perception of laboratory-fired samples of body-coloured ceramic.

The objective of this investigation is to test by common perception, the colour fidelity of laboratory-fired samples of ceramic. Thirty-two ceramic discs were constructed in a thickness similar to that used for ceramic veneers using eight shades from each of four different manufacturers. A group of 20 'adept' observers colour matched the samples in strictly controlled viewing conditions using a Vita Lumin (Vita Zahnfabrik) shade guide. Samples were categorised as 'positive matches'(matching the expected shade), 'agreed shades' (matching an unexpected shade), or as 'unidentified shades' (no match). The Vita Lumin (Vita Zahnfabrik) colour 'value' index was used as a reference to categorise colour 'value' differences between observed and expected shade. Colour 'value' selection was divided into three groups: (1) matching colour 'value', (2) shades of higher colour 'value' than expected or (3) shades of lower colour 'value' than expected. Only six of the 32 samples examined were perceived to be 'positive matches' with the recommended shade guide. Fourteen 'agreed shades' were found while the remaining 12 shades were regarded as 'unidentified shades'. The vast majority of observations disagreed with the manufacturers' designated shade. A significant trend was found favouring higher 'value' (lighter) shades than those specified by the manufactures. Significant differences in the pattern of shade matches and disagreements between brands were also found. Alternative shade determination systems and/or ceramic colour modifications are required if colour fidelity between the shade guide and the materials tested is to be improved.