Measurements and modelling of the influence of dentine colour and enamel on tooth colour

Abstract

ObjectivesWe provide a quantitative predictive model for the extent to which coloured dentine, visible through the enamel, contributes to tooth colour. Our model uses (L*,a*,b*) measurements rather than spectral measurements. MethodsWe have used a model system, composed of a slice of bovine enamel placed on top of coloured paper. We have measured the colour of the enamel–paper combination, as an analogue for a tooth, and have related this to the colour of the paper, as an analogue for dentine. By changing the paper colour, we have been able to explore how the colour of dentine determines tooth colour, according to our model system. We have also compared hydrated and desiccated samples. ResultsIn qualitative terms, superimposing the enamel on top of the paper increases the “lightness” for all colours tested except white while simultaneously reducing the chromaticity, a measure of the extent to which the colour differs from grey. Desiccated enamel is much more effective at increasing the lightness and reducing the chromaticity than hydrated enamel. Quantitatively, our measurements are reproduced by the mathematical model we have developed to within 2% in “lightness” and about 8% in chromaticity. ConclusionsWe are able to predict the colour of an analogue for a tooth, composed of bovine enamel and coloured paper, from the colour of an analogue for the dentine, the coloured paper alone, with good accuracy. This understanding provides insights into the role of dentine colour in determining tooth colour. Clinical SignificanceOur work helps quantify the importance of dentine colour, compared to other, extrinsic causes of colour, such as staining, in determining the visible colour of teeth. Our predicted colours represent a baseline to which extrinsic sources will add.