A new shading concept based on natural tooth color applied to direct composite restaurations

Objective: Patient demands have prompted manufacturers to improve intrinsic optical properties of resin composites and clinicians to refine application procedures. The aim of this study is to present a shading concept based on colorimetric L*a*b* and contrast ratio data of human dentin and enamel. Method and materials: Extracted teeth of the A and B Vita shade groups (n = 8 per group) were sectioned according to 2 different planes to measure specific color (using the CIE L*a*b* system) and opacity (contrast ratio). Standardized samples of enamel and dentin shades of a new composite system (Miris, Coltène Whaledent) were submitted to the same colorimetric evaluation for comparison with natural tissues. Results: Comparison of teeth from the Vita groups A and B having the same chroma showed limited variations regarding a* (green to red) and b* (blue to yellow) values; the only significant variation was the increasing b* values (yellow) with increasing chroma (A1 to A4 and B1 to B3). As for dentin contrast ratio, limited differences were reported, while enamel proved to increase in translucency with age (reduced contrast ratio). Conclusion: These data served as the foundation of the so-called natural layering concept, which makes use of 2 basic composite masses (dentin and enamel) that optically mimic natural tissues. This concept allows for simplified clinical application and layering of composite, as it uses only 1 universal dentin hue with several chroma levels and 3 enamel types for young, adult, and old patients, each exhibiting specific tints and translucency levels. Keywords: CIE L*a*b*, contrast ratio, dentin color, natural layering technique