Calculation of colour resulting from composite/compomer layering techniques

Abstract

This study determined the influence of optical properties of constituent layers on the colour of double-layer aesthetic filling materials. Multiple regression equations for the Commission Internationale de I'Eclairage (CIE) L*, a* and b* of layered materials were calculated from the optical values of the covering and underlying layers. Specimens (10 mm diameter, 1 mm thickness) of two light-cured resin composites and one compomer of seven to 11 shades were used. CIE L*, a* and b* values of each specimen were measured with a colour spectrophotometer backed by a standard white background. The scattering coefficient (S), absorption coefficient (K), contrast ratio (C) and translucency parameter (T) were calculated. Double-layered specimens were formed in optical contact by joining two different shades from the same material, or resin composite as covering with a compomer underlying layer. Each of the L*, a* and b* of layered material was used as a dependent variable, and 14 optical values of underlying and covering layers were used as independent variables in forward regression analysis (P = 0.01). CIE L* after layering had a positive correlation with S of covering layer (correlation coefficient; beta = 0.79-0.91, P < 0.01) and a correlation with L* of underlying layer (beta = 0.14-0.16). CIE a* after layering had a correlation with a* of covering layer (beta = 0.83-0.94) and a correlation with a* of underlying layer (beta = 0.30-0.56). CIE b* after layering had a correlation with b* of covering layer (beta = 0.77-0.90) and a correlation with T of covering layer (beta = 0.40-0.59). The layered colour of these materials can be predicted by the derived regression equations within the limitations of this study. CIE L*, a* and b* values of double-layer material are mainly influenced by S, CIE a* and b* of covering layer, respectively.

The influence of stratification on color and appearance of resin composites

“…A previous study [30] concluded that the optical properties of the cover material generally had a greater influence on color impression of layered samples than those of the underlying material. The influence of the cover layer in the total color perception increased distinctly with the layer thickness.…”

Relationship between Color and Translucency of Multishaded Dental Composite Resins

“…Since Filtek Supreme and Esthet.X composite resins have been developed for clinical usage by multi-layering technique, the resulting restorations in this technique is determined by several factors including translucency, color, and thickness of each layer [1]. Therefore accurate knowledge regarding the translucency and color of materials is fundamental to the layering technique.…”

“…Understanding and correct analysis of the optical properties of the natural dentition such as color and translucency and the differences between the natural teeth and restorative materials are very important in accurate and consistent shade selection and the proper use of restorative materials in order to achieve clinical success [1–3]. …”

Shade distribution of indirect resin composites compared with a shade guide

“…Therefore, in addition to the optical properties of the material itself, background color and layering effect would influence the final color of a restoration, which was already studied in previous studies. 23,24 These factors should be considered when the results of the present study are applied to clinical situation.…”