Influence of layering thickness on the color parameters of a ceramic system

OBJECTIVES: The aim of this study was to establish by means of a spectrophotometer the influence of each layer of a porcelain fused to metal (PFM) ceramic system on the color parameters (Lightness, Chroma and Hue) of the final restoration. METHODS: One ceramic system (Vita VM13, Vita Zahnfabrik, Bad Säckingen, Germany) was evaluated. 40 ceramic discs were fabricated with a proprietary steel mold and individually checked after firing with a digital calliper to control the thickness of each layer. 4 different total ceramic thicknesses in 2M3 shade were evaluated. For each thickness 2 different layering patterns were analyzed. The layering thickness range for Base Dentin was 0.25-0.90 mm, for Transpa Dentin 0.35-0.75 mm, for Enamel 0.15-0.50 mm. Easyshade (Vita Zahnfabrik) clinical spectrophotometer was used for color comparison with the reference color data of the selected shade stored into the device. RESULTS: One-way ANOVAs showed that the factor 'layering pattern' significantly influenced the DeltaE, DeltaC, DeltaH and DeltaL (p<0.001). Greater thicknesses of Base Dentin resulted in a more Chromatic shade. Conversely, greater thicknesses of Transpa Dentin and Enamel reduced the Chroma of the color. An increase in the Enamel layer thickness resulted in a reduction of the Lightness (Value) and vice-versa. SIGNIFICANCE: The variation in thickness of the various layers significantly influenced the final color of the artifact. The variation found should be taken into account in order to obtain the aimed shade, in relationship with the total thickness of the ceramic veneer.