∆ ∆E) of acrylic resins related to powder-to-liquid ratio, sample thickness and trade marks Diferenças de unidades de cor (∆ ∆ ∆ ∆ ∆E) de resinas acrílicas em função de proporções, espessuras e marcas

The purpose of this study was to verify color differences (∆E) of acrylic resins using specimens with 6, 4 and 2mm of thickness. The acrylic resins tested were two medium pink - Classico and Vipi - and three 66-shade materials - Dencor (Classico), Vipi-cor (Vipi) and Duralay (Reliance). By means of a spectrophotometer were obtained the color parameters (L*, a*, b*). ∆E values were determined according to the following conditions: 1) +10, -10 and -20 powder/liquid ratios (in wt%) compared to the normal ratio recommended by the manufactu- rer; 2) 4 and 2mm thicknesses compared to the 6mm control; 3) comparison between pink-colored resins and among the three 66-colored resins. Results led us to conclude that under a clinical point of view, variations on the powder/liquid ratio had little influence on color alteration when compared to the normal ratio, as the grea- test value (∆E=1.6) would not be noticeable by a large number of examiners. When compared to the 6mm con- trol, it was demonstrated that specimens with 4mm of thickness did not show great color alteration (∆E=1.7 maximum), whereas the 2mm specimen suffered unsatisfactory alterations, which, depending on the material and ratio, reached ∆E=8.4. Color similarity between pink-colored resins was good, but differences among 66- colored resin were unsatisfactory (up to ∆E=16.2).