| Statement of problem:The ability of a dentist to select and communicate an acceptable shade match to a dental laboratory may be the most important factor in esthetic restorative dentistry.Objective:1. To compare the two methods of shade measurement (shade guide and spectro-photometer).2. To evaluate and compare the color difference of the total color replication process and the direction of the individual color parameters for dental porcelain from three companies.Materials and method:The fabricated shades (A2) of 3 different porcelain companies were determined visually and instrumentally using vita lumin shade tab (A2) and spectrophotometer. Corresponding porcelain disks made of (0.8 mm metal, 0.2mm opaque, 0.8 mm dentin, 0.5mm enamel) and glaze were fabricated with each of porcelain (Vita VMK 95, Ceramco 3, Ceramax) company. The colour of the fabricated disks and master disks were measured with a spectroradiometer with a 450/00 using {C.I.E 1931(xyz)} parameter. Analysis of variance (ANOVA) was applied to evaluate within group differences among the porcelain groups for total colour difference (D.E) and direction of colour parameters (D.L, D.RG, D.YB).Result:The largest mean (D.E) was recorded for Ceramax and least for Vita VMK 95.A significant difference (P= 0.015) was found in yellow and blue axis (D.YB). Data collected further showed no significant difference or correlation between shade selection methods and the evaluated clinical criteria. The amount of change within each colour parameters was dependent on the porcelain system, as well as the amount of change among colour parameters.Conclusion:1.Samples made with different brands of porcelains have noticeably different shade despite having the same Vita Lumin Shade Guide.2.Different brands of porcelain differ from each other more in redness and yellowness.3.Different brands of porcelain differ from each other more in lighter than darker shades.
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