Reproducibility of tooth color gradation using a computer color-matching technique applied to ceramic restorations

Statement of problem. To reproduce tooth color precisely, an objective methodology based on color science is required. However, perception-based techniques are still the primary method for color matching in restorative dentistry. Purpose. This study evaluated the accuracy of reproduction of color gradation for ceramic restorations using a Computer Color Matching (CCM) technique employing a prototype program and spectrophotometric data measurements. Materials and methods. The colors of 10 target-shade tabs of the Vitapan 3D Master shade guide were measured at 4 regions of crowns from the cervical to the incisal area using a spectrophotometer. Tooth-shaped CCM ceramic specimens (30 specimens; 3 specimens for each of 10 target-shade tabs), the same size and shape as target-shade tabs, were fabricated according to the CCM prescriptions calculated using a prototype CCM program. The colors of CCM ceramic specimens and target-shade tabs were compared in 10 incremental areas from gingival to incisal (each measuring 1 mm high X 3 mm wide). The color differences, DeltaE, DeltaL*, Deltaa*, and Deltab*, were calculated. The color difference DeltaE values were analyzed by a repeated measures analysis of variance (P<.0001). Three prosthodontists evaluated CCM specimens by perception techniques. Results. The mean color difference (DeltaE) values were clinically acceptable (below 3.6) for incremental areas 3 through 10 and unacceptable for areas I and 2 (gingival area). Highly significant differences in the mean of DeltaE values among target-shade tabs (P<.0001), areas (P<.0001), and target-shade tab-by-arca interaction effects (P<.0001) were noted. However, perceptional evaluation indicated "Definitive match" or "Approximate match" for all CCM specimens. Conclusion. The CCM technique tested in this study utilizing 4 measurements on target-shade tabs Could reproduce tooth color gradation from incisal to precervical regions with clinically acceptable results.