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Reproducibility of tooth color gradation using a computer color-matching technique applied to ceramic restorations
Shigemi Ishikawa-Nagai1, Kanji Ishibashi, Osamu Tsuruta
1Department of Restorative Dentistry and Biomaterials Sciences, School of Dental Medicine, Harvard University, Boston, MA 02115, USA. shigemi_nagai@hsdm.harvard.edu
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, Delta E, Delta L* , Delta a* , and Delta b* , were calculated. The color difference Delta E 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 (Delta E) values were clinically acceptable (below 3.6) for incremental areas 3 through 10 and unacceptable for areas 1 and 2 (gingival area). Highly significant differences in the mean of Delta E values among target-shade tabs (P <.0001), areas (P <.0001), and target-shade tab-by-area 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.
