Comparison Of Three Computer-aided Shade Matching Instruments For Measuring Tooth Color

Color determination in dentistry can be divided into two categories: visual and instrumental. Visual color determination, by comparison of the tooth with standard shade guides, is the most frequently applied method in dentistry. Because the tooth and the shade guide are observed directly by dentists, it is considered as a subjective process. General variables such as external light conditions, experience, age, and fatigue of the human eye and physiological variables such as color blindness may lead to inconsistencies and bias. Visual determination of shade selection has been found to be unreliable and is a continuing problem in dentistry. Since their introduction to dentistry, spectrophotometers and colorimeters have been used primarily in research and not in clinical practice. Instrumental color measurement offers a potential advantage over visual color determination because instrumental readings are objective, can be quantified, and are more rapidly obtained. Up to now, an increasing number of computer-aided instruments for tooth shade selection have been used in clinical practice. However, the color measurement principle, color measurement mode, system design and color analysis methods of these instruments are different, which may also lead to inconsistencies and bias. Therefore, the performance of different computer-aided shade matching instruments is need for investigation. The purpose of this study was to evaluate the performance of three computer-aided shade matching instruments (Vita Easyshade, ShadeEye NCC and Shadepilot) for measuring tooth color, with the attempt to provide valuable information for their clinical application.The first part is the comparison of the accuracy and reliability of three instruments and visual color determination. Color measurements were made of two kinds of commercial shade guides (5 Vita Classical and 5 Vita 3D Master shade guides). Shade tabs were placed in the middle of a gingival matrix (Shofu Gumy). Measurements were made of the central region of the shade tab respectively. For the accuracy assessment, each shade tab was measured once. For the reliability assessment, each shade tab was measured twice. For Vita Easyshade and ShadeEye NCC, the accuracy of Vita Classical shade guide output system is significant higher than Vita 3D Master shade guide output system. Shadepilot and Vita Easyshade produced a significant higher accuracy than ShadeEye NCC and visual method. The reliability of all the three instruments was high and no significant difference was revealed among them. All instruments showed significantly higher reliability than visual method.The second part is the comparison of performance of three instruments for measuring natural tooth color. The maxillary right central incisors of 85 patients and 5 Vita Classical shade guides were measured. L*a*b* values and shade matches to Vita Classical shade guide system were determined for all teeth. The CIEL*a*b* colorimetric system was used to calculate the accurate tooth color that each instrument theoretically supposed to be displayed. Reliability and accuracy were then calculated for each instrument. When output in Vita Classical shade guide system, no significant difference was revealed between the accuracy of Vita Easyshade and ShadeEye NCC, however, both of these two instruments produced a significant lower accuracy than Shadepilot. The reliability of all the instruments was high, and there was no significant difference among them. L*a*b* values with the three instruments were significant different.The third part is the comparison of the agreement of the shade matching results and the color accordance between the natural tooth and the shade tab selected by the three instruments and visual color determination. Color measurements were made of the maxillary right central incisors of 85 patients. A spectrophotometer (CM-700d/600d) was used to measure the L*a*b* values of the 85 incisors and five Vita Classical shade guides. The color difference (DeltaE) between the tooth and Vita Classical shade tab which was selected by the three instruments and visual method were calculated. Results demonstrated that the color difference of all groups (6～8) were higher than the clinical perceptibility thresholds(3.7). Regarding DeltaE, no significant difference was found between Shadepilot and ShadeEye NCC, and between Vita Easyshade and visual method. But Shadepilot and ShadeEye NCC had significant lower DeltaE than Vita Easyshade and visual method. It indicated that Shadepilot and ShadeEye NCC had better color accordance between the natural tooth and the shade matching results. The pair-agreements of the shade matching results of the three instruments and visual color determination were lower than 50%, and no significant difference was revealed.In conclusion, this study was a comprehensive and systematic comparison of the accuracy, reliability, pair-agreements of the shade matching results and color accordance between the natural tooth and the shade matching results of three computer-aided instruments and visual color determination with color measurements were made of shade guides and natural teeth. The reliability of all the three instruments was higher than visual method. Shadepilot showed better tooth color measurement performance than Vita Easyshade and ShadeEye NCC, and it's the only instrument which showed definitely higher accuracy than visual method. The pair-agreements of the shade matching results of instrumental and visual color determination were low. At the present time, instrumental color determination can not completely replace visual color determination.