In vivo tooth-color measurement with a new 3D intraoral scanning system in comparison to conventional digital and visual color determination methods.

STATEMENT OF PROBLEM: Three-dimensional (3D) intraoral scanning systems allow for the simultaneous acquisition of 3D information about tooth surfaces and a photorealistic view of the patient's tooth colors. AIM: The goal of this study was the in vivo comparison of a new 3D scanner with a color acquisition mode and conventional visual and digital color measurements. MATERIALS AND METHODS: The colors of 40 teeth of 20 patients were evaluated in seven ways: 1) By dentists using the Vita 3D-Master; 2) By dental technicians using the Vita 3D-Master; 3) With the 3Shape Trios device; 4) With the Vita Easyshade device; 5) With the Vita Easyshade Advance device; 6) With the SpectroShade device; and 7) With the SpectroShade Micro device. Digital measurements of Groups 3 to 7 were repeated three times for each tooth. For all groups, both the CIE Lab values and the Vita 3D-Master values were recorded. The repeatability and relative accuracy of the Vita 3D-Master values were analyzed statistically using Pearson's chi-squared test (α < 0.05). ΔE values were calculated from the CIE Lab values, which served as a basis for performing multidimensional scaling (MDS) and evaluating differences between the groups using the one-way ANOVA with post hoc Tamhane's test (α < 0.05). RESULTS: The results of the ΔE values showed that clinically relevant differences between the evaluation by dentists, dental technicians, and the intraoral scanning device (3Shape) are negligible. The intraoral 3D scanning device (Group 3) and the digital systems (Groups 4 to 7) did not differ significantly in the repeatability of color shade management. The SpectroShade Micro (Group 7) had significantly better relative accuracy than the other devices. CONCLUSIONS: The results demonstrate that intraoral scanning systems can be used to measure both tooth color and tooth surface in 3D. CLINICAL IMPLICATIONS: Intraoral optical scanning devices allow for the acquisition of accurate 3D surface data. Tooth color can be evaluated simultaneously and can be used to determine the color of restorations without requiring additional conventional color-measurement methods.

Accurate shade image matching by using a smartphone camera.

PURPOSE: Dental shade matching by using digital images may be feasible when suitable color features are properly manipulated. Separating the color features into feature spaces facilitates favorable matching. We propose using support vector machines (SVM), which are outstanding classifiers, in shade classification. METHODS: A total of 1300 shade tab images were captured using a smartphone camera with auto-mode settings and no flash. The images were shot at angled distances of 14-20cm from a shade guide at a clinic equipped with light tubes that produced a 4000K color temperature. The Group 1 samples comprised 1040 tab images, for which the shade guide was randomly positioned in the clinic, and the Group 2 samples comprised 260 tab images, for which the shade guide had a fixed position in the clinic. Rectangular content was cropped manually on each shade tab image and further divided into 10×2 blocks. The color features extracted from the blocks were described using a feature vector. The feature vectors in each group underwent SVM training and classification by using the "leave-one-out" strategy. RESULTS: The top one and three accuracies of Group 1 were 0.86 and 0.98, respectively, and those of Group 2 were 0.97 and 1.00, respectively. CONCLUSIONS: This study provides a feasible technique for dental shade classification that uses the camera of a mobile device. The findings reveal that the proposed SVM classification might outperform the shade-matching results of previous studies that have performed similarity measurements of ΔE levels or used an S, a*, b* feature set.

Tooth Shade-Matching Ability Between Groups of Students with Different Color Knowledge.

PURPOSE: The aim of this study was to evaluate the effect of gender and knowledge of color in dentistry on the visual shade-matching ability of dental students with no experience in shade matching and without identification skills. MATERIALS AND METHODS: A total of 32 color-normal participants, 16 female (F) and 16 male (M), completed all phases of the experiment. The control group did not listen to a 60-minute lecture (FNL = females that did not listen; MNL = males that did not listen); the other group listened to a lecture about color in dentistry (FL = females that listened; ML= males that listened). The Toothguide Training Box (TTB) (VITA Zahnfabrik) was used. The final exam consisted of a total of 15 lightness-chroma-hue tasks. The correct selection of lightness (L*), chroma (C*), and hue (h*) was observed, as was the computed shade-matching score, ΣΔE*ab, for each participant. Mann-Whitney U test was used for statistical analysis of the data (α = .05) (SPSS 22.0 for Windows [IBM]). RESULTS: Gender was found to play an important role in shade matching. The FL group selected L* better (L* = 12.11) in comparison with the MNL group (L* = 11.00), which is not significantly different (P = .19). The FL group selected L* better in comparison with the ML group (L* = 10.57), which is not significantly different (P = .10). The FNL group selected C* statistically significantly better (C* = 9.86) than did the ML group (C* = 8.57) (P = .016). The shade-matching score, ΣΔE*ab, for group FL (ΣΔE*ab = 22.50) and group ML (ΣΔE*ab = 31.79) was marginally statistically significant (P = .06). CONCLUSION: A 60-minute lecture from the field of color in dentistry has a minimal impact on tooth-shade matching, whereas gender plays an important role.

Learning Shade Differentiation Using Toothguide Trainer and Toothguide Training Box: A Longitudinal Study with Dental Students.

The positive training effect achieved with the Toothguide Training Box (TTB) has been demonstrated in previous studies. The aim of this study was to investigate the training effect with the TTB at six and 12 months using standardized color tests. The study involved 101 dental students. The participants were divided into two study groups and one control group. Ten standard color samples were determined under uniform environmental conditions with VITA 3D-Master. The control group (N=30) took the color test after one week. Study group 1 (N=49) took the color test after six months and study group 2 (N=22) at 12 months for the first time by following the TTB curriculum. The control group achieved an average ΔEt1=0.85. In study group 1, the ΔEt2 was 2.29, and in study group 2, ΔEt3=2.25. The results after six and 12 months were highly significant compared to the control group (α=0.001). Dependence was determined only with regard to gender. In this study, the TTB quickly led to an improvement in tooth color differentiation among students. After six months, there was a decrease in the training effect. These results suggest that the TTB curriculum should be provided at the end of preclinical training.

Evaluation of reliability and validity of three dental color-matching devices.

PURPOSE: To assess the repeatability and accuracy of three dental color-matching devices under standardized and freehand measurement conditions. MATERIALS AND METHODS: Two shade guides (Vita Classical A1-D4, Vita; and Vita Toothguide 3D-Master, Vita), and three color-matching devices (Easyshade, Vita; SpectroShade, MHT Optic Research; and ShadeVision, X-Rite) were used. Five shade tabs were selected from the Vita Classical A1-D4 (A2, A3.5, B1, C4, D3), and five from the Vita Toothguide 3D-Master (1M1, 2R1.5, 3M2, 4L2.5, 5M3) shade guides. Each shade tab was recorded 15 continuous, repeated times with each device under two different measurement conditions (standardized, and freehand). Both qualitative (color shade) and quantitative (L, a, and b) color characteristics were recorded. The color difference (ΔE) of each recorded value with the known values of the shade tab was calculated. The repeatability of each device was evaluated by the coefficient of variance. The accuracy of each device was determined by comparing the recorded values with the known values of the reference shade tab (one sample t test; α = 0.05). The agreement between the recorded shade and the reference shade tab was calculated. The influence of the parameters (devices and conditions) on the parameter ΔE was investigated (two-way ANOVA). Comparison of the devices was performed with Bonferroni pairwise post-hoc analysis. RESULTS: Under standardized conditions, repeatability of all three devices was very good, except for ShadeVision with Vita Classical A1-D4. Accuracy ranged from good to fair, depending on the device and the shade guide. Under freehand conditions, repeatability and accuracy for Easyshade and ShadeVision were negatively influenced, but not for SpectroShade, regardless of the shade guide. CONCLUSION: Based on the total of the color parameters assessed per device, SpectroShade was the most reliable of the three color-matching devices studied.

Influence of personality on tooth shade selection.

PURPOSE: The harmonious shade matching of restorations with adjacent natural teeth is a prerequisite for a successful esthetic restoration. Color is a combined effect of the physical properties of an object, the light source, and the perception of the observer. The interpretation of color is influenced by both the physiological and psychological health of an individual. It is critical to understand the influence of an individual's psychological state on the shade selection procedure to achieve better shade matching and post-treatment patient counseling. The aim of this study was to evaluate the influence of personality on tooth shade selection capability. MATERIALS AND METHODS: Two porcelain fused to metal (PFM) discs were fabricated. A reference shade was determined using a spectrophotometer (Vita Easyshade, Vita). The personalities of volunteers were identified using a Myers- Briggs Type Indicator (MBTI) questionnaire. The volunteers visually identified the shade of the two PFM discs under a controlled light source. The mean color difference was determined between the visual and the spectrophotometer values. The data thus obtained was statistically analyzed with Kruskal-Wallis and post-hoc comparison tests to ascertain the difference between the groups. RESULTS: The groups that performed better in tooth shade selection were ENTJ (2.923 ± 2.36), ISTJ (3.086 ± 2.56), ENFJ (3.197 ± 2.936), and ESTJ (3.431± 2.78). The groups INTP (9.383 ± 3.30), ISTP (9.133 ± 3.44), ISFP (8.737 ± 2.81), and INTJ (8.480 ± 3.35) showed poor tooth shade selection ability. The Kruskal- Wallis test showed lower mean rank for group ENTJ (89.75), followed by ISTJ (92.25), and ENFJ (94.80). CONCLUSION: Within the limitations of this study, it was concluded that there was a statistically significant difference between the different personalities with regard to tooth shade selection ability.

Dental color matching: A comparison between visual and instrumental methods.

The aim of this study was to compare the agreement rate (%) and color difference (ΔE*ab) of three dental color-measuring devices, with the visual shade identification. The tooth color were determined by two operators, which were advised to select a VITA classic shade tab in each other's agreement. The Shadepilot (SP), CrystalEye (CE) and ShadeVision (SV) were used to measure tooth color. Statistically analyses include agreement rate (%), color difference (ΔE*ab), McNemar test (p=0.05), Student's t-test (p=0.05) and Bland Altman scatterplots. The SP had an agreement of 56.3% with the visual shade determination, the CE 49.0% and SV 51.3%. ΔE*ab of the visually and instrumentally selected shade tabs and natural teeth were frequently above the threshold for acceptability. Comparing both methods, for SP ΔE*ab values differ in a range of clinical acceptability.

Shade selection of primary maxillary anterior teeth in children using Vitapan classical shade guide.

AIM: The purpose of this study was to determine the closest matching shade for primary maxillary anterior teeth from the most widely used Vitapan classical shade guide available for permanent teeth. MATERIALS AND METHODS: A total of 313 children aged between 3 and 5 years were evaluated. Vitapan classical shade guide was used to determine the shade of six primary maxillary anterior teeth. Scores obtained were noted down in a scoring sheet and values were tabulated. Data collected were tabulated and statistically analyzed using Pearson Chi-square test. RESULTS: A1 was found to be the closest matching shade for primary maxillary anterior teeth. D3 was found to be the least prevalent shade for primary maxillary anterior teeth. There was no statistical significant difference in the shades among teeth of same quadrant (p > 0.05) and also between teeth of right and left quadrants (p > 0.05), respectively. CONCLUSION: A1 shade of Vitapan classical shade guide is the most prevalent shade for primary maxillary anterior teeth and can be satisfactorily reproduced to all primary maxillary anterior teeth in general.

A clinical study relating CIELCH coordinates to the color dimensions of the 3D-Master System in a Spanish population.

STATEMENT OF PROBLEM: The 3D-Master System comprises 26 physical shade tabs and intermediate shades. Determining the relationship among all the groups of lightness, chroma, and hue of the 3D-Master System (Vita Zahnfabrik) and the L*, C*, and h* coordinates is important, because according to the manufacturer, 2 Toothguide 3D-Master shades need to be mixed in a 50:50 ratio to create an intermediate shade. PURPOSE: The purpose of the study was to relate the lightness, chroma, and hue groups of the 3D-Master System with the polar coordinates of the CIELAB chromatic space, L*, C*, and h*, and to quantify the shades tabs and intermediate shades of the 3D-Master System according to color coordinates. MATERIAL AND METHODS: The middle third of the facial surface of a natural maxillary central incisor was measured with an Easyshade Compact spectrophotometer (Vita Zahnfabrik) in 1361 Spanish participants aged between 16 and 89 years. Natural tooth color was recorded in the 3D-Master nomenclature and in the CIE L*, C*, and h* coordinates system. The program used for the present descriptive statistical analysis of the results was SAS 9.1.3. RESULTS: In the L* variable, the minimum was found at 47.0 and the maximum at 91.3. In the C* variable, the minimum was found at 5.9 and the maximum at 49.8, while for h*, the minimum was 67.5 degrees and the maximum 112.0 degrees. CONCLUSIONS: Despite the limitations of this study, the 3D-Master System was found to be arranged according to L*, C*, and h* coordinates in groups of lightness, chroma, and hue. The corresponding groups of lightness, chroma, and hue can be estimated on the basis of L*, C*, and h* coordinates.

Evaluating the ability of dental technician students and graduate dentists to match tooth color.

STATEMENT OF PROBLEM: The ability of dental technician students to match tooth shade with the Vita 3D-Master shade guide and Toothguide Training Box has not been investigated. PURPOSE: The purpose of this study was to evaluate and compare the shade-matching ability of dental technician students and graduate dentists using the Vita 3D-Master shade guide. MATERIAL AND METHODS: Twenty-nine dental technician students (DTS group) and 30 graduate dentists (GD group) participated in this study. The Toothguide Training Box (TTB) was used to train the participants and test their shade-matching abilities. Shade-matching ability was evaluated with 3 exercises and a final test, all of which are components of the TTB. The number of mistakes for each participant for value (L), chroma (c), and hue (h) were recorded during the exercises and the final test, and the mistake ratios were calculated. Color difference (ΔE) values for each shade were calculated from the L*, a*, and b* values of the Vita 3D-Master shade guide for each participant in both groups. The Mann-Whitney U test was used to determine statistically significant differences between the L, c, and h mistake ratios of the 2 groups, and the Student t test was used to determine statistically significant differences between the final test scores and the ΔE values of the groups (α=.05). RESULTS: The mistake ratio for L in the GD group was significantly higher than that of the DTS group (P<.05), whereas the mistake ratio for h in the DTS group was higher (P<.001). No significant differences were observed between the groups regarding the mistake ratios for c (P>.05). With regard to the final test scores and the ΔE values, no significant differences were found between the groups (P<.001), and the DTS group received higher scores than the GD group (912 and 851). The mean ΔE values for the DTS and GD groups were 1.72 and 2.92. CONCLUSIONS: DTSs made more mistakes in the h parameter than GDs, and GDs made more mistakes in the L parameter than DTSs. With regard to the final test scores and the ΔE values, DTSs were more successful in shade matching than GDs.

Evaluation of an optimized shade guide made from porcelain powder mixtures.

STATEMENT OF PROBLEM: Color errors associated with current shade guides and problems with color selection and duplication are still challenging for restorative dentists. PURPOSE: The purpose of this study was to evaluate an optimized shade guide for visual shade duplication. MATERIAL AND METHODS: Color distributions (L*, a*, and b*) of the maxillary left central incisors of 236 participants, whose ages ranged from 20 to 60, were measured with a spectrophotometer. Based on this color map, an optimized shade guide was designed with 14 shade tabs evenly distributed within the given color range of the natural incisors. The shade tabs were fabricated with porcelain powder mixtures and conventional laboratory procedures. A comparison of shade duplication by using the optimized and Vitapan Classical shade guides was conducted. Thirty Chinese participants were involved, and the colors of the left maxillary incisors were selected by using 2 shade guides. Metal ceramic crowns were fabricated according to the results of the shade selection. The colors of the shade tabs, natural teeth, and the ceramic crowns were measured with a spectrophotometer. The color differences among the natural teeth, the shade tabs, and the corresponding metal ceramic crowns were calculated and analyzed (α=.017). RESULTS: Significant differences were found in both phases of shade determination and shade duplication (P<.017). The total number of color errors with the optimized shade guide was 3.5, which was significantly less than that of Vitapan, 5.1 (P<.001). CONCLUSIONS: The optimized shade guide system improved performance not only in the color selection phase but also in the color of the fabricated crowns.

Selecting VITA classical shades with the VITA 3D-master shade guide.

PURPOSE: Although the VITA 3D-Master (3D) shade guide offers improved shade-matching performance, many dental materials are only available in VITA Classical (VC) shades. This study aimed to clarify whether it is possible to convert 3D shades determined by observers into VC shades (indirect method) without adding a clinically significant error in comparison with direct shade determination using the VC shade guide. MATERIALS AND METHODS: Forty ceramic specimens were fabricated. L*a*b* values were recorded using a spectroradiometer. Sixty participants (35 dentists, 15 technicians, and 10 students) were recruited and asked to determine the shades of specimens using the VC and 3D shade guides under standardized conditions. Conversion tables were constructed by allocating the closest VC shade tab to every matched 3D shade and by use of an optimization algorithm (indirect methods). Differences between ΔE values for VC matches and for the indirect methods were evaluated using t tests. RESULTS: A mean ΔE (SD) of 4.34 (2.00) for VC and 4.22 (2.21) for 3D was observed (P = .040). Compared with direct shade matching using VC, the indirect method with the optimized tables resulted in a mean ΔE of 4.32 (1.96), which was not significantly different (P = .586). CONCLUSIONS: Within the limitations of this study, the conversion tables were suitable for the determination of tooth color using the 3D shade guide followed by conversion into VC shades without adding a clinically significant error.

Shade determination using camouflaged visual shade guides and an electronic spectrophotometer.

The aim of the present study was to compare a camouflaged visual shade guide to a spectrophotometer designed for restorative dentistry. Two operators performed analyses of 66 subjects. One central upper incisor was measured four times by each operator; twice with a camouflaged visual shade guide and twice with a spectrophotometer Both methods had acceptable repeatability rates, but the electronic shade determination showed higher repeatability. In general, the electronically determined shades were darker than the visually determined shades. The use of a camouflaged visual shade guide seems to be an adequate method to reduce operator bias.

The effect of various disinfectants on dental shade guides.

STATEMENT OF PROBLEM: Dental shade guides are used to evaluate tooth color before prosthodontic procedures and are subjected to disinfection after use. The effect of disinfection on shade guides has not been thoroughly investigated. PURPOSE: The purpose of this study was to evaluate the effect of disinfectants on the color of shade tabs. MATERIAL AND METHODS: Changes in the color (ΔE) of VITA Classical Shade Guide tabs were measured with a VITA Easyshade spectrophotometer in the CIELAB system and calculated after being subjected to Cavicide, Asepticare TB, Sporicidin, and distilled water (control) over a simulated period of 2 years. Statistical analysis was accomplished by a 2-way analysis of variance followed by the Tukey honestly significant difference (HSD) test (α=.05). RESULTS: A significant difference was noted in the degree of shade tab color change, depending on the type of disinfectant used (F=153.2, P<.001). No significant difference was noted in the amount of shade tab color change that occurred after disinfection among the different shade tabs used (F=0.611, P=.865), nor was a significant interaction noted between the type of disinfectant and the different shade tabs used (F=0.7, P=.919). Asepticare TB showed the least significant amount of change (ΔE=0.401), and Sporicidin (ΔE=0.889) and the control (ΔE=0.969) showed significantly more color change than Asepticare TB but less than Cavicide (ΔE=1.198). CONCLUSIONS: The average total CIELAB color difference for 50% human perceptibility is approximately 1 unit (under standardized laboratory conditions). In the oral cavity, however, an average change of 3.7 ΔE units could still allow teeth to be perceived as having the same color. Therefore, although the results are statistically significant, they may not be clinically important.

Influence of ceramic color and translucency on shade match of CAD/CAM porcelain veneers.

OBJECTIVE: To investigate the influence of translucency of CAD/CAM ceramic milling blocks on the final color of porcelain veneer cemented using resin cement with two different opacities. MATERIALS AND METHODS: A standardized incisal lap preparation was made on a maxillary right central incisor that was duplicated using composite resin material (Z250, A4, 3M ESPE). The resin dies were individually laser scanned (Bluecam, Sirona) in order to build a 3D model of the porcelain veneer on the CAD software (Cerec 3D). Three types of milling blocks were used to fabricate the required restorations: multichromatic, high translucency, and low translucency milling blocks (IPS Empress CAD, A1 Vita shade tab). The milled veneers were polished, glazed, and bonded on the resin dies using high opacity and low opacity resin cements (Panavia F2.0). A digital shade guide device (Easyshade Advance, Vita) was used to measure color parameters (CIE Lab values) at the incisal, middle, and cervical third of each cemented restoration. ΔE values of the cemented veneers were calculated against the target color (A1). RESULTS: Cementation of porcelain veneers resulted in significant color change of the resin die (A4) as ΔE values ranged between 8.9 and 13.7. However, the type of milling block did not have an observable effect on final color as the measured ΔE values, against original die color, were very close for the multichromatic block (ΔE = 10.7 ± 0.1), high translucency (ΔE = 9.7 ± 0.09), and low translucency blocks (ΔE = 13.4 ± 0.11). The opacity of the used resin cement did not affect the final shade match, as the observed ΔE values using either high opacity and low opacity resin cement were less than 2 for the three used ceramic blocks. The greatest color difference was observed between the incisal third of multichromatic veneers (ΔE = 8.9) and the cervical third of low translucency veneers (ΔE = 13.7), while for the rest of the test groups this shift was not clinically observable (ΔE < 2.5). CONCLUSION: Within the limitations of this study, the shade match of CAD/CAM porcelain veneers was not influenced by the translucency of used milling block or the opacity of the resin cement.

Composite shade guides and color matching.

Finding reliable systems that can help the clinician match the color of direct composite restorations is often an issue. After reviewing several composite shade guides available on the market and outlining their main characteristics and limits (unrealistic specimen thickness, not made with the same material the clinician will use, only a few allow to overlap enamel tabs on dentin ones), the authors evaluated the reliability of a system designed to produce self-made standardized "tooth-shaped" shade guide specimens. Small changes in composite enamel thickness may determine huge differences in esthetic outcomes. In conclusion, the results showed that all the specimens demonstrated comparable enamel thickness in all the examined areas (cervical, middle, incisal).

Shade matching quality among dental students using visual and instrumental methods.

OBJECTIVES: Study aims were to compare shade matching quality between visual and machine-aided shade selection among dental students and to evaluate the effect of experience and gender. METHODS: A total of 204 undergraduates and interns participated. They were briefed about colour matching using a visual method with a Vita-3D Master system and a spectrophotometer. Participants with colour vision deficiency were excluded. Six maxillary anterior teeth of a maxillary blue stone cast were replaced with six maxillary artificial teeth. Participants selected the best shade match using each method. A daylight illuminator with the GTI mini-matcher colour viewing system was used during the test. The results were statistically analysed with SPSS version 19 with 95% confidence intervals. Frequencies and Chi-square tests were used to analyse the data, at α=0.05 and with P<0.05 indicating significance. RESULTS: Among the participants, 36.3% visually selected the correct shade, and 80.4% did so using the Easy Shade Compact machine. Experience (P=0.177) and gender (P=0.560) did not affect visual shade selection; in addition, with the Easy Shade Compact device, males and females equally mastered its use (P=1.0), and experience did not influence outcomes (P=0.552). CONCLUSIONS: The shade matching device was significantly better than the conventional visual method. With both techniques, neither experience nor gender influenced shade matching quality. CLINICAL SIGNIFICANCE: Visual tooth colour matching is unreliable and inconsistent because of various subjective and objective factors, and the use of a colour measuring device might improve the quality of shade matching among dental students.

Assessing the accuracy of computer color matching with a new dental porcelain shade system.

STATEMENT OF PROBLEM: In a previous study, a novel computer color matching system for dental ceramic restoration was developed, and 21 new shades were established. Theoretically, a natural tooth color can be accurately reproduced by combining 2 or 3 ceramic mixtures from the database of 21 new shades. PURPOSE: The purpose of this study was to test the use of these shades in conjunction with the computer color matching system to determine their ability to accurately reproduce the body color of 29 shade tabs from a shade guide (VITAPAN 3D-Master). MATERIAL AND METHODS: Disks of 21 reference shades were prepared with porcelain (Cerabien CZR) and polished to 1.0 mm thickness. A spectrophotometer was used to measure the reflectance values from 380 to 780 nm for each disk; the scattering coefficient and absorption coefficient were determined. By using the reflectance values and the scattering and absorption coefficients, the computer color matching program generated porcelain prescriptions incorporating proportions from the 21 reference shades to reproduce the shade tabs. Disks were fabricated from the prescriptions, polished to 1.0 mm thickness, then placed over a zirconia core plate and measured with the spectrophotometer. The color differences (ΔE*) between the shade tabs and the corresponding ceramic disks were calculated. Statistical analysis was performed with the 1-sample t test. RESULTS: The ΔE* values between computer color matching specimens and the target shade tabs varied from 0.5 to 1.9, with an average ΔE* of 1.3, which was significantly less than the clinically detectable ΔE* threshold of 1.6 (P<.001). CONCLUSIONS: The computer color matching system with the established 21 new shades is accurate and effective for reproducing tooth shades.

Differences between the human eye and the spectrophotometer in the shade matching of tooth colour.

OBJECTIVES: The aim of this work was to assess the agreement between instrumental and visual colour matching. METHODS: Shade selection with the 3DMaster Toothguide (Vita-Zahnfabrik) was performed for 1361 maxillary central incisors and compared with the shade obtained with the EasyShade Compact (Vita-Zahnfabrik) spectrophotometer. RESULTS: We observed a greater correlation between the objective method and the subjective one in the colour dimension of lightness (Kappa 0.6587), followed by hue (Kappa 0.4337) and finally chroma (Kappa 0.3578). CONCLUSION: The colour dimension in which the greatest agreement is seen between the operator and the spectrophotometer is value or lightness. CLINICAL SIGNIFICANCE: This study reveals differences between the measurement of colour via spectrophotometry and the visual shade selection method. According to our results, there is better agreement in the value or lightness colour dimension, which is the most important one in the choice of tooth colour.