Validation and reliability of visual assessment with a shade guide for tooth-color classification

This study evaluated the validity and reliability of the visual assessment of tooth color using a commercial shade guide. Ninety-two individuals were randomly selected from subjects enrolled in a randomized controlled trial comparing two formulations of carbamide peroxide. Initially, each individual had the color of his or her six maxillary anterior teeth (n=552) determined by one examiner using a digital spectrophotometer (Vita Easyshade). Then, a visual assessment was made by two calibrated examiners using a shade guide (Vitapan Classical). Reliability was evaluated either by kappa coefficient when all the colors were grouped into two categories (dark and light) or by weighted kappa when all 16 colors of the shade guide were considered. The digital spectrophotometer (Vita Easyshade) was used as the gold standard to calculate sensitivity and specificity of the visual assessment. The reliability of the visual assessment using two color categories was "substantial" (k=0.69). When all colors of the shade guide were considered, the reliability was "mild" (kw=0.33). Sensitivity and specificity of the visual assessment with respect to the gold standard was 86.9% and 81.9%, respectively. Despite its subjectivity, visual assessment of tooth color using the Vitapan Classical shade guide is a valid method, with good reliability for differentiating between dark and light colors.     

Interexaminer reliability in clinical measurement of L*C*h* values of anterior teeth using a spectrophotometer

PURPOSE: The objective of this study was to investigate interexaminer reliability in the clinical measurement of the L*C*h* (lightness/value, chroma, hue) values of anterior teeth using a spectrophotometer (Vita Easyshade). MATERIALS AND METHODS: The basic color of the maxillary right central incisors and canines of 23 subjects was spectrophotometrically determined by 4 clinicians and an experienced user (development manager) of the spectrophotometer. Also, to analyze the effect of different training with the instrument on interexaminer reliability, 2 of the clinicians were instructed in the use of the spectrophotometer by the experienced examiner, whereas the others instructed themselves by studying the operating manual. RESULTS: Agreement between all examiners was acceptable to excellent (intraclass coefficient > 0.4). The mean value of the measured differences for the central incisors of all subjects for L* values was 5 (for C* = 3.8, h* = 2.7 degrees) and for canines, the mean L* was 4.5 (C* = 3, h* = 1.6 degrees). Results from comparison of the 2 different training methods were inconsistent. Agreement with the experienced examiner ranged from not acceptable (C* values for incisors of self-instructed examiners) to excellent. CONCLUSION: The distribution of the measurements of 1 subject could lead to deviations in color, probably with clinical impact. For canines, the measurements were at least equally reproducible (in some cases significantly more reproducible) compared to central incisors. Because of the small number of examiners and the inconsistent results, it was not possible to reach a definite conclusion about the effect of different training methods on interexaminer reliability.     

Comparison of two over-the-counter tooth whitening products using a novel system

Tooth whitening is one of the most widely accepted esthetic procedures in dentistry. Various treatment options include in-office and prescribed at-home bleaching procedures, over-the-counter bleaching kits, and whitening dentifrices. This study evaluated and compared a 6% hydrogen peroxide tooth bleaching gel delivered on polyethylene film (HP) with an 18% carbamide peroxide brush-applied liquid gel (CP). A total of 59 subjects completed this 2-week, examiner blind, randomized, parallel group study. Both treatments were applied twice daily for 2 weeks according to the manufacturer's instructions. Evaluations for oral safety and Vita tooth shade were conducted by a dental examiner at baseline and 2 weeks after product use. In addition, the ShadeVision System was used to determine changes in Vita shade and L*a*b* values. Based on both the examiner and ShadeVision System assessments, both treatments significantly improved tooth shade. Improvements in Vita tooth shade based on the adjusted mean for HP were 2.64 (P < 0.001) and 2.33 (P < 0.001) for the examiner and ShadeVision System assessments, respectively, compared with improvements of 1.04 (P = .004) and 0.42 (P = 0.029) for CP users, respectively. The difference between treatments was found to be significant for both the examiner (P = .005) and ShadeVision (P = .001) assessments. Findings from the L*a*b* data derived from the ShadeVision System were in agreement with Vita assessments, with significant differences for changes in L*, a*, and b* in favor of HP users (P = .001). In this study, the ShadeVision method of color analysis was relatively easy to use and demonstrated significant differences between 2 OTC whitening products using both Vitapan and L*a*b* means of assessment.     

应用数码相机测定天然牙色彩的初步研究

目的:评价数码相机用于牙科配色的可行性与合理性。方法:使用Canon EOS D60单反式数码相机,在稳定光源环境(D65标准光源)、固定拍摄参数(光圈f/2.8,快门1/45s,图像格式RAW)条件下,拍摄161例亚裔人群的双侧天然上颌中切牙(年龄为20～40岁);图像经Camera RAW for Adobe Photoshop 8.0专业软件处理后,观察天然牙的色彩特征,采集天然牙色彩数据,数据经统一的色彩空间CIEL*a*b*/C*H°转换后,使用SAS8.1统计软件作进一步描述性分析及Wilcoxon检验。结果:被测牙体49.8%色彩分布不均匀,14.1%表现为异常染色;天然牙色度范围L*39.928～75.681,a*-1.543～5.8284,b*5.5764～22.591;色差容忍度△Eab<2.8NBS。结论:天然牙色度参数与测色手段和方式密切相关,数码相机作为牙科比色方法,在天然牙色彩信息全面采集、色彩信息准确传递方面,具有独特优势。     

Accuracy and precision of a system for assessing severity of tooth wear

PURPOSE: The purpose of this study was to introduce a computer-assisted quantitative tooth wear-analyzing system and test its accuracy and precision. MATERIALS AND METHODS: An image of a horizontally projected dental arch was captured, and the facet area of each tooth was calculated using a digital image analyzer. For normalization, the facet area of the individual tooth was divided by the total area of the corresponding tooth; this result was the tooth wear score. The accuracy and precision of this method were determined through the intraclass correlation coefficient using 10 dental casts. Tooth wear on the dental casts of 50 subjects was actually measured. RESULTS: The accuracy of the tooth wear score determined by a newly trained examiner was greater than 0.85 of the intraclass correlation coefficient; this was tested against the score determined by consensus of three experienced examiners. The reproducibility within a 1-week interval was also greater than 0.85. With regard to the tooth wear score from 50 sets of dental casts, the distribution of tooth wear was generally consistent with data reported in the literature. CONCLUSION: The results suggest that the newly trained examiner can exhibit adequate accuracy and precision after appropriate training in identifying tooth wear facets. Recorded data from 50 subjects added face validity to this new system.     

Comparison of visual analog shade matching,a digital visual method with a cross-polarized light filter,and a spectrophotometer for dental color matching

Statement of problemDuring the selection of tooth color, subjective communication with the laboratory and an incorrect color registration technique can lead to a poor color match of a restoration to adjacent teeth and oral structures.PurposeThe purpose of this cross-sectional study was to compare color registration and color matching in a young Chilean population with 3 different methods: visual with a shade guide, digital visual with a cross-polarized filter, and instrumental with a spectrophotometer.Material and methodsA total of 60 young volunteers were selected for tooth color registration of the maxillary right central incisor by using 3 different methods. Tooth color registration was performed using the CIELab and ΔE coordinate system.ResultsSignificant differences were detected between the coordinates recorded by the visual analog method in comparison with the other 2 methods. In contrast, no significant differences were found between the L1 and b1 coordinates of the spectrophotometer and the digital visual method with use of a cross-polarization filter. The ΔE obtained between the visual shade and spectrophotometer was 7.35, and the ΔE between the digital visual method with the use of a cross-polarization filter and the spectrophotometer was 6.12.ConclusionsNo statistically significant differences were observed in the digital image with the cross-polarization filter and the spectrophotometer in the L1 and b1 coordinate of the CIELab system. In contrast, the visual analog method led to large differences with the other methods under study. The ΔE of the digital visual method with the use of cross-polarization filters and the spectrophotometer was 6.2, considered as an acceptable color mismatch (<ΔE 6.8).     

Clinical performance of a newly developed spectrophotometric system on tooth color reproduction

STATEMENT OF PROBLEM: Matching a natural maxillary central incisor to a metal ceramic crown is one of the most difficult challenges in clinical dentistry due to the limitations of dental shade guides and the subjectivity of perceptual evaluation. PURPOSE: The purpose of this study was to assess the clinical effectiveness of a spectrophotometric shade-matching system on tooth color reproduction. MATERIAL AND METHODS: Two metal ceramic crowns were fabricated for a maxillary central incisor for 36 patients using 2 shade-matching techniques. The first technique was conventional visual matching using 3 shade guide systems, and the second was an instrument-based color-matching technique using a new spectrophotometric system. Color difference (DeltaE) values between the contralateral natural tooth and each of the 2 crowns were calculated in the cervical, middle, and incisal regions. The DeltaE values were compared using a Student's t test (alpha=.05). Three calibrated examiners evaluated the color match by ranking it from 1 to 10 (10 = perfect match; 1 = no match; < or =8, accepted; > or =7, rejected). McNemar's test was used to calculate the odds ratio of accepting restorations fabricated using a spectrophotometric system to conventional methods. RESULTS: Results revealed that the mean DeltaE values of crowns matched with the spectrophotometer were significantly lower than those using a conventional technique (P<.001). The odds ratio of 12.5 was calculated, indicating that conventionally matched crowns were more likely to be rejected than those matched using the spectrophotometer (P<.001). CONCLUSIONS: In this clinical study, crowns fabricated using a dedicated spectrophotometer had a significantly better color match and a lower rate of rejection due to shade mismatch compared to crowns fabricated with a conventional shade-matching method.     

牙科着色氧化钇稳定四方多晶氧化锆陶瓷的制备及颜色性能

目的添加不同着色剂组合配制着色的牙科氧化钇稳定四方多晶氧化锆（3Y-TZP）陶瓷,并测定其颜色性能。方法将TZ-3Y-S粉体与一定组分的着色剂球磨混合后,在200 MPa压力下等静压成型,在1 500 ℃烧结2 h,烧制5种具有一定颜色的氧化锆材料,每个颜色组分别制备10 mm×10 mm×0.5 mm和10 mm×10 mm×1 mm着色氧化锆陶瓷片,在黑色背景下用柯尼卡美能达CM-2600d分光光度计进行颜色测定,并与VITA In-Ceram YZ染色液比色板颜色作比较。结果通过对粉体进行着色,配制出具有一定颜色的本体着色氧化锆陶瓷材料,颜色明度逐级降低,饱和度逐渐增大,2种厚度3Y-TZP陶瓷的颜色片色差较小,颜色空间范围是L*：67.76～77.78;a*：-2.19～3.80;b*：12.13～25.01。与VITA In-Ceram YZ染色液比色板相比,颜色空间近似,但明度的最低值仍较高。结论着色氧化锆陶瓷材料适宜用于临床上与饰面瓷颜色匹配,有必要再进一步研究低明度的着色氧化锆色片。     

应用牙科分光光度比色仪对钴铬合金基底表面4种全瓷冠色度学特征的研究

目的 采用牙科分光光度比色仪评估钴铬合金基底表面4种全瓷冠各部位的色度学参数及与目标色片的色差。方法制作钴铬合金基牙预备体（钴铬合金基底）,分别戴入Procera氧化铝（Pro-Alu）、Procera氧化锆（Pro-Zir）、Lava氧化锆（Lava-Zir）、二矽酸锂增强压铸玻璃陶瓷IPS E.max Press（E.max-HO）4种材料的底冠,并烧结与底冠相同材料的体瓷,制作成全瓷冠。采用牙科分光光度比色仪对钴铬合金基底及底冠、体瓷戴入后样本的颈1/3、体1/3、切1/3区域进行测色。以Vitapan Classical比色板A2色体瓷片为对照,比较各组样本与目标色片A2的色差。结果4种底冠均提高基牙的L*和b*值,a*值下降（除Lava-zir底冠颈部外）;4种底冠L*（除Pro-Zir与Lava-Zir切端、Lava-Zir与E.max-HO颈部外）、a*、b*值均有统计学差异。戴入体瓷后,4种全瓷冠L*值略下降（除Pro-Alu体瓷外）,a*、b*值明显上升。4种体瓷与A2体瓷色差ΔΕ均小于4。结论4种全瓷冠对金属基底都有良好遮色性,虽然明度、彩度有差别,但颜色一致性在临床可接受范围。     

Spectrophotometric and visual shade measurements of human teeth using three shade guides

PURPOSE: To compare spectrophotometric vs. visual color identification of tooth shade on the basis of three different commercially available shade guides. METHODS: On 54 subjects, two operators (with >10 years experience) independently selected the best match of the middle third of one of the patient's upper central incisors, using consecutively three shade guides (Vita Lumin Vacuum, Chromascop, Vita 3D Master). After each individual shade match, the same operator performed a shade measurement with a SpectroShade spectrophotometer. RESULTS: The Vita Lumin shade guide appeared to provide the most consistent results between human and spectrophotometrical evaluation, although Vita 3D Master offered a greater variety of colors. In approximately 47% of the cases, the spectrophotometer provided more accurate results than visual selection. From a clinical point of view, this is a noteworthy improvement in the complex process of color match for indirect restoration.     

Conventional visual vs spectrophotometric shade taking for porcelain-fused-to-metal crowns: a clinical comparison

This study tested the shade match of single porcelain-fused-to-metal restorations with the adjacent dentition when the restorations were fabricated according to data from conventional visual shade matching or from a new spectrophotometric system. The samples of a Vita Classic shade guide were measured with the spectrophotometer to determine the CIE L*a*b* color parameters. Three clinicians independently selected the best match to a maxillary right or left incisor needing a restoration in 10 patients. The 10 incisors were then measured using a reflectance spectrophotometer. CIE L*a*b* coordinates were directly recorded on the spectrophotometer's detector area using a standard light source. Resulting conventional and spectrophotometric restorations were tested intraorally for best match with the adjacent incisor using conventional shade matching versus spectrophotometric measuring. Total color difference was calculated, and all groups were statistically analyzed. Initial shade evaluation matched for all three visual shade selections in two cases. In six cases only two evaluators matched, and in the remaining two cases all three visual selections differed. In contrast, in nine of 10 cases all three spectrophotometric shade selections matched. Additionally, in nine of 10 cases delta E values of visually assessed tooth shades were higher than spectrophotometrically assessed delta E values. Resulting delta E values for conventional crowns compared to spectrophotometric crowns were significantly higher. Finally, in nine of 10 cases spectrophotometric crowns were preferred over conventional crowns for definitive cementation when evaluated visually. Spectrophotometric shade analysis and communication can be used efficiently for fabrication of porcelain-fused-to-metal restorations.     

The colors of mixtures of dental opaque porcelains

The colors of mixtures of dental opaque porcelains and modifiers were measured with use of the CIE L*a*b* uniform color space. Mixtures of dental porcelains were tested to duplicate the range of human tooth colors. Vertical movements in the yellow and blue directions were obtained. Horizontal movements in the red and green directions were achieved. Reflectance measurements were made with use of a spectrophotometer with an integrating sphere. Spectrophotometer measurements were converted to absolute reflectance and then used to calculate CIE a*b* values for a 2 degrees standard observer and for illuminant C. Movements in the yellow, red, blue, and green directions for adequate simulation of the tooth color range can be demonstrated with use of dental opaque and modifier porcelains.     

Evaluation of visual and spectrophotometric shade analyses: a clinical comparison of 3758 teeth

This study aimed to evaluate the performance of visual and spectrophotometric tooth shade analysis. Two operators independently selected the best match of 3758 anterior teeth of 106 patients at 3 different dates, using the Chromascop-Complete shade guide. Additionally, tooth color was analyzed 3 consecutive times using a reflectance spectrophotometer. Spectrophotometry showed high agreement values (89.6%); both examiners agreed in 49.7% of the measurements. Visual assessment resulted in significantly darker ratings than spectrophotometry (P < .0005). However, a positive association was observed for both procedures (P = .548). Spectrophotometric shade determination seems to be significantly more reproducible than the visual procedure.     

Effectiveness of different carbamide peroxide concentrations used for tooth bleaching: an in vitro study

Objectives

This in vitro study evaluated the effectiveness of three carbamide peroxide concentrations used for tooth bleaching treatments.

Material and Methods

Sixty bovine dental slabs (6x6x3 mm) were obtained, sequentially polished, submitted to artificial staining (baseline) and randomized into four groups (n=15), according to the bleaching agent concentration: distilled water (control), 10% (CP10), 16% (CP16) or 37% (CP37) carbamide peroxide. CP10 and CP16 were covered with 0.2 mL of the respective bleaching gels, which were applied on enamel surface for 4 h/day during two weeks. Samples of CP37 were covered with 0.2 mL of the bleaching gel for 20 min. The gel was light activated by two 40-s applications spaced by 10-min intervals. The gel was renewed and applied 3 times per clinical session. This cycle was repeated at 3 sessions with 5 days of interval between them. Tooth shade evaluations were done with a digital spectrophotometer at T0 (baseline), T1 (after 1-week of treatment) and T2 (1-week post-bleaching). Tooth shade means were statistically analyzed by Kruskal-Wallis and Friedman''s tests and color parameters were analyzed by two-way ANOVA and Tukey''s test (p<0.05).

Results

At T1 and T2 evaluations, tooth shade was significantly lighter than at baseline for all treatment groups, considering the color parameters ΔL*, Δa*, Δb*, ΔE* (p<0.001) or tooth shade means (p<0.001). CP37 group showed lower shade mean change than CP10 and CP16 at T1 (p<0.01), but this difference was not statistically significant at T2 (p>0.05).

Conclusions

One week after the end of the treatment, all carbamide peroxide concentrations tested produced similar tooth color improvement.     

Comparison of in vivo visual and computer-aided tooth shade determination

The aim of this study was to evaluate the performance of shade-determining devices. For the daily practitioner, it is essential to know whether modern computer-aided shade selection is reliable in everyday life. So the question of how the clinical usability of these machines could be rated has to be clarified. In the following, three actual devices available in the market were compared using a human observer's perception. The SpectroShade device (MHT Optic Research AG, 8155 Niederhasli, Switzerland), the ShadeVision device (X-Rite Co., Grandville, USA) and the Digital Shade Guide DSG4 (A. Rieth, 73614 Schorndorf, Germany) were assessed with respect to their agreement with the color perception of three examiners looking at 57 test persons (six teeth each for a total of 342). Shades were reported in Vita Classical shades. It could be demonstrated that every single human examiner showed a significantly higher agreement value (human group on average 40.2%) when compared with the remaining five methods than each computer-aided tooth shade determination device. The devices reached on average only a value of 28.6%, whereas the X-Rite ShadeVision showed a significant better result (33.2%) than the MHT SpectroShade and Rieth DSG4 (27.0 and 25.7%). Identical shade results given by all three methods of a group (group of three devices and three humans) were found to be rather low for the computer-aided devices (9.9%) compared with humans (36.7%). All six methods together agreed in 3.3% of the cases. It becomes evident that the methods—especially the computer-aided shade determination—are rather divided about the respective tooth color. Deficiencies of the instrumental as well as the visual detection become obvious. The best agreement level was performed by the human examiners. The best agreement of the evaluated devices was obtained—generally as well as among the human testers—by the X-Rite ShadeVision system, followed at a statistically significant distance by the MHT SpectroShade and the Rieth DSG4. The agreement among the examiner group was 52.9%, significantly better than that of each device compared to this group (31.3% on average). Color detection and its realization are very complex. As shown, in many cases, computer-aided color shade determination of natural teeth seems to not reflect human perception. Clinical Relevance For color determination of natural teeth, there is significant disagreement between the shade selected by human perception and the shade obtained with computer-aided instrumentation.     

Metameric effect between natural teeth and the shade tabs of a shade guide

Corcodel N, Helling S, Rammelsberg P, Hassel AJ. Metameric effect between natural teeth and the shade tabs of a shade guide. Eur J Oral Sci 2010; 118: 311–316. © 2010 The Authors. Journal compilation©2010 Eur J Oral Sci The objective of this study was to evaluate metameric effects, that is, the dependence of the colours of teeth and shade tabs on the illuminant used. The colours of 49 teeth of 37 participants and of the corresponding shade tabs of the 3D‐Master (VITA Zahnfabrik; colour match ΔE_ab< 2) were measured using an intra‐oral spectrophotometer (VITA Easyshade). Spectral reflectance data (from 400 to 700 nm) were recorded. Commission Internationale de l’Éclairage (CIE) L*a*b* values were calculated for D65 (reference daylight), A (incandescent light), and TL84 (store/office light) as reference illuminants. A modified metamerism index (Mod‐M) and hue‐angle ratios were calculated to express differences between tooth and tab colour relative to the difference observed under D65 illumination. The Mod‐M for teeth and tabs was greater than unity (indicating a greater colour difference relative to D65) by 57.1% for A and by 49.3% for TL84. Hue‐angle ratios of teeth and tabs using the test illuminants were different from those obtained using the standard illuminant D65. If teeth and shade tab matching is conducted using daylight illumination, the colour difference may not be the same under other lighting conditions, leading to perceptible, or even unacceptable, colour differences under these conditions.     

Color perception among different dental personnel

This study investigated the differences in color perception among distinct groups of dental personnel. Four groups of dental personnel (10 dental technicians, 15 final-year dental students, 15 general practitioners and 10 prosthodontists) were asked to match seven test tabs of shades A1, A4, B2, B3, C2, C4 and D3 (Z100 shade guide, 3M Dental Products, St Paul, MN 55144, USA) against a standard Vita shade guide under similar lighting conditions. The results obtained were computed into L*a*b* values using a small-area colorimeter (Dental Colorimeter, Minolta Camera Pte Ltd). The data were analyzed using one-way ANOVA/post-hoc Scheffe's test at significant level p<0.05. The results showed significant differences in deltaE (color difference) between the dental technicians and the clinicians for shade C4. The significant difference that was observed in deltaE for dark shades between dental personnel was mainly contributed to a disparity in L* values. A significant difference in deltaL* was observed between dental technicians and prosthodontists for shade C4.     

Coverage errors of two shade guides

Dental shade guides contain a limited selection of colors compared to those found in human teeth. An error in shade selection is thus introduced, since many tooth colors must be defined by approximation to the nearest shade of the guide. The Bioform and Vita Lumin guides, and a combination of the two, were spectrophotometrically compared to the published colors of 335 human teeth. The minimum CIE L*a*b* color difference was calculated for each tooth using each shade guide. The average of these color differences was defined as the coverage error. The Bioform and Vita shade guide coverage errors were not significantly different, but the coverage error was significantly lower when the combination was used. The use of both guides in shade selection is recommended to reduce the coverage error.     

Repeatability of dental shade by digital spectrophotometry in current,former, and never smokers

Cigarette smoking contributes to poor oral health and dental discoloration. Therefore, stopping smoking may translate into measurable amelioration of dental shade indices. We compared dental shade parameters by digital spectrophotometry among current, former, and never smokers and verified their repeatability at 7 and 30 days. Dental shade parameters (CIE L*a*b* and corresponding whiteness index for dentistry-WID) were measured in current, former, and never smokers with a digital spectrophotometer (Vita Easyshade V) on three separate study visits: at baseline (day 0), at day 7, and day 30. Dental shade parameters were analyzed in 18 current, 18 former, and 20 never smokers. The repeatability of shade parameters was consistent in current, former, and never smokers. L*, a*, b*, and WID show significant short and long-term repeatability (p < 0.0001, by regression analyses). The mean (± SD) WID score of 13.42 (± 4.9) in current smokers was significantly lower compared to the WID score of 20.38 (± 5.3) in never smokers (p = 0.001). No significant differences were observed between current and former smokers and between former smokers and former smokers. Dental shade measurements by digital spectrophotometry were highly reproducible and showed that teeth whiteness of current smokers is substantially inferior compared to never smokers. Objective discrimination of dental shade can be a valuable regulatory science endpoint for investigating oral hygiene and dental aesthetics of consumer care products, smoking cessation medications, and tar-free tobacco products (e-cigarettes, heated tobacco products, oral nicotine products) for cigarette substitution.

Clinical trial registration: the study was not registered in ClinicalTrials.gov considering that it is a pilot study, parts of a larger project with ID: NCT04649645