Color difference for shade determination with visual and instrumental methods: a systematic review and meta-analysis

Assessing Discrimination and Acceptance for Lightness and Chroma During Shade Selection: A Comparison of Dental and Non-Dental Professionals

Background/Objectives: Tooth color is key in determining aesthetic appearance during restorative and prosthodontic treatments. To establish a more reliable methodology for shade selection, this study investigated differences in the discrimination and acceptance of tooth color between dental and non-dental professionals, focusing on color attributes such as lightness and chroma. Methods: This study included 30 dentists, 30 dental technicians, 30 patients, and 30 dental students. They were asked to compare pairs of shade tabs with different lightness and chroma from the VITA Toothguide 3D-MASTER® (VITA Zahnfabrik, Bad Säckingen, Germany). The number of answers in which participants could discriminate color differences (discrimination numbers) and answers in which they could not accept color differences (non-acceptance numbers) were recorded. Statistical analysis was performed using Spearman's rank correlation coefficient, the Mann-Whitney U test, the Kruskal-Wallis test, and multiple regression analysis (p < 0.05). Results: Significant factors influencing lightness discrimination were participant group and age, while those influencing acceptance were subject group and sex. Conclusions: This study revealed differences in the discrimination and acceptance of lightness and chroma between dental and non-dental professionals, particularly concerning lightness. Dental technicians exhibited a higher discrimination ability and stricter acceptance of lightness and chroma, regardless of age. Based on an understanding of these characteristics, appropriate shade selection and adequate communication will be important.

Color Comparison Between Intraoral Scanner and Spectrophotometer Shade Matching: A Systematic Review and Meta-Analysis

OBJECTIVE

This systematic review and meta-analysis compared the accuracy of intraoral scanners and spectrophotometers in determining tooth shade.

MATERIALS AND METHODS

An electronic search of five databases (PubMed, Scopus, Embase, Web of Science, CENTRAL) was conducted on October 19, 2023. A total of 163 studies were identified from the databases, of which 23 articles were eligible for inclusion. In vivo and in vitro quasi-experimental studies were included. After data extraction, a quantitative analysis was performed to determine the accuracy of the intraoral scanner in subgroups using four outcomes: trueness and precision with different measurement locations. A random-effects model was used to pool effect sizes. The pooled proportion with a 95% confidence interval (CI) was used for the effect size measure.

RESULTS

Eleven articles were included in the meta-analysis. Trueness with the intraoral scanner was between 0.28 (CI: 0.09-0.60) and 0.38 (CI: 0.24-0.53). Repeatability was between 0.81 (CI: 0.64-0.91) and 0.85 (CI: 0.74-0.92). Trueness showed low, and precision had moderate certainty of evidence.

CONCLUSION

The trueness of shade matching with intraoral scanners is low compared to spectrophotometers, although the precision is considered high and is similar to spectrophotometers.

CLINICAL SIGNIFICANCE

Shade determination with intraoral scanners is not recommended.

Impact of Vision Defects on Tooth Shade Selection: A Comparative of Spectrophotometry and Shade Guides in a Cross-Sectional Clinical Study

Introduction: Tooth shade selection is a fundamental factor in the success of dental restorations, and visual impairment may adversely affect this process. The aim of this cross-sectional clinical study was to determine whether visual impairment influences shade selection using two methods: spectrophotometry and shade guides. Materials and Methods: The sample consisted of 2796 maxillary and mandibular teeth, and shade selection was measured subjectively with a shade guide (VITA Classic, VITA Zahnfabrik) and objectively with a spectrophotometer (VITA Easyshade® V, VITA Zahnfabrik, Bad Säckingen, Germany). In all cases, three measurements were taken on each tooth, with a waiting time of 15 min between samples. Shade selection was compared between observers with normal vision, myopia, astigmatism, and hyperopia. Results: The results show that myopic subjects perceived the lower central incisors (2.63, p < 0.05), upper lateral incisors (2.42, p < 0.05), lower lateral incisors (2.34, p < 0.05), and lower canines (2.64, p < 0.05) more clearly. Non-astigmatic subjects perceived the lower second premolar as lighter than astigmatic subjects (-2.01, p < 0.05). Conclusions: It can be concluded that myopes see teeth more clearly, but no differences have been found in astigmatism and hyperopes.

Comparative evaluation of intraoral scanners and a spectrophotometer for percent correct shade identification in clinical dentistry

OBJECTIVES

The study aimed to assess the percent correct shade identification of four intraoral scanners (IOS) and a spectrophotometer, focusing on how reliably each device selects the correct tooth shade compared to a visual observer's selection. The research question addresses how much clinicians can trust the device-selected shade without visual verification.

MATERIALS AND METHODS

Sixteen participants with natural, unrestored teeth were included. The teeth evaluated were tooth 21 (left maxillary central incisor), tooth 23 (left maxillary canine), and tooth 26 (first left maxillary molar). Tooth color was measured using four IOS devices and the Vita Easyshade V in three regions: incisal, middle, and cervical. The nearest 3D Master shade selected by each device was compared to the visual observer's selection. The percent exact match, acceptable match (> 1.2, ≤ 2.7 ∆Eab), and mismatch type A (< 2.7, ≤ 5.4 ∆Eab) were calculated. Statistical analysis was performed using a chi-square test with a 95% confidence level.

RESULTS

The overall clinical pass rate was highest for Carestream (78.2%), followed by Easyshade (63.5%), Primescan (51.2%), Trios (39.5%), and Medit (31.3%). Carestream also recorded the highest rate of mismatch type A (47.7%). Significant differences between devices were observed for all categories (p < 0.05).

CONCLUSIONS

Carestream demonstrated the highest overall clinical pass rate, while Medit exhibited the lowest. The study highlights the variability between devices in shade matching performance.

CLINICAL RELEVANCE

This study highlights the importance of considering device performance when relying on IOS or spectrophotometers for shade selection without visual assessment, as the reliability can vary significantly across devices.

How many tooth colors are there?

OBJECTIVES

This study aimed to estimate the number of distinct tooth colors using a large dataset of in-vivo CIELAB measurements. It further assessed the coverage error (CE) and coverage error percentage (CEP) of commonly used shade guides and determined the number of shades needed for an ideal guide, using the Euclidean distance (ΔEab) and thresholds for clinical perceptibility (PT) and acceptability (AT) as evaluation criteria.

METHODS

A total of 8153 untreated maxillary and mandibular anterior teeth were measured in vivo using calibrated dental photography. Cardinality was applied to determine the number of unique natural tooth colors. The CE and CEP were calculated for the Vita Classical and Vita 3D-Master shade guides, while the cardinality method was also used to estimate the number of shades required to adequately cover the estimated gamut of natural tooth colors.

RESULTS

The cardinality analysis revealed 1173 unique natural tooth colors. The CE for the Vita Classical shade guide was 4.1 ΔEab, with a CEP of 75 % beyond AT, while the 3D-Master shade guide had a CE of 3.3 ΔEab and a CEP of 70 % beyond AT. Based on cardinality computation, 92 discrete shades are required to adequately cover the estimated gamut of natural tooth colors with a CE of 1.2 ΔEab and CEP of 0.3 % beyond AT.

CONCLUSIONS

Cardinality computations estimated 1173 unique tooth colors while 92 discrete shades are estimated for full coverage. Such a number is impractical for physical shade guides, but new digital tools and 3D printing may offer future solutions. Both, the Vita Classical and 3D-Master shade guides do not fully represent the range of natural tooth colors.

CLINICAL SIGNIFICANCE

This study highlights the limitations of existing shade guides and underscores the potential for new developments.

In Vitro Evaluation of the Effectiveness and pH Variation of Dental Bleaching Gels and Their Effect on Enamel Surface Roughness

Objectives: Potential adverse effects and pH-related effectiveness of bleaching agents have raised some concerns. The aim of this study was to compare three bleaching agents containing hydrogen peroxide (HP) and carbamide peroxide (CP) in terms of whitening effectiveness, pH variation, and changes in enamel surface roughness. Methods: After controlled staining with a black tea solution, 42 human enamel specimens underwent bleaching treatment using the following agents: HP 40%; HP 35%; CP 16%. Color changes were evaluated according to the CIEDE2000 system. Gel pH was measured before and after each application. Surface roughness (Sa) was assessed through optical 3D profilometry before and after bleaching treatment. Results: The whitening effectiveness was similar for HP 40% and HP 35% while CP 16% had significantly lower results. HP 40% showed a remarkable pH acidification (-0.41), while HP 35% and CP 16% showed a mild increase in pH values (+0.26 and +0.03, respectively), and the differences between HP 40% and HP 35% and between HP 35% and CP 16% were statistically significant. Sa slightly decreased in all groups after bleaching, with no significant differences among them and a significant difference in HP 40% before and after treatment. Conclusions: Similar bleaching results were achieved regardless of pH and HP concentration for HP-based agents, while a lower bleaching effect was observed for the less concentrated CP-based agent, as anticipated. Higher HP and greater tendency to pH instability induced more pronounced modifications of surface roughness. This in vitro study suggests that bleaching gels with neutral and stable pH ensure good bleaching effectiveness and are less likely to cause enamel surface changes.

A Comparative Study of Tooth Shade Selection Methods Between Visual, Smartphone Camera, and Vita Easyshade Spectrophotometer

OBJECTIVES

Recently, dental esthetics have increasingly emphasized appearance, with tooth shade selection complicated by the enamel and dentin's translucency and opacity. Smartphone cameras are useful for shade matching. Currently, no study has directly compared the accuracy of this method. Therefore, the aim of this study is to compare the accuracy of the visual method, smartphone photography, and the Vita Easyshade spectrophotometer, particularly for chroma, value, and hue.

METHODS

This cross-sectional study involved a convenient sample of 82 dental students from the College of Dental Medicine at Umm Al-Qura University, including those in their 5th, 6th, and 7th (intern) years. The VITA classical shade guide was utilized to compare three methods of shade selection: the conventional visual method, smartphone photography, and the Vita Easyshade spectrophotometer. The percentage accuracy for each method was calculated with a 95% confidence interval (CI), using the visual method as the reference standard. Statistical comparisons of the shade selection methods, as well as gender differences, were performed using a Chi-Square test. Fisher's exact test was applied where expected cell counts were below five. Stata software was used with a significance threshold of 0.05.

RESULTS

The current study included 82 subjects; 42 were females and 40 were males. There was no significant difference between male and female students in the measured accuracy by using the three methods except for hue when the photo method was used (p=0.015). For chroma (p=0.094), value (p=0.965), and hue (p=0.094), the photo method was comparable in accuracy to the visual method. The accuracy was slightly higher for the photo method, but this difference was not statistically significant. The Easyshade was also comparable to the visual method in chroma (p=0.674), significantly lower when assessing value (p=0.002) and not statistically lower when assessing hue (p=0.094). Comparing the results of the same method, the accuracy of shade selection was highest for chroma, followed by value, and lowest for hue.

CONCLUSION

Within the limitations of this study, digital photography using a smartphone camera may serve as a reliable method for clinicians in shade selection during clinical practice.

A comparative study of shade-matching performance using intraoral scanner, spectrophotometer, and visual assessment

This study aimed to explore the clinical applicability of the shade-matching function in intraoral scanners. This study measured the tooth colors of maxillary anterior dentitions of 83 adults using visual matching, a spectrophotometer, and a scanner according to two color systems: VITA Classical (VC) and VITA 3D-Master (V3D). Agreement between each method was assessed by weighted Cohen's kappa coefficient (KW, α = 0.05). For V3D, the overall agreement between the scanner and spectrophotometer (KW = 0.498) was higher than that between the scanner and visual matching (KW = 0.473). Similarly, the agreement between the scanner and spectrophotometer (KW = 0.283) was higher than that between a scanner and visual matching (KW = 0.140) for VC. Regarding tooth position, the highest agreement between the scanner and spectrophotometer was observed on the right central incisor (KW = 0.542) for V3D. Tooth color measurement with a scanner was comparable to that with a spectrophotometer, especially on the central incisors when using the VITA 3D-Master system. A scanner could serve as an alternative to a spectrophotometer for shade selection. However, color matching should still be visually verified.

Bridging instrumental and visual perception with improved color difference equations: A multi-center study

OBJECTIVES

This multicenter study aimed to evaluate visual-instrumental agreement of six color measurement devices and optimize three color difference equations using a dataset of visual color differences (∆V) from expert observers.

METHODS

A total of 154 expert observers from 16 sites across 5 countries participated, providing visual scaling on 26 sample pairs of artificial teeth using magnitude estimation. Three color difference equations (ΔE*ab, ∆E00, and CAM16-UCS) were tested. Optimization of all three equations was performed using device-specific weights, and the standardized residual sum of squares (STRESS) index was used to evaluate visual-instrumental agreement.

RESULTS

The ΔE*ab formula exhibited STRESS values from 18 to 40, with visual-instrumental agreement between 60 % and 82 %. The ∆E00 formula showed STRESS values from 26 to 32, representing visual-instrumental agreement of 68 % to 74 %. CAM16-UCS demonstrated STRESS values from 32 - 39, with visual-instrumental agreement between 61-68 %. Following optimization, STRESS values decreased for all three formulas, with ΔE' demonstrating average visual-instrumental agreement of 79 % and ∆E00 of 78 %. CAM16-UCS showed average visual-instrumental agreement of 76 % post optimization.

SIGNIFICANCE

Optimization of color difference equations notably improved visual-instrumental agreement, overshadowing device performance. The optimzed ΔE' formula demonstrated the best overall performance combining computational simplicty with outstanding visual-instrumental agreement.

Comparing Skin Tones to Shades of Upper Anterior Teeth: An Observational Study among Nigerian Adults

BACKGROUND

Skin tones may be predictive of anterior tooth shade. An analysis of the relationship of skin tone to anterior tooth shade within a population may facilitate the prescription of complete dentures with optimal esthetics and realism.

AIM

This study aimed to assess the relationship between skin tones and shades of upper anterior teeth among a diverse Nigerian adult population.

METHODS

The study was conducted between February and December 2022 among consecutive healthy adults recruited from dental clinics of five teaching hospitals in four cities located across four geopolitical zones of Nigeria. Skin tones were recorded using the National Immigration Service (NIS) Skin Color scale. The Vitapan Classic® shade guide was used to record the tooth shade of the upper central incisors and canines. Bivariate and multivariate tests of associations were performed, and predictive probabilities were developed.

RESULTS

A total of 1070 adults with a mean age of 30.8 ± 10 years participated in the study. NIS skin tones 6 (29.8%) and 5 (27.7%) were the most common, while hues A (48.7% in incisors and 48.4 % in canines) and B (41.1% in incisors and 40.1% in canines) were predominant. The values of the incisors and canines were positively related to skin tone (P = 0.001) and age (P = 0.001 for incisors and P = 0.003 for canines). Hue was also significantly associated with skin tone for canines (P = 0.01) and gender (P = 0.001). Regression models showed increasingly darker skin tones were positively related to duller values for incisor teeth (β = 0.173, OR =1.19, P < 0.001). The values for canines were more likely to be >2 (β = 0.118, OR =1.12, P = 0.01), but without significant positive relationship to increasingly darker skin tones (β = -0.99, OR =0.91, P = 0.22).

CONCLUSION

Skin tones were associated with upper anterior tooth shade. There was a positive relationship between skin tones and the shades of upper anterior teeth. Skin tones could guide the clinician in shade selection during complete denture prescriptions.

Clinical Comparative Study of Shade Measurement Using Two Methods: Dental Guides and Spectrophotometry

Tooth color is a determining factor in the fabrication of dental prostheses. The aim of the present study is to compare two measurement methods used in the field of dentistry: dental guides and spectrophotometry. A total of 2768 natural teeth were measured using the Vita Classical and Vita 3D-Master dental guides (Vita-Zahnfabrik, Bad Säckingen, Germany), as well as a Vita Easyshade Compact spectrophotometer (Vita-Zahnfabrik). The measurements were carried out by one operator under suitable illumination conditions at 5500 degrees Kelvin. The obtained results show that the measurements obtained with the Vita Classical dental guide classifies teeth into the A-B categories, while the spectrophotometer preferentially classifies teeth into the B-C categories. The correlation coefficients obtained with the dental guides ranged from -0.32 to -0.39 (p < 0.01), while those for the spectrophotometer ranged from -0.35 to -0.55 (p < 0.01). Therefore, we can conclude that the spectrophotometer is more reliable and reproducible in its measurements than the dental guides.

Effect of Ceramic Thickness and Technician Variability on the Shade Duplication of Dental Ceramo-Metallic Restorations

Ceramic thickness and technicians' manipulative variables are critical factors affecting the resultant shade of dental ceramo-metallic restorations. This study investigated the effect of the following variables on shade duplication of ceramo-metallic specimens: (a) ceramic thickness; (b) differences between several technicians (inter-technician variability); and (c) the ability of each technician to repeat the resultant shade (intra-technician variability). Ninety ceramo-metallic specimens were prepared and divided into three main groups (n = 30/gp) according to the different technicians who built up the veneering ceramic of the specimens. Each group was further subdivided into three subgroups (n = 10/subgroup) according to the thickness of the ceramic (1, 1.5, and 2 mm built over a 0.5 mm-thick metal substructure). Three different technicians were asked to follow the same protocol as regards the same ceramic batch (Shade 3M2, Vita VM13, Zahnfabrik, Germany), firing temperature, and number of firing cycles. Meanwhile, each technician followed his own protocol with regard to other ceramic manipulative variables. The duplicated shades of the specimens were investigated using the Vita Easyshade spectrophotometer by using the verify shade mode. Color difference (∆E) values were calculated between the target shade (3M2) and the duplicated shades of the specimens automatically by the Vita Easyshade spectrophotometer (Vita, Zahnfabrik, Germany). The effect of ceramic thickness and inter- and intra-technician variability on the duplication of the target shade was investigated. The results showed that the effect of ceramic thickness on the duplicated shades depended on inter-technician variability. High inter-technician variability (∆E = 2-6.4) was noticed in contrast to low intra-technician variability (∆E = 0.2-1.5). It could be concluded that proper shade-duplication of ceramo-metallic restoration was a cumulative technique intimately related to manipulative variables and ceramic thickness.