Differences in lightness, chroma, and hue in the anterior teeth of quinquagenarians and septuagenarians

Dental color measurement to estimate age in adults: a systematic review and meta-analysis

Age estimation is a major challenge in anthropology and forensic odontology laboratories, as well as in judicial settings, as one of the tools used in human identification. The aim of this study was to evaluate the usefulness of age estimation methods based on the accurate measurement of tooth color changes. A systematic review was carried out following the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses and in compliance with Cochrane criteria recommendations (PROSPERO registration number CRD 42022343371). An electronic search was performed in the following databases: Pubmed, Web of Science, Medline, Current Contents Connect, SciELO, KCI-Korean Journal Database, Derwent Innovations Index and Russian Citation Index. The search strategy yielded a total of 18 articles. A randomized meta-analysis model of the results for the CIE L*a*b* color variables stratified by age (less than 30 years, 30-60 years, 60 years and older) was performed with 9 of the 18 studies included in this systematic review. According to our results, sex and location of color measurement are the most influential factors in color estimation. All studies were carried out in healthy anterior teeth by spectrophotometry as the most commonly used method for color measurement, with CIE L*a*b* being the most commonly analyzed parameters. Studies based on age as a dependent variable showed R2 values between 0.28 and 0.56, being higher in ex vivo teeth. Studies based on age as an independent variable showed R2 values ranging from 0.10 to 0.48. The random model showed high heterogeneity for the L*, a* and b* parameters in all age groups, which is explained by discrepancies in age range and non-standardized conditions for color measurement. This systematic review highlights the need to protocolize age estimation studies that measure tooth color, in order to apply this method in different forensic settings.

Three-dimensional representation of the Vita Toothguide 3D-Master: An in vivo clinical study

STATEMENT OF PROBLEM

The Vita Toothguide 3D-Master (Vita Zahnfabrik) is considered the dental shade guide in which the three dimensions of color - lightness, hue, and chroma - are most well-ordered in the CIELAB color space. No research has yet explored how well the Vita Toothguide 3D-Master is ordered in the 3D color space by recording color coordinates in vivo.

PURPOSE

To evaluate the spatial color distribution of the Vita Toothguide 3D-Master's lightness, chroma, and hue groups and its 26 physical shade tabs.

MATERIALS AND METHODS

The dental color (L*, C*, h°, a*, and b* color coordinates) of a healthy maxillary central incisor was recorded for 1361 participants (aged between 18 and 89 years) using a Vita Easyshade Compact spectrophotometer (Vita Zahnfabrik). The R 2.7.2. statistics program was used to create the visual representations.

RESULTS

The five lightness levels are those that are best distributed in the color space, in relation to the L* coordinates, followed by the chroma group and, finally, the hue group. The 5M1, 5M2, and 5M3 physical shade tabs are situated at a greater distance apart from the other tabs in the color space.

CONCLUSIONS

The Vita Toothguide 3D-Master's 26 physical shade tabs are satisfactorily distributed in three-dimensional space, although strict mathematical criteria are not followed. The natural dental shades that fall lower on the lightness scale are the most poorly represented by the physical shade tabs.

CLINICAL IMPLICATIONS

Darker teeth are poorly represented by the Vita Toothguide 3D-Master's physical shade tabs. The spatial distribution of dental shade guides needs to be improved to ensure they provide homogeneous coverage of the entire chromatic spectrum corresponding to natural teeth. This would help reduce the errors inherent to the subjective visual color selection process.

3D Master Toothguide Is Adequate to Subjective Shade Selection?

Background and Objectives: To study the validity and the degree of representability of the toothguide 3D Master, with 26 physically shade tabs, on the natural tooth colour on a sample of the Spanish population. Materials and Methods: Natural tooth colour was measured in a sample of 1361 Spanish participants of both genders distributed within an age range of 18 and 89 years of age. The colour coordinates were calculated and the frequency of the 26 physically shade tabs of the toothguide as well as the “intermediate shades” (without physical representation in toothguide) through the Easyshade Compact (Vita-Zahnfabrik) spectrophotometer using the 3D Master System nomenclature. The colour differences between the “intermediate shades” were calculated using the Euclidean formula (ΔEab*). The program used for the present descriptive statistical analysis of the results was SAS 9.1.3. Results: A total of 49 “intermediate shades” were registered in 816 participants (60%). The colour coordinates of the 49 ‘intermediate shades’ cover colour coordinates ranging from 0M1.5 (L* 100.0, C* 7.70, h* 112.2) to 5M2.5 (L* 56.8, C* 35.8, h* 78.5). Not all possible 3D Master System’s “intermediate shades” were registered in the population studied. 82.4% of the colour differences among the “intermediate shades” were clinically unacceptable (ΔEab* ≥ 5.5 units). Conclusions: Only 40% of the population studied presented a natural tooth colour belonging to the 3D Master Toothguide’s physical shade tabs.

Proposal for a gingival shade guide based on in vivo spectrophotometric measurements

PURPOSE

The purpose of this study was to propose and assess a shade guide for pink gingival aesthetics using a Spanish population sample.

MATERIALS AND METHODS

The L*, C*, h, a* and b* coordinates of 259 participants were measured using a spectrophotometer in 3 standardized points along the attached gingiva of the maxillary central incisors. A hierarchical clustering analysis was applied to obtain separate solutions regarding the number of shade tabs. For each of the solutions obtained, color differences (ΔE*) were calculated using the CIELab and CIEDE2000 formulas, and the proposed shade guide was selected considering (1) the color differences between tabs and (2) the coverage error of each of the solutions.

RESULTS

The proposed shade guide consisted of 8 gingival shade tabs and achieved CIELab and CIEDE2000 coverage errors of less than the respective 50:50% acceptability thresholds (ΔE*=4.6 units and ΔE00=4.1). The coordinates for the various gingival shade tabs were as follows: Tab 1: L*43.3, a*21.9, b*12.3 (1.6); Tab 2: L*42.9, a*34.1, b*19.1; Tab 3: L*46.5, a*25.8, b*10.9; Tab 4: L*46.5, a*27.3, b*15.1; Tab 5: L*49.6, a*23.5, b*16.8; Tab 6: L*51.5, a*19.7, b*13.6; Tab 7: L*55.9, a*22.0, b* 15.0; and Tab 8: L*56.0, a*19.9, b*18.8.

CONCLUSION

The CIELab and CIEDE2000 coverage errors for the 8 shade tabs of the proposed gingival shade guide were significantly lower than those of other guides. Therefore, despite the limitations of this study, the proposed guide is more appropriate for matching gingival shade in the Spanish general population.

Creating Benchmark of Color Skin Viability Based on Digital Photograph Using Mini Mobile Medical Photo Studio Prototype

BACKGROUND

This study is aimed to set a benchmark of skin color and texture index based on digital photographs for living and nonliving skin.

MATERIALS AND METHODS

Photography was taken with standardized camera inside a Mini Mobile Medical Photo Studio (MiniMoPS) prototype. A pilot analysis was conducted by comparing color and surface texture of 16 living and cadaveric skins each. Baseline data of viable and nonviable skin were obtained and analyzed using ImageJ software for its color tone, components, and texture index. Results were expressed as total digital number (TDN).

RESULTS

MiniMoPS prototype consists of a dusty white foldable acrylic box, blue Pantone 635C background, and two 8-Watt light bulbs on the ceiling. The whole box is covered with a thick white cotton fabric to eliminate the influence of environmental light. The prototype was tested for its light intensity with David Quiles Lightmeter in various environments setting. It showed a constant result for skin photographs. The best probable cutoff point for skin color is TDN 138.1 (sensitivity 81.3%; specificity 100%). Cadaveric skin shows a higher texture digital number than living skin ([155.4 ± 25.0] versus 120 [80-135]; P = 0.001).

CONCLUSIONS

In regards of color, TDN >138 is a cutoff point for nonliving skin. Texture index 120 is a benchmark for living skin, whereas nonliving skin indicates 155.

A study on the color distribution of natural teeth by age and gender in the Korean population with an intraoral spectrophotometer

OBJECTIVE

To investigate the distribution of natural tooth shades by age and gender in the Korean population with a spectrophotometer.

MATERIAL AND METHODS

A total of 674 human subjects were recruited and divided into three age groups; young (16-30), middle (31-59), and elderly (60-89). Each group was then subdivided according to gender. Color was measured on the upper central incisor and CIELab color coordinates were obtained. CIEDE2000 color differences ( ΔE₀₀ ) between genders within each age group and between age groups for both genders were calculated. Two-way analysis of variance (ANOVA) was used to identify the influence of age and gender on each color variable.

RESULTS

The most frequent color in the Korean population was 2L1.5. L* values decreased, while b* values increased with age (P < .05). There was a significant interaction between gender and age on b* values; F (2668) = 3.489, P = .031, partial η²  = 0.010, and observed power = 0.652. Females generally have lighter and less chromatic central incisors compared to males. The ΔE₀₀ values between genders in elderly groups were beyond acceptability threshold.

CONCLUSIONS

The central incisors were getting darker, more yellowish, and reddish with age. Information on the chromatic range of natural teeth by age and gender could help to select colors for esthetic dental restorations.

CLINICAL SIGNIFICANCE

Dentists should consider an unacceptable color mismatch between the restorations and natural dentition that can occur over time.

Comparison of two color-difference formulas using the Bland-Altman approach based on gingiva color space

The objectives of this study were to determine the relationship between the results provided by the classical CIELab (ΔE_ab*) and the CIEDE2000 (ΔE00) formulas and the gingival color space using the Bland and Altman limits of agreement, to use this relationship to establish the equivalences between the gingival color thresholds of perceptibility of both formulas, and to evaluate whether the relationship between ΔE_ab* and ΔE00 is modified depending on the axis in which the changes occur. The means of the L*, a*, and b* coordinates of the 21 gingiva porcelain samples (Heraceram, Heraeus Kulzer Mitsui Chemical Groups) were used and the differences in color were calculated in 210 pairs of samples using the CIELab (ΔE*ab) and CIEDE2000 (ΔE00) color-difference formulas. The results obtained with these formulas were compared and the limits of agreement after a logarithmic transformation of the data were obtained. The relationship between both formulas was ln ΔE₀₀ = - 0.22 + ln ΔE_ab*. The results obtained with the CIELab formula were between 1.01 (95% confidence interval 0.98-1.03) and 1.54 (95% confidence interval 1.52-1.59) times higher than those obtained with the CIEDE200 formula. In the gingiva color space, the scale factor between the CIEDE2000 and CIELab values changes from 0.63 to 1.02, such that providing an accurate scale factor between both values proves difficult. The pairs with the highest ratio were those where the difference in color was mainly due to changes in lightness, whereas the pairs with the smallest ratio were those where the difference in color was mainly due to changes in the blue-yellow or green-red axes.

Spectrophotometric Evaluation of Anterior Maxillary Tooth Color Distribution According to Age and Gender

PURPOSE

To determine the effects of age and gender on the color distribution of the right maxillary central, lateral incisors, and canine teeth.

MATERIALS AND METHODS

The tooth color was measured using the VITA Easyshade V spectrophotometer with a total of 202 volunteers (89 men, 113 women). The age distribution in this study was between 15 and 70 years old (average: 31). A grey background color was used to prevent background reflection while performing the color measurements.

RESULTS

According to the VITAPAN Classical shade guide, the tooth color distribution of the central and lateral incisors showed a maximum of A2, with a maximum of B3 for the canine teeth. When comparing the International Commission on Illumination L^* , a^* , and b^* values (CIELab color space coordinates) of the teeth with subject gender, statistically significant differences were not found between gender and the L^* and b^* values (p > 0.05); however, a statistically significant difference was observed between gender and the a^* values (p < 0.05).

CONCLUSION

When the distribution ratio of tooth color was examined, different ratios were determined based on gender and age and between the maxillary central, lateral incisors, and canine teeth. A uniform tooth color should not be chosen for anterior restorations, and factors such as gender and age should be considered when making a color selection for patients.

Tooth colour and whiteness: A review

OBJECTIVES

To review current knowledge concerning the application of colour science on tooth colour and whiteness description, measurement, distribution and its psychological impact.

DATA SOURCES

"Scopus" databases were searched electronically with the principal keywords tooth, teeth, colour, white, whiteness. Language was restricted to English and original studies and reviews were included. Conference papers and abstracts were excluded.

CONCLUSIONS

The appearance and colour of teeth are a common concern for patients across many populations and are associated with an increased desire for treatments that improve dental aesthetics, including tooth whitening. The application of colour science in dentistry has allowed the precise description of tooth colour and whiteness. Coupled with the advances in instrumental tooth colour measurement, such as spectrophotometers, colorimeters, spectroradiometers and digital imaging systems, these parameters are quantifiable in a reproducible and robust manner. These principles have been applied to the tooth colour distribution in many study populations, indicating, in general, differences in tooth colour for subject age and gender, but not for ethnicity. Psychophysical studies on tooth colour and whiteness via third party assessment of images indicate that whitened teeth lead to judgements that are more positive on personality traits such as social competence and appeal, intellectual ability and relationship satisfaction.

Changes of tooth color in middle and old age: A longitudinal study over a decade

OBJECTIVE

To evaluate changes in tooth color for 2 age cohorts (younger cohort, YC: 1950-1952; older cohort, OC: 1930-1932) over a mean observation period of 8 years.

MATERIAL AND METHODS

Sixty-one participants with 106 upper central incisors were subjected to baseline and follow-up examinations (YC: n = 46/OC: n = 15). International Commission on Illumination color coordinates of 1 or 2 unrestored test teeth for each participant were recorded by use of a spectrophotometer (VITA Easyshade 1) during both measurement times. Changes of color coordinates during the study period were evaluated by use of generalized linear mixed models with the variable "participant" as random effect. ΔE_ab and E₂₀₀₀ color differences were calculated between baseline and follow-up.

RESULTS

Significant changes in color coordinates were observed, with the exception of lightness in OC. The direction of the changes depended on the cohort. A decrease of lightness (value) was observed in YC (ΔL = 4.0; P < .001) whereas in OC chroma increased (ΔC = -3.3; P < .001). For both groups, a significant shift to more reddish tooth colors was observed. In almost all cases, color differences between baseline and follow-up exceeded the 50:50 acceptability thresholds for color differences (ΔE = 2.7) in both YC (≈90%) and OC (≈80%).

CONCLUSIONS

For both quinquagenarians and septuagenarians, clinically relevant changes in tooth color were observed after a decade; these could affect the long-term success of prosthetic restorations in terms of a satisfactory color match between natural teeth and dental prostheses. In contrast with the findings of cross-sectional studies, the changes were partially age-group-specific.

CLINICAL SIGNIFICANCE

Tooth color can change over a decade. When fixed dental prostheses are planned, one should consider that changes of tooth color could lead to mismatch between a restoration and adjacent teeth during the period in clinical service.

Clinical Study of the 3D-Master Color System among the Spanish Population

PURPOSE

To study whether the shades of the 3D-Master System were grouped and represented in the chromatic space according to the three-color coordinates of value, chroma, and hue.

MATERIALS AND METHODS

Maxillary central incisor color was measured on tooth surfaces through the Easyshade Compact spectrophotometer using 1361 participants aged between 16 and 89. The natural (not bleached teeth) color of the middle thirds was registered in the 3D-Master System nomenclature and in the CIELCh system. Principal component analysis and cluster analysis were applied.

RESULTS

75 colors of the 3D-Master System were found. The statistical analysis revealed the existence of 5 cluster groups. The centroid, the average of the 75 samples, in relation to lightness (L*) was 74.64, 22.87 for chroma (C*), and 88.85 for hue (h*). All of the clusters, except cluster 3, showed significant statistical differences with the centroid for the three-color coordinates (p <0.001).

CONCLUSIONS

The results of this study indicated that 75 shades in the 3D-Master System were grouped into 5 clusters following coordinates L*, C*, and h* resulting from the dental spectrophotometer Vita Easyshade compact. The shades that composed each cluster did not belong to the same lightness color dimension groups. There was no special uniform chromatic distribution among the colors of the 3D-Master System.

Study of the most frequent natural tooth colors in the Spanish population using spectrophotometry

PURPOSE

To identify the most frequent natural tooth colors using the Easyshade Compact (Vita -Zahnfabrik) spectrophotometer on a sample of the Spanish population according to the 3D Master System.

MATERIALS AND METHODS

The middle third of the facial surface of natural maxillary central incisors was measured with an Easyshade Compact spectrophotometer (Vita Zahnfabrik) in 1361 Caucasian Spanish participants aged between 16 and 89 years. Natural tooth color was recorded using the 3D Master System nomenclature. The program used for the present descriptive statistical analysis of the results was SAS 9.1.3.

RESULTS

The results show that the most frequent dental color in the total sample studied is 3M1 (7.05%), followed by the intermediate shade 1M1.5 (6.91%) and 2L1.5 (6.02%).

CONCLUSION

According to the research methodology used, and taking into account the limitations of this study, it can be proposed that the most frequent color among the Spanish population is 3M1; the most common lightness group is 2; the most frequent hue group according to the 3D Master System is M and the most frequent chroma group is 1.5.

Natural Tooth Color Estimation Based on Age and Gender

PURPOSE

Assessment of the predictability of tooth color coordinates according to the CIELab system to estimate the color of the maxillary central incisor based on patient age and gender.

MATERIAL AND METHODS

The tooth color of one of the maxillary central incisors of 1361 Caucasian Spanish individuals aged 16 to 89 years, male and female, was measured using the Easyshade compact spectrophotometer. Color coordinates L*, C*, h*, a*, and b* were recorded according to age and gender.

RESULTS

The results obtained show that differences in age account for 45% of the total variation of the L (lightness) coordinate; 21% of the variation in coordinate a*, and 17% of the variation in coordinate b* is due to the same reason. At a confidence level of 95% it may be proposed that the mean estimated color difference (ΔE_ab *) between real natural color and that predicted by the linear regression model is between 6.4 and 6.9 units.

CONCLUSIONS

In this sample of Caucasians from Spain, teeth became darker yellow and more reddish with increasing age. The L* coordinate is most strongly related to tooth color in aging.

Correlation of natural tooth colour with aging in the Spanish population

OBJECTIVES

To analyse natural tooth colour in the Spanish population according to the colour coordinates lightness (L*), chroma (C*), hue (h*), red-green axis (a*) and yellow-blue axis (b*) in order to quantify the correlation and changes of tooth colour with age and sex.

METHODS

Natural tooth colour was measured in a sample of 1,361 Spanish participants of both sexes distributed within an age range of 16 to 89 years. The Easyshade Compact spectrophotometer was used and the CIELAB and CIELCh systems were followed.

RESULTS

Pearson's bivariate correlations between age and colour coordinates were highly significant for L* (r=-0.674, P≤0.001), h* (r=-0.468, P≤0.001) and C* (r=0.417, P≤0.001). The correlation between age and colour coordinates was stronger for men than for women, for all colour coordinates. The results showed that C*, b* and a* increased by 0.60, 0.56 and 0.26 units/year on average, respectively, whereas L* and h* decreased progressively with age (by 0.60 units/year, on average), and colour differences increased in a systematic way as the gap between the ages being compared grew wider.

CONCLUSIONS

The strongest correlation was found between age and L*, then between age and h* (both inverse relationships) and then between age and a*, C* and b* (direct relationships). In addition, a similar degree of change in the colour coordinates L*, C* and h* (of 0.60 units/year on average) was observed for natural tooth colour. Knowledge of the chromatic range of natural teeth may help to choose colour for the replacement of missing elements.