Cristina Gómez-Polo

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.

Comparison of the CIELab and CIEDE2000 color difference formulas.

STATEMENT OF PROBLEM Many color specification systems and color differences have been proposed to improve the correlation between color measurement and visual perception. Although color differences can be quantified using either the CIELab formula (ΔE*(ab)) or the recently introduced CIEDE2000 formula (ΔE00), which captures the perceived color difference better is unknown. PURPOSE The purpose of this study was to evaluate the CIELab and CIEDE2000 formulas to determine which best reflects the difference in color perception and whether color perception differs by sex. MATERIAL AND METHODS Forty participants grouped 18 dental resin disks (color range: from 73.6 to 87.5 for L*; from -1.6 to 3.4 for a*; from 18.1 to 36.6 for b*), the only requirement being that each group was formed of disks with chromatically indistinguishable colors. Each participant was free to choose the number and composition of the groups. With the results obtained, a dissimilarity matrix was generated, and nonmetric multidimensional scaling (MDS) was applied to it to obtain the coordinates of the disks within a Euclidean space. RESULTS The linear correlation coefficient between the interpoint distances of the MDS configuration (MDS_total sample) and the color differences with the CIELab formula (ΔE*(ab)) was 0.176 (P=.029), whereas with the CIEDE2000 formula (ΔE00) it was 0.289 (P<.001). For the configuration obtained in the womens group (MDS_w), the correlation between the interpoint distances and the CIELab color differences was 0.230 (P=.004), and the CIEDE2000 color difference was 0.328 (P<.001). For the configuration obtained in the mens group (MDS_m), the color differences calculated with both formulas reflected the perceived differences more poorly. CONCLUSIONS Within the limitations of this study, the CIEDE2000 formula reflected the color differences perceived by the human eye better than the CIELab formula (ΔE*ab). In addition, women were confirmed to be more sensitive than men to color differences.

Comparison of two color-difference formulas using the Bland-Altman approach based on natural tooth color space.

STATEMENT OF PROBLEM Several formulas to measure color differences have been proposed to improve the correlation between color measurements and visual perception. Despite the progress obtained, equating between formulas is complex, rendering the exchange of information in scientific papers difficult. PURPOSE The purpose of this study was to determine the relationship between the results provided by classic CIELab (ΔEab∗) and the CIEDE2000 (ΔE00) formulas in the natural tooth color space using the Bland and Altman limits of agreement, to use this relationship to establish the equivalences between the tooth color thresholds of acceptability and perceptibility of both formulas, and to evaluate whether the relationship between ΔEab∗ and ΔE00 is modified depending on the axis on which the changes occur. MATERIAL AND METHODS The L∗, a∗, and b∗ means coordinates in the 26 shade tabs of the Toothguide 3D Master were used, and color differences were calculated in 325 pairs of shade tabs 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. RESULTS The linear relationship between both formulas was ΔE00 =0.66ΔE∗ab. The results obtained with the CIELab formula were between 1.15 (95% confidence interval 1.11 to 1.18) and 2.09 (95% confidence interval 2.03 to 2.15) times higher than those obtained with the CIEDE2000 formula. CONCLUSIONS In the natural tooth color space, the scale factor between CIEDE2000 and CIELab values changes from 0.46 to 0.90, such that providing an accurate scale factor between both values is difficult. Furthermore, the ΔE00/ΔE∗ab ratio increases with the increase in ΔL∗ and the decrease in Δb∗. The pairs for which the ratio is highest are those in which the difference in color is mainly due to changes in lightness, whereas the pairs for which the ratio is the smallest are those in which the difference in color is mainly due to changes on the blue-yellow axis.

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.

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 (ΔEab *) 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.

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.

Association Between Personality Traits and Oral Health–Related Quality of Life: A Cross-Sectional Study

PURPOSE The aim of this study was to investigate the oral health-related quality of life (OHRQoL) among subjects with typical, atypically positive, and atypically negative personality trait scores within the five basic dimensions of personality (neuroticism, extroversion, openness, agreeableness, and conscientiousness). MATERIALS AND METHODS A total of 235 subjects not seeking dental treatment were recruited from the families and acquaintances of dental students from the University of Salamanca. The 14-item Oral Health Impact Profile (OHIP-14) was used to capture the impact on their OHRQoL. The Neouroticism-Extroversion-Openness Personality Inventory Revised was applied to assess personality profiles. People were classified as having negatively atypical, typical, or positively atypical (PAP) personality, depending on whether the sum of the Z scores was < -1, between -1 and 1, or > 1, respectively. Pearson correlation, analysis of variance, and logistic regression test were used for the statistical analyses. RESULTS The sample was comprised of highly educated adults (aged 18-80 years) with good oral health habits. PAP subjects suffered significantly more in the dimension of psychologic discomfort (0.6 ± 0.7) than did their counterparts (0.3 ± 0.6), but the global impact in OHRQoL was comparable. Personality was weakly correlated with OHIP-14. The perception of dental treatment needs was found to be the major predictor of the impact on OHRQoL, but the number of negatively atypical deviated personality traits and the agreeableness raw score also had an effect. CONCLUSION The risk of perceiving an impact on OHRQoL is significantly higher in individuals perceiving treatment needs and increases proportionally to the number of negatively atypical personality traits.

Clinical study on natural gingival color

The aims of the study were: to describe the gingival color surrounding the upper incisors in three sites in the keratinized gingiva, analyzing the effect of possible factors which modulate (socio-demographic and behavioral) intersubject variability; to study whether the gingiva color is the same in all three locations and to describe intrasubject color differences in the keratinized gingiva band. Using the CIELAB color system, three reference areas (free gingival margin, keratinized gingival body, and birth or upper part of the keratinized gingiva) were studied in 259 individuals, as well as the related socio-demographic factors, oral habits and the chronic intake of medication. Shadepilot™ spectrophotometer was used. Descriptive and inferential statistical analysis was performed. There are statistically significant differences between males and females for coordinates L* and a* in the middle and free gingival margin. For the b* coordinate, there are differences between males and females in the three locations studied (p < 0.05). The minimum and maximum coordinates in which the CIELAB natural gingival space is delimited are L* minima 28.3, L* maximum 65.4, a* minimum 11.1, a* maximum 37.2, b* minimum 6.9, and b* maximum 25.2*. Age, smoking, and the chronic intake of medication had no significant effect on gum color. There are perceptible color differences within the keratinized gingiva band. These chromatic differences must be taken into account if the prosthetic characterization of gingival tissue is to be considered acceptable. There are significant differences between the color coordinates of the three sites studied in the keratinized gingiva of men and women.

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.

Interim restoration using dynamic abutments to re-treat a single-implant crown with a labial angulation: A clinical report

The cause of some peri-implant problems may be primarily attributable to the design of the prosthesis. A screw-retained interim implant may be advisable for reversibility and to avoid peri-implant cement, although screw retention may be difficult for maxillary anterior implants with a labial angulation. In the treatment described, a interim screw-retained crown was attached to a dynamic abutment with a lingual screw access hole to obtain a correctly fitting restoration.