Repeatability and reliability of human eye in visual shade selection

The metameric effect of monolithic zirconias with varying yttrium ratios

PURPOSE

To evaluate the metameric disparities among monolithic zirconia materials with differing yttrium compositions across various lighting conditions.

MATERIALS AND METHODS

Thirty-six square-shaped zirconia samples measuring 10 × 10 × 0.5 mm were prepared from monolithic zirconia materials with three different yttrium contents. A 0.2 mm thick layer of polymerized dual-polymerizable self-adhesive resin cement was created using a silicone mold with the same dimensions as the prepared zirconia specimens. To evaluate metamerism, color measurements were conducted using a spectrophotometer device on a neutral gray background in a color measurement cabinet that offers four different illumination environments. All samples underwent aging by subjecting them to 10000 thermal cycles using a thermal cycle tester. Following thermal aging, color measurements were taken once more, and the data were recorded using the CIE L*, a*, b* color system. Two-way ANOVA and Post-hoc Bonferroni tests were employed to analyze the data.

RESULTS

It was observed that there was no statistical difference among the color measurements made in different illumination environments of the monolithic zirconia ceramics used to evaluate metamerism (P > .05). This observation remained consistent both before and after thermal aging. After thermal aging, the color of monolithic zirconia materials exhibited a tendency towards red and yellow hues, accompanied by a decrease in brightness levels.

CONCLUSION

It can be stated that different illumination conditions did not affect the metamerism of monolithic zirconia materials, but there was a color change in monolithic zirconia materials after a thermal aging period equivalent to one year.

Clinical Performance of Newly Developed Android Mobile Digital Application on Tooth Shade Reproduction: A Multicenter Randomized Controlled Clinical Trial

Aim

This study aimed to determine the clinical effectiveness of android mobile digital application shade matching on tooth shade reproduction.

Setting and Design

This was a double-blind randomized controlled clinical trial (REF/2021/03/042258).

Materials and Methods

Thirty participants were selected from the two dental centers. The participant who required full-coverage restorations in one of the central incisors with adjacent central incisor untouched was the main inclusion criteria. Three metal-ceramic or all-ceramic crowns were fabricated with reference shades from Vita Three-Dimensional (3D) Master shade guide, Vita Easyshade spectrophotometer, and mobile application for each participant. ΔE values between reference maxillary central incisor and metal-ceramic and all-ceramic crowns were measured for each participant. In addition, two operators and participants observed the clinical agreement between for each crown on a visual analog scale.

Statistical Analysis Used

ANOVA statistics and Turkey's post hoc test were used for ΔE value. Kappa statistics was used for clinical agreement.

Results

Mean ΔE value of fabricated metal-ceramic and all-ceramic crowns and reference maxillary central incisor of Vita 3D Master shade guide was significantly higher than Vita Easyshade spectrophotometer and mobile digital application (P = 0.004). However, ΔE values of Vita Easyshade and mobile digital application were contiguous. However, ΔE value of Vita 3D Master was lower than clinically acceptable value of intraoral color difference. Kappa value figured moderate agreement for Vita Easyshade and mobile digital application and slight to no agreement for Vita 3D Master.

Conclusion

Within the limitations of the study, the Android mobile digital application can turn up as a reliable method for shade selection.

The effect of color vision resolution on intra-oral shade-selection accuracy

BACKGROUND

Dentists must be able to identify subtle color changes as shade-matching is crucial in aesthetic dentistry.

OBJECTIVE

To determine whether color discrimination ability is related to shade-matching accuracy among dentists.

METHODS

The sensitivity of the normal-color vision population to different colors was investigated using Farnsworth Munsell 100 Hue (FM-100) test results. The FM-100 test was administered to 37 dentists at the Hospital of Stomatology, Jilin University. Sensitivity of dentists with normal-color vision to different colors was investigated using the FM-100 test. Participants were instructed to arrange color caps of various colors according to the gradual change in colors and the results were scored. Visual shade matching test using Vita 3D-MASTER shade guide was performed to determine shade-matching accuracy. The relationship between color discrimination ability and shade-matching accuracy was analyzed. The number of misplaced color caps in the FM-100 test was also calculated.

RESULTS

The FM-100 test revealed that 16 and 21 participants had excellent and average color discrimination ability, respectively, and their shade-matching accuracies were 68.75% and 66.67%, respectively. No significant difference was observed in the shade-matching accuracy between the two groups. No significant correlation was observed between the color discrimination ability and shade-matching accuracy. In addition, the number of wrong color caps on the 43-63 color tray with the transition from blue-green to blue-purple was the highest according to Friedman's test.

CONCLUSION

Color discrimination ability of dentists does not affect their visual shade-matching accuracy. Additionally, people with normal color vision are not sensitive to the transition from blue-green to blue-purple.

An Overview of Shade Selection in Clinical Dentistry

The selection of an accurate tooth shade has always been a challenging task for dental practitioners in restoring the natural appearance of teeth. Various factors can influence shade selection, such as different lighting conditions, clearness and opaqueness of teeth, eye fatigue, aging and color vision problems. It is imperative to have a sound knowledge about the concept of shades and its selection protocol for obtaining good esthetics outcomes. To attain the best esthetics, four elementary contributing factors are essential: exact position, shape, surface texture and shade. The current analysis focuses on several features of shade, sensitivity of shades, optical properties of the teeth, visual and innovative instrumental techniques for shade selection, protocols for shade selection and factors affecting dental shade selection.

Shade Selection in Esthetic Dentistry: A Review

When fabricating a restoration, patient satisfaction with the shade match is essential. The patient's level of satisfaction may not be the same as that of the dental practitioner. Esthetic expectations have dramatically increased in the last few years. Color and shade determination are generally considered difficult in dental practice. Most prostheses fail esthetically owing to improper shade selection. A good understanding of color shade guides is essential for precise shade matching, but the paucity of dental practitioners’ knowledge of color science because of the numerous available shade guides creates a challenge. This comprehensive review sheds light on shade selection, different shade guides, and shade matching devices commonly used in dental practice. Studies published in PubMed/MEDLINE, ScienceDirect, Scopus, and Dentistry and Oral Science Source from the past 15 years were included.

Evaluation of accuracy and characteristics of tooth-color matching by intraoral scanners based on Munsell color system: an in vivo study

To compare the accuracy of visual and instrumental methods for tooth-color matching based on three attributes in the Munsell color system and to investigate the characteristics of intraoral scanners for tooth-color matching. Shades of the cervical, middle, and incisal third region of 130 maxillary anterior teeth were matched visually by an experienced prosthodontist (EP) using Vita classical A1-D4 (VC) and Vita System 3D-Master (V3D) shade guides, and digitally by a spectrophotometer (Vita Easyshade V, VE) and two intraoral scanners (3Shape TRIOS 3, T3; TRIOS 4, T4). VE was used as a reference. The reproducibility of the three test groups was examined by repeating the measurements in triplicate. The overall trueness of the three test groups (from high to low) was T3 > EP > T4 for VC values (p < 0.01), and T3, EP > T4 (p < 0.01) for V3D. The trueness of T3 in incisal regions was lower than cervical and middle regions. When hue or lightness was correct, the mismatched chroma in test groups was smaller than VE (p < 0.01). The repeatability of EP was the poorest (p < 0.01). The color-matching trueness of T3 was higher than EP and T4. The reproducibility of intraoral scanners was better than visual methodology.

Visual and digital tooth shade selection methods, related effective factors and conditions, and their accuracy and precision: A literature review

OBJECTIVE

Despite developments of dental shade selection methods, shade selection is still a challenge affecting esthetic outcomes. The purpose of this review was to discuss visual and digital shade taking methods, related effective factors and conditions, and their accuracy and precision to find out the most accurate, precise shade selection method available in dentistry.

OVERVIEW

The key terms of accuracy, background, ceramic, color, colorimeter, color analysis, color science, color measurement, color measuring instrument, color matching, composite resin, dental/tooth shade guide, digital camera, esthetics, imaging, imaging application/program/ software, intraoral scanner, light source, photography, precision, shade, shade matching/ determination/prediction/reproduction/selection, shade taking device, spectrophotometer, spectrophotometry, tooth color measurement, tooth color/shade, and visual perception were used separately and jointly to detect related English-language articles published between January 1, 1985, and January 1, 2021. Electronic/non-electronic searches of Google Scholar/PubMed/Scopus/Web of Science were accomplished. Consequently, 249 articles were considered. Accordingly, the digital methods show higher accuracy and precision compared to the visual methods while requiring to be enhanced regarding accuracy to achieve ideal shade taking results.

CONCLUSIONS

Dental spectrophotometers provide the highest overall accuracy and precision among different shade selection methods while needing clinical setting to control related effective factors/conditions and technological improvement to perform optimally.

CLINICAL SIGNIFICANCE

Different factors can affect the accuracy and precision of tooth shade selection methods and devices. The understanding of these effective factors may lead to a standard shade taking protocol using accurate, precise methods and devices.

Effects of abutment tooth and luting agent colors on final color of high-translucent zirconia crowns

PURPOSE

This study aimed to evaluate the effects of the tooth portion evaluated and the colors of the abutment tooth and resin luting agent on the final color of monolithic zirconia crowns.

METHODS

Monolithic zirconia crowns were fabricated for left maxillary central incisors using two shades (A2 and A3) of highly translucent monolithic zirconia disks. A model of the abutment tooth was fabricated using resin core materials (white: W; dentin: D). The color of the crowns was measured with try-in pastes (clear: C; brown: B) as a resin-luting agent substitute. The measurement was performed after placing the crown on the model with the attached abutment tooth with try-in paste. The color of three labial portions (cervical, body, and incisal) was evaluated using a dental spectrophotometer. The color difference (ΔE) between the CIELab values of the zirconia disks and the final me asurement of zirconia crowns was calculated.

RESULTS

The ΔE between the crown of the A2 shade and the zirconia disk of the A2 shade had the highest ΔE value in the body portion with W-B (ΔE=3.92). Similarly, the A3 shade had the highest ΔE value in the cervical portion, with W-B (ΔE=4.27). The results of three-way ANOVA showed that the ΔE values were influenced by the tooth portion evaluated and the color of the abutment tooth.

CONCLUSIONS

The final color of the monolithic zirconia crowns was significantly in fluenced by the tooth portion evaluated and the color of the abutment tooth.

Can identical dental shade guides be used interchangeably?

OBJECTIVE

To determine if identical dental shade guides can be used interchangeably considering their precision.

MATERIALS AND METHODS

Twenty Vita classical (VC) and Vita 3D-Master (VM) shade guides were subjected to spectrophotometric measurements and their CIELab values were measured in three shade tab regions: incisal, middle, and cervical and also in total. The mean L*, a*, and b* values for analogous shade tabs were calculated to identify CIELab values for typical shades. ∆E₀₀ color differences between a typical shade and its analogous shade tabs were measured. ∆E₀₀ values were compared with perceptibility (∆E₀₀  = 0.8) and acceptability (∆E₀₀  = 1.8) thresholds using one-sample t test (α = 0.05). An error was considered when the ∆E₀₀ value was greater than the threshold. Subsequently, the shade guides' precision scores were calculated.

RESULTS

Mean ∆E₀₀ values ranged between 0.3 and 0.5 for VC tabs and between 0.3 and 0.6 for VM tabs. Precision scores for both shade guides ranged from 83.3% to 100%, considering the perceptibility threshold. Regarding the acceptability threshold, precision scores for VC ranged from 93.3% to 100%, while the precision scores for VM were 100%.

CONCLUSIONS

Owing to high precision of VC and VM, identical dental shade guides can be used interchangeably.

CLINICAL SIGNIFICANCE

Using identical dental shade guides interchangeably may affect the color results of restorative treatments. This study identified high levels of precision for identical shade tabs of Vita classical and Vita 3D-Master across different batches. Thus, similar dental shade guides can be used interchangeably.

Effect of Three Wavelengths of Diode Laser on the Efficacy of Bleaching of Stained Teeth

Objectives:

Light irradiation and heat have been used to accelerate the process of tooth bleaching. This study aimed to assess the efficacy of conventional bleaching compared to laser-bleaching using three different wavelengths of diode lasers.

Materials and Methods:

In this in-vitro experimental study, 40 extracted human central incisors were immersed in a coloring solution made of tea, coffee, and cola for 21 days. The L*, a*, and b* color parameters were measured before and after the immersion using spectrophotometry. The teeth were then randomly divided into four groups (n=10) as follows: group 1: 810-nm diode laser + Biolase Laser White 20, group 2: 940-nm diode laser + Biolase Laser White 20, group 3: 980-nm diode laser + Biolase Laser White 20, and group 4: conventional bleaching with Opalescence Boost without laser irradiation. One-way analysis of variance (ANOVA) was used to assess the effect of laser type and bleaching technique on color parameters.

Results:

The 940-nm (ΔE=28.5896) and 810-nm laser groups (ΔE=21.2382) showed the highest and the lowest bleaching efficacy, respectively; however, the groups were not significantly different in terms of bleaching efficacy (P>0.05).

Conclusion:

Laser-bleaching with 810-, 940- and 980-nm wavelengths of diode laser has an efficacy similar to that of conventional bleaching but in a shorter period. No difference was noted between different laser wavelengths in terms of bleaching efficacy.

Tooth Shade Preferences among the General Public

PURPOSE

To identify laypersons' most preferred tooth shade as a function of observer and patient factors, namely patients' skin shade and observers' socio-demographics.

MATERIALS AND METHODS

Two online surveys using computer-designed perioral images with different shades of the skin and teeth were distributed to participants in Montreal (Canada) and San Francisco (USA). The first survey (n = 120) was designed to assess public preferences of tooth shade value, hue and chroma as a function of the skin color of the perioral image (model), and the demographic characteristics of the observer. The first survey included 6 sets of 9 identical perioral images. A different skin shade (from very dark to very light) was used for each set of images, and each set of images presented teeth with different tooth shades which included three different levels of value (2M1, 3M1, 4M1), hue (3L1.5, 3M1, 3R1.5), and chroma (3M1, 3M2, 3M3) of the Vita 3D Master shade guide. Participants were asked to choose their preferred image for each category (value, hue, chroma) within each set of skin shades. A second survey was performed to pinpoint the tooth shade that is preferred the most by the general public. In this survey, images with four tooth shades (1M1, 2M1, 3M1, 4M1) and 6 skin shades were distributed (n = 70). Ordinal logistic regression was used to identify significant predictors of preferred tooth shades.

RESULTS

Most of the participants preferred teeth with the highest value (54%), a neutral hue (59%) and the lowest chroma (89%). About 75% of the participants preferred 1M1 the lightest tooth shade over other shades regardless of their demographics or skin color of the model. Among the observer-related variable, age was the most significant predictor of people preferred tooth shade (p = 0.019).

CONCLUSION

This study showed that there are common preferences in terms of tooth shade value, hue and chroma among participants regardless of demographic variables and facial skin shades. This data could guide dentists for tooth shade selection in the clinical practice.

Tooth shade analysis and selection in prosthodontics: A systematic review and meta-analysis

Aim:

To evaluate the methods of the dental shade selection and provide a summary of different factors affecting the shade selection.

Design and Setting:

The systematic review and meta-analysis.

Materials and Methods:

The electronic search of the peer-review articles between 2002 and 2018 was carried out the by using the PRISMA guidelines. A total twenty-one studies related to the visual shade methods, instrumental shade methods, and the factors affecting the shade selections was evaluated. The search strategy was based on the PICOS framework.

Statistical Analysis:

There was statistically significant heterogeneity (Q = 1038.1518, df = 20, and P < 0.0001). The statistics of fixed-effect model reported an MD of − 0.0970 (95% CI = −0.1391, −0.0549). The random-effect model reported an MD of − 0.0862 (95% CI = −0.5866, 0.4142).

Result:

The review evaluated the 21 studies of tooth colour science that met with the inclusion criteria and search criteria. The meta-analysis of the 21 combined studies reported acceptable homogeneity (i² = 98%) which indicates a statistically significant difference between the treatment and control groups.

Conclusion:

The VES spectrophotometer reported the highest accuracy, reliability, and repeatability in shade selection followed by photo colorimetric method. The Vita 3D master shows more consistent results in repetitive shade selection. Knowledge and training of the shade selection protocol are necessary for proper shade matching

Precision of a Reflectance Spectrophotometer in Measuring Anterior Tooth Color

Background:

Intraorally, a common instrumental approach for measuring tooth color is reflectance spectrophotometry.

Objective:

To evaluate the precision of a reflectance spectrophotometer in accurately measuring anterior tooth color.

Methods:

The twelve labial surfaces of the anterior teeth of sixteen patients were measured spectrophotometrically (SpectroShadeTM Micro) on three non-consecutive days (1st, 2nd, 8th). Tooth color was converted to L*, a* and b* colorimetric values; intra-examiner repeatability was assessed in ΔΕ-units between two same day repeated measurements. Intra-examiner reproducibility was measured for the effect of tooth type, time and their interaction.The linear effect of the acquisition angle on the colorimetric values of each tooth was also estimated.

Results:

The highest values of systematic or random error occurred for teeth #33, #43 and #32. There were no statistically significant differences in systematic or random errors for any tooth between the three measurement days. Statistically significant differences were found for tooth type (p=0.039), whereas time and tooth and time interaction were not statistically significant. A statistically significant linear correlation was found between the L* and a* values and the acquisition angle for teeth #12 and #31, (p<0.008).

Conclusion:

The reflectance spectrophotometer provided a precise measurement of tooth color in-vivo since the systematic and random errors generated were below the threshold for perceivable color mismatches (ΔΕ<1). In rejection of the null hypotheses, the tooth type (maxillary central incisors) and variation of the acquisition angle of image capture (L* and a* parameters in teeth #12 and #31) affected the reproducibility of intraoral spectrophotometric measurements.

A Digital Shade-Matching Device for Dental Color Determination Using the Support Vector Machine Algorithm

In this study, we developed a digital shade-matching device for dental color determination using the support vector machine (SVM) algorithm. Shade-matching was performed using shade tabs. For the hardware, the typically used intraoral camera was modified to apply the cross-polarization scheme and block the light from outside, which can lead to shade-matching errors. For reliable experiments, a precise robot arm with ±0.1 mm position repeatability and a specially designed jig to fix the position of the VITA 3D-master (3D) shade tabs were used. For consistent color performance, color calibration was performed with five standard colors having color values as the mean color values of the five shade tabs of the 3D. By using the SVM algorithm, hyperplanes and support vectors for 3D shade tabs were obtained with a database organized using five developed devices. Subsequently, shade matching was performed by measuring 3D shade tabs, as opposed to real teeth, with three additional devices. On average, more than 90% matching accuracy and a less than 1% failure rate were achieved with all devices for 10 measurements. In addition, we compared the classification algorithm with other classification algorithms, such as logistic regression, random forest, and k-nearest neighbors, using the leave-pair-out cross-validation method to verify the classification performance of the SVM algorithm. Our proposed scheme can be an optimum solution for the quantitative measurement of tooth color with high accuracy.

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.

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.

Effect of the Purple Corn Beverage "Chicha Morada" in Composite Resin during Dental Bleaching

During dental bleaching the staining potential of the surface would increase. This study aims to evaluate the staining susceptibility of one bleached composite resin after the exposure to three different beverages: Peruvian purple corn based beverage (chicha morada), green tea, and distilled water. Thirty disk-shaped specimens of one nanofill composite resin were prepared. The specimens were then divided into six groups (n = 5): purple corn (P), purple corn + bleaching (PB), green tea (T), green tea + bleaching (TB), distilled water (W), and distilled water + bleaching (WB). In groups that received bleaching, two sessions of bleaching with 35% hydrogen peroxide were done. Following bleaching, specimens were exposed to each liquid thirty minutes daily. Color was measured with a digital spectrophotometer. For statistical analysis, color measurement differences between the obtained results were used: during bleaching, after bleaching, and during + after bleaching. Two-way ANOVA was used to compare the color changes in the resins of all groups (p < 0.05). We conclude that all the evaluated beverages produced changes of color in the composite resin regardless of the bleaching procedure. However, purple corn was the only beverage that caused a perceptible color change (ΔE > 3.3).

Real-time local experimental monitoring of the bleaching process

OBJECTIVE

The purpose of this article was to investigate a new setup for tooth bleaching and monitoring of the same process in real time, so to prevent overbleaching and related sideeffects of the bleaching procedure.

BACKGROUND DATA

So far, known bleaching procedures cannot simultaneously monitor and perform the bleaching process or provide any local control over bleaching.

MATERIALS AND METHODS

The experimental setup was developed at the Institute of Physics, Zagreb. The setup consists of a camera, a controller, and optical fibers. The bleaching was performed with 25% hydrogen peroxide activated by ultraviolet light diodes, and the light for monitoring was emitted by white light diodes. The collected light was analyzed using a red-green-blue (RGB) index. A K-type thermocouple was used for temperature measurements. Pastilles made from hydroxylapatite powder as well as human teeth served as experimental objects.

RESULTS

Optimal bleaching time substantially varied among differently stained specimens. To reach reference color (A1, Chromascop shade guide), measured as an RGB index, bleaching time for pastilles ranged from 8 to >20 min, whereas for teeth it ranged from 3.5 to >20 min. The reflected light intensity of each R, G, and B component at the end of bleaching process (after 20 min) had increased up to 56% of the baseline intensity.

CONCLUSIONS

The presented experimental setup provides essential information about when to stop the bleaching process to achieve the desired optical results so that the bleaching process can be completely responsive to the characteristics of every individual, leading to more satisfying results.