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.

The Role of Intraoral Scanners in the Shade Matching Process: A Systematic Review.

PURPOSE: The variation in findings with regards to the accuracy and precision of intraoral scanners for shade selection are no doubt confusing for clinicians who may find it difficult to make evidence-based decisions. The aim of this systematic review is to provide a comprehensive and in-depth assessment of available studies to determine the viability of using intraoral scanners for the purpose of shade matching. The PICO-guided research question is as follows: when shade matching, are intraoral scanners as valid as visual or other digital shade measuring devices in determining tooth colors. METHODS: Electronic databases including PubMed/MEDLINE, SCOPUS, EBSCO, Cochrane, and ProQuest were systematically searched for articles published between January 1, 2011 and December 30, 2021 using the main search terms: "intraoral scanners," "scanners," "TRIOS," "CEREC," "Planmeca," "Medit," "digital dentistry" in concurrence with one of the following keywords: "EasyShade" OR "shade selection" OR "shade matching" OR "shade" OR "tooth color" OR "tooth shade" OR "digital shade matching." Bibliographies of included articles and the following journals were searched for relevant articles: Journal of Prosthetic Dentistry, Journal of Prosthodontics, Journal of Esthetic and Restorative Dentistry, Journal of Advanced Prosthodontics, and Journal of Dentistry. A total of 15 articles were included in the review. RESULTS: Intraoral scanners are highly repeatable for shade matching, and outperformed visual shade matching. Accuracy varied significantly between studies, with the majority recommending the use of visual shade matching to confirm/verify the intraoral scanner results. Setting intraoral scanners to the Vita 3D Master shade guide improved both accuracy and precision. Shade matching with intraoral scanners may be influenced by external factors such as ambient light sources and incorrect use or manipulation. CONCLUSION: Intraoral scanners set to the Vita 3D Master shade guide may be used for shade matching, but shade should be verified with visual shade matching. Further studies are required to address limitations of current studies.

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.

Effects of treatment with aqueous and acid-based coloring liquid on the color of zirconia.

STATEMENT OF PROBLEM: To preserve the mechanical property of color-treated zirconia for optimal restoration longevity, aqueous colorants have been developed as an alternative to acid-based coloring agents. However, little is known regarding the effects of aqueous colorants on the color of zirconia. PURPOSE: The purpose of this in vitro study was to compare the effect of aqueous coloring liquids with acid-based coloring liquids on the color of zirconia. MATERIAL AND METHODS: Eighty monolithic zirconia specimens (10×10×2 mm) were fabricated and divided into 4 groups according to their color treatment: unshaded zirconia (control), precolored zirconia, aqueous coloring liquid on zirconia, and acid-based coloring liquid on zirconia. The shaded zirconia specimens were further divided into 3 subgroups based on the number of coloring applications used (1, 3, or 6). The International Commission on Illumination (CIELab) color coordinates were measured by spectrophotometry. RESULTS: Significant differences in the CIE a∗ and b∗ values were observed between the specimen groups treated with the aqueous coloring liquid and the acid-based coloring liquid (P<.001). Increasing the number of colorings resulted in an increase in the CIE a∗ and b∗ values and a decrease in the CIE L∗ values in all the groups (P<.001). CONCLUSIONS: Treatment with aqueous coloring liquid on zirconia produced a greater redness or yellowness compared with treatment with acid-based coloring liquid. The coloring of zirconia lowered its brightness and imparted a red/yellow hue.

A Painting Technique Using Ceramic Pigments for the Artificial Iris of an Ocular Prosthesis Guided by Applying Newton's Color Wheel.

This article describes a simple method for painting an artificial iris for the manufacturing of an ocular prosthesis with dark and light tones, both with excellent esthetic results. The challenge of choosing colors around the pupil and medium zone during painting is aided by the application of Newton's color wheel theory. This technique provides a safer choice of color during the painting procedure by using a mixture of ceramic pigments.

Analysis of Shade Matching in Natural Dentitions Using Intraoral Digital Spectrophotometer in LED and Filtered LED Light Sources.

PURPOSE: To evaluate the shade matching capabilities in natural dentitions using Vita Toothguide 3D-Master and an intraoral digital spectrophotometer (Vita Easyshade Advance 4.0) in various light sources. MATERIALS AND METHODS: Participants between 20 and 40 years old with natural, unrestored right maxillary central incisors, no history of bleaching, orthodontic treatment, or malocclusion and no rotations were included. According to their shades, subjects were randomly selected and grouped into A1, A2, and A3. A total of 100 participants (50 male and 50 female) in each group were chosen for this study. Shade selection was made between 10 am and 2 pm for all light sources. The same examiner selected the shade of natural teeth with Vita Toothguide 3D-Master under natural light within 2 minutes. Once the Vita Toothguide 3D-Masterwas matched with the maxillary right central incisor, the L*, a*, and b* values, chroma, and hue were recorded with Vita Easyshade Advance 4.0 by placing it on the shade tab under the same light source. The values were statistically analyzed using one-way ANOVA and Tukey's HSD post hoc test with SPSS v22.0 software. RESULTS: The mean ∆E*ab values for shades A1, A2, and A3 for groups 1, 2, and 3 were statistically significantly different from each other (p < 0.001). CONCLUSION: The intraoral digital spectrophotometer showed statistically significant differences in shade matching compared to Vita Toothguide 3D-Master. Incandescent light showed more accurate shade matching than the filtered LED, LED, and daylight.

Effect of metal opaquer on the final color of 3 ceramic crown types on 3 abutment configurations.

STATEMENT OF PROBLEM: The effect of a recently introduced metal opaquer when used to mask the color of a titanium abutment under ceramic crown systems is unknown. PURPOSE: The purpose of this study was to compare the color coordinates of 3 ceramic crown types-characterized monolithic lithium disilicate (LDC) (IPS e.max; Ivoclar Vivadent AG), layered lithium disilicate (LDL) (IPS e.max; Ivoclar Vivadent AG), and layered zirconia (ZL) (H.C. Starck)-on 3 abutment configurations, nonopaqued titanium (Ti), resin opaqued titanium (Op), and zirconia (Zir). In addition, the color differences (CIEDE2000) were evaluated among the 3 crown types on 3 different abutment substrates. MATERIAL AND METHODS: Ten Ti disks (10×1 mm) were fabricated with computer-aided design and computer-aided manufacturing (CAD-CAM) to represent the Ti abutments. Five Ti specimens were opaqued (Op) (whiteMetal Opaquer wMO; Blue Sky Bio), and 5 were not opaqued (Ti). Ten zirconia disks were fabricated with CAD-CAM and sintered (10×1.2 mm). Five disks were used as backings to represent Zir abutments, and 5 disks were layered with 1 mm of porcelain (B1, IPS e.Max Ceram; Ivoclar Vivadent AG) to represent layered zirconia crowns (ZL). Ten lithium disilicate plates (14×14×1.2 mm) were sectioned from CAD blocks (B1 IPS e.Max CAD; Ivoclar Vivadent AG). Five plates were layered with the same porcelain (B1, 1 mm), and 5 plates were surface characterized and glazed. An LDL crown on a Zir abutment configuration was used as the control. The 3 simulated crown types (n=5) were optically connected to each of the 3 abutment types, and the color of the 9 groups was measured using a spectroradiometer. Measured data were reported in CIELab coordinates. CIELab data were used to calculate color differences between the control and the 8 experimental groups. Color data were summarized for each group, and analyzed by repeated-measures ANOVA. For pairwise comparisons, a Bonferroni correction of t tests was used, and for interpretive analysis of resulting color difference data, a 1-way ANOVA and subsequent Tukey testing for pairwise comparisons were used. RESULTS: The statistical significance of the analysis of color coordinates was found to be P≤.002. Although 3-way interaction was not found to be significant (P=.335), all three 2-way interactions of the main effects were found to be significant (P≤.002). All crown types on the Zir abutment revealed color differences from the control group. The color differences of the crown types on the Op and Zir abutment configurations compared with the control (LDL/Zir) were not (P>.05) statistically different. CONCLUSIONS: Colors of tested crown systems on Ti backing were each unacceptably different from the control group. Colors of these systems on zirconia backing were not perceivably different. Use of opaquer on titanium backing resulted in a small color difference from the control group (P>.05) for each crown system, demonstrating that it may be used to prevent the unfavorable metal show-through that can influence the final color of all ceramic crown systems tested.

Evaluation of small-group education on the shade determination ability of preclinical dental students-A controlled clinical trial.

OBJECTIVES: To evaluate the effect of small-group education including practical training on dental students' shade determination performance compared with a control group. METHODS: Sixty-three non-colour-blind preclinical students were asked to participate and belonged to an intervention (n = 31) and a control (n = 32) group, respectively. All students received a lecture on dental shade determination. The members of the intervention group were educated and practically trained in small groups in addition. Ten volunteers, each with unrestored upper right middle and lateral incisors, were recruited. The students of both the intervention and control groups were then asked to determine the colour of the volunteers' test teeth using the 3D-Master shade guide (Vita Zahnfabrik, Bad Säckingen, Germany) under artificial daylight illumination. For analytical purposes, the CIE L*a*b* coordinates were obtained using a spectrophotometer. Colour differences, ΔE, between all shade tabs selected by the students and the natural teeth were calculated. ΔE observed in the intervention and control groups were compared using t tests. In addition, a multi-level regression model was adjusted for age and gender. RESULTS: Mean (SD) ΔE between the shade tabs selected by the students and the natural teeth in the intervention and control groups were 3.8 (2.1) and 4.3 (2.3), respectively (P < .001). The effect of group membership was reproduced in multivariate analysis whereas age and gender did not reach statistical significance. CONCLUSIONS: With more intensive education and practical training the ability to perform clinical shade determinations improved for students without previous clinical experience. The results obtained support the idea of implementing thematic small-group education in the dental curriculum.

Technique to Match Gingival Shade when Using Pink Ceramics for Anterior Fixed Implant Prostheses.

Use of pink gingival ceramics can reduce the necessity for extensive surgical procedures attempting to restore missing soft and hard tissues in the maxillary esthetic zone. Selecting the appropriate shade for pink porcelain poses a challenge, especially when the patient presents with a high smile line. This paper describes a simple and effective technique to facilitate shade selection for gingival ceramics to match the patient's existing gingival shade.

An In Vitro Investigation of Veneered Zirconia-Based Restorations Shade Reproducibility.

PURPOSE: To examine the effects of the veneering technique on the shade reproducibility of zirconia-based crowns. MATERIALS AND METHODS: An artificial tooth was prepared with a 1.2 mm heavy chamfer finish line and 8° taper. The prepared tooth was scanned using CAD/CAM technology to fabricate 45 cobalt chromium (CoCr) testing dies. One CoCr die was scanned, and 45 zirconia copings were milled and devided according to the veneering technique into 3 groups of 15 specimens each: layering veneering (LV) using Vita Vm9, overpressing veneering (OV) using Vita Pm9, and digital veneering (DV) using Vita Triluxe forte. All veneering layers had the same shade (A2). The specimens were cemented onto the testing dies using glass inomer cement. A spectrophotometer was used to measure the shade coordinates (L, C, h, a, b) for a Vita A2 shade tab and for each specimen. Both the CIE Lab (ΔEab ) and the CIE DE2000 (ΔE00 ) color difference formulas were applied to compare the shade tab and the study groups. One-way ANOVA and multiple comparison Bonferroni tests were applied for statistical analysis of the results. RESULTS: Means and standard deviations (SDs) of ΔEab were 2.3 ± 1.3 for LV, 3.5 ± 0.8 for OV, and 4.0 ± 0.7 for DV. Means and SDs of ΔE00 were 1.4 ± 0.8 for LV, 2.1 ± 0.5 for OV, and 3.1 ± 0.4 for DV. ΔEab of LV group was significantly lower (p < 0.05) than both OV and DV groups, whereas the difference in ΔEab between OV and DV groups was not significant (p = 0.39). The differences in ΔE00 between all groups were significant (p < 0.05). CONCLUSIONS: LV group was superior to other groups in terms of shade reproducibility. The ΔEab and the ΔE00 values of LV and OV groups were within clinically acceptable ranges; however, the ΔEab and the ΔE00 values of group DV were beyond the clinically acceptable ranges. The ΔE00 formula demonstrated a statistically significant difference between OV and the DV groups, while the ΔEab formula did not. The zirconia veneering technique had a significant influence on the shade reproducibility of zirconia-based crowns.

A Study on Possibility of Clinical Application for Color Measurements of Shade Guides Using an Intraoral Digital Scanner.

PURPOSE: To assess if color measurement with intraoral scanner correlates with digital colorimeter and to evaluate the possibility of application of a digital scanner for shade selection. MATERIALS AND METHODS: The L*a*b* values of the five shade tabs (A1, A2, A3, A3.5, and A4) were obtained with an intraoral scanner (TRIOS Pod) and a colorimeter (ShadeEye). Both devices were calibrated according to the manufacturer's instructions before measurements. Color measurement values were compared with paired t-test, and a Pearson's correlation analysis was performed to evaluate the relationship of two methods. RESULTS: The L*a*b* values of the colorimeter were significantly different from those of the digital scanner (p < 0.001). The L* and b* values of both methods were strongly correlated with each other (both p < 0.05). The device repeatability in both methods were reported to be excellent (p < 0.05). Within the limitations of this study, color measurements with digital intraoral scanners and computer-assisted image analysis were in accordance with those of the colorimeter with respect to L* and b* values; however, all the coordinates of shade tabs were significantly different between two methods. CONCLUSIONS: The digital intraoral scanner may not be used as the primary method of color selection in clinical practices, considering significant differences in color parameters with colorimeter. The scanner's capability in shade selection should be further evaluated.

Evaluation of a Novel Computer Color Matching System Based on the Improved Back-Propagation Neural Network Model.

PURPOSE: To explore the feasibility of a novel computer color-matching (CCM) system based on the improved back-propagation neural network (BPNN) model by comparing it with the traditional visual method. MATERIAL AND METHODS: Forty-three metal-ceramic specimens were fabricated by proportionally mixing porcelain powders. Thirty-nine specimens were randomly selected to train the BPNN model, while the remaining four specimens were used to test and calibrate the model. A CCM system based on the improved BPNN model was constructed using MATLAB software. A comparison of the novel CCM system and the traditional visual method was conducted by evaluating the color reproduction results of 10 maxillary central incisors. Metal-ceramic specimens were fabricated using two color reproduction approaches. Color distributions (L*, a*, and b*) of the target teeth and of the corresponding metal-ceramic specimens were measured using a spectroradiometer. Color differences (ΔE) and color distributions (ΔL*, Δa*, and Δb*) between the teeth and their corresponding specimens were calculated. RESULTS: The average ΔE value of the CCM system was 1.89 ± 0.75, which was lower than that of the visual approach (3.54 ± 1.11, p < 0.01). With respect to color distributions, substantial differences were found between the two color-matching systems, except for ΔL* (p > 0.05). CONCLUSION: The novel CCM system produced greater accuracy in color reproduction within the given color space than the traditional visual approach.

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.

Influence of the color of composite resin foundation and luting cement on the final color of lithium disilicate ceramic systems.

STATEMENT OF PROBLEM: Lithium disilicate restorations are commonly used, particularly in the anterior region. The color of the underlying composite resin foundation (CRF) and luting cement may negatively affect the color of lithium disilicate ceramic restorations. PURPOSE: The purpose of this in vitro study was to investigate the effect of CRF and resin cement materials on the color of lithium disilicate ceramics in 2 different translucencies. MATERIAL AND METHODS: Twenty disks (11×1.5 mm, shade A2) were fabricated from medium-opacity (mo) (n=10) and high-translucency (ht) (n=10) lithium disilicate (Lds) blocks (IPS e.max Press). Five CRF disks (11×3 mm) were fabricated in 5 different shades (A1, A2, A3, B2, C2) and 30 resin cement disks (11×0.2 mm) in the shades of translucent (Tr), universal (Un=A2), and white-opaque (Wo). Ceramic specimens were placed on each CRF, and the resin cement combination and color was measured with a spectrophotometer. CIELAB color coordinates were recorded, and the color coordinates of both ceramics on the shades of the A2 CRF and resin cement were saved as the control. Color differences (ΔE00) between the control and test groups were calculated. Data were analyzed with 3-way analysis ANOVA and compared with the Tukey HSD test (α=.05). RESULTS: The ΔE00 values were influenced by the shades of the CRF, resin cement materials, and also their interactions (P<.05). The ΔE00 values were not affected by the ceramic type. The ΔE00 values of the Wo cement groups (1.73 to 2.96) were significantly higher than those of the other cement shades (0.88 to 1.29) for each ceramic type and CRF shade (P<.05). CONCLUSIONS: Lithium disilicate ceramics in 2 different translucencies were similarly influenced by the color of the underlying cement and CRF. When translucent and universal cement shades were used, the core shade did not affect the final color of the ceramics. White opaque cement caused clinically unacceptable color changes in both ceramics on all shades of CRFs except the C2 CRF and when high translucency ceramic was used on the A2 CRF. These changes were clinically acceptable, but perceptible.

Effect of artificial toothbrushing and water storage on the surface roughness and micromechanical properties of tooth-colored CAD-CAM materials.

STATEMENT OF PROBLEM: Because of the different composition of resin-ceramic computer-aided design and computer-aided manufacturing (CAD-CAM) materials, their polishability and their micromechanical properties vary. Moreover, depending on the composition of the materials, their surface roughness and micromechanical properties are likely to change with time. PURPOSE: The purpose of this in vitro study was to investigate the effect of artificial toothbrushing and water storage on the surface roughness (Ra and Rz) and the micromechanical properties, surface hardness (Vickers [VHN]) and indentation modulus (EIT), of 5 different tooth-colored CAD-CAM materials when polished with 2 different polishing systems. MATERIAL AND METHODS: Specimens (n=40 per material) were cut from a composite resin (Paradigm MZ100; 3M ESPE), a feldspathic ceramic (Vitablocs Mark II; Vita Zahnfabrik), a resin nanoceramic (Lava Ultimate; 3M ESPE), a hybrid dental ceramic (Vita Enamic; Vita Zahnfabrik), and a nanocomposite resin (Ambarino High-Class; Creamed). All specimens were roughened in a standardized manner and polished either with Sof-Lex XT discs or the Vita Polishing Set Clinical. Surface roughness, VHN, and EIT were measured after polishing and after storage for 6 months (tap water, 37°C) with periodic, artificial toothbrushing. The surface roughness, VHN, and EIT results were analyzed with a nonparametric ANOVA followed by Kruskal-Wallis and exact Wilcoxon rank sum tests (α=.05). RESULTS: Irrespective of polishing system and of artificial toothbrushing and storage, Lava Ultimate generally showed the lowest surface roughness and Vitablocs Mark II the highest. As regards micromechanical properties, the following ranking of the CAD-CAM materials was found (from highest VHN/EIT to lowest VHN/EIT): Vitablocs Mark II > Vita Enamic > Paradigm MZ100 > Lava Ultimate > Ambarino High-Class. Irrespective of material and of artificial toothbrushing and storage, polishing with Sof-Lex XT discs resulted in lower surface roughness than the Vita Polishing Set Clinical (P≤.016). However, the polishing system generally had no influence on the micromechanical properties (P>.05). The effect of artificial toothbrushing and storage on surface roughness depended on the material and the polishing system: Ambarino High-Class was most sensitive to storage, Lava Ultimate and Vita Enamic were least sensitive. Artificial toothbrushing and storage generally resulted in a decrease in VHN and EIT for Paradigm MZ100, Lava Ultimate, and Ambarino High-Class but not for Vita Enamic and Vitablocs Mark II. CONCLUSIONS: Tooth-colored CAD-CAM materials with lower VHN and EIT generally showed better polishability. However, these materials were more prone to degradation by artificial toothbrushing and water storage than materials with higher VHN and EIT.

The translucency effect of different colored resin cements used with zirconia core and titanium abutments.

PURPOSE: The purpose of this study was to evaluate the effect of the different color of resin cements and zirconia cores on the translucency parameter (TP) of the restoration that simulates the implant-supported fixed prosthesis using titanium base on the bottom. MATERIALS AND METHODS: Zirconia core plates (Zr-Zahn) were prepared in A2 shades (n = 11). Resin cement plates (3M ESPE) were prepared in A2, A1, translucent (TR) shades (n = 11). The initial color measurements and were measured on zirconia core plates, and resin cements plates using a spectrophotometer. Then, the resin cement plates were placed below the zirconia core plates, and the second measurements were done. The final measurements were done after placing the titanium discs in the bottom. The data were analyzed with two-way analysis of variance and Tukey honestly significant differences tests (α = 0.05). RESULTS: The highest TP values were recorded for A1-colored resin specimens and the lowest for zirconia core plates in the first measurement (P < 0.05). The addition of zirconia core decreased the TP values in all tested resin cement groups (P < 0.05). The highest TP value was recorded for A1-colored resin cement with zirconia core plates and the lowest for A2 and TR with zirconia core plates after second measurements (P < 0.05). The addition of titanium decreased the TP of the zirconia core plate and resin cement combination (P < 0.05). CONCLUSIONS: The addition of a zirconia core under the resin cement dramatically reduced the TP values, and the presence of a titanium layer decreased the TP value and caused a darker appearance.

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.

Lighting conditions used during visual shade matching in private dental offices.

STATEMENT OF PROBLEM: To our knowledge, no data are available on the actual lighting that is used for visual shade matching in private dental offices. PURPOSE: The purpose of this study was to determine the shade matching practices and interest in continuing education in dental practices and to determine the quantity and quality of the ambient lighting used during visual shade matching in a sample cohort of dentists in private practices. MATERIAL AND METHODS: Thirty-two private practices were enrolled, and each completed a 1-page survey on the clinic's shade matching practices. A spectrophotometer was used to measure the ambient lighting in each practice, collecting data on color temperature (Kelvin), color rendering index (CRI), and light intensity (foot candles/fc). A 2-sided nonparametric sign test was used to compare the true median color temperature with the standard (5500°K). A 1-sided t test was used to compare the CRI with the standard (CRI >90) (α=.05 for all statistical analyses). RESULTS: All dental practitioners surveyed used mainly visual shade matching in their practices. Of those, 87.5% showed interest in attending continuing education on this topic, with 56.3% preferring a clinical demonstration course. The mean color temperature was 4152.9°K and was significantly different from the standard 5500°K (P<.001). The 1-sided t test indicated that the mean CRI was less than 90 (P=1). The 95% confidence interval for the intensity was 80.7 to 111.6 fc. CONCLUSIONS: The ambient light in the majority of the 32 dental private practices measured was not ideal for visual shade matching.

Influence of light source, polarization, education, and training on shade matching quality.

STATEMENT OF PROBLEM: Many factors influence the quality of shade selection, and isolating how significantly each of these factors influences results is difficult. PURPOSE: The purpose of this in vitro study was to compare results of shade matching using handheld lights with or without a polarizing filter with results obtained using a professional viewing booth and to analyze the influence of education and training on shade selection outcome. MATERIAL AND METHODS: A total of 96 third-year dental students (evaluators) were randomly separated into 4 groups. Each group was assigned 1 of 2 handheld shade-matching devices (lights) with or without a polarizing filter. Each group performed a shade matching exercise using the handheld light or a professional viewing booth. The exercise consisted of matching shade tabs placed in a typodont to a commercial shade guide. Each group repeated this procedure 4 times over a 9-week period. A lecture on shade matching was presented at the fifth week of the study, between "before" and "after" shade matching procedures. RESULTS: Shade matching scores with handheld lights (7.8) were higher than scores of shade matching with the viewing booth (7.2). The mean scores for before (7.2) and after (7.8) shade matching (with education and training in between) were significantly different. The combined effect of light and education and training improved the shade matching score by 1.2, from 6.8 in the before sessions using the viewing booth to 8.0 in the after sessions using handheld lights. A 21% increase in the number of evaluators who selected 1 of 4 best matches was recorded, 10% for handheld lights versus viewing booth after education and training versus before sessions and 11% between after sessions using handheld lights versus before sessions using viewing booth. CONCLUSIONS: Within the limits of the study, the shade matching scores with handheld lights were significantly better than the results obtained using a viewing booth (P<.01). Using a handheld light with or without a polarizing filter did not influence shade matching results. Mean shade matching scores were significantly better after education and training (P<.01). Light combined with education and training resulted in the greatest increase in shade matching quality.

Improved Construction of Auricular Prosthesis by Digital Technologies.

Implant-retained auricular prostheses are a successful prosthetic treatment option for patients who are missing their ear(s) due to trauma, oncology, or birth defects. The prosthetic ear is aesthetically pleasing, composed of natural looking anatomical contours, shape, and texture along with good color that blends with surrounding existing skin. These outcomes can be optimized by the integration of digital technologies in the construction process. This report describes a sequential process of reconstructing a missing left ear by digital technologies. Two implants were planned for placement in the left mastoid region utilizing specialist biomedical software (Materialise, Belgium). The implant positions were determined underneath the thickest portion (of anti-helix area) left ear that is virtually simulated by means of mirror imaging of the right ear. A surgical stent recording the implant positions was constructed and used in implant fixtures placement. Implants were left for eight weeks, after which they were loaded with abutments and an irreversible silicone impression was taken to record their positions. The right existing ear was virtually segmented using the patient CT scan and then mirror imaged to produce a left ear, which was then printed using 3D printer (Z Corp, USA). The left ear was then duplicated in wax which was fitted over the defect side. Then, it was conventionally flasked. Skin color was digitalized using spectromatch skin color system (London, UK). The resultant silicone color was mixed as prescribed and then packed into the mold. The silicone was cured conventionally. Ear was trimmed and fitted and there was no need for any extrinsic coloring. The prosthetic ear was an exact match to the existing right ear in shape, skin color, and orientation due to the great advantages of technologies employed. Additionally, these technologies saved time and provided a base for reproducible results regardless of operator.