Analysis of shade-matching ability in dental students: a comparative study under clinical and correcting light conditions.

BACKGROUND: Selecting the ideal tooth shade is essential to the success of aesthetic dental restorations. Students' cognitive abilities are involved in the multifaceted and intricate process of shade matching. Hence, the present study aimed to assess and compare the shade-matching ability of undergraduate dental students in various years of dental education under clinical and correcting light. METHODS: This comparative cross-sectional study was instigated amongst male 4th, 5th, and 6th-year students of the dental complex of King Faisal University, Kingdom of Saudi Arabia. A total of 72 male dental students assessed the shade under clinical (fluorescent light) and correcting light (handheld Dental Base Light) by using VITA Classical shade guides. Statistical analysis was done using SPSS version 23 (Armonk, NY, USA). The Chi-square test was used to evaluate the association between correct and incorrect shade matching under correcting and clinical light. RESULTS: Out of 72 male students, 22(30.6%) were from the 4th year, 26(36.1%) were from the 5th year, and 24(33.3%) were from the 6th year, with a mean age of 22.92 ± 1.01 years. The majority of the 6th-year students selected shade of anterior tooth # 11 correctly under clinical and correcting light, and 3(12.5%) students selected incorrectly under clinical and correcting light, with a statistically significant association among them (p = 0.004). As far as the shade selection of the posterior tooth is concerned, a statistically significant difference was observed under clinical light among all clinical students (p = 0.008). CONCLUSION: The clinical performance of dental students in shade matching improved with advancing years of dental education. Additionally, the shade matching ability of all groups of dental students was superior under correcting light compared to conditions under clinical light.

Effect of group and individual education on shade matching competency of dental students.

PURPOSE: To evaluate the influence of group and individual education on shade matching quality using a visual color competency test to match shade tab pairs from two Vita classical A1-D4 shade guides. METHODS: 60 dental students, 21-25 years old (39 females, 21 males) participated in the study. All participants passed a color deficiency test before the experiment. The examination was voluntary and approved by the corresponding Ethics Committee. Students were randomly divided into three groups (n=20): one control group, NE (no education) and two experimental groups - GE (group education) and IE (individual education). The study was performed in three phases. In the "before" (B - Phase 1) and "after" (A - Phase 3) phase, all groups had to match 16 pairs of tabs from two Vita classical A1-D4 shade guides, with the shade designations hidden by custom letter markings. All tabs were mixed on a gray surface illuminated by color-correcting light. In Phase 2 (between B and A), GE had only group education, while IE received additional individual education and training. The control group did not participate in Phase 2. Means and standard deviations were calculated, and differences were compared using the one-way ANOVA, ANCOVA test, and Student t-test for dependent samples (α= 0.05). RESULTS: The NE group matched 10.3 (3.2) and 10.4 (2.9) tab pairs in the before and after phases, respectively. Corresponding results for GE were 11.1 (2.2) and 14.4 (1.9) and 9.5 (3.6) and 15.0 (1.5) for IE, respectively. In Phase 1 (B), no statistically significant difference was recorded among the groups (P= 0.260). The experimental groups achieved a statistically significant improvement compared with the control group in Phase 3 (A) (P< 0.001). Both experimental groups achieved statistically significant improvement within the group after education, GE (P< 0.001) and IE (P< 0.001). Within the limitations of this study, it was concluded that both experimental groups had statistically significant progress in shade matching. The group that received individual education (IE) made statistically significant progress compared with the group that received group education (GE). No statistically significant difference was found in the results of the control group between Phase 1 and Phase 3 of the study. CLINICAL SIGNIFICANCE: Improving the shade matching ability facilitates the work of dentists and dental technicians and enhances the esthetics of dental restorations.

Influence of different abutment materials on the color of implant-supported restoration: A laboratory study.

PURPOSE: To investigate the effect of different abutments and crowns on the color of implant-supported restorations. METHODS: Zirconia and lithium disilicate (e.max) disks with A2 shade were fabricated to represent two crowns. The implant abutments were untreated titanium, opaqued titanium, anodized titanium, A2 shade zirconia and white zirconia. 4.0 mm-thickness zirconia and e.max specimens were used as references respectively. The crowns were placed on tested abutments with a drop of clear glycerin between them and the color was measured using a digital spectrophotometer. CIELab values were recorded to evaluate color differences (ΔE) between tested specimens and the references. RESULTS: Titanium abutments presented higher color differences than zirconia. The ΔE values with untreated titanium were higher than those with opaqued titanium. No differences were found between untreated titanium and anodized titanium for zirconia crowns. The ΔE values of zirconia crowns showed no significant differences between shade A2 zirconia and white zirconia abutments; e.max crowns showed a significant difference. The zirconia crown ΔE values were lower than those of e.max for all titanium and A2 zirconia abutments. Lithium disilicate crowns and zirconia abutments may be more suitable for implant-supported restorations. Opaqued titanium abutment may improve color in esthetic regions when a ceramic abutment cannot be used. CLINICAL SIGNIFICANCE: Lithium disilicate crowns and zirconia abutments may be an effective method to achieve excellent color matching in esthetic regions with implant-supported restorations.

Chroma-dependence of CIEDE2000 acceptability thresholds for dentistry.

OBJECTIVES: Determine visual 50:50% color difference acceptability thresholds (AT) for regions of the dental color space with varying chromaticity. METHODS: A 40-observer panel belonging to two different groups (dentists and laypersons) evaluated 144 dental resin composites pairs (divided in three different sets of 48 pairs according to chroma value: Low Chroma (LC), Medium Chroma (MC) and High Chroma (HC) placed 40 cm away and inside of a viewing cabinet (D65 Standard light source; diffuse/0° geometry). A Takagi-Sugeno-Kang (TSK) fuzzy approximation was used for fitting the data points and calculate the 50:50% acceptability thresholds in CIEDE2000. A paired t-test was used to evaluate the statistical significance between thresholds differences and Bonferroni correction was applied. RESULTS: The CIEDE2000 50:50% AT were ∆E00 = 2.84, ∆E00 = 2.31 and ∆E00 = 1.80 for LC, MC and HC sets of sample pairs, respectively. The 50:50% AT values were statistically significant between the different sets of sample pairs, as well as the 50:50% AT values obtained for different observer groups. CONCLUSIONS: 50:50% CIEDE2000 acceptability thresholds for dentistry are significantly different depending on the chromaticity of the samples. Observers show higher acceptability for more achromatic samples (low chroma value) than for more chromatic samples. CLINICAL SIGNIFICANCE: The difference in the AT for distinct regions of the dental color space can assist professionals as a quality control tool to assess clinical performance and interpret visual and instrumental findings in clinical dentistry, dental research, and subsequent standardization processes.

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.

Influence of individual education and training on quality of color matching in dentistry.

OBJECTIVES: To evaluate the influence of the group and individual education of students on shade matching quality. Secondary study objective included a survey-assessment of quality and difficulty level of color matching. MATERIALS AND METHODS: Forty dental student participants in Integrated Academic Studies of Dentistry at the Faculty of Medicine, University of Nis (26 female, 14 male) 21-25 years old, signed consent to voluntarily participate in the research. The Ethics Committee of the Clinic of Dentistry, Faculty of Medicine, University of Nis, approved the study under number 14/11-2019-2EO. They were randomly divided into two groups (n = 20), experimental (IE, individual education) and control (GE, group education). Each group was divided into four subgroups (n = 5). The study was performed in three phases. In Phase I (I) and III (III), students matched the shade of the maxillary central left incisor (#9) using three different shade guides. Each of the students served as a "patient" for shade matching, while the other members of the subgroup, individually (VMI ) and as a team (VMT ), visually matched the tooth shade. In Phase II (between phases I and III), group IE received standard group and individual education and training, while group GE had only group education. Shade matching results in before and after education were compared with results obtained by an intraoral spectrophotometer. CIELAB (∆E*), and CIDE2000 color differences (∆E00 ) were calculated. The color differences between VMI or VMT and ES readings were graded. In addition, the students rated the level of difficulty and quality of shade matching from 1 to 5, signifying the most to least difficult, and the worst to best match, respectively. Means and standard deviations were calculated. Differences were compared using the Student t-test. RESULTS: Means (s.d.) of CIEDE2000 color differences for VMI before and after IE were 4.5 (1.5) and 3.3 (0.9), respectively. Corresponding values for group GE were 4.4 (1.4) and 4.0 (1.0), respectively. As compared with GE, group IE achieved 15% better results for the best matches and 27.5% for one of the three best matches in by-point comparison. Mean (s.d.) results for VMT in the experimental group before and after IE were 3.6 (2.4) and 2.8 (1.6), respectively. Corresponding results for the control group were 4.4 (2.1) and 3.5 (1.7), respectively. Group IE had statistically higher VMI and VMT scores than GE, while, for GE, only VMT scores were statistically higher. Group IE achieved better results in by-point comparison. After education and training, the students rated the shade matching as more precise and less difficult. Results were significantly better for Quality (IE) (sig = 0.010) and Difficulty (GE) (sig = 0.021). CONCLUSIONS: Within the limitations of the study, the experimental group achieved significantly better results in individual color matching after education and training than the control group, while both groups made progress in team color matching. Both groups rated shade matching more accurate and easier after education. CLINICAL SIGNIFICANCE: Improving the quality of shade matching is expected to enhance the esthetics of dental restorations, increase patient satisfaction, and reduce color corrections.

In-vivo repeatability of three intra-oral spectrophotometers.

OBJECTIVE: The objective was to assess the repeatability of three spectrophotometers, based on the CIELCh factors and shadeguide reference measurements. MATERIALS AND METHODS: Color analysis was performed using three devices: Rayplicker, Easyshade 4, and Easyshade V. Five repeated measures were performed by the same operator, on the right central maxillary incisor of 30 patients. The CIELCh factors were retrieved and the intra-class correlation was calculated. The Vita Classical and Vita 3D Master shadeguides were used to evaluate the respective Fleiss' Kappa factors. RESULTS: Rayplicker and Easyshade V demonstrated strong intra-class correlation based on the CIELCh factors: 0.98, 0.99, and 0.91 for Rayplicker, and 0.95, 0.99, and 0.93 for Easyshade V, for the L*, C*, and h* parameters, respectively. Regarding the repeatability of the shadeguide data, while Easyshade 4 had the best repeatability when using the Vita Classical as a reference, Rayplicker and Easyshade V showed better repeatability when using the Vita 3D Master. CONCLUSION: These findings suggest that both Rayplicker and Easyshade V are reliable devices for measuring CIELCh parameters. In terms of shadeguide references, the reliability of spectrophotometers is generally lower compared to the CIELCh measurements. CLINICAL SIGNIFICANCE: Given their good repeatability, both the Rayplicker and the Easyshade V spectrophotometers are reliable tools for prosthetic dental practices.

Comparison between direct and indirect "digital image" dental visual shade matching considering the effect of clinical experience and gender.

INTRODUCTION: Shade matching is an essential procedure to obtain an esthetic prosthesis. The Direct Visual Shade Matching (DSM) method using shade guides is the most used method by dentists. However, The Indirect Visual Digital Shade Matching (ISM) method based on digital imaging is concerned to be reliable and useful in determining shade matching in dental practice. Several factors such as method, clinical experience, and gender can affect the success of shade matching. AIM OF THE STUDY: This study aimed to compare these two methods and evaluate the effect of experience and gender on the results. MATERIALS AND METHODS: Three volunteers' maxillary central incisor teeth were evaluated using (DSM) and (ISM) methods by 87 examiners (42 males, 45 females). These examiners were further divided into three groups based on their clinical experience: Undergraduate Preclinical Dental Students (UPDS) with 31 examiners, Undergraduate Clinical Dental Students (UCDS) with 34 examiners, and Postgraduate Dental Students from the Department of Prosthodontics (PDS) with 22 examiners. The spectrophotometer device results of three teeth were considered as a reference for shade matching. Statistical analyses of the data were performed using Kruskal-Wallis, Mann-Whitney U, and Chi-square tests. RESULTS: No significant difference was found between indirect and direct methods according to Perfect Matches (p > 0.05). However, according to Shade Matching Deviation Score (SMDS) values a statistically significant difference was found between the two methods where the best result was obtained with the ISM method (p < 0.05). There was a significant difference between the PDS group and the other two groups in terms of clinical experience (p < 0.05). There was no significant difference between gender groups (p > 0.05). CONCLUSION: Digital images, captured under standardized lighting conditions, may serve as a reliable alternative method for direct shade matching. The (ISM) method requires a camera, related accessories, and computer skills. However, as these tools are commonly available nowadays, the focus for practitioners should be on effectively learning and applying these tools to achieve the best results. While clinical experience plays a significant role in the shade matching process, gender does not appear to have a substantial influence. CLINICAL SIGNIFICANCE: This study found no significant differences between the (DSM) and (ISM) methods, leaving the clinical relevance of this method open to debate. However, the ISM method yielded superior responses. Despite requiring specialized tools, conditions, and training, the widespread use of cameras and computers in modern clinics makes the necessary equipment and software readily available. This method enhances clinician-technician communication, potentially improving prosthesis esthetics and patient satisfaction, especially for less experienced clinicians or those with color deficiencies. Further research is crucial to determine its clinical significance.

Effect of the coloring liquid shade and dipping time on the color, transparency, and flexural strength of monolithic zirconia.

STATEMENT OF PROBLEM: The impact of different coloring liquid shades and dipping times on the color, transparency, and flexural strength of monolithic zirconia ceramics is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the effects of different coloring liquid shades (A2, 3M2, and 5M2) and dipping times (no dipping, 30 seconds, 60 seconds, and 90 seconds) on the color difference (ΔE00), relative translucency parameter (ΔRTP00), and 3-point flexural strength (σ) of monolithic zirconia ceramics. MATERIAL AND METHODS: Yttria-stabilized zirconia (3Y-TZP, 3 mol%) was cut into Ø16×1.2-mm plates (n=10) and 25×4×1.2-mm bars (n=15), which were colored using 3 shades of coloring liquid at 4 dipping times. Color coordinates were measured on a gray background by using a digital spectrophotometer with an integrating sphere attachment. The color and translucency differences were evaluated using 50:50% perceptibility (PT00 and TPT00) and acceptability (AT00 and TAT00) thresholds. The 3-point flexural strengths of the bar-shaped specimens were measured using a universal testing machine and analyzed using the Weibull distribution to calculate the Weibull modulus (m) and characteristic fracture strength (σ0). The data were analyzed with the 2-way ANOVA, Kruskal-Wallis, and LSD post hoc tests (α=.05). RESULTS: Both shade and dipping time significantly affected the color and translucency of monolithic zirconia (P<.001). The ΔE00 was above the PT00 for all groups, with only 3M2-90 and A2-60 being below the AT00. The main cause of color differences was the difference in lightness. Only A2 showed ΔRTP00 below the TPT00 (A2-30 (ΔRTP00=0.26), A2-60 (ΔRTP00=0.29), and A2-90 (ΔRTP00=0.46)). All experimental groups showed translucency differences below TAT00. In addition, only the dipping time had a significant effect on the flexural strength of zirconia (P<.001). CONCLUSIONS: The optical properties of monolithic zirconia ceramics were affected by the shade and dipping time of the coloring liquid. The mismatch in lightness was the main reason for the color difference. The dipping time affects the flexural strength of monolithic zirconia, whereas the shade of the coloring liquid did not seem to influence flexural strength.

Microwave disinfection of facial silicone prostheses, Part 1: Color stability.

STATEMENT OF PROBLEM: The choice of cleaning method is an important consideration for lengthening the serviceable time of facial prostheses as microbial organisms and biofilms could degrade facial prostheses and cause skin irritation. Whether microwave disinfection is a suitable cleaning method without degradation of the properties of a prosthesis is unclear. PURPOSE: The purpose of this in vitro study was to measure the color stability of 6 commonly used facial silicone elastomers after microwave disinfection over a simulated 1.5-year period. MATERIAL AND METHODS: Six different facial silicone elastomers: MDX4-4210, MDX4-4210/Type A, M511, A-2186, VST-50, and A-2000 were mixed with intrinsic silicone white opacifier (except for the control group) and subsequently combined with 4 silicone intrinsic pigment color groups: red (R), yellow (Y), burnt sienna (B), and a mixture of R+Y+B (M). The control group was a silicone elastomer without opacifier or pigment. Each of the 30 experimental groups consisted of 5 specimens (N=150). Five specimens were placed in a 250-mL Erlenmeyer flask filled with 160 mL of tap water. Seven flasks were then placed in a 660-W microwave oven. An exposure of 6 minutes was used according to the antimicrobial efficacy of microwave disinfection protocol on facial silicone prostheses with a final water temperature of 60 °C for 18 times (simulating 1.5 years of microwave disinfection with one 6-minute exposure monthly). A spectrophotometer was used to measure reflectance color change values (∆E). Color differences were calculated following CIELab (∆E*ab) and CIEDE2000 (∆E00) formulae. ∆E*ab and ∆E00 were statistically analyzed by a linear mixed effects model with 3 factors (silicone type, color shade, and time) using the R Statistical software program (α=.05). RESULTS: Both ∆E*ab and ∆E00 of all silicone elastomers studied were less than the visual perceptibility thresholds (∆E*ab<1.1 and E00<0.7) and were considered clinically acceptable (∆E*ab<3.0 and E00<2.1) after the 1.5-year simulation of microwave disinfection. Yellow and blue pigments had more effect on MDX4-4210 and M511, while red pigment had more effect on MDX4-4210, MDX4-4210/Type A, and M511 (P<.05). Nevertheless, the values were still below the perceptibility threshold (∆E*ab≤1.0 and E00<0.6). CONCLUSIONS: All 6 facial silicone elastomers maintained clinically acceptable color after 18 months of exposure to microwave disinfection.

Quantitative examination of factors influencing the colour reproduction ability of lithium disilicate glass-ceramics.

BACKGROUND: Effects of ceramic translucency, layer thickness, and substrate colour on the shade of lithium disilicate glass-ceramic restorations proved to be significant in several studies, however, quantitative, numerical results on the relationship between the colour difference and these parameters are still lacking. The purpose of this in vitro study was to quantitatively determine how the colour reproduction ability of a lithium disilicate glass-ceramic is affected by its translucency, layer thickness, and substrate colour. METHODS: Ceramic samples were prepared from A2 shade IPS e.max CAD blocks with high and low translucencies (HT and LT) in a thickness range of 0.5-2.5 mm (+/- 0.05 mm). Layered samples were acquired utilizing composite substrates in 9 shades; transparent try-in paste was used. The spectral reflectance of the specimens was assessed under D65 standard illumination with a Konica Minolta CM-3720d spectrophotometer. The CIEDE2000 colour difference (ΔE00) between two samples was analysed using perceptibility and acceptability thresholds set at 50:50%. Statistical analysis involved linear regression analysis and the Kruskal-Wallis test. RESULTS: An increase in the thickness of 0.5 mm reduced the ΔE00 of the HT samples to 72.8%, and that of the T samples to 71.1% (p < 0.0001). 7 substrates with HT and LT specimens had significantly different results from the mean (p < 0.05). A thickness of 0.5 mm is not sufficient to achieve an acceptable result at any level of translucency, while the low translucency ceramic at a thickness of 1.5 mm gave acceptable results, except for severely discoloured substrates (ND8 and ND9). CONCLUSIONS: The colour reproduction ability of lithium disilicate glass-ceramics is significantly affected by their translucency, layer thickness, and 7 substrates out of 9 substrates examined.

A system for reliable composite shade matching: Custom shade tabs and an intra-oral mockup.

OBJECTIVE: This article introduced a systematic approach to matching composite and tooth shades to create esthetic restorations that visually integrate seamlessly with the patient's tooth and surrounding dentition. A basic explanation of color science was presented to aid the clinician in adopting this systematic approach to color matching. To demonstrate the need for custom shade guides, an objective analysis of composites from different companies was performed by recording the color coordinate values of multiple composites and then calculating CIEDE2000 color differences. Different locations on the tooth were analyzed using the same identified shade from different companies, as well as using the same composite shade applied in different thicknesses. A case report documented the clinical application of these shade matching techniques. CLINICAL CONSIDERATIONS: Shade matching, particularly in the anterior esthetic region, can be challenging, which can result in patient dissatisfaction with the esthetic result. Stock shade tabs are not a reliable indicator of actual composite shades. CONCLUSIONS: The most predictable esthetic results were achieved by using custom shade guides as an entry point, followed by a direct composite color mockup intraorally. CLINICAL SIGNIFICANCE: To consistently meet the esthetic demands of today's patients, dentists need reliable tools when selecting a composite shade for restorations. Composites with the same shade designation vary in color and shade designation cannot be relied upon for accurate shade selection. The use of custom shade guides and an intra-oral mockup can enhance the esthetic outcome.

Effect of cross-polarization filters on the trueness of colors obtained with a single-lens reflex camera, macro lens, and a ring flash.

OBJECTIVE: To investigate the effect of cross-polarization filters on the colors of shade tabs obtained with a digital single-lens reflex (DSLR) camera, macrolens, and a ring flash. MATERIALS AND METHODS: Digital images of four shade tables (1M1, 3L2.5, 3R2.5, and 5M3) from the VITA Toothguide 3D-Master shade guide were taken using a DSLR camera, 100 mm macrolens, and ring flash with two different cross-polarizing filters (Polar_eyes and Filtropolar), and without (Nonpolarizer; n = 7). The CIE L*a*b* color coordinates of digital images were calculated and remeasured with a spectroradiometer (SR). The color differences (ΔE00 ) between the SR and digital images were calculated and analyzed with the two-way analysis of variance (ANOVA) and Tukey HSD test (α = 0.05). RESULTS: ΔE00 values of all test groups were higher than the clinically acceptable threshold (∆E00 > 1.80). While the ∆E00 values of Filtropolar (6.19 ± 0.44) and Polar_eyes (7.82 ± 0.23) groups were significantly higher than the Nonpolarizer (4.69 ± 0.32) for the 1M1 shade tab, ∆E00 value of Polar_eyes (6.23 ± 0.34) was significantly lower than Nonpolarizer (10.71 ± 0.48) group for 5M3 shade tab (p < 0.05). CONCLUSION: The color-matching results of tested digital photography techniques with and without cross-polarization were unacceptable, compared to a spectroradiometer. While digital photography with Polar_eyes cross-polarizing filter has closer results to the reference device for the low-in-value shade table (5M3), for the high-in-value shade table (1M1), improved results were obtained without a cross-polarizing filter. CLINICAL SIGNIFICANCE: The cross-polarization filters are increasingly used in dentistry for tooth color communication with digital photography techniques. However, the digital photography techniques with-without cross-polarization filterers should be improved to obtain clinically acceptable color-matching results.

Opacifiers on color stability of maxillofacial silicone under aging and Indian weathering conditions: An in vitro study.

STATEMENT OF PROBLEM: Resistance to long-term color change is a desirable property for facial prosthetic elastomers. Evidence for the color stability of maxillofacial silicones under aging and hot and humid Indian weathering conditions is lacking. PURPOSE: The purpose of this in vitro study was to evaluate the effect of adding opacifiers on the color stability of maxillofacial silicone under human aging and Indian weather conditions. MATERIAL AND METHODS: A total of 93 specimen disks were obtained from the A-2186, platinum-based, room-temperature vulcanized, maxillofacial silicone elastomer by using a Ø30×6-mm stainless-steel die. The specimens were divided into 3 main groups (n=30), C (control), T (titanium dioxide), and B (barium sulfate), and 1 additional specimen (n=1) from each group was stored in a closed box and further subgrouped as outdoor weathering (COut, TOut, BOut), acidic perspiration (CAcid, TAcid, BAcid), sebum (CSebum, TSebum, BSebum) (n=10), and visual comparison (CVis, TVis, BVis) (n=1). Baseline L∗, a∗, b∗ values were recorded by using a spectrophotometer and visual perception. The specimens were subjected to human and extraoral aging conditions, and the values were recorded again after 6 months. Data were analyzed statistically by using analysis of variance (ANOVA) and post hoc analysis with the Tukey post hoc test. RESULTS: In group C, the mean color change for COut was 3.69 ±0.49; CAcid, 3.58 ±0.68; and CSebum, 7.53 ±0.22 (P<.001). In group T, the mean color change for TOut was 2.60 ±0.24; TAcid, 2.35 ±0.13; and TSebum, 4.91 ±0.44 (P<.001). In group B, BOut was 1.59 ±0.28, BAcid was 1.46 ±0.28, and BSebum was 4.03 ±0.71 (P<.001). The specimens containing barium sulfate showed the maximum color stability. The least color stability was observed in all specimens exposed to sebum solution and was significantly different (P<.001) from the outdoor weather and acidic perspiration specimens. Visually perceivable color changes were observed in specimens exposed to the sebum solution. CONCLUSIONS: The addition of titanium dioxide and barium sulfate as opacifiers resulted in clinically acceptable color change when exposed to outdoor weathering and acidic perspiration but not in sebum solution.

Effect of ultraviolet protective agents on maxillofacial silicone elastomer, part 1: Color stability after artificial aging.

STATEMENT OF PROBLEM: Silicone elastomers have been widely used for rehabilitation of facial defects for more than 50 years. However, color change is the most common problem limiting the service life of facial prostheses. Whether the addition of ultraviolet protectives may enhance color stability of these materials is unclear. PURPOSE: The purpose of this in vitro study was to investigate the effect of ultraviolet protectives on the color stability of maxillofacial silicones after artificial aging. MATERIAL AND METHODS: Six color groups (unpigmented, white, yellow, red, blue, and mixed) of addition-type maxillofacial silicone were prepared. Four ultraviolet protectives benzophenone-3, ethylhexyl methoxycinnamate, titanium dioxide, and ethylhexyl salicylate at 0.5% and 1% concentrations by weight were incorporated into the silicone before polymerization. The specimens were artificially aged in an accelerated weathering chamber for 300 and 600 hours and in a thermocycling device. The color change values (E) of the maxillofacial silicones were evaluated. Data were statistically analyzed by using 4-way ANOVA. The differences were compared by the Tukey honestly significant difference test (α=.05). RESULTS: Benzophenone-3 and ethylhexyl methoxycinnamate protectives did not reduce the ΔE values, and the 1% titanium dioxide groups exhibited lower ΔE values than the 0.5% titanium dioxide groups. Ethylhexyl salicylate protective generally reduced the ΔE values significantly in all color and aging groups when compared with the control groups (P<.05). In all control and ultraviolet protective groups, the highest ΔE values were seen with the red color in 300 and 600 hours of aging. Generally, no significant difference (P>.05) was seen in the ΔE values, which were clinically acceptable among the thermocycled color groups. After 600 hours of accelerated aging, the ΔE values were found to be higher than the values of 300-hour aging. CONCLUSIONS: Ethylhexyl salicylate protective incorporated into maxillofacial silicones may improve color stability.

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.

The accuracies of three intraoral scanners with regard to shade determination: An in vitro study.

PURPOSE: To compare the accuracies of three intraoral scanners for shade determination function in vitro, and to preliminarily investigate the shade-matching characteristics of the three intraoral scanners. MATERIALS AND METHODS: The shade of the middle third region of each shade tab on the Vita Classical A1-D4 shade guide (VC) was measured with a spectrophotometer (Vita Easyshade V, VE) and three intraoral scanners, including CEREC Omnicam (OM), 3Shape TRIOS 3 (T3), and TRIOS 4 (T4). A conversion table between VC values and CIELAB values was established from the database of VE to analyze the trueness. The reproducibility of the instruments was then compared by repeating the measurements five times. RESULTS: The mean color difference for each instrument was highest in the OM, followed by the T4, and lowest in the T3 and VE, respectively. The L* and a* value for OM, and the b* value for T4, were significantly different from those for VE (p <0.05). The reproducibility of the instrument was highest in the VE (Fleiss' kappa: 0.95), followed by the T3 (Fleiss' kappa: 0.89), T4 (Fleiss' kappa: 0.87), and OM (Fleiss' kappa: 0.78). CONCLUSIONS: Of the three intraoral scanners, the trueness was best on the T3. The reproducibility of all the instruments was excellent.

Visual and instrumental coverage error of two dental shade guides: an in vivo study.

OBJECTIVES: This study aims to evaluate in vivo the color agreement between natural teeth and dental shade guides by means of visual and instrumental coverage error ([Formula: see text]) index. MATERIALS AND METHODS: The color of the middle third of 735 incisors was visually determined by two evaluators using the Vita Classical (VC) and Vita 3D Master (V3DM) shade guides. The color match between the natural tooth and the shade tab was rated as poor (P), good (G), or optimum (O) by each observer. CIE color coordinates of the target teeth and shade tabs of VC and V3DM were instrumentally measured using a clinical spectrophotometer. Visual ([Formula: see text]) and instrumental ([Formula: see text]) coverage error indexes were computed using CIELAB and CIEDE2000 metrics for both shade guides. For [Formula: see text] calculation, only the concordant inter-observer determination on tooth shade rated as O-O or O-G was used. The results were evaluated using perceptibility (PT, [Formula: see text]= 1.2, [Formula: see text]= 0.8) and acceptability (AT, [Formula: see text]= 2.7, [Formula: see text]= 1.8) color thresholds for dentistry. RESULTS: VC and V3DM exhibited [Formula: see text] (2.5, 3.2, and 3.2, 2.7 CIELAB units; 1.9, 2.3, and 2.8, 2.4 CIEDE2000 units, respectively, for O-O and O-G match) and [Formula: see text] (4.7, 4.8, and 4.1, 4.6 CIELAB units; 3.3, 3.4, and 3.4, 3.6 CIEDE2000 units, respectively, for O-O and O-G match) values greater than 50:50% AT for both color difference formulas. [Formula: see text] contributes more than 50% (53.2-82.4% range) to the [Formula: see text] value. This contribution depends on the shade guide used and the quality of the visual rating. CONCLUSIONS: The evaluated shade guides exhibited visual coverage errors above acceptability thresholds, largely due to the contribution of the instrumental coverage error to the visual coverage error. CLINICAL RELEVANCE: It necessary to further improve commercially available dental shade guides to facilitate achievement of satisfactory esthetics results in clinical practice.

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.

Accuracy and repeatability of different intraoral instruments on shade determination compared to visual shade selection.

OBJECTIVE: To evaluate the accuracy and repeatability of intraoral instruments used for shade determination compared to visual shade selection (VSS). MATERIALS AND METHODS: A total of 20 subjects and 10 observers, balanced by gender, participated in the study. Observers performed VSS of the upper right central incisor from each subject. Instrumental shade determination of the same teeth was performed using a spectrophotometer (Easyshade V) and intraoral scanners (CEREC Omnicam, Primescan, Trios 3 and Trios 4). Vita Classical shade nomenclature was used to record the shade designation for all instruments and VSS. The accuracy of the instruments was determined by comparing the instrument readings with the most frequent visual shade selected. The percentage of accuracy was obtained by comparing the number of agreements with the number of comparisons. The percentage of repeatability was obtained by comparing the number of repeated shades with the number of shade measurements in each group. Accuracy was compared using Cochran Q test followed by pairwise comparisons using multiple McNemar's tests with Bonferroni correction. Repeatability of the instruments was evaluated using Cronbach's alpha. RESULTS: Omnicam showed a significant lower accuracy than the other instruments (p < 0.05). No statistical difference on repeatability was found among the different instruments (p > 0.05). It was not found any statistical differences for VSS accuracy among the observers (p = 0.437) and between genders (p = 0.867). CONCLUSION: Instrumental repeatability (≥75%) and similar accuracy between the best performed instruments (69%-77.5%) and the observers performance (65%-90%) supports the use of high-performance instruments for dental shade determination. CLINICAL SIGNIFICANCE: Most instruments (Easyshade V, Primescan, Trios 3, and Trios 4) showed similar accuracy performance to observers in the VSS.