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.

Harmonizing color measurements in dentistry using translucent tooth-colored materials.

BACKGROUND: Since color measurements are relative, the discrepancy among different instruments is alarmingly high. This multicenter study evaluated the effectiveness of instrument calibration and inter-instrument harmonization of different spectrophotometers with the same optical geometry using tooth-colored, translucent dental materials. METHODS: The coordinating center (CC) spectrophotometer was calibrated using the NPL Ceram Series II set. Two sets of 10 specimens, labeled 1 to 10 and I to X (10 mm in diameter and 1 mm thick), were tested at CC and three research sites (RS1, RS2, and RS3) using the same d/8° optical geometry spectrophotometers. Calibration factors were calculated for each material and site to obtain the average calibration factors for sets 1-10, set I-X, and the combination of both. The differences among the non-corrected and corrected reflection values were calculated using CIEDE2000 (DeltaE00) and CIELAB (DeltaEab) color difference formulas and were submitted to ANOVA and Tukey test (α = 0.05). RESULTS: A significant decrease of color differences between non-corrected as compared to corrected measurements was recorded for all CC-RS and RS-RS comparisons. The reduction of DeltaE00 values between non-corrected and corrected for CC-RS1, CC-RS2, and CC-RS3 were 83.1%, 77.2%, and 73.6%, respectively. The corresponding DeltaE00 values for RS1-RS2, RS1-RS3, and RS2-RS3 comparisons, indirectly compared in the experiment, were 84.2%, 82.8%, and 68.5%, respectively. There was a significant reduction of DeltaE00 and DeltaEab color difference for all combined RS pairs and each of three RS pairs, corrected with one of two specimen sets calibration factors separately. CONCLUSIONS: Calibration and harmonization of color measurements in dentistry using tooth-colored, translucent restorative materials significantly decreased measurement discrepancies between the coordinating center and research sites and among pairs of research sites.

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.

Staining- and aging-dependent changes in color and translucency of 3D-printed resin-modified ceramics.

PURPOSE: To evaluate staining- and aging-dependent changes in the color and translucency of 3D-printed resin-modified ceramics (RMC). METHODS: Specimens (n= 5 per condition and material) were fabricated from test materials: Permanent Crown Resin (PCR), Crowntec (CT), Vita Enamic (VE) and Tetric CAD (TC). Specimens were stained in wine, coffee, tea, and water (control) and exposed to artificial accelerated aging (AAA). Color measurements were obtained using a spectrophotometer at baseline (T0) and at 3.5 (T1) and 7 (T2) days after immersion. For AAA, measurements were obtained at baseline (T0) and after exposure to controlled irradiance of 150 kJ/m² (T1) and 300 kJ/m² (T2). Mean and standard deviations were calculated on CIEDE2000 color differences (ΔE00), translucency parameter (TP00) and treatment-dependent changes in the translucency parameter (ΔTP0 0). Differences between materials and test conditions were tested by one-way ANOVA (α= 0.05). Results were additionally interpreted using visual color difference thresholds in dentistry ΔE00= 0.8 for the 50:50 perceptibility threshold (PT) and ΔE00= 1.8 for the 50:50 acceptability threshold (AT). ΔTP00 values were interpreted using 5058;50 TPT00= 0.6 and 50:0% TAT00= 2.6. RESULTS: Statistically significant differences were found among the materials when exposed to the different test conditions. At the T0-T1 time interval, the highest color difference was found with wine (0.1-2.2) on all materials except CT, which showed the highest ΔE00 with AAA (2.5). The second highest color differences were obtained upon exposure to AAA (0.2-2.5) and tea (0.5-1.1). The TP00 at baseline ranged from 5.1 to 9.8. Significant differences in ΔTP00 were found among the tested materials and staining/aging conditions, but no significant differences were found among the staining/aging intervals (T0-T1, T0-T2 and T1-T2). CLINICAL SIGNIFICANCE: Staining- and artificial aging-dependent changes of 3D-printed and milled resin modified ceramics used for definitive restorations could represent a challenge in terms of restoration acceptability or dissatisfaction. Staining and aging conditions produced significant color changes, while translucency changes were not significant.

Multicenter study on visual color difference thresholds. A secondary analysis of light, medium, and dark tooth-colored specimens.

PURPOSE: This secondary analysis further analyzed variations in the 50:50% perceptibility and acceptability thresholds (PT and AT, respectively) pertaining to light, medium, and dark tooth-colored specimen sets. METHODS: Primary raw data from the original study was retrieved. Visual thresholds (Perceptibility - PT and Acceptability - AT) were analyzed among the three specimen sets - light, medium, and dark. The Wilcoxon signed-rank test was used for paired specimens, and the Wilcoxon rank-sum nonparametric test was used for independent specimens (α= 0.001). RESULTS: The 50:50% CIEDE2000 PT and AT values were significantly higher for the light-colored specimen set when compared with the medium and dark-colored specimens: 1.2, 0.7, 0.6, respectively (PT) and 2.2, 16, 14 (AT), respectively (P< 0.001). Independent of the observer group, the highest PT and AT values were always found for the light-colored specimen sets (P< 0.001). Dental laboratory technicians had the lowest visual thresholds, but not significantly different from the other observer groups studied (P> 0.001). Similarly, all research sites had statistically higher visual thresholds for the light-colored specimen set than for the medium- or dark-colored sets, except for two sites that showed statistically similar results for medium-colored specimens but were significantly different from the dark-colored set. Among the different research sites, sites 2 and 5 registered significantly higher PT thresholds for the light specimens (1.5 and 1.6, respectively), and site number 1 had a significantly higher AT threshold relative to the other sites. The 50:50% perceptibility and acceptability thresholds were significantly different among light-, medium-, and dark-colored specimens for different research sites and observer groups. CLINICAL SIGNIFICANCE: The visual perception of color difference related to light-, medium-, and dark-colored specimens varied based on observer group and their geographic location. Therefore, a greater understanding of factors that affect visual thresholds, with the observers being "the most forgiving" for color differences among the light shades, will allow diverse clinicians to overcome some of the challenges of clinical color matching.

Colour stability of 3D-Printed orthodontic brackets using filled resins.

OBJECTIVE: To determine the effect of common beverages and accelerated aging on the colour stability of filled resins, which could potentially be used for fabrication of 3D-printed orthodontic brackets. MATERIALS AND METHODS: GR-17.1 (shades A1, A2, and A3), and GR-10 Guide resins (pro3dure medical, Eden Prairie, MN) were printed on an Asiga MAX UV printer into discs 2 mm thick, with a diameter of 10 mm, and then post-print processed as per manufacturer's instructions. Discs were immersed in 5 mL of coffee, tea, red wine, or distilled water for 7 days. Another group was subjected to accelerated aging in accordance with ISO Standard 4892-2. Ten samples were produced per resin, per treatment condition. Colour measurements were taken on the discs before and after treatment using a spectrophotometer against white and black reference tiles to assess colour and translucency differences with the CIEDE2000 colour difference formula. RESULTS: While initial colour of the printed resin discs was acceptable, all resin groups underwent significant colour change during the experiment. Red wine and coffee produced the greatest colour and translucency change, followed by tea, with accelerated aging producing the least change in colour and translucency. CONCLUSION: The 3D-printed resins tested underwent significant changes in colour and translucency following exposure to endogenous and exogenous sources of staining, which may affect their acceptability for fabrication of aesthetic orthodontic brackets.

Effects of staining and artificial aging on optical properties of gingiva-colored resin-based restorative materials.

OBJECTIVES: To evaluate CIEDE2000/CIELAB differences in color (ΔE00/ΔEab), and translucency parameter (ΔTP00/ΔTPab), and gloss of gingiva-colored resin-based restorative materials upon staining/aging. MATERIALS AND METHODS: Disc-shaped, 10 mm in diameter, and 2-mm-thick samples (n = 5/group) were made from giomer (Beautifil II gingiva), oligomer-based (crea.lign GUM gel), CAD/CAM polymethyl-methacrylate-based (IvoBase CAD), PMMA-based (ProBase Hot), and dimethacrylate-based (SR Nexco Paste Gingiva). Color and gloss were recording using a benchtop spectrophotometer and gloss meter, respectively, at baseline (T0), and upon staining in coffee or red wine for 60 (T1) and 120 h (T2), or artificial aging of 150 kJ/m2 (T1) and 300 kJ/m2 (T2). Three-way analysis of variance (materials x staining conditions x time intervals), Tukey's test (α = 0.05), and Pearson's correlation test were used in analytical statistics. RESULTS: CIEDE2000 color differences ranged from 1.0 to 4.4 (coffee), 1.5 to 5.3 (wine), and 0.9 to 2.0 after artificial aging, with ΔE00 values being significantly higher for Beautifil than other materials (p < 0.05). ΔTP00 values ranged from 0.2 to 0.7 and were statistically higher upon staining in wine compared to artificial aging (p < 0.05). Gloss values at T0 were 76.7-87.0. Beautifil exhibited the lowest gloss retention (50.8-60.2%) after staining, compared to > 90% of other materials (p < 0.05). ΔE00/ΔEab and ΔTP00/ΔTPab were positively correlated (p < 0.0001). CONCLUSIONS: Color, translucency, and gloss changes of gingiva-colored restorative materials were material- and staining/aging-dependent. Generally, wine caused greatest changes in color (with IvoBase CAD being the most color stable) and translucency parameter. All materials except Beautifil gingiva II exhibited staining- and aging-dependent gloss retention greater than 90% for all compared time intervals. CLINICAL RELEVANCE: Optical properties of resin-based gingiva-colored restorative materials depend on material, staining/aging conditions, and exposure time. Certain materials should be avoided in individuals with high consumption of red wine and coffee.

Color adjustment potential of resin composites: Optical illusion or physical reality, a comprehensive overview.

OBJECTIVE: The objective was to provide a comprehensive overview of color interactions between resin composite (RC) and its surroundings, analyze the design and results of respective research studies, and provide clinical and research recommendations. OVERVIEW: Resin composite (RC) materials can adjust their color to that of surrounding enamel and dentin to a different extent. This phenomenon has been referred to as the "chameleon effect" in dental jargon, while color blending/adjustment/shifting/assimilation is more scientific terms. Studies that evaluated the color adjustment potential of RCs have employed different methods. This article discusses the (a) terminology used to describe color adjustment potential, (b) color science theories associated with color adjustment, (c) design of respective studies, including methods, specimens, and calculations, and (d) their outcome and reported results. Clinical implications and future directions related to the color adjustment potential of RCs are also provided. CONCLUSIONS: Factors that influence the color adjustment potential of RCs are classified into three categories: (1) material type, (2) cavity design, and (3) the substrate surrounding the restoration. Each factor can be optimized to enhance color matching and the restorative outcome. CLINICAL SIGNIFICANCE: A material that blends well and exhibits pronounced color adjustment potential would likely improve the color match and therefore the esthetic outcome. These materials "work" for dental professionals by compensating for their suboptimal shade matching and/or lack of an excellent match in the used material. This review aims to further the understanding of the inherent properties of RCs and allow clinicians to fully utilize them to place RC restorations and minimize the time spent on modifying or replacing existing ones. Hence, the outcomes would encompass the increased chairside efficiency, enhanced esthetic outcome, and patient satisfaction.

Applications of artificial intelligence in dentistry: A comprehensive review.

OBJECTIVE: To perform a comprehensive review of the use of artificial intelligence (AI) and machine learning (ML) in dentistry, providing the community with a broad insight on the different advances that these technologies and tools have produced, paying special attention to the area of esthetic dentistry and color research. MATERIALS AND METHODS: The comprehensive review was conducted in MEDLINE/PubMed, Web of Science, and Scopus databases, for papers published in English language in the last 20 years. RESULTS: Out of 3871 eligible papers, 120 were included for final appraisal. Study methodologies included deep learning (DL; n = 76), fuzzy logic (FL; n = 12), and other ML techniques (n = 32), which were mainly applied to disease identification, image segmentation, image correction, and biomimetic color analysis and modeling. CONCLUSIONS: The insight provided by the present work has reported outstanding results in the design of high-performance decision support systems for the aforementioned areas. The future of digital dentistry goes through the design of integrated approaches providing personalized treatments to patients. In addition, esthetic dentistry can benefit from those advances by developing models allowing a complete characterization of tooth color, enhancing the accuracy of dental restorations. CLINICAL SIGNIFICANCE: The use of AI and ML has an increasing impact on the dental profession and is complementing the development of digital technologies and tools, with a wide application in treatment planning and esthetic dentistry procedures.

Effect of Staining and Aging on Translucency Parameter of CAD-CAM Materials.

OBJECTIVES: To evaluate different intervals of exposure to staining solutions and artificial aging on translucency parameter (TP00) of CAD-CAM materials. MATERIAL AND METHODS: One millimeter thick square-shaped specimens (N = 288) were cut from Cerasmart (CS), IPS e.max (IE), Lava Ultimate (LU), Shofu HC (SH), Vita Enamic (VE), and Vita Suprinity (VS) and were divided into laboratory and chairside polishing. Reflection wavelength spectra, CIE D65 standard illuminant, 2 ° standard observer, SCI, UV included, SAV aperture, 6 mm diameter, were recorded at 10 nm sensitivity against white and black calibration tiles using a benchtop spectrophotometer. Subsequently, they were converted into CIEDE 2000 TP00. After baseline measurements (T0), the specimens were divided as follows (n = 8): staining in coffee (C) and wine (W), for 60 (T1) and 120 hours (T2), and accelerated artificial aging (A). Artificial aging (ISO 4892-2 standard) was performed in two cycles of 150 KJ/m2, for T1 and T2, respectively. TP measurements were repeated at T1 and T2. Data of TP00 retention were submitted to analysis of variance and Fisher's PLSD multiple comparison test (α=0.05). RESULTS: Fisher's PLSD critical differences among materials, time intervals and staining/aging were 0.16, 0.11 and 0.11, respectively. SH showed the highest TP00 followed by LU > CS > IE = VS > VE. For all time intervals, the lowest TP00 retention was observed with C. W, and A presented similar values. CONCLUSIONS: Translucency Parameter was a time and staining/aging-dependent material. In majority of cases, it decreased upon staining/aging.

Colour stability of 3D-printed resin orthodontic brackets.

OBJECTIVE: To evaluate the colour stability of polymeric resins that could be used to 3D-print orthodontic brackets. DESIGN: In vitro, laboratory study. MATERIALS AND METHODS: Disc-shaped specimens were fabricated via 3D printing using three resins: Dental LT; Dental SG; and Clear. Five conditions were evaluated for each resin (n = 10 per treatment per resin) to assess its corresponding effect on colour and translucency: immersion in (1) red wine, (2) coffee, (3) tea and (4) distilled water (control), and (5) exposure to accelerated aging. Colour and translucency measurements were made before and after exposure using a spectrophotometer. Mean colour differences (ΔE00) and changes in translucency parameter (ΔTP00) were calculated for each sample using the CIEDE2000 colour difference formula. RESULTS: Statistically significant effects of the resin material, the treatment condition and interactions effects of material and condition were observed for ΔE00 and ΔTP00 (P < 0.001). The most pronounced changes in colour (ΔE00) were a result of the staining effects of wine on all three resins, ranging from 14.5 ± 0.6 to 20.8 ± 1.2. Dental LT, Dental SG and Clear resins all showed changes in colour when exposed to certain staining agents. Dental SG and Clear resins exhibited changes in colour with aging, while the colour of Dental LT resin remained stable with aging. CONCLUSIONS: The colour changes of the resins investigated does not support their use in 3D-printed aesthetic bracket applications.

Color compatibility between dental structures and three different types of ceramic systems.

BACKGROUND: To assess color compatibility between dental structures (human enamel and dentine) and three different types of ceramic systems. METHODS: Samples (1 and 2 mm-thick) of extracted tooth (containing dentine and enamel areas) and three ceramic systems with different shades and opacities (HT-High Translucent, T-Translucent) were prepared for this study: Vita Suprinity-VS (HT, T; A1, A2, A3, A3.5, B2, C2, D2) (Vita Zahnfabrik); Vita Enamic-VE (HT, T; 1M1, 1M2, 2M2, 3M2) (Vita Zahnfabrik) and Noritake Super Porcelain EX-3-NKT (A1, A2, A3, A3.5, B2, C2, D2) (Kuraray Noritake Dental). Reflectance measurements of all samples were performed over black backgrounds using a non-contact spectroradiometer (SpectraScan PR-670, Photo Research) under a CIE 45°/0° geometry. CIE L*a*b* color parameters were measured and CIELAB/CIEDE2000 color differences (ΔE00/ΔE*ab) and corresponding Coverage Error (CE) of ceramic system for dentine or enamel samples were calculated. Color data was analyzed using one-way ANOVA and post-hoc multiple comparisons tests. CE values were interpreted by comparisons with available 50:50% acceptability color threshold (AT) for dentistry. RESULTS: Statistically significant differences in lightness were found among all ceramic systems and human dentine (p < 0.001), while no significant differences were registered between enamel and VSHT, T and VEHT. 1 mm dentine showed no statistical differences with VST and VSHT for a* coordinate, while 2 mm dentine showed no significant differences (p > 0.05) with VEHT. Thin samples (1 mm) of dentine and enamel showed significant statistical differences (p < 0.05) for b* coordinate with less translucent materials (NKT, VET and VST). For dentine samples, none of the ceramic materials provided a CE lower than AT. VSHT provided the best CE for 1 mm-thick (CE00 = 1.7, CEab = 1.9) and for 2 mm-thick (CE00 = 2.3; CEab = 2.5) enamel samples. CONCLUSIONS: Color coordinates of evaluated esthetic ceramic systems were statistically different from those of human dentine in almost all cases. The evaluated ZrO2 lithium silicate glass-ceramic (VS), with its two levels of translucency, provided lower CE values with human enamel samples while conventional feldspathic ceramic (NKT) and hybrid ceramic systems (VE) demonstrated a better color compatibility with dentin samples.

Staining and aging-dependent changes in color of CAD-CAM materials.

STATEMENT OF PROBLEM: Consumption of some beverages and aging may affect the color of dental materials used in fixed prosthodontics, but their effect on recently introduced materials is not well known. PURPOSE: The purpose of this in vitro study was to evaluate staining, aging, and the exposure interval on color changes of computer-aided design and computer-aided manufacturing (CAD-CAM) resin nanoceramics (RNC), polymer-infiltrated ceramic-network (PICN) materials, and lithium silicate and lithium disilicate ceramics. MATERIAL AND METHODS: A total of 288 square-shaped, 1-mm-thick specimens prepared from Cerasmart, IPS e.max, Lava Ultimate, Shofu HC, Vita Enamic, and Vita Suprinity were polished by using laboratory and chairside methods in accordance with the manufacturers' instructions. Color data were recorded with a benchtop spectrophotometer, and CIEDE2000 color differences (ΔE00) were calculated. After the baseline measurements (T0), the specimens were divided into 3 groups (n=8) and exposed to staining in coffee and wine and to accelerated artificial aging. The specimens were stored in staining solutions at 37 °C for 60 (T1) and 120 hours (T2). Accelerated aging was performed by using a xenon lamp weathering test chamber for a total exposure of 150 (T1) and 300 kJ/m2 (T2). The results were analyzed by using the t test, ANOVA, and the Tukey honestly significant difference test (α=.05). Color differences of ΔE00 ≤0.8 and ≤1.8 corresponding to the 50:50% perceptibility threshold and 50:50% acceptability threshold were used to interpret the results. RESULTS: As color differences (ΔE00) between laboratory and chairside polishing were not statistically significant (T=-0.81, P=.418), only the results for chairside polished specimens were presented. Color differences for the T0-T1 comparisons ranged from 0.2 to 4.2, T0-T2 from 0.3 to 6.5, and T1-T2 from 0.1 to 2.3. ANOVA showed significance of factors and for interactions (P<.05). Lithium silicate-based and lithium disilicate-based ceramic materials were more color stable than RCN and PICN materials on exposure to coffee and red wine. Color changes greater than acceptability threshold after immersion in coffee were recorded for 3 (T0-T1), 4 (T0-T2), and 2 (T1-T2) materials. Corresponding findings after immersion in wine were 1, 3, and 0 and after artificial aging 0, 2, and 0. ΔE00 and ΔEab values were highly correlated (R2=0.97). CONCLUSIONS: No difference was found in color stability among laboratory and chairside polished specimens. Coffee caused the greatest color changes for T0-T2 interval. Staining-dependent color differences increased with increased exposure, except for IPS e.max and Vita Suprinity. For artificial aging, color change appeared to be material dependent.

Stainability of acrylic resin materials used in CAD-CAM and conventional complete dentures.

STATEMENT OF PROBLEM: The effect of staining beverages on the color of dentures made with computer-aided design and computer-aided manufacturing (CAD-CAM) is unknown. PURPOSE: The purpose of this in vitro study was to evaluate the stainability of acrylic resins used in CAD-CAM-fabricated complete dentures compared with conventional materials. MATERIAL AND METHODS: Acrylic resin denture teeth from 3 different manufacturers (2 conventional and 1 milled) were obtained (N=45). Denture base acrylic resin specimens were made with 3 different techniques (compression molding, injection molding, and milling) (N=45). Conventional and/or milled acrylic resins were used to make specimens comprising both denture teeth and denture base acrylic resins (4 conventional, 2 milled denture bases with bonded teeth, and 1 all-milled) (N=105). All specimens were then immersed in coffee, red wine, or distilled water as control. The CIELab color differences between before and after immersion were determined by using a VITA Easyshade spectrophotometer. The tooth-denture base interface of the denture blocks was evaluated visually for the presence of stain. The CIELab data were analyzed by using ANOVA, and chi-square test was used for visual assessment (α=.05). RESULTS: Significant interactions were found between each acrylic resin material and each staining solution immersion when compared with distilled water immersion (P<.001). Denture teeth had similar color change after immersion in coffee (P=.149), while the most pronounced color change was observed with Portrait teeth upon immersion in wine (P<.001). Injection-molded denture base specimens exhibited less color change upon staining in wine than compression-molded or milled specimens (P<.001). Upon staining in coffee, milled specimens were not significantly different from injection- (P=.053) and compression-molded specimens (P=.180). The chi-square test showed a significant association between processing technique and stain accumulation at the tooth-denture base interface when evaluated visually (P<.001). Stain accumulation was greatest with compression-molded specimens (58%), followed by injection-molded (43%) and milled specimens with bonded teeth (8%). Monolithic teeth with milled denture base had no stain deposits at the tooth-denture base interface. CONCLUSIONS: The stainability of milled acrylic resins was no better than that of conventional materials. However, CAD-CAM milled denture blocks with teeth and base acrylic resins had greater resistance to stain accumulation at the tooth-denture base interface than those of conventional processing methods.

Instrumental and visual evaluation of the color adjustment potential of resin composites.

OBJECTIVE: To evaluate the instrumental and visual color adjustment potential (CAP-I, CAP-V), of resin composites. METHODS: Resin composites tested were Omnichroma, Filtek Supreme Ultra, TPH Spectra, Herculite Ultra, and Tetric EvoCeram. Two types of specimens, "dual" and "single" were evaluated. For dual specimens, class I preparations (4 mm-diameter, 2 mm-depth), were created in denture teeth and restored with test resin composites. For single specimens, replications of denture teeth were created using the test resin composites (n = 5) and compared with unrestored denture teeth. Reflectance values were obtained using a spectroradiometer. CAP-I and CAP-V were calculated. Fisher PLSD intervals for comparison of means were calculated at the 0.05 level of significance. RESULTS: CAP-I ranged between 0.02 and 0.67. The Fisher PLSD interval for comparisons between single/dual color differences was 0.09 (P < .0001, power 1.0) and for comparisons between materials and shades 0.18 and 0.33, respectively (P < .0001, power 1.0). CAP-V ranged between 0.16 and 0.60. The Fisher PLSD interval for comparisons between single/dual visual color differences was 0.05 (P < .0001, power 1.0) and 0.08 and 0.14 for comparisons between materials and shades, respectively (P < .0001, except Herculite Ultra-Tetric EvoCeram and certain shade pairs). CONCLUSIONS: Instrumental color differences and visual rating of single specimens were the greatest for Omnichroma, indicating the largest mismatch, while the instrumental and visual color differences of dual specimens were the smallest. Omnichroma had the most pronounced CAP-I followed by Tetric EvoCeram>TPH Spectra = Filtek Supreme Ultra >Herculite Ultra. Similarly, Omnichroma exhibited the most pronounced CAP-V followed by Tetric EvoCeram>TPH Spectra = Herculite Ultra = Filtek Supreme Ultra. CLINICAL SIGNIFICANCE: Resin composites with pronounced CAP blends with surrounding enamel and dentin, resulting in reduced color differences and therefore improving the esthetic appearance of the restoration, simplifying the shade matching and compensating for any color mismatch.

Acceptability and perceptibility thresholds in dentistry: A comprehensive review of clinical and research applications.

OBJECTIVE: The objective was to provide a literature review on perceptibility and acceptability thresholds in dentistry and corresponding recommendations. OVERVIEW: A literature review on visual thresholds included findings on the judgments of the color and appearance of tooth-, gingiva- and skin-colored restorative dental materials. Discrepancies in study design contributed to inconsistencies in the research findings of some studies. These differences are related to (a) number of observers and inclusion criteria, (b) specimen number and size, (c) color measurement instrument and the setup and formulas used, (d) psychophysical experiment, (e) data processing (fitting method), and (f) % perceptibility or % acceptability values. A straightforward, consistent and practical model for the clinical and research application and interpretation of visual thresholds and recommended protocols for threshold research were provided. CONCLUSIONS: Visual thresholds are of paramount importance as a quality control tool and guide the evaluation and selection of dental materials and their clinical performance. Although clinical shade matching conditions and method are rarely controlled, research on visual thresholds, especially when aiming to set standards for the profession, must be carefully planned and executed. CLINICAL SIGNIFICANCE: Perceptibility and acceptability thresholds define visual match or mismatch of color, translucency, and whiteness in dentistry. Clinical and research findings cannot be fully interpreted in terms of real-life relevance without comparison with perceptibility and acceptability tolerances.