ΔE Mean Values Research Articles

Color stability and marginal adaptation of ceramic veneers cemented using different composite resins.

The purpose of this study was to compare the color stability and marginal adaption of lithium disilicate veneers before and after thermocycling using various resin composite materials employed as cement. Laminate veneer preparation was done on an acrylic tooth according to standardized procedures. The veneer preparations were duplicated into twenty-one dies. The veneers were fabricated from lithium disilicate using the CEREC in Lab system. According to the cement type, the twenty-one die specimens were randomly divided into three equal groups: group I, with light cured adhesive resin cement (N.=7), group II, with flowable light cured composite, and group III, with preheated nano filled composite. The cemented specimens underwent 5000 thermocycling cycles. Color was assessed using a reflective spectrophotometer. The vertical marginal gap, following cementation and thermocycling, was measured using a digital microscope. One-way ANOVA followed by Tukey's post-hoc test was used to statistically assess the data. After thermocycling, there was no statistically significant difference in ΔE among cement type groups for color stability (P=0.369). However, the preheated composite showed the lowest ΔE mean values. Within adhesive resin cement and flowable composite groups, marginal gap means values recorded after thermocycling were significantly higher than those after cementation (P=0.013 and P<0.001, respectively). Although preheated composite cement showed the highest marginal discrepancy, it would be the best choice regarding color stability.

Effect of Seashell and Eggshell Nanoparticles on Tooth Color Changes after Bleaching Using CIE L*C*H Color Space

BackgroundDemineralization of dental structures is one of the post-bleaching effects. Remineralizing agents are recommended to overcome this problem. Synthesis of biomaterials from natural sources rich in calcium remains a viable and more economical option. Post-remineralization discoloration caused by such materials could disappoint patients who prefer whiter teeth; therefore, the color changes caused by such materials should be a concern during selection of the remineralizing protocol after bleaching.AimThis study aimed to evaluate the effect of seashell and eggshell nanoparticles on tooth color changes after bleaching using CIE L*C*H color space.Materials and MethodsForty natural maxillary incisors were enrolled in this study. Teeth were divided into four groups according to the applied treatment, G1: seashells paste for 2 minutes, G2: eggshells paste for 2 minutes, G3: 2% NaF gel for 1minute, and G4: received no treatment (control), then all specimens were stored in artificial saliva for 24hrs. The color of the specimens was determined according to the CIE L*C*H color space using a spectrophotometer at baseline, after bleaching, and after remineralization. Colors were compared using the ΔL*, ΔC*, and ΔH* parameters as well as the total color difference (ΔE) after bleaching and remineralization.ResultsAfter bleaching; there was a statistically significant difference between the experimental groups for ∆C, ∆H, and ∆E. After remineralization, there was a statistically significant difference in the mean values of ΔL, ΔC, ΔH, and ΔE between groups, the lowest mean value of (ΔE) recorded with eggshells, followed by 2% NaF gel, then seashells, while the highest mean value of ΔE was recorded with the control group.ConclusionsAfter bleaching, nano-eggshells and 2% NaF maintained the post-bleaching color, indicating the recovery of the damaged enamel surface. Enamel treatment using seashells could negatively affect the effectiveness of whitening.

Effect of Different Bleaching Methods on Optical Behaviors of CAD/CAM Ceramics

Background: The present study aimed to survey the influence of two different bleaching techniques on changes of color, translucency, and whiteness of the four CAD/CAM materials. Methods: The monolithic blocks of Vita Suprinity, Vita Enamic, IPS e.max CAD, and Katana Zirconia were sectioned to discs with thickness of 2 mm (n=30 / each group). Samples from each type of ceramic were assigned to three subgroups: 1) the 40% hydrogen peroxide for 20 minutes; 2) the 16% carbamide peroxide for three hours/day for 2 weeks; and 3) the control. Then CIELab coordinates of each sample were evaluated before and after the intervention by a spectrophotometer. Final color change (ΔE), Whiteness (ΔWI D), and Translucency Parameter (ΔTP) were calculated. Two-way ANOVA test was adopted to analyze the data (α=0.05). Results: Type of ceramic, bleaching subgroups, and interaction between them had a statistically significant influence on mean values of ΔE, ΔWID. The influence of bleaching subgroup on the mean value of ΔTP was also significant (P&lt;0.001). Conclusions: Carbamide peroxide 16% for three hours/day and for two weeks caused the most considerable changes in final color, whiteness, and translucency of the all tested CAD/CAM materials. Maximum color change and whiteness were detected in the Vita Enamic, which were clinically unacceptable.

Influence of Light-curing Units on Surface Microhardness and Color Change of Composite Resins after Challenge

The aim of this study was to evaluate microhardness and color change (ΔE) of composite resins, light cured with different light emission diodes (LEDs) and submitted to artificial accelerated aging (AAA). Two composite resins with lucirin- TPO photoinitiator were selected: Tetric N-Ceram (Ivoclar Vivadent, A1) and Vit-l-escence (Ultradent, WO).A resin with the only camphorquinone photoinitiat or was chosen as a negative control: Filtek Z350XT (3M ESPE, WD). Disc-shaped specimens were prepared (5 mm diameter; 1.5 mm thick) and photopolymerized with an LED with one wavelength (Radii-Cal, SDI) or multiple wavelengths (Valo, Ultradent), for each composite resin (n = 10). Surface microhardness and color evaluations were performed immediately after specimen preparation and after AAA. Microhardness results were analyzed using Kruskal-Wallis and Mann-Whitney tests for multiple comparisons. To compare the evaluation of microhardness at different times, the Wilcoxon test was used. Mean values of ΔE, ΔL, Δa, and Δb were evaluated using two-way analysis of variance (ANOVA), and Tukey test for multiple comparisons (a = 0.05). Regarding microhardness, a statistically significant difference between the two LEDs was observed for Vit-lescence after AAA. When comparing composite resins that were light-cured with the same device, FiltekZ350XT obtained the greatest microhardness. All groups presented a statistically significant decrease in microhardness from the initial time to the AAA. Regarding ΔE, no statistically significant difference between the two LEDs was observed. When comparing composite resins, FiltekZ350XT showed the highest ΔE values. In general, an LED with multiple wavelengths influenced the microhardness of only one resin containing lucirin-TPO after AAA. The ΔE was more influenced by the composite resin than the LED device. The knowledge of composite resin with deficiencies in the polymerization mechanism could contribute to preventing restorations to become more susceptible to color change and reduction of the mechanical strength.

Shade Stability of Polymer-Infiltrated and Resin Nano Ceramics.

Background:The esthetics plays an increasingly significant role in today's dentistry.Objective:The objective was to investigate the shade stability of a polymer-infiltrated and a resin nano ceramic in comparison to a conventional feldspar ceramic and an acrylate polymer.Methods:20 specimens of each of the materials, CAD-Temp (CT), Mark II (M), VITA Enamic (VE) and Lava Ultimate (LU), were prepared using the standard method. These were divided into groups (n=5) and placed in the following stain solutions: Distilled water, coffee, Coca-Cola and red wine for 14 days. The shade of each specimen was measured before and after using a spectrophotometer (n=5). The data were analyzed using ANOVA and Tukey's test (p ≤ 0.05).Results:The largest ΔE mean values were observed in CT by Coca-Cola (4.38 ± 0.41), in M by coffee (5.95 ± 0.62), in VE (6.02 ± 0.78) and LU (8.61 ± 0.30) by red wine. LU had the largest and strongest overall shade differences (total score: SSC=16.95) and CT the least (SSC=8.74). Overall shade differences of VE (SSC=12.03) and M (SSC=12.48) were statistically indistinguishable. After 14 days, only Coca-Cola caused clinically relevant shade differences in CT (ΔE > 2.7); this was also caused by coffee, Coca-Cola and red wine in M and coffee and red wine in VE and LU.Conclusion:On average, VE showed fewer shade differences than LU. After 14 days of immersion, shade differences which exceeded the clinical acceptance threshold of ΔE=2.7 were shown by CT in Coca-Cola, by M in coffee, Coca-Cola and red wine, and by VE and LU in coffee and red wine.

THE EFFECT OF TEA AND COFFEE ON THE COLOR STABILITY OF BULK AND INCREMENTAL FILL RESIN COMPOSITE

Objective: Two types of tea and coffee were selected to examine the color stability of bulk fill and incremental fill resin composite after storage for one and seven days. Materials and methods: A total of 150 resin composite discs (Filtek™ Z350), bulk fill (Xtra-fil) and (Filtek bulk) were prepared using a cylindrical mold (2x4). Ten specimens of each restorative material were left in distilled water for one day to be used for baseline color assessment. Then each tested material where either placed in black coffee, black tea, lemon ice tea or coffee milk beverages for one day or seven days inside an incubator at 36±1 °C. The relative spectral reflectance of each specimen was assessed using a spectrophotometer after storage in these beverages. Results: Kruskal-Wallis statistical test showed that there is a statistically significant difference between the three tested restorative materials after storage for one day and after 7 days in all the storage beverages where (p < 0.05). At the two aging periods, Z350 showed the statistically significant highest ΔE, X-tra fil showed the lowest statistically significant ΔE, while there was no statistically significant difference in the mean values of ΔE of Filtek bulk and these two materials. Regarding the effect of storage beverages on each restorative material at the two storage periods, black tea caused the highest statistically significant ΔE, while coffee milk caused the lowest statistically significant ΔE in the three tested resin composite.

Influence of shade, curing mode, and aging on the color stability of resin cements

The color stability of resin cements is essential for aesthetic restorations. Aim: To evaluate the influence of shade and aging time on the color stability of two light-cured and two dual-cured resin cements. Methods: The CIE-Lab color parameters (n=6) were measured immediately after sample preparation and at 7, 30 and 90 days of aging in distilled water. The color difference (ΔE) was calculated and then analyzed by three-way ANOVA for repeated measures and Tukey's HSD test (α=0.05). Results: ΔE was higher for transparent resin colors, followed by dark and light colors. The mean values of ΔE were lower for both light-cured resin cements compared to the dual-cured cements. As the aging time increased, ΔE values increased. Conclusions: The light-cured resin cements showed greater color stability. The lighter shades of luting were more likely to display a greater color change.

Tooth discoloration induced by calcium-silicate-based pulp-capping materials.

Objectives:The aim of this study was to evaluate tooth discoloration induced by contact with various calcium silicate-based pulp capping materials in the presence or absence of blood in vitro.Materials and Methods:Eighty bovine samples were divided into six experimental groups and two control groups according to the type of material used (ProRoot [PR], Endocem [EC], or EndocemZr [ECZ]) and the presence or absence of contamination with blood. A spectrophotometer was used to calculate the color difference (ΔE) between the baseline measurement (after placement of materials) and measurements taken 1, 2, 4, and 8 weeks. The results were analyzed with repeated measures analysis of variance, Tukey's post-hoc tests and independent t-tests (P = 0.05).Results:The PR group and EC group showed significantly higher mean values of ΔE than the negative control group after 2 weeks (P < 0.05), whereas ECZ did not. There were larger ΔE values when there was contact with blood, especially in PR and EC group (P < 0.05).Conclusions:ECZ which contains zirconium oxide as a radiopacifier showed less discoloration irrespective of blood contamination compared to PR and EC.

Effect of staining agents on color change of composites

Composite resins are materials that can present color changing when exposed to pigments. Objective: The aim of this study was to evaluate, in vitro, the color changing of composites after immersion in different substances for different periods. Material and methods: Two microhybrid composite resins: Charisma (Heraeus – Kulzer) and Opallis (FGM) were used. Red wine and acai pulp were also used as immersion medium. For this study, 32 specimens with 10 mm of diameter and 2 mm of thickness were used, divided into 4 groups: Group 1 – Opallis composite immersed in red wine solution; Group 2 – Opallis composite immersed in acai berry pulp solution; Group 3 – Charisma composite immersed in red wine solution; Group 4 – Charisma composite immersed in acai berry pulp solution. The specimens were evaluated in the following time periods: T0 – baseline, T1 – 24 hours, T2 – 48 hours, T3 – 72 hours and T4 – 96 hours. For the assessment of staining, a spectrophotometer for colorimetry was used (Color Guide 45 / 0, PCB 6807 BYK-Gardner Gerestsried GmBH, Germany), and the values obtained were transferred to a computer and recorded according to CIELAB system. Results: The data were evaluated using Kruskal-Wallis non-parametric tests with the following ���ΔE mean values for � �the immersion periods of 24, 48, 72 and 96 hours, respectively: G1 – 7.35, 7.84, 9.04,10.48; G2 – 2.92, 4.15, 4.30, 4.64; G3 – 3.14, 7.35, 8.13, 8.43, G4 – 4.49, 5.99, 6.92, 6.76. Conclusion: Red wine showed a higher tendency toward altering the composite color than acai berry pulp. In addition, no significant difference was found concerning to the behavior of the two composite resins. Concerning to the immersion time periods, significant differences were only observed among the groups in the 24 hour time period.

Effect of the framework material on the final color of all-ceramic restorations

OBJECTIVES: to evaluate the effect of the type of ceramic framework material on the final color of all-ceramic restorations. The hypotheses tested were: (1) the final color of the restoration is different than the porcelain shade selected initially to veneer the framework and (2) different framework materials result in different colors of all-ceramic restorations. METHODS: Steel models simulating abutment teeth were used to design all-ceramic fixed partial dentures (FPDs). The FPDs were produced using three different framework materials (n=8): (YZ) yttria partially stabilized tetragonal zirconia polycrystal (LAVA, 3M); (IZ) glass-infiltrated alumina/zirconia (Vita In-Ceram Zirconia); (AL) polycrystalline alumina (Vita In-Ceram AL). Each framework was veneered with the recommended porcelain, VM9 for YZ and VM7 for IZ and AL groups (Vita). The porcelain shade used was 2M2. A uniform thickness of 1.2 mm of porcelain was applied around the retainers. The color difference (ΔE) and lightness difference (ΔL) between the selected porcelain shade (2M2) and the color of the final restoration were obtained using a clinical spectrophotometer (VITA Easyshade). Statistical analysis was performed using One-Way ANOVA and Tukey’s test (α=0.05). RESULTS: The ΔE mean values, standard deviation and statistical ranking for the experimental groups were: (YZ) 2.38 ± 0.44b; (IZ) 2.92 ± 0.67ab; (AL) 3.43 ± 0.84a. AL group showed the highest ΔE and ΔL mean values. IZ showed an intermediate ΔE value and statistically similar to AL and YZ groups. There was no significant difference between ΔL values for YZ and IZ groups. CONCLUSION: Although the color difference between all experimental groups and the porcelain shade selected to veneer the restorations could be visually detected (ΔE&gt;1.0), only AL showed a difference above the clinical threshold (ΔE&gt;3.0). Thus, the first study hypothesis was partially accepted. In addition, the type of framework ceramic influenced the final restoration color, accepting the second study hypothesis.

The effect of a coupling medium on color and translucency of CAD–CAM ceramics

ObjectivesTo evaluate color and translucency of ceramics and the influence of a coupling medium (G – glycerin) on these optical properties, testing the hypothesis that glycerin influences the translucency values regardless the evaluation method. MethodsFive specimens from A2-shaded ceramics (IPS e.max CAD HT and LT, IPS Empress CAD HT and LT, Paradigm C, and Vita Mark II) were fabricated from ceramic blocks and polished to 1.0±0.01mm in thickness. A spectrophotometer (Vita Easyshade) was used to measure the CIELAB coordinates and the reflectance value (Y) of specimens placed on white and black backgrounds. The translucency parameter (TP) and the contrast ratio (CR) were calculated. Another spectrophotometer (Lambda 20) was used to measure the direct light transmittance (T%) of the specimens. The color and the CIELAB coordinates were evaluated using the Vita Easyshade on neutral grey background and values were used to calculate difference in color (ΔE). All evaluations were repeated using G and values were recorded. Data were statistically analyzed using Anova, Tukey and Student's t-test (α=0.05) and Pearson's correlation. ResultsAlthough the mean translucency values were significantly different for each method (TP and CR), they were strongly correlated (r2=0.97), even when G was used (r2=0.96). ConclusionThe coupling medium significantly influenced the mean values of ΔE and translucency. Clinical significanceColor and translucency values cannot be compared if measured using different coupling media (e.g. air and liquid glycerin).

The effects of different shades of resin luting cement on the color of ceramic veneers

The purpose of this study was to quantitatively evaluate the effects of different shades of light-polymerized resin cement on the color of two different thicknesses (0.5 mm and 0.7 mm) of three different ceramic materials (Esthetic, e.max, and ZirPress). A spectrophotometer (Color Eye 7000A - CIE (L*a*b*) was used to measure the color of specimens on the control substrate without cement, and then on (Translucent, White Opaque, B0.5, A1, and A3 of RelyX™ Veneer cement). The mean values of color difference (ΔE) were higher for Esthetic, followed by ZirPress, with the lowest values for e.max. The mean values of ΔE decreased when the thickness of ceramic increased from 0.5 mm to 0.7 mm. It was observed that the White Opaque had significantly increased ΔE values when compared with (TR, B0.5, A1, and A3), whereas no significant difference between B0.5 and TR, and between B0.5 and A3.

Assessment of Color Parameters of Composite Resin Shade Guides Using Digital Imaging versus Colorimeter

This study evaluated the color parameters of resin composite shade guides determined using a colorimeter and digital imaging method. Four composite shade guides, namely: two nanohybrid (Grandio [Voco GmbH, Cuxhaven, Germany]; Premise [KerrHawe SA, Bioggio, Switzerland]) and two hybrid (Charisma [Heraeus Kulzer, GmbH & Co. KG, Hanau, Germany]; Filtek Z250 [3M ESPE, Seefeld, Germany]) were evaluated. Ten shade tabs were selected (A1, A2, A3, A3,5, A4, B1, B2, B3, C2, C3) from each shade guide. CIE Lab values were obtained using digital imaging and a colorimeter (ShadeEye NCC Dental Chroma Meter, Shofu Inc., Kyoto, Japan). The data were analyzed using two-way analysis of variance and Bonferroni post hoc test. Overall, the mean ΔE values from different composite pairs demonstrated statistically significant differences when evaluated with the colorimeter (p < 0.001) but there was no significant difference with the digital imaging method (p = 0.099). With both measurement methods in total, 80% of the shade guide pairs from different composites (97/120) showed color differences greater than 3.7 (moderately perceptible mismatch), and 49% (59/120) had obvious mismatch (ΔE > 6.8). For all shade pairs evaluated, the most significant shade mismatches were obtained between Grandio-Filtek Z250 (p = 0.021) and Filtek Z250-Premise (p = 0.01) regarding ΔE mean values, whereas the best shade match was between Grandio-Charisma (p = 0.255) regardless of the measurement method. The best color match (mean ΔE values) was recorded for A1, A2, and A3 shade pairs in both methods. When proper object-camera distance, digital camera settings, and suitable illumination conditions are provided, digital imaging method could be used in the assessment of color parameters. Interchanging use of shade guides from different composite systems should be avoided during color selection.