Effect of shade and opacity on color differences and translucency of resin composite veneers over lighter and darker substrates.

To evaluate color differences (ΔE00) and translucency parameters (TP) from mono, bi, and trilayer resin composite veneers using different opacities and shades of resin composite over lighter and darker simulated tooth-colored substrates. Mono, bi, and trilayer veneers (1.5 mm) (n = 12) were made using two shades (A1 and A2) and three opacities (enamel, body, and dentin) of resin composite over simulated lighter (A1) and darker (C4, and C4+) tooth-colored substrates. CIEDE2000 formula was used to calculate ΔE00 considering simulated tooth-colored substrate versus opacities in distinct mono, bi, and trilayer combinations of resin composite over the simulated tooth-colored substrate. The TP was calculated using color coordinates measured over standard white and black backgrounds. Differences in ΔE00 and TP values were calculated with a Three-way Analysis of Variance followed by Tukey's post-hoc test. A1E and A1B monolayer veneers showed similar TP values. Significantly higher ΔE00 values were observed over darker (C4 and C4+), and lower over lighter (A1) simulated tooth-colored substrate. Bilayer and trilayer veneers using dentin opacity provided similar ΔE00 values over the darker tooth-colored substrate. Distinct shades and opacities of resin composite layer combinations over lighter and darker tooth-colored substrates significantly affected TP and ΔE00 values. A1 shade and dentin opacity of monolayer resin composite veneers yielded higher ΔE00 values over darker tooth-colored substrates.

Optical properties of dental zirconia, bovine dentin, and enamel-dentin structures.

OBJECTIVE: To evaluate the optical properties and the relative translucency parameter of Ceramill ZI White (3Y-TZP) and Ceramill Zolid FX White (5Y-PSZ) zirconia ceramic systems and compare them with those of the bovine dentin and enamel/dentin structures. MATERIALS AND METHODS: 3Y-TZP and 5Y-PSZ zirconia ceramic systems were evaluated. A 0.5-mm-thick 3Y-TZP (3Y-NC.5), 0.5-mm-thick (5Y-NC.5), and 1.4-mm-thick (5Y-C.14) were used. A 0.5-mm-thick dentin specimens and 1.4-mm-thick enamel/dentin specimens (n = 5) were obtained from anterior bovine maxillary teeth. Scattering, absorption, transmittance, and albedo coefficient were calculated using Kubelka-Munk's model. Data were statistically analyzed using Kruskal-Wallis and Mann-Whitney tests (p < 0.001), and goodness-of-fit coefficient (GFC). Relative translucency parameter differences were evaluated using translucency thresholds. RESULTS: Reflectance, scattering, absorption, and transmittance properties were wavelength dependent. Good matches (GFC ≥ 0.999) in spectral reflectance were observed between 0.5-mm-thick dentin and 1.4-mm-thick enamel/dentin, and 3Y-NC.5 and 5Y-NC.5. Scattering was the main optical extinction process during light interaction with zirconia and dental structures, as indicated by albedo coefficient. Translucency differences were acceptable only for 3Y-NC.5 and the dentin structure, and 5Y-C.14 and the enamel/dentin structure. CONCLUSIONS: Optical properties of 3Y-TZP and 5Y-PSZ dental zirconia differed from each other and from bovine dental structures. Nevertheless, 3Y-TZP showed similar relative translucency parameter to bovine dentin. CLINICAL SIGNIFICANCE: To achieve the best esthetic results in restorative dentistry, it is crucial for clinicians to know about the optical properties of 3Y-TZP and 5Y-PSZ and to be able to compare these properties with those of dental structures.

Effect of coffee staining and simulated oral hygiene methods on the color and translucency of a nanoceramic resin.

OBJECTIVE: Evaluate the color and translucency of a nanoceramic resin subjected to hygiene practices and immersion in coffee over time. MATERIALS AND METHODS: Specimens (n = 80, HT and LT, 0.5-mm thick) of a nanoceramic resin were obtained and were divided in groups according to the simulated oral hygiene: no intervention (NT), brushing with an electric brush and water (BN), brushing with an electric brush and toothpaste for 10 s (BT), and immersion in mouthwash for 30 s (MW). Oral hygiene practices were repeated after staining in coffee solution for 15, 48, 336, 1440, 8640, and 35,040 min. Spectral wavelengths were recorded with a spectrophotometer at each time. ∆E00, ∆L', ∆C', ∆H', and TP00 were calculated by CIEDE2000 and were evaluated by 2-way ANOVA, repeated measures ANOVA, and Tukey's HSD test (α = 0.05). RESULTS: ANOVA showed significance among factors for ΔE00 (p < 0.05), with higher ΔE00 for NT-HT (11.7) and NT-LT (11.2). After T6 (2-year simulation), the lowest values were found for BT-HT (5.3) and BT-LT (4.9). All groups showed a reduction in lightness and translucency and increased chroma and hue. However, the smallest variations were found in the BT groups (p < 0.05). CONCLUSIONS: Brushing with toothpaste effectively minimized the color change of NCRs caused by coffee staining. CLINICAL SIGNIFICANCE: Oral hygiene practices, such as brushing with toothpaste, might be important to minimize staining of nanoceramic resin restorations, especially in patients who frequently consume coffee.

Translucency of bulk-fill composite materials: A systematic review.

OBJECTIVES: To conduct a systematic review on the translucency of bulk-fill (BF) composite materials, evaluating the factors influencing it and its clinical implications. MATERIALS AND METHODS: A systematic search was performed on four databases (Embase, Medline/PubMed, Scopus, and Web of Science) for articles published until October 2, 2023. Search terms were: "translucency," "translucency parameter," "contrast," "contrast ratio," "bulk," "bulk-fill," "bulk fill," "composite," "resin," "resin based," "resin-based," "restoration," and "dental." In vitro studies, written in English language, investigating BF resin-based composites translucency were included. The risk of bias was performed with the RoBDEMAT tool. RESULTS: Of 590 screened articles, 13 were included in this review. They investigated 11 high-viscosity BF and 5 low viscosity ones. The limited number of the identified studies and the heterogeneity of the extracted data did not allow to conduct a meta-analysis. CONCLUSIONS: BF materials exhibit variability in translucency due to variations in experimental designs and the heterogeneous composition. CLINICAL SIGNIFICANCE: BFs may behave differently in masking the substrate or in blending capacity.

Effect of aging and fiber-reinforcement on color stability, translucency, and microhardness of single-shade resin composites versus multi-shade resin composite.

OBJECTIVE: The purpose of this study was to evaluate the effect of aging and fiber-reinforcement on the color stability, translucency, and microhardness of single-shade resin composites versus multi-shade resin composite. MATERIALS AND METHODS: Four resin composites (Filtek Z250, Omnichroma, Vittra APS Unique, Zenchroma) were tested. Three subgroups of specimens were prepared for each of the composites: control, polyethylene fiber-reinforcement, and glass fiber-reinforcement- groups (n = 10/per group). The samples were subjected to aging for 10,000 thermal cycles. Color differences (ΔE00 ) were calculated after aging. Relative translucency parameter (RTP00 ) and microhardness values were calculated before and after aging. A two-way analysis of variance and the generalized linear model was used (p < 0.05). RESULTS: The lowest and highest ΔE00 values were found for Filtek Z250 (0.6 ± 0.2) and Omnichroma resin composites (1.6 ± 0.4), respectively. The ΔE00 value of the polyethylene fiber-reinforcement group (1.2 ± 0.6) was significantly higher than the ΔE00 value of the glass fiber-reinforcement group (1.0 ± 0.4, p < 0.001). The RTP00 value of the glass fiber-reinforcement group (1.92 ± 0.78) was significantly higher than the RTP00 value of the polyethylene fiber-reinforcement group (1.72 ± 0.77, p < 0.001). The highest microhardness values were found in glass fiber-reinforcement group (76.48 ± 17.07, p < 0.001). CONCLUSION: Single-shade resin composites were more translucent, had higher color change, and lower hardness than multi-shade resin composite. For relative translucency and microhardness, statistical significance was found in the material and fiber type interaction. The glass fiber-reinforcement provided higher translucency, lower color change and higher microhardness values than polyethylene fiber-reinforcement group after aging. Thermocycling had a significant impact on the color stability, translucency parameter, and microhardness of the tested resin composite materials. CLINICAL SIGNIFICANCE: Single-shade resin composite materials have greater color-changing potential. The glass fiber-reinforcement optimize resin material mechanical properties and color stability more than polyethylene fiber-reinforcement.

Effect of artificial aging on optical properties and crystalline structure of high-translucency zirconia.

PURPOSE: To investigate the effect of different in vitro aging protocols on the optical properties and crystalline structure of high-translucency (HT) zirconia. MATERIALS AND METHODS: Thirty-six specimens of HT and extra-high translucency (XT) zirconia were divided into three groups: control (CO)-no treatment; hydrothermal aging (HA)-autoclave aging for 12.5 h at 134°C, 2 bar; clinically related aging (CRA)-aging in the chewing simulator for 1.2 million cycles, followed by 50,000 thermocycles (5-55°C) and immersion in HCl (pH 1.2) for 15 h. Optical properties, crystalline structure, and surface roughness were analyzed and compared using analysis of variance (5% significance level). RESULTS: There was no statistically significant effect of aging on translucency (p = 0.10), but CRA promoted the development of a high contrast ratio (p = 0.03). Aging did not cause significant color changes for HT (p = 0.65) or XT (p = 0.36). The proportion of monoclinic crystals increased to 40% for HT-zirconia after HA and 5% after CRA. No monoclinic crystals were detected for XT groups. There was no effect of aging on surface roughness (p = 0.77). CONCLUSIONS: Although hydrothermal aging has been widely used to verify zirconia crystalline stability, it did not generate an effect similar to clinically related aging on the optical properties and crystalline structure of zirconia. HA affected the crystalline structure of HT-zirconia, and CRA compromised the optical properties of XT zirconia.

Effect of thickness on color and translucency of a multi-color polymer-infiltrated ceramic-network material.

OBJECTIVES: To evaluate the effect of thickness on color and translucency of a multi-color polymer-infiltrated ceramic-network (PICN) material. METHODS: Specimens of 0.5, 1.0, 1.5 mm thicknesses were obtained by sectioning VITA ENAMIC® multiColor (E-MC) High Translucent CAD-CAM blocks (1M1-HT, 1M2-HT, 2M2-HT, 3M2-HT, and 4M2-HT). Spectral reflectance and color coordinates were measured on white and black backgrounds using a spectroradiometer, CIE D65 illuminant and CIE 45°/0° geometry. CIEDE2000 color and translucency differences (ΔE00 and ΔTP00 ) between thicknesses and adjacent layers were evaluated using their respective 50:50% perceptibility and acceptability thresholds (PT00 and AT00 ). RESULTS: In general, ΔE00 between thicknesses for all shades and layers were above AT00 in general. Chroma decreased from cervical to incisal layers with statistically significant differences (p < 0.05), and ΔE00 between sequential layers were above PT00 , for all shades and thicknesses. TP00 decreased from 0.5 to 1.5 mm and increased from cervical to incisal layers for all shades with statically significant translucency differences (p < 0.05). In general, for all thicknesses, TPT00 < ΔTP00 < TAT00 for sequential layers. CONCLUSIONS: The gradient in color and translucency of E-MC PICN material was influenced by the thickness of the CAD-CAM block. In addition, color and TP transition values between the layers depends on the thickness and shade. CLINICAL SIGNIFICANCE: The effect of thickness must be taken into account by dental technicians and dentists when CAD-CAM multicolor PICN materials are used.

Effect of thickness on color appearance of multilayer CAD/CAM composite resin blocks.

The aim of this study was to evaluate the effect of thickness on the color appearance and translucency parameter (TP) of multilayer CAD/CAM composite resin blocks. Four brands of A3-shade multilayer CAD/CAM composite resin blocks were examined (Katana Avencia, CERASMART Multi, KZR-CAD HR Block 4 E-va, and Block HC Hard AN). Six specimens of five thicknesses were prepared for each brand, yielding 120 specimens in total. CIEL*a*b* values were determined using a spectrophotometer against black and white backgrounds, and the TP was calculated. The color differences (ΔE00) between layers (cervical/middle/incisal) and brands for each thickness against the black background were calculated using the CIEDE2000 system. As a result, on the black background, L* of the incisal layer was greater while a* and b* were smaller than those of the cervical layer for all brands. The ΔE00 values between the cervical and middle layers (1.23-3.27) were smaller than those between the cervical and incisal layers (3.98-5.67) and those between the middle and incisal layers (3.14-5.92). TP decreased with increasing block thickness. Some TP differences between layers were significant, but they were less than 2.75. In conclusion, the color appearance of CAD/CAM blocks was significantly influenced by both the thickness and layer. L*a*b* decreased with thickness, and a negative exponential relationship between TP and thickness was observed for all layers and brands.

Influence of Arabic Qahwa Beverage on Optical and Mechanical Properties of Lithium Disilicate Glass Ceramics and Zirconia Restorative Materials.

AIMS: The study aims to assess the effect of Arabic Qahwa (AQ) on the color parameters of lithium disilicate glass ceramic (LDGC), IPS e.max computer-aided design (CAD), and multilayered zirconia CAD/ computer-aided manufacturing (CAM) ceramic materials after immersion in AQ and also, to measure the biaxial fracture strength and fracture modes of the tested materials. MATERIALS AND METHODS: Sixty circular specimens were milled from LDGC and zirconia. Before AQ immersion, the color parameters of the specimens L, a, and b were measured and recorded using a spectrophotometer on white, black, and gray background and analyzed after AQ staining and aging for 14 days. Biaxial compressive forces and fracture types were recorded. The collected data were analyzed with SPSS for descriptive statistics, one-way analysis of variance, and post hoc tests. RESULTS: The overall TP values were 16.79 and 15.85 for LDGC and zirconia, respectively. The recorded ΔE* values were 2.63 and 2.99 for LDGC and zirconia, which have no remarkable difference. The TP values after AQ staining were slightly lesser. Subgroup analysis revealed considerable differences in TP values among zirconia specimens under both backgrounds, whereas substantial differences in ΔE* values were observed between LDGC and zirconia under white background only. Lithium disilicate glass ceramic (LDGC) had higher biaxial fracture forces than zirconia. Reparable, semi-reparable, and non-reparable fractures comprised 60, 30, and 10% of the overall fracture modes, respectively, with significant differences between and within groups (p = 0.034). CONCLUSION: AQ staining had a marked effect on the TP and ΔE* values of the tested CAD/CAM materials, but the values were within clinically acceptable levels. The optical properties were dependent on the material. Lithium disilicate glass ceramic (LDGC) had higher biaxial fracture forces than zirconia. Reparable fracture was the dominant type among the examined materials. CLINICAL SIGNIFICANCE: Glazed surface for any CAD/CAM ceramic prostheses is highly recommended. Both tested materials are strongly recommended to be used for AQ consumers.

Effect of different polymerization times on color change, translucency parameter, and surface hardness of bulk-fill resin composites.

Background: Polymerization plays an important role in the optical and mechanical properties resin composite materials. Aim: The current study aimed to evaluate the effect of different polymerization times on the color change, translucency parameter (TP), and surface hardness of resin composites after thermocycling. Materials and Methods: Microhybrid resin composite (Filtek Z250; used in the control group) and bulk-fill resin composites (Filtek One Bulk-Fill Restorative, Tetric EvoCeram Bulk-Fill, and Tetric N-Ceram Bulk-Fill) were used. Each bulk-fill composite was placed as a single layer. Polymerization of the bulk-fill composites in the first group was completed in 20 s, and that in the second group was completed in 40 s (n = 10). Filtek Z250's polymerization was completed with 2 mm (20 s) + 2 mm (20 s). The color change (ΔE00) and translucency parameter (TP00) were calculated using the CIEDE2000 formula. Before and after thermocycling, the TP and surface hardness values were measured. The data were analyzed using one- and two-way analysis of variance, paired-samples t-test, and Tukey's test (P < 0.05). Results: After thermocycling, the ΔE00 values of the resin composite samples were 1.66-2.56. Compared to the control group, the Filtek One Bulk-Fill 20 s group exhibited the lowest color change values. The Filtek Z250 group exhibited lower TP and significantly higher microhardness values than the other bulk-fill resin groups before and after thermocycling (P < 0.05). There were no observed differences in the Tetric N-Ceram and Tetric EvoCeram groups before and after thermocycling. Conclusion: Under the conditions of 10,000 thermal cycles, different curing times did not affect the color change and hardness values of the bulk-fill materials. However, differences were observed among the composite materials. After thermocycling, the surface hardness and TP values decreased in all the resin composites. Depending on the material content, effective results can be obtained from the 20 s polymerization of bulk-fill resin composites.

Effect of different fabrication steps on color and translucency of a CAD-CAM feldspathic ceramic.

OBJECTIVE: To evaluate color differences (ΔE) of different fabrication steps performed on a feldspathic ceramic and relative translucency parameter (RTP) after glazing; and to evaluate their effects on the color parameters: L*, a* and b*. MATERIAL AND METHODS: Computer-aided design/computer-aided manufacturing (CAD-CAM) feldspathic maxillary right central incisor ceramic crowns (Cerec Blocs; 1.4 mm thickness) were fabricated through scanning a model preparation and milling. A total of 20 specimens were used and different parameters were compared with each other for color difference (ΔE): original block, milling, polishing, glazing and try-in cements; RTP was measured after glazing. Color parameters (L*, a*, and b*) were evaluated after each step with a spectrophotometer (Vita Easyshade V) and compared using the CIEDE2000 formula. Statistical analyses were done using one-way ANOVA and post-hoc tests. RESULTS: The highest ΔE value was observed for Original versus Milling group (4.73) and the lowest for Polishing versus Glazing (0.49). RTP after glazing presented a value of 12.01. L*, a*, and b* parameters were different among groups. Milling group was the one that presented more differences compared to the Original block regarding L*, a*, and b* parameters. CONCLUSIONS: Different fabrication steps resulted in perceptible color differences within themselves, and L*, a*, and b* parameters changed according to each step. All milling specimens presented unacceptable color differences when compared to the other steps, and milling specimens showed all color parameters (L*, a*, and b*) statistically different compared to the Original block. A high RTP value was observed, demonstrating that, at 1.4 mm thickness, the feldspathic ceramic presented high translucency, showing that opacification of substrate might be necessary. CLINICAL SIGNIFICANCE: Different fabrication steps can greatly affect the optical properties of the feldspathic ceramic restoration studied and cause a relevant impact when compared to the ceramic block itself. Crowns evaluated right after milling presented the highest color differences. In order to obtain optical properties as close as possible to the original feldspathic ceramic block, either polishing or polishing and glazing needs to be performed.

How will surface conditioning methods influence the translucency and color properties of CAD-CAM resin-matrix ceramics with different thicknesses?

OBJECTIVE: It was aimed to evaluate the effect of various surface-conditioning methods on the translucency and color properties of resin-matrix ceramics (RMCs) with different types and thicknesses. MATERIALS AND METHODS: Rectangle-shaped RMCs were prepared from Voco Grandio, Brilliant Crios, Lava Ultimate, GC Cerasmart, and Vita Enamic blocks at 0.5 and 1.0 mm thicknesses. Specimens were divided into four groups: control, airborne-particle abrasion (APA), 2 and 3 W Er, Cr:YSGG laser irradiations (L2W , L3W ) (n = 15). The color values of specimens were recorded before and after surface-conditioning using a spectrophotometer. The translucency parameter (RTP00 ) and color difference (ΔE00 ) values were calculated. Data were statistically analyzed using three-way ANOVA and Tukey post hoc tests. RESULTS: The translucencies of RMCs decreased after all surface-conditioning procedures. L caused more decline in translucency of materials than APA. All ΔE00 values were under the acceptability threshold except for APA-applied Voco Grandio at 0.5 mm. Differences in ΔE00 values between APA and L3W groups were significant (P˂0.05); while differences between L2W and L3W groups were insignificant (P > .05). In all experimental groups, ΔE00 values decreased with increasing thickness of RMCs. CONCLUSIONS: L and APA significantly affected the translucency and color properties of RMCs. APA was found more favorable than L. CLINICAL SIGNIFICANCE: Clinicians should carefully use surface conditioning methods, considering their impact on the optical characteristics of RMCs, especially when the restoration is thin.

Effect of shade and sintering temperature on the translucency parameter of a novel multi-layered monolithic zirconia in different thicknesses.

OBJECTIVE: The objective of the present research was to evaluate the effect of sintering temperatures (1350°C, 1450°C, and 1600°C) of a novel multi-layered esthetic zirconia material (Katana 12Z/STML) on the grain sizes and on the translucency parameters (TP00 ) for 2 different shades (A2-A3) and 2 different thicknesses (1-1.5 mm). MATERIAL AND METHODS: A total of 120 non-sintered specimens were randomly divided into three subgroups according to sintering temperatures. The TP00 and grain sizes of the sintered specimens were calculated. Statistical analyses were performed using 3-way ANOVA, 1-way ANOVA, and Tukey's post hoc tests. RESULTS: TP00 increased 1.2 to 1.5 times as the specimen thickness decreased from 1.5 to 1 mm (P ≤ .05). The lowest TP00 values were recorded for sintering at 1350°C for the investigated thicknesses and shades (P ≤ .05). The interaction of sintering temperature and shade was significant (P ≤ .05). Grain sizes were ordered according to sintering temperature as 1350°C < 1450°C < 1600°C (P ≤ .05). CONCLUSIONS: TP00 values decreased with the increase in the thickness of the monolithic zirconia. The sintering temperatures and their interaction with shade significantly affected TP00 values. The grain size increased with increasing sintering temperature. CLINICAL SIGNIFICANCE: The translucency of a novel multi-layered monolithic zirconia increased with higher sintering temperatures and lower thickness. The grain size increased with the increase in the sintering temperature. The sintering temperature of 1600°C led to a significant change in translucency for shade A3.

Does the Translucency of Novel Monolithic CAD/CAM Materials Affect Resin Cement Polymerization with Different Curing Modes?

PURPOSE: The translucency of CAD/CAM blocks influences the polymerization efficiency of resin cement used underneath. The aim of this study is to evaluate the influence of the translucency parameters (TPs) of current monolithic CAD/CAM blocks on the microhardness of light-cured or dual-cured resin cement. MATERIALS AND METHODS: 100 specimens were prepared from five types of CAD/CAM blocks (Mark II, Suprinity, Enamic, e.max, Ultimate), and their TP values were measured by spectrophotometry; 100 resin cement specimens (Duolink) were cured underneath five ceramic specimen groups by indirect LED light for 40 seconds with dual-cure (with catalyst) and light-cure (without catalyst) polymerization modes. Control group resin cement specimens (n = 20) were cured with both polymerization modes by direct LED light without any ceramic disc, making 120 resin cement specimens in total. The specimens were then stored in a dry environment for 24 hours before measurement of the polymerization depth with a digital micrometer. Vickers hardness measurements were performed at different resin cement sections. The results were statistically analyzed with 1-, 2-, and 3-way ANOVA, Student's t-test and Tukey's HSD test (α = 0.05). RESULTS: The highest TP values occurred for Suprinity and Ultimate, whereas the lowest TP value occurred for Enamic (p < 0.01). The depth of cure and Vickers hardness values changed proportionally with TP value. In all specimens, dual polymerization provided higher depth of cure and Vickers hardness values than those obtained using light polymerization (p < 0.01). In all specimens except Enamic, the hardness value differences between the sections were statistically insignificant (p > 0.05). In Enamic, the hardness values for both polymerization types decreased significantly in the deeper sections (p < 0.01). CONCLUSIONS: Lower depth of cure was observed as the amount of transmitted light decreased in the investigated materials. In clinical practice, light-cured resin cements may result in inadequate polymerization for ceramic materials with lower TP values. Zirconia-reinforced lithium silicate and nanoceramic resins may be reliable restorative materials for a restoration with both optimal esthetics and sufficient mechanical strength resulting from proper polymerization.

Translucency of Zirconia Ceramics before and after Artificial Aging.

PURPOSE: The aging of zirconia ceramics (Y-TZP) is associated with tetragonal to monoclinic phase transformation. This change in microstructure may affect the optical properties of the ceramic. This study examines the effect of aging on the translucency of different zirconia materials. MATERIALS AND METHODS: 120 disc-shaped specimens were fabricated from four zirconia materials: Cercon ht white, BruxZir Solid Zirconia, Zenostar T0, Lava Plus (n = 30 per group). Accelerated aging was performed in a steam autoclave (134°C, 0.2 MPa, 5 hours). CIELab coordinates (L*, a*, b*) and luminous reflectance (Y) were measured with a spectrophotometer before and after aging. Contrast ratio (CR) and translucency parameter (TP) were calculated from the L*, a*, b*, and Y tristimulus values. The general linear model (Bonferroni adjusted) was used to compare both parameters before and after aging, as well as between the different zirconia materials (p ≤ 0.05). RESULTS: CR and TP differed significantly before and after aging in all groups tested. Before aging, Zenostar T showed the highest and Lava Plus showed the lowest translucency. After aging, Cercon ht and Zenostar T showed the highest and BruxZir and Lava Plus the lowest translucency. CONCLUSIONS: Aging reduced the translucency in all specimens tested. Furthermore, translucency differed between the zirconia brands tested. Nevertheless, the differences were below the detectability threshold of the human eye. The aging process can influence the translucency and thus the esthetic outcome of zirconia restorations; however, the changes in translucency were minimal and probably undetectable by the human eye.

The Effect of Surface Treatments on the Mechanical and Optical Behaviors of CAD/CAM Restorative Materials.

PURPOSE: To evaluate the effect of different surface treatments on mechanical and optical properties of lithium disilicate ceramic (IPS e.max CAD), 2 resin nanoceramics (Lava Ultimate, GC Cerasmart), and polymer-infiltrated ceramic network material (Vita Enamic). MATERIALS AND METHODS: CAD/CAM blocks were sectioned into 4 × 1 × 14 mm3 bars for three-point bending test and 1 × 8 × 8 mm3 square specimens were obtained for color and translucency measurements. Bar-shaped and square specimens were divided into five groups according to the surface treatment method as: control (no treatment), hydrofluoric acid etching, airborne-particle abrasion, 2 W and 3 W Er,Cr:YSGG laser irradiation (n = 10). Three-point bending test was carried out on a universal test machine with a 1 mm/min crosshead speed. Color and translucency measurements were performed with a spectrophotometer and repeated after surface treatments. Flexural strength, translucency parameter, and ΔE values were calculated and data were statistically analyzed using one-way ANOVA and Bonferroni post hoc tests. ΔE values >1.2 and >2.7 were considered as perceptible and unacceptable, respectively. RESULTS: All surface treatment methods decreased the flexural strength of all tested materials (P < 0.05) except for 2 W laser-irradiated and airborne-particle abraded Vita Enamic and 2 W laser irradiated Lava Ultimate (P > 0.05). Color changes of lithium disilicate specimens were not perceptible except for airborne-particle abraded specimens. All ΔE values of resin-based materials were above the perceptibility threshold. Acid-etched and 3 W laser-irradiated GC Vita Enamic specimens revealed unacceptable color changes. The translucencies of resin-based materials significantly decreased after all surface treatment applications. CONCLUSIONS: Surface treatments affected the flexural strength and optical properties of CAD/CAM restorative materials. Er,Cr:YSGG laser irradiation with 2 W energy level may be an alternative surface treatment method for CAD/CAM materials.

How light attenuation and filler content affect the microhardness and polymerization shrinkage and translucency of bulk-fill composites?

OBJECTIVES: The purpose of this study was to investigate the microhardness, polymerization shrinkage, and translucency of bulk-fill composites (BFCs) which have different light attenuation properties and filler contents. MATERIALS AND METHODS: Five BFCs [Filtek Bulk Fill (FB), SureFil SDR (SS), Venus Bulk Fill (VB), SonicFill (SF), and Tetric N-Ceram Bulk Fill (TB)] and two resin-based composites (RBCs) [Tetric N-Ceram (TN) and Filtek Z350XT Flowable (ZF)] were chosen. Numbers of transmitted photons, refractive index, microhardness at different thicknesses, polymerization shrinkage, and translucency parameter (TP) were evaluated. RESULTS: Attenuation coefficients (ACs) based on measured photons ranged from -0.88 to -1.90. BFCs, except SF, had lower AC values than TN or ZF, and BFCs, except TN, had smaller refractive index decreases between top and bottom surfaces. Regardless of an exponential decrease in photon counts, microhardness decreased linearly as specimen thickens. Moreover, microhardness of BFCs showed smaller top-to-bottom decreases (11.5-48.8 %) than TN or ZF (57.3 and 71.5 %, respectively). BFCs with low filler contents showed lower microhardness and higher polymerization shrinkage than those of high filler contents. Also, BFCs had significantly higher (p < 0.001) TP values than TN or ZF. CONCLUSION: BFCs attenuated light less than RBCs. However, some BFCs had much lower top surface microhardness and higher polymerization shrinkage than tested RBCs. CLINICAL RELEVANCE: Despite the convenience of bulk filling, careful selection of BFC is advised because some BFCs have worse microhardness and polymerization shrinkage than RBCs due to their lower filler contents.

Effect of shade, opacity and layer thickness on light transmission through a nano-hybrid dental composite during curing.

OBJECTIVE: The aim of this study was to investigate the effect of shade and opacity on the change in light transmission through different thicknesses of a nano-hybrid composite during curing. MATERIALS AND METHODS: Twelve different shades of Venus Diamond (Heraeus Kulzer) were placed in disk shaped molds with thickness of 1, 2, and 3 mm (n = 3 per group) and cured with an LED light-curing unit. Initial, final and average irradiance, and the total amount of energy passing through the specimen were measured using the MARC Resin Calibrator at every 10s for a total of 40s. The translucency parameter and the contrast ratio were obtained using a chromameter. Results were analyzed with ANOVA/Tukey's test (α = 0.05). RESULTS: All shades and all thicknesses (up to 3 mm) experienced an increase in light transmittance during curing. The majority of the increase occurred during the initial 10s exposure, with significant increase occurring from subsequent exposures only in thicker specimens (i.e., 3 mm). The increase in irradiance at the bottom during curing was dependent on shade, with darker shades and greater depths of material showing less increase. CONCLUSIONS: For one specific resin composite formulation, an increase in translucency occurs as cure progresses, and the increase is enhanced for composites with greater lightness and lower contrast ratio. CLINICAL SIGNIFICANCE: Composites demonstrate increased light transmittance as curing progress, which may improve depth of cure. The thicker composite showed the least increase in light transmission within the same shade. The increase in translucency is enhanced for composites with great lightness and lower contrast ratio.

Relative Translucency of a Multilayered Ultratranslucent Zirconia Material.

AIM: The aim of this study was to compare the translucency parameter (TP) of ultratranslucent multilayered (UTML) zirconia according to thickness and layer level. MATERIALS AND METHODS: Rectangles of UTML zirconia with four layers [dentin layer (DEL), first transitional layer (FTL), second transitional layer (STL), and enamel layer (ENL)] and four different thicknesses (0.4, 0.6, 0.8, and 1 mm) were milled from blanks. Digital images were taken in a dark studio against white and black backgrounds under simulated daylight illumination and international commission on illumination (CIE) Lab* color values recorded using Photoshop Creative Cloud software. The TP was computed and compared according to thickness and layer level using analysis of variance (ANOVA) followed by Bonferroni post hoc analysis for multiple comparisons. Significance was set at p < 0.05. RESULTS: In each thickness, TP values were similar between any two layers. The significant effect of thickness on the TP was observed only in the first two layers. In the DEL, translucency was significantly greater at 0.4 mm than all other thicknesses. In the FTL, differences were significant between 0.4 and 0.8 mm and between 0.4 and 1 mm. CONCLUSION: The investigated zirconia does not seem to show gradational changes in relative translucency from dentin to enamel levels regardless of the thickness used. Thickness affected the TP only in the first two layers with better translu-cency at 0.4 mm. CLINICAL SIGNIFICANCE: Since relative translucency does not seem to be significantly different between layers, clinicians can modify the apicocoronal positioning of the UTML layers within the restoration according to the desired Chroma without any implications on the clinically perceived translucency. While the thickness of 0.4 mm may be suggested for anterior esthetic veneers because of its higher translucency, the other thicknesses of 0.6 to 1 mm can be used to mask colored abutments in full contour restorations.

The Effect of Core and Veneering Design on the Optical Properties of Polyether Ether Ketone.

This study aimed to evaluate the effect of core shade and core and veneering thickness on color parameters and translucency of polyether ether ketone (PEEK). Sixty PEEK discs (0.5 and 1 mm in thickness) with white and dentine shades were veneered with A2 shade indirect composite resin with 0.5, 1 and 1.5 mm thickness (n=5). Cores without the veneering material served as controls for translucency evaluation. Color parameters were measured by a spectroradiometer. Color difference (ΔE00) and translucency parameters (TP) were computed. Data were analyzed using one-way ANOVA and Tukey's test (for veneering thickness) and independent t-test (for core shade and thickness) via SPSS 20.0 (p⟨0.05). Regarding the veneering thickness, white cores of 0.5 mm thickness showed significant differences in all color parameters. In white cores of 1 mm thickness and dentine cores of 0.5 and 1 mm thickness, there were statistically significant differences only in L∗, a∗ and h∗. The mean TP was significantly higher in all white cores of 1 mm thickness than dentine cores of 1 mm. Considering ΔE00=3.7 as clinically unacceptable, only three groups had higher mean ΔE00 values. Core shade, core thickness, and the veneering thickness affected the color and translucency of PEEK restorations.