Low Translucency Research Articles

Masking Tetracycline Stained Teeth: Effect of Translucency and Thickness of Multiple CAD-CAM Masking Tetracycline Stained Teeth: Effect of Translucency and Thickness of Multiple CAD-CAM Veneer Materials and Shades of Resin Cements

Abstract This study aimed to assess the masking potential of different CAD-CAM veneer restorations to restore tetracycline-stained teeth. One-hundred-eight CAD-CAM ceramic discs, shade 1M1, with high (HT) and low (LT) translucencies and 1mm and 0.7mm thicknesses were prepared from three CAD-CAM materials (IPS-e.max-CAD (EMC), VITA Enamic (VE) and Vita Suprinity (VS)). Resin cements, shades A1, white opaque (WO) and translucent (T), were used for cementation against a dark base. Color differences (ΔE*) between the restorations (veneer/resin cement/dark base) and a standard 1M1 shade-guide-tab were calculated. Mann-Whitney-U and Wilcoxon-signed-rank tests; and one-way ANOVA, Kruskal-Wallis and Bonferroni-post-hoc tests were used to compare between two and three groups respectively (P ≤0.05). Groups EMC-LT-0.7-T, VE-LT-1-A1 and VE-LT-1-T rendered restorations with ΔE* below the perceptibility threshold (<1.74), while EMC-LT-0.7-A1 and all LT-0.7mm VE restorations were within the acceptability threshold (<3.48). VS had significantly higher (ΔE*) compared to of EMC and VE materials. Ceramic thicknesses had no significant effect on (ΔE*), while the effect of translucency level of the ceramics and the shade of resin cement was significant. It was concluded that low translucency ceramic veneers can better mask darkly stained teeth, irrespective of their thicknesses, with resin cements shades affecting the color of the final restorations.

Effect of the ceramic translucency on the long-term water sorption and solubility of resin cements

Aim: The aim of this study was to evaluate the influence of the translucency of ceramic on water sorption and solubility of resin cements over time. Methods: Lithium disilicate ceramic slides (15x15x1 mm), A1 in color and with different translucencies (high-medium-low) were manufactured; and a glass slide with similar dimension was used as control. Under every slide, 15 specimens (8x0.5 mm) from each resin cement were prepared: light-cured (RelyX Veneer); conventional dual-cured (RelyX ARC); and self-adhesive dual-cured (Rely-X U200). The specimens were then sub-divided according to the period of evaluation (immediately, after 6 and 12 months of storage) (n=5). To evaluate the loss or gain of mass, the specimens were dried until a constant mass was reached. Subsequently, they were divided according to the respective period of storage at 37°C in distilled water and weighed immediately following removal from water. After each period, specimens underwent a new dehydration. Values from water sorption and solubility were calculated and statistically analyzed (Anova 3-way/Tukey test). Results: The lower translucency resulted in greater water sorption and solubility for all cements, regardless of the experimental period. The self-adhesive dual-cured cement showed higher water sorption under all experimental periods and had worse values after 1 year aging. Differences among solubility could only be detected after aging, and the light-cured material had higher values after 6 and 12 months. Conclusions: It could be concluded that the low degree of translucency can negatively influence the passage of light and interfere on the durability of the resin cement. The conventional dual-cured resinous agent seemed to be less affected by such condition.

Effect of repeated firing on the translucency of CAD-CAM monolithic glass-ceramics

Statement of problemThe effects of multiple firings on the translucency of newly introduced computer-aided design and computer-aided manufacturing (CAD-CAM) glass-ceramics have not been well evaluated. PurposeThe purpose of this in vitro study was to assess the changes in the translucency of high-translucency (HT) and low-translucency (LT) lithium disilicate (LDS) and zirconia-reinforced lithium silicate (ZLS) glass-ceramics of 0.6 and 1 mm thickness during crystallization, correction, and glaze firing cycles. Material and methodsEighty specimens in 8 groups (n=10) were sectioned and polished to obtain thicknesses of 0.6 and 1 mm. The specimens were then fired in 3 cycles, and the color coordinates were measured by using a spectrophotometer after each cycle. The translucency parameter (TP) and the contrast ratio (CR) were calculated to determine the translucency level. The data were analyzed by using a statistical software program. The TP and CR data after each firing cycle were compared within each group by using repeated-measures ANOVA. Pair-wise comparisons were made by using a multiple paired t test. Comparisons between the 2 thicknesses of different materials were made by using the independent t test (α=.05). ResultsRepeated firings significantly increased the translucency of 0.6-mm LT-LDS and decreased the translucency of 0.6-mm HT-ZLS (P<.017). No significant changes were noted in the translucency of specimens of 1-mm thickness after repeated firings. Also, 0.6-mm-thick specimens of all materials had significantly higher translucency than 1-mm-thick specimens (P≤.001). The highest translucency was noted in HT-LDS, followed by HT-ZLS. ConclusionsRepeated firings significantly affected the translucency of LDS and ZLS CAD-CAM glass-ceramics. The translucency increased with decreasing thickness.

Shade reproduction and the ability of lithium disilicate ceramics to mask dark substrates.

ObjectivesThis study aimed to evaluate the ability of lithium disilicate ceramics to reproduce the A2 shade and to mask A4 substrates.Materials and MethodsTwenty-four discs (8 mm in diameter, shade A2) of high translucency (groups 1–3) and low translucency (groups 4–6) of IPS e.max ceramic with different thicknesses (0.5, 0.75, and 1 mm) were fabricated as monolithic structures. In addition, discs of medium opacity (group 7–8) with different core/veneer combinations (0.3 mm/0.7 mm and 0.5 mm/0.5 mm) were fabricated as bilayer structures. Specimens were superimposed on an A4 substrate (complex). The color changes of the complex were measured using a spectrophotometer on a black background, and the ΔE values of the complex were compared with either the A4 substrate or the A2 shade tab. One-way analysis of variance, the Tukey honest significant difference test, and the Fisher test were used to analyze the data (p < 0.05).ResultsSignificant between-group differences were found for comparisons to both the A4 substrate and the A2 shade (p < 0.05). When compared with the A4 substrate, the ΔE values in all groups were in the non-acceptable range. When compared with the A2 shade, the ΔE values in all groups, except groups 2 and 3, were in the clinically acceptable range.ConclusionsAll translucencies and thicknesses masked the underlying dark substrate. However, the low-translucency IPS e.max Press better reproduced the A2 shade.

Comparative Evaluation of the Translucency of Monolithic Zirconia

New techniques are being developed to invent zirconia with high translucency and better esthetics leading to the development of several brands of monolithic zirconia. The aim of this study is to compare the translucency of three brands of zirconia available for the fabrication of monolithic restorations. An in vitro study was designed to compare the translucency of three brands of zirconia available for the fabrication of monolithic restorations: Zirlux Zirconia (Vivadent Ivoclar), Zenostar Zr Translucent Zirconia (Weiland), and BruxZir Zirconia (Glidewell). All specimens were prepared to 0.5 mm thickness. Thirty zirconia specimens from each material were finished and polished. After drying, specimens were fired according to the manufacturers' recommendations. A spectrophotometer (Color i5) was used for the translucency test. Each specimen was presented at the view port permitting the light to hit the center of the specimen. Results were saved into the software until all measurements were completed. The data were then transferred to an Excel sheet where translucency parameters were calculated. The one-way analysis of variance (ANOVA) test and the post hoc Bonferroni test were performed to analyze the results. The one-way ANOVA test revealed that there was a statistically significant difference between the groups. This study showed lower translucency of BruxZir in comparison to Zenostar and Zirlux when tested under standardized conditions. There is a statistically significant difference in the translucency between the different brands of zirconia available for monolithic restoration fabrication. Different brands of zirconia have different degrees of translucency. Material selection should be customized in each case.

SPECTROPHOTOMETER ANALYSIS OF CAD-CAM ZIRCONIA REINFORCED LITHIUM SILICATE AND LITHIUM DISILICATE GLASS CERAMICS

INTRODUCTION: Matching dental ceramic translucency is the optimal esthetic goal in restorative dentistry. Several types of ceramics evolved over the years in an attempt to optimize physical mechanical and optical properties of the previous types. OBJECTIVES: The aim of this study is to compare and analyze light transmission, light reflection and light absorption of high translucency zirconia reinforced lithium silicate ceramic, low translucency zirconia reinforced lithium silicate ceramic, high translucency lithium disilicate glass-ceramic and low translucency lithium disilicate glass-ceramic. MATERIALS AND METHODS: Serial cutting of the E.max cad and Vita suprinity blocks was done using isomet 4000 micro-saw microtome. Ten ceramic specimens were obtained for each material, 5 of which were 1.5 mm thick and the other 5 were 1 mm thick to be veneered by 0.5 mm of the corresponding veneering material according to manufacturer's instruction. Spectrophotometric analysis was carried out for the forty ceramic specimens. RESULTS: Light transmission for the four groups of zirconia reinforced lithium silicate was significantly higher than their corresponding groups of lithium disilicate (p < 0.005). Light reflection and light absorption for the four groups of zirconia reinforced lithium silicate was significantly lower than their corresponding groups of lithium disilicate (p < 0.005). Veneering increased light transmission and light reflection however it decreased light absorption for both materials significantly. CONCLUSIONS: Translucency of zirconia reinforced lithium silicate is better than lithium disilicate. Veneering improved optical properties for both zirconia reinforced lithium silicate and lithium disilicate.

Effects of glazing methods on the optical and surface properties of silicate ceramics

PurposeThis study aims to evaluate the effect of different glazing methods on translucency parameter (TP), contrast ratio (CR), opalescence parameter (OP), surface roughness (Ra) and topography of the silicate ceramics. MethodsSeventy specimens (10×10×1mm) were fabricated from lithium disilicate (IPS e.max CAD, abbreviated as E) and zirconia-reinforced lithium silicate (Vita Suprinity, abbreviated as VS) ceramics and divided into 7 subgroups (n=10) according to the polishing and glazing procedures: (1) mechanical polishing before-crystallization (m-BC), (2) mechanical polishing after-crystallization (m-AC), (3) glaze powder/liquid after-crystallization (pl-AC), (4) glaze-paste before-crystallization (gp-BC), (5) glaze-paste after-crystallization (gp-AC), (6) glaze-spray before-crystallization (gs-BC), (7) glaze-spray after-crystallization (gs-AC). Color and Ra measurements were performed. CIEL*a*b* and CIEXYZ parameters were recorded and TP, CR, and OP values were calculated. Data were analyzed using two-way ANOVA and Tukey HSD tests (α=0.05). ResultsIn E groups, the highest Ra value was found in gs-AC (1.66±0.14μm) while the lowest value was found in pl-AC (0.68±0.08μm). In VS groups, the highest Ra value was found in gp-BC (1.64±0.25μm) while the lowest value was found in m-AC (0.77±0.06μm) (p<0.05). The mean TP value of E (17.62±0.73) was found to be higher than VS (15.37±1.16). The CR (0.72±0.030) and OP (12.06±0.74) values of VS were found higher than CR (0.57±0.02) and OP (6.72±0.40) values of E. ConclusionsZirconia-reinforced silicate ceramics have higher opalescence and lower translucency values than lithium disilicate ceramics. Increase in surface roughness reduces translucency. Glaze powder/liquid after-crystallization is the most effective way to reduce surface roughness of lithium disilicate ceramics while that is mechanical polishing after-crystallization for zirconia-reinforced silicate ceramics.

Optical properties of currently used zirconia-based esthetic restorations fabricated with different techniques.

The aim was to evaluate the effects of different types of monolithic zirconia (MZ) and fabrication techniques on the optical properties of newly generated zirconia-based materials after aging. Sixty specimens (n = 10) were prepared. For the groups layering-veneering (LV), overpressing (OP), porcelain fused to zirconia (PFZ), and cutback (CB), 3Y-TZP, IPS e.max ZirCAD was prepared as the core material (0.5 ± 0.01 mm). For full-contour (FC) technique, 3Y-TZP was used for MZ-LT (low translucency) and 4Y-TZP was used for MZ-MT (medium translucency). L*, a*, b*, chroma (C), and relative translucency (RTP) were measured before (L1 *, a1 *, b1 *, C1 , RTP1 ) and after (L2 *, a2 *, b2 *, C2 , RTP2 ) UV aging. Statistical analyses were performed by one-way ANOVA with Tukey's test and paired sample t tests (P = .05). Fabrication techniques significantly affected the L*, a*, b*, C, RTP, and ΔE00 values (P ˂ .01). The highest L1 * value was found in MZ-LT; followed, in order, by OP, PFZ, LV, CB, and MZ-MT. The highest b1 * and C1 values were found in OP, while MZ-MT had the lowest values (P ˂ .05). FC had the highest RTP values for MZ-MT (13 ± 0.9 RTP1; 11.2 ± 0.9 RTP2 ), and the lowest RTP values were found for MZ-LT (8.5 ± 0.9 RTP1; 8.3 ± 1.2 RTP2 ) (P ˂ .01). Aging caused significant differences in the L*, a*, b*, C, and RTP values (P < .05). The color changes were between 0.9 and 2.1 ΔE00 . The fabrication technique significantly affected the optical properties. UV aging caused zirconia-based restorations to become darker and more yellow, red, saturated, and opaque. Fabrication techniques with different zirconia structures affected the optical properties of the restoration, even when the same shades were chosen. If more translucent restorations are needed, choosing 4-YTZP with the FC technique is better than veneering with 3-YTZP. Choosing 3-YTZP with the FC technique produces more esthetic results if brighter and more opaque restorations are needed.

Effect of accelerated staining and bleaching on chairside CAD/CAM materials with high and low translucency.

The aim of the study was to assess the effect of staining and bleaching on CAD/CAM materials with high (HT) and low translucency (LT or T). Samples were stored in coffee and subsequently bleached. CIELAB parameters were recorded at baseline, after coffee immersion, after bleaching. Translucency parameter (TP), whiteness index (WID) and color changes were calculated (ΔE00). Influence of staining and bleaching was analyzed with repeated-measures ANOVA and color differences between materials were analyzed with one-way ANOVA (α=0.05). Staining and bleaching significantly affected CIELAB parameters and WID for all materials (p<0.001). TP was significantly influenced by staining and bleaching for Crios and Enamic (p<0.05). Mean color differences were significantly different between materials (p<0.001). The greatest color changes due to staining were observed for Lava Ultimate while the lowest for e.max CAD. Both coffee staining and bleaching induced greater color changes for HT materials of the same brand compared to LT.

Impact of high-speed sintering on translucency, phase content, grain sizes, and flexural strength of 3Y-TZP and 4Y-TZP zirconia materials

Statement of problemThe lengthy sintering time of zirconia is costly and limits applications. The consequences of shortening the sintering time are mainly unknown. PurposeThe purpose of this in vitro study was to test and compare 2 high-speed sintering protocols and 1 conventional sintering protocol on the translucency, phase content, grain sizes, and flexural strength of 3 zirconia materials. Material and methodsIn total, 450 specimens of 3 zirconia materials—two were 3 mol% yttria-stabilized tetragonal zirconia polycrystals (3Y-TZPs), Ceramill ZI and Zolid (ZD), and a 4 mol% yttria-stabilized tetragonal zirconia polycrystal (4Y-TZP), Zolid HT+ (n=150)—and 5 thicknesses (1.0, 1.5, 2.0, 2.5, and 3.0 mm; n=30) were sintered according to 2 high-speed sintering protocols (final temperature 1570 °C and 1590 °C; n=10) and a reference sintering protocol (1450 °C; n=10). After measuring the monoclinic phase content with Raman spectrometry (n=3), the specimens were polished, and translucency was determined. The biaxial flexural strength of specimens with a thickness of 1.0 mm and 1.5 mm was tested (n=20). Statistical evaluation included 1-way ANOVA, the Kolmogorov-Smirnov, Kruskal-Wallis, Mann-Whitney-U, and Spearman-Rho tests and the Bonferroni correction (α=.0011). ResultsFor ZI, the sintering protocols did not affect the translucency or biaxial flexural strength. ZD and HT+ showed significantly lower translucency for high-speed sintering protocols (P≤.001), but the biaxial flexural strength remained the same after the high-speed sintering protocol at 1590 °C. Grain sizes increased with increasing final sintering temperature for ZI and HT+, whereas translucency generally decreased with increasing material thickness. No monoclinic phase was detected in any group. ConclusionsThe flexural strength was maintained with high-speed sintering but led to a decrease in translucency for ZD and HT+.

Optical parameters and hardness of two maxillofacial elastomers after immersion in different solutions of Brazilian green propolis extract

Statement of problemMaxillofacial elastomers undergo physical and mechanical degradation with disinfecting solutions. Solutions of Brazilian green propolis extract may be suitable alternatives for infection control of maxillofacial prostheses. However, their effects on the properties of the material are unknown. PurposeThe purpose of this in vitro study was to evaluate the effect of disinfection with solutions of Brazilian green propolis extract on the transmittance, translucency parameter, contrast ratio, and hardness of 2 maxillofacial elastomers (MDX4-4210 and MED-4014). Material and methodsFifty disk-shaped specimens (3×10 mm) of each elastomer were randomly and equally divided into 4 groups of disinfectant agents and 1 control group: 3 separate groups of 11% green propolis extracts including aqueous (PAQ), glycolic (PGL), and alcoholic (PAL), a 2% chlorhexidine gluconate (CHX) group, and the control group of distilled water. Specimens were subjected to disinfection by immersion 3 times a week for 60 days. Color differences (ΔE values) were calculated with CIELab and CIEDE2000 formulas. Optical parameters and Shore A hardness were determined at 2 time points: at baseline and after the period of specimen disinfection. Data were analyzed by parametric and nonparametric analysis of variance and by multiple-comparison tests (α=.05). ResultsThe ΔE values of specimens immersed in 11% PAL were not clinically acceptable for either elastomer. Regarding translucency parameter and contrast ratio, the immersion in 11% PAL and 11% PGL resulted in greater opacity and lower translucency of the material. Mean Shore A hardness values were not statistically significantly different at baseline or after 60 days of immersion in the solutions. ConclusionsThe solution of Brazilian green propolis extract tested showed changes in optical parameters. Elastomers immersed in 11% alcoholic green propolis extract showed clinically unacceptable color and translucency changes. All hardness values of the tested elastomers were clinically acceptable after immersion in all tested disinfectant groups.

In vitro color stainability and relative translucency of CAD-CAM restorative materials used for laminate veneers and complete crowns

Statement of problemAssessing the long-term stainability and durability of restorative materials is an important parameter for determining clinical success and longevity. Information remains limited regarding the color stainability and translucency of the recently introduced ceramic materials for restorative treatment. PurposeThe purpose of this in vitro study was to compare the effect of cyclic immersion in hot and cold coffee on the color stainability and translucency of 6 computer-aided design and computer-aided manufacturing (CAD-CAM) restorative materials at thicknesses which represent a laminate veneer and a complete crown. Material and methodsCAD-CAM restorative materials including zirconia-reinforced lithium silicate ceramic (Celtra Duo), lithium disilicate glass-ceramic (IPS e.max CAD), polymerized resin nanoceramic (Lava Ultimate), integrated ceramic and acrylate polymer network material (VITA ENAMIC), zirconia-reinforced lithium silicate (VITA SUPRINITY), and zirconia (VITA YZ HT) were studied in 2 thicknesses for laminate veneer (0.7 mm) and complete crown application (1.3 mm to 1.5 mm). For each specimen, color difference on a gray backing was calculated using a spectroradiometer between its baseline color and after 6000 cycles of coffee thermocycling. The colors of the specimens on the black and white backings were used to calculate the relative translucency parameter from the CIEDE2000 color difference formula. An ANOVA and the Bonferroni-corrected Student t tests were used for testing statistical significance (α=.05). ResultsNo difference was found among the means of color change after coffee thermocycling between any 2 materials for the crown thickness (P>.999), and no difference was found among the means of color change between the 2 thickness groups within each material (P≥.187). However, the mean color change of the resin nanoceramic material in laminate veneer application (0.7 mm) was greater than that of every other material in the veneer thickness group (P<.001), and the mean color change of the integrated ceramic and acrylate polymer network material was greater than that of the lithium disilicate glass-ceramic material studied at the veneer thickness (P=.014). Translucency was found to be lower for complete crown thickness compared with laminate veneer thickness within each combination of material and coffee thermocycling (P<.001). The translucency of the lithium disilicate glass-ceramic material studied at the laminate veneer thickness was also found to be higher after coffee thermocycling (P=.033). Furthermore, several differences among materials were found for each combination of thickness and coffee. ConclusionsColor change after coffee thermocycling of the resin nanoceramic material was beyond the acceptability threshold. The lower translucency found for crown thickness compared with veneer thickness was verified.

Esthetic smile rehabilitation of enamel hypomineralized teeth with E-max prosthesis: Case report

Developmental enamel hypomineralization is a condition affect quality of enamel result in low translucency and opacity area that compromise patient smile. Lithium disilicate Emax prosthesis report a superior properties in esthetic treatment. This report is aimed to determine the effectiveness of lithium disilicate (E-max) prosthesis in managing esthetic demand of patient with enamel hypomineralized teeth.

Comparative evaluation of the masking ability of lithium disilicate ceramic with different core thickness on the shade match of indirect restorations over metallic substrate: An In vitro study

Purpose:The purpose of this in vitro study was to comparatively evaluate the masking ability of lithium disilicate ceramic with different core thickness on the shade match of indirect restorations over metallic substrate.Materials and Methods:A total of 30 heat pressed lithium disilicate ceramic discs of low translucency were fabricated with diameter 10mm and thickness of 1 mm, 1.3 mm and 1.6mm with each thickness consisting of 10 samples to be used in the study. Thirty Ni-Cr metal discs of diameter 10mm were used to simulate metallic substrates .The colour difference of the lithium disilicate ceramic disc before and after cementation were measured using CIE LAB system.Results:The mean colour difference (ΔE) of Group I,Group II, Group III before cementation with the Ni-Cr metal discs was 17.32,13.01 and 11.73 respectively. The mean colour difference (ΔE) of Group I,Group II, Group III after cementation with the Ni-Cr metal discs was 16.32,12.10, 11.05 respectively.Conclusion:The mean colour difference of the three groups were found to be more than the clinically acceptable perceptibility threshold (ΔE < 3.3) indicative of reduced masking ability of all the three groups of ceramic discs over metallic substrate used in this study.

The Effect of Ceramic Type and Background Color on Shade Reproducibility of All-Ceramic Restorations.

To investigate the effects of background color on shade reproduction using CAD/CAM zirconia and lithium disilicate ceramics. A plastic tooth was prepared for an all-ceramic crown and scanned. Tooth-shaped light background dies were manufactured. Full-contour crowns were milled from translucent zirconia (ZT) and low translucency lithium disilicates (E [LT]). Copings from opaque zirconia (Z) and medium opacity lithium disilicate (E[MO]) ceramics were milled and layered with veneering porcelain to full contour. Metal copings were used to produce a dark background. Specimens were divided into 8 groups with 3 variables: background color, ceramic type, and translucency. Crowns were cemented using composite resin cement. Color was measured with a spectrophotometer. Color difference (∆E) was calculated using the CIEDE2000 formula between the specimens and the target shade, A1. Statistical analysis was performed using a nested design 3-way ANOVA and Tukey multiple comparisons. The closest ∆E to target shade was produced by E (LT) (2.13 ± 0.19) on the dark background. This increased significantly to 2.90 ± 0.19 on the light background (p = 0.03). The e.max (MO) groups significantly increased (p = 0.001) to 4.40 ± 0.22 and 4.47 ± 0.4, (p = 1.00) for the dark and light backgrounds, respectively. ∆E for the zirconia groups were higher and ranged from 4.85 ± 0.48 to 5.60 ± 0.48 in the ZT groups (p = 0.04) and 6.5 ± 0.82 to 7.75 ± 0.53 (p = 0.001) for Z groups from dark to light backgrounds. There was an overall lack of chromaticity between the specimens and the target shade A1 CONCLUSIONS: Ceramic color was affected by ceramic type, background, and translucency. Lithium disilicate appeared to be better than zirconia in shade reproduction. Less-opaque materials matched the target shade better, while opaque materials and low translucencies were more suitable for dark backgrounds.

Optical properties and colorimetric evaluation of resin cements formulated with thio-urethane oligomers.

The aim of this study was to evaluate the color parameters and optical properties of resin cements (RCs) formulated with thio-urethanes (TUs). Six TUs were synthesized by combining thiols (pentaerythritol tetra-3-mercaptopropionate [PETMP] or trimethylol-tris-3-mercaptopropionate [TMP]) with di-functional isocyanates (1,6-Hexanediol-diissocyante [HDDI] [aliphatic-AL] or 1,3-bis(1-isocyanato-1-methylethyl) benzene [BDI] [aromatic-AR] or Dicyclohexylmethane 4,4'-Diisocyanate [HMDI] [cyclic-CC]). TUs (20 wt%) were added to a BisGMA/UDMA/TEGDMA matrix. Filler was introduced at 60 wt%. Fluorescence was evaluated through an UV-light emitting equipment. Coordinates L*, a*, and b* were obtained in the black and white reflectance to evaluate the contrast ratio (CR) and translucency parameter (TP00 ). The coordinates obtained from transmittance were used to evaluate lightness (L*), chroma (C*), color difference (ΔE00 ) after 6 month, and whiteness index for Dentistry (WID ). RCs formulated with TUs presented significantly higher CR, and fluorescence (with T_AR). Significantly lower C*, L*, and TP00 (except for P_AR and T_AL) were also observed in RCs containing TUs. ΔE00 were not significant among the materials. WID was not influenced. RCs composed by TU oligomers present higher CR and lower translucency. The material also present higher fluorescence depending on the oligomer used. The use of thio-urethanes to formulate resin cements can ensure a luting material with improved potential to mask colored substrates due to the higher contrast ratio and lower translucency obtained. A final higher fluorescence of restoration is also expected with the use of specific oligomer.

Ag-chitosan nanocomposites in edible coatings affect the quality of fresh-cut melon

The effect of incorporating Ag-chitosan nanocomposites into chitosan coatings on the quality of fresh-cut melon over 13 d at 5 °C has been studied. The respiration rate of fresh-cut melon was reduced after coating treatments. Particularly, the coating with red claw crayfish-extracted chitosan (including red claw crayfish-extracted Ag-chitosan nanocomposites) showed lower RR increments during storage compared to that of the rest of coatings. Coated samples reached a steady-state atmosphere within packages of 12.6–16.2 kPa of CO2/2.3–3.7 kPa of O2 after 9–10 d. Softening was prevented in advanced storage periods by the coating with red claw crayfish-extracted chitosan (including red claw crayfish-extracted Ag-chitosan nanocomposites). The colour, soluble solids content, sucrose, glucose and fructose, pH, TA, and citric and malic acids were not greatly affected by the coating treatments. Furthermore, the coating with red claw crayfish-extracted chitosan (including red claw crayfish-extracted Ag-chitosan nanocomposites) showed the highest total vitamin C content after 13 d at 5 °C compared to the rest of the coating treatments. The coated samples were better sensory-scored than were the uncoated samples. Particularly, the coating with red claw crayfish-extracted chitosan (including red claw crayfish-extracted Ag-chitosan nanocomposites) showed lower translucency, which is the most important visual alteration in fresh-cut melon. Only the coating with red claw crayfish-extracted chitosan (including red claw crayfish-extracted Ag-chitosan nanocomposites) induced a microbicidal reduction (0.6 log units) from days 10 to 13. We conclude that the coating with red claw crayfish-extracted chitosan (including red claw crayfish-extracted Ag-chitosan nanocomposites) has the potential to be applied in the fresh-cut industry to extend the shelf-life of these products.

Effect of Different Veneering Techniques on Shear Bond Strength and Translucency of Bi-layered Zirconia Ceramics

Purpose. This study was designed to compare the effect of different veneering techniques (CAD-on, Press-on and manual layering) on the shear bond strength of veneering ceramics to zirconia framework and translucency of bi-layered zirconia based ceramics. Materials and Methods: A total of forty-eight zirconia samples were fabricated and were divided into three equal groups (n=16) according to the veneering technique used: Group (I): samples veneered using CAD-on technique. Group (II): samples veneered using Press-on technique and Group (III): samples veneered using manual layering technique. The samples of each group were subdivided into two equal subgroups (n=8) according to the testing procedure: Subgroup (A): for translucency parameter (TP). Subgroup (B): for shear bond strength. All samples were thermocycled in thermocycling device. Samples of subgroup (A) were tested for translucency parameter (TP) by using a reflective spectrophotometer. Samples of subgroup (B) were tested by using a universal testing machine. Failure modes of fractured samples were evaluated using stereomicroscope and scanning electron microscope (SEM).Data were statistically analyzed. Results: CAD-on veneered samples, group (1), recorded higher mean translucency parameter (11.099±0.452) than manual layering veneered samples, group (3), which recorded lower translucency parameter (5.463±1.255). CAD-on veneered samples, group (1), recorded higher mean shear bond strength (16.262±4.492) than Press-on veneered samples, group (2) which recorded lower shear bond strength (8.584±1.606). Conclusions: CAD-on veneered samples showed superior translucency parameter and shear bond strength than Press-on veneered samples.

Influences of the processing method and sintering temperature on the translucency of polycrystalline yttria-stabilized tetragonal zirconia for dental applications

The achievement of a high esthetic value in polycrystalline yttria-stabilized tetragonal zirconia (Y-TZP)-based dental restorations is hindered by the low translucency of Y-TZP. Thus, this study investigated the effects of processing method and sintering temperature on the translucency of Y-TZP for dental applications. Wet (slip casting) and dry (cold isostatic pressing) processing methods were used. Y-TZP specimens were fabricated by applying the processing methods and sintering at different temperatures (1450–1650 °C). The mechanical, morphological, and optical properties of the Y-TZP specimens were examined and compared. The specimens were benchmarked with a commercial Y-TZP, namely, Cercon©. Results showed that wet processing produced higher mechanical properties and translucency than dry processing. This finding can be mainly attributed to the higher capability of wet processing than dry processing in alleviating the agglomeration in Y-TZP. Among the several specimens that were tested, the slip-casted Y-TZP that was sintered at 1600 °C showed the optimum mechanical properties (99.5% density and 12.7 GPa hardness) and translucency (35% light transmission) for dental applications. Furthermore, the light transmission achieved in this study was approximately three times higher than that of the commercial Y-TZP (13%), thereby indicating a potential alternative to replace the commercial Y-TZP. Highly translucent Y-TZP with excellent mechanical properties was developed in this study through wet processing with a sintering temperature of 1600 °C. The developed Y-TZP can be an alternative to commercial products to produce a highly esthetic dental restoration.

Effect of Light-Cured Resin Cement Application on Translucency of Ceramic Veneers and Light Transmission of LED Polymerization Units.

To evaluate the effect of light-cured resin cement application based on etching and silanization on the translucent property of ceramic veneers in different thicknesses, testing the hypothesis that the surface treatment and subsequent resin cement application could influence the translucency of ceramic veneers. The relationship between translucency of ceramic veneers and light transmission irradiated by LED polymerization units was also determined. 40 specimens (10 mm diameter) were fabricated from IPS e.max Press HT A2 ceramic ingots, and polished to 0.3 ± 0.01 mm, 0.5 ± 0.01 mm, 0.7 ± 0.01 mm, 1.0 ± 0.01 mm, and 1.5 ± 0.01 mm thick (n = 8/group). One surface of each disc was etched with HF acid, silanized with Monobond-S, and applied with a light-cured resin cement (Variolink N Transparent Base). Before and after the above procedure, the total luminous transmittance (τ) of all specimens was assessed by a spectrophotometer in a wavelength range of 380-780 nm. A handheld radiometer was used to measure the light intensity irradiated by three LED polymerization units. Light transmission (LT) through ceramic specimens after resin cement application was calculated. Data were statistically analyzed using two-way ANOVA (p = 0.05) and Tukey's test. The correlation between translucency (τ) of ceramic veneers after resin cement application and light transmission (LT) of curing units was statistically evaluated using Spearman correlation test (p = 0.05). With the increase of ceramic thickness, the transmittance decreased significantly (p < 0.05). For the 0.3-mm, 0.5-mm, and 0.7-mm-thick groups, the transmittance of ceramic specimens was statistically significantly lower after resin cement application (p < 0.05). The r value of Bluephase C8 was 0.988, 0.977 for Bluphase, and 0.883 for Bluephase 20i, indicating that the light transmission (LT%) was positively correlated to the translucency of ceramic veneers, regardless of the type of curing units. After the light-cured resin cement application based on etching and silanization, the ceramic veneers (less than 0.7-mm thick) were less translucent, and the translucency decreased when the thickness increased. Because of the lower translucency of ceramic veneers, the light intensity of LED units transmitted to resin layer would decrease when curing.