Translucency Parameter Values Research Articles

Two-step sintering suppresses grain growth and improves flexural strength of dental zirconia

ObjectivesThis study aimed to elucidate the effect of various two-step sintering (TSS) protocols on the physical, mechanical, and optical properties of partially stabilized zirconia with different yttria dopant concentrations (Y-PSZ). MethodsDisc-shaped specimens were obtained from most widely used commercial dental zirconia powders of various Y contents (Tosoh Corp.) by uniaxial pressing followed by cold-isostatic pressing. Densification was carried out using TSS protocols with varying temperatures for both sintering steps. Relative density (ρRel), microstructure, and phase content were analyzed. Biaxial flexural strength (σ) and translucency parameter (TP) were evaluated. ResultsThe TSS results were compared with optimized conventional sintering (CS) results from a previous study for the same Y-PSZ compositions. TSS 3Y-PSZ and 4Y-PSZ reached similar ρRel to those of their CS counterparts, whereas 5Y-PSZ failed to achieve that regardless of TSS protocol. TSS yielded less cubic phase compared to CS, especially for 3Y-PSZ and for higher temperatures. TSS suppressed the grain growth throughout the temperature range investigated, promoting smaller grains than CS (p < 0.05). The TP values for TSS Y-PSZ were lower than those of CS (p ≤ 0.0001), except for 3Y-PSZ. The σ values for TSS Y-PSZ were significantly higher than those of CS (p ≤ 0.0002).Significance: TSS increased strength without significantly jeopardizing the optical properties of various Y-PSZ compositions relative to their CS counterparts. This alternative sintering method appears to be a promising technique for controlling grain growth while eliminating porosities in dental Y-PSZ ceramics, thus potentially enhancing the clinical longevity of zirconia restorations.

Research of Optical Properties and Biocompatibility in Different Zones of Multilayered Translucent Zirconia on Hydrothermal Aging.

We assessed the changes in optical properties and biocompatibility of transition zones in multilayered translucent monolithic zirconia exposed to prolonged hydrothermal aging and compared the results to those with different yttrium oxide contents. Four types of zirconia blocks from IPS e.max ZirCAD were used: 3Y-TZP e.max ZirCAD LT (ZL), 4Y-TZP e.max ZirCAD MT (ZM), 5Y-TZP e.max ZirCAD MT Multi (ZT), and 3Y/5Y-TZP e.max ZirCAD Prime (ZP). A total of 120 specimens (15.0 mm diameter and 1.5 mm height) were fabricated and divided into three groups (n = 10). The aging process for the specimens was conducted in an autoclave set to 134 °C and 0.2 MPa, with durations of 0 h (control), 5 h (first aged), and 10 h (second aged). The optical properties and biocompatibility were analyzed, followed by a statistical analysis of the data (α = 0.05). Before and after aging, ZL and ZP exhibited the lowest color changes. ZT exhibited the highest average transmittance and translucency parameter values, while ZL had the lowest. The water contact angle test showed the highest value in ZM and lowest in ZL across all the aging stages. ZL, ZM, and ZP showed a considerable decrease in the water contact angle; however, ZT did not. A cell counting kit-8 assay showed ZL had the highest value, while ZM had the lowest. A filamentous actin test exhibited the highest value in ZL and lowest in ZM. In the vinculin analysis, ZL and ZT exhibited the lowest values, whereas ZM and ZP had the highest. 3Y/5Y-TZP exhibited a balanced performance across critical parameters, such as color stability, translucency, and biocompatibility, aligning with 3Y-TZP. While 5Y-TZP demonstrated superior translucency, it confirmed the lowest color stability, whereas 3Y-TZP achieved the highest biocompatibility. These properties provide clinicians with a reliable material option that ensures superior esthetic outcomes and long-term prognosis, ultimately contributing to improved patient satisfaction and clinical longevity.

Comparison of the Ability to Mask the Color of Endodontic Filling Materials Using Several Types of Base Materials

In clinical pediatric dentistry, a base material with optical properties, including transparency, that can mask the color of the material used for root canal-filling is preferred. This study aimed to examine the optical properties of various base materials by thickness. The disk-shaped specimens were photopolymerized and fabricated using Ionosit (IN), TheraCal LC (TL), TheraCal PT (PT), and A2 shade of Filtek&lt;sup&gt;TM&lt;/sup&gt; Supreme Flowable Restorative (FZ), Fuji II LC (FL), and Ketac&lt;sup&gt;TM&lt;/sup&gt; Fil (KF) with 1 and 2 mm thickness. The color parameters of these specimens were measured using a spectrophotometer on a black and white background and were measured using the same method on a mold containing Vitapex® and gutta-percha. The translucency parameter (TP) and color difference were calculated for each group. The Kruskal-Wallis and Bonferroni tests were used in the statistical analyses. The TP decreased when the thickness was 2 mm compared with 1 mm. The TP values of TL and PT were the lowest at all thicknesses. The TP values of 2 mm thickness in all molds filled with Vitapex® and gutta-percha were the lowest for TL, PT, KF, and IN. In TL and PT, the color difference before and after the application of the canal-filling material was the smallest, regardless of material thickness. Within the limits of this in vitro study, TL, PT, KF, and IN demonstrated better masking of the color of canal-filling material.

Translucency and colour masking ability of hybrid CAD/CAM materials with different thicknesses: in vitro study

ObjectiveTo evaluate effect of material thickness and translucency of two different hybrid CAD/CAM materials on their masking ability.Materials and Methods40 rectangular-shaped specimens (12 × 14 mm) were obtained from Vita Enamic and Grandio blocks at 0.5 and 1 mm-thick (n = 10/group). Colour parameters of specimens were measured on PMMA tooth-coloured replica backgrounds (A2, C4) and black, white backings using dental spectrophotometer. Translucency parameter (TP) and masking ability (∆E00) values of tested materials with 0.5, and 1 mm thicknesses were calculated. Quantitative variables were compared between groups using student t-test.ResultsTP and ∆E00 significantly decreased as thickness of tested materials increased. Grandio showed significantly higher TP values. There were significantly lower ΔE00 values for Vita Enamic compared to Grandio at 1 mm thickness and inversely insignificant at 0.5 mm. The 0.5 mm-thick ∆E00 of tested materials was above clinical acceptability threshold, whereas, 1 mm-thick did not exceed showing better masking properties.ConclusionsThickness is more effective for colour masking than translucency. In thin thickness, the masking ability is less effective, irrespective of tested materials. Translucency of tested materials was affected by their composition. Both hybrid CAD/CAM materials are promising alternatives for masking dark discolouration at 1 mm-thick.

Effect of Coffee Thermocycling on Color Stability and Translucency of CAD-CAM Polychromatic High Translucent Zirconia Compared With Lithium Disilicate Glass Ceramic.

To evaluate the effect of coffee thermocycling on color stability and translucency of CAD-CAM polychromatic high translucent zirconia compared with lithium disilicate glass ceramic. Sixteen rectangular plates (14 × 16 × 1.0 mm) of two ceramic materials (IPS E.max CAD (IEC), IPS E.max ZirCAD Prime [IZP]) were prepared. Each specimen was measured for color coordinates using a spectrophotometer following 30,000 cycles of coffee thermocycling. CIELAB formula was used to determine color and translucency differences (ΔE and ΔTP). The means of ΔE and ΔTP were compared using independent samples t-test and were evaluated using their respective 50%:50% perceptibility and acceptability thresholds (PT and AT). One-way analysis of variance was performed to evaluate the translucency parameter (TP) and surface roughness (Ra) of each material. Mean ΔE values of IEC (4.69) and IZP (4.64) were higher than the AT (ΔE ≤ 2.7) with no significant difference found between the two groups (p = 0.202). Considering the TP, only IEC showed a statistically significant increase in TP value (p < 0.001). However, the mean ΔTP of IEC (3.25) remained within the range of acceptability (1.3 < ΔTP ≤ 4.4). Within the limitations of this current study, the color stability of all materials was clinically affected by coffee thermocycling. In terms of translucency, only lithium disilicate glass ceramic was influenced by coffee thermocycling. High translucent zirconia had superior translucency stability compared to lithium disilicate glass ceramic.

Effect of artificial aging on optical properties of ultra-translucent zirconia ceramics of different brands.

This work aimed to evaluate the effect of artificial aging on the translucency and color difference (ΔE) of ultra-translucent zirconia and provide a reference for clinical application. The discs of ultra-translucent zirconia from six brands (Wieland, 3M ESPE, Amann Girrbach, Kuraray Noritake, Upcera, and Besmile) were cut and sintered according to each manufacturer's product instructions; the experimental groups were named ZNT, LVP, AG, KAT, UPC, and BSM, respectively. IPS e.max Press was used as the control group (PLT). The specimens (n=6) were prepared with a diameter of 14 mm and a thickness of 1 mm. The specimens were subjected to artificial aging treatment according to the following conditions: in an autoclave at 134 ℃ at 0.2 MPa for 4, 8, and 12 h. According to the CIE1976Lab system, the CIE L*, a*, and b* values of the specimens before and after aging were measured by a co-lorimeter. The translucency parameter (TP) and ΔE were calculated. The mean TP values of each group before aging inorder were PLT>KAT>AG>ZNT>BSM>UPC>LVP. We found no significant difference in translucency in all experimental groups after aging for 4 and 8 h compared with those before aging. After 12 h of aging, the TP values of the KAT and ZNT groups were not significantly different from those before aging, but the TP values of the AG, BSM, LVP, and UPC groups were significantly lower than those before aging (P<0.05). The TP value of the control group was significantly higher than that of the other experimental groups at different stages (P<0.05). ΔE=3.3 was considered the visible color difference, and ΔE was less than 3.3 in all groups after 4 h of aging. After aging for 8 h, ΔE of the UPC group was slightly higher than 3.3. ΔE of the BSM and UPC groups was greater than 3.3 after 12 h of aging. The TP and ΔE of different brands of ultra-translucent zirconia may change after various aging times. The translucency of some zirconia showed a decreasing trend and the color difference showed an increasing trend with the aging time.

The effect of deviations in sintering temperature on the translucency and color of multi-layered zirconia

ObjectThis study aimed to investigate the changes in the translucency and color of four different multi-layered zirconia materials when the sintering temperature were inaccurate.Materials and methodsTwo hundred zirconia samples (11 × 11 × 1.0 mm) of four multi-layered zirconia, Upcera TT-GT (UG), Upcera TT-ML (UM), Cercon xt ML (CX), and Lava Esthetic (LE), were divided into five subgroups according to the sintering temperature: L1 (5% lower temperature), L2 (2.5% lower temperature), R (recommended sintering temperature), H2 (2.5% higher temperature), H1 (5% higher temperature). After sintering, color coordinates were measured. Then the translucency parameter (TP) values, and the color differences (between the inaccurate sintering temperature and the recommended temperature) of each zirconia specimen were calculated. Statistical analysis was performed by using three-way ANOVA tests, the one-way ANOVA, and Tukey’s post hoc test.ResultsThree-way ANOVA results showed that material type, sintering temperature, specimen section, and their interactions significantly influenced the TP values (except for the interactions of specimen section and sintering temperature) (P < .05). TP values of zirconia specimens were significantly different in the inaccurate sintering temperatures (P < .05), except for the cervical and body sections of UG group (P > .05). Compared with recommended sintering temperature, higher sintering temperature caused higher TP values for CX, but lower for LE. Three-way ANOVA results showed that material type, sintering temperature, and their interactions significantly influenced the ∆E00 values (P < .05). There were no significant differences in ∆E00 values of UM and CX groups at different inaccurate sintering temperatures, and were clinical imperception (except for UM-L1) (∆E00 < 1.25). ∆E00 values of all zirconia specimens showed clinically acceptable (∆E00 < 2.23).ConclusionThe deviations in sintering temperature significantly influenced the translucency and color of tested multi-layered zirconia. The trends of translucency in the multi-layered zirconia depended on material type and the color changes of all zirconia materials were clinically acceptable at inaccurate sintering temperatures.

Effects of Coloring Liquid Dipping Time and Surface Finishing Procedures on the Optical Properties of Monolithic Zirconia.

Monolithic zirconia restorations can be produced from self-colored or uncolored blocks. The coloring procedure of uncolored blocks and surface treatments may affect the appearance of the restoration. The purpose of this study is to evaluate the effect of liquid coloring and surface treatments on optical properties of translucent monolithic zirconia. All specimens were cut from zirconia blocks with a thickness of 1 mm. Specimens were dipped in the coloring liquids for 3 min, 5 min, and 7 min and then divided into groups of 10 specimens for surface treatments. Glaze and mechanical polishing were applied, and the color of the specimens was measured under the D65 lighting condition with a spectrophotometer device. Color values obtained from the CIE Lab formula and the translucency parameter (TP), opalescence parameter (OP), and contrast ratio (CR) were calculated. The normality of the data was confirmed with the Shapiro-Wilk test. A three-way analysis of variance (ANOVA) was used to assess the effect of dipping time, liquid shade, and surface treatments. The effect of liquid shade and dipping time on the TP, OP, and CR parameters were statistically significant, and the TP values were reduced with the application of coloring liquid. Mechanical polishing groups had higher OP values and lower TP values than glazed groups. In cases where high translucency is required, it may be advisable to use self-colored blocks and apply glaze as a surface treatment to achieve the desired optical properties.

Influence of Thickness on the Translucency Parameter and Whiteness Index of Single-Shade Resin Composites.

The study aimed to evaluate the effect of thickness on the translucency parameter (TP) and whiteness index for dentistry (WID) of single-shade resin composites compared with a multi-shade resin composite after thermocycling. A total of 100 resin composite samples of five brands (Filtek Z250, Omnichroma, Vittra APS Unique, Zenchroma, and Charisma Diamond One) with thicknesses of 2 mm and 4 mm were prepared (n=10). CIE L*a*b* coordinates were obtained using a spectrophotometer. The resin composite samples were subjected to 10,000 thermocycles. Before and after thermocycling, TP values were calculated with the CIEDE2000 formula, and whiteness values were calculated using the WID. The influence of thickness, resin composite, and aging on these variables was analyzed using the generalized linear model (p<0.05). Omnichroma and Filtek Z250 exhibited, respectively, the highest and the lowest TP00 values compared with the other resin materials (p<0.001). The TP00 values of Zenchroma and Diamond One were similar (p>0.05). Vittra APS Unique had a lower TP than Zenchroma and Diamond One (p<0.001). Before thermocycling, the highest WID showed the combination of Vittra APS Unique with thicknesses of 2 mm (48.33±1.18). After thermocycling, the highest WID was shown in the combination of Vittra APS Unique with thicknesses of 2 mm (45.33±0.55) and 4 mm (46.23±0.94) (p<0.001). After thermocycling, the lowest WID was for the combination of Filtek Z250 with thicknesses 2 mm (21.16±0.93) and 4 mm (20.70±0.91) (p<0.001). The TP and WID values of the resin composites varied across different composites and thicknesses. Single-shade resin composites of different thicknesses demonstrated higher translucency and whiteness values than multi-shade resin composite, both before and after thermocycling.

Effect of Printing Layer Thickness on Optical Properties and Surface Roughness of 3D-Printed Resins: An In Vitro Study.

To investigate the impact of printing layer thickness on the optical properties and surface roughness of various 3D-printed resins manufactured by digital light processing (DLP) and indicated for provisional and definitive restorations. A total of 240 specimens from four different 3D-printing resins-VarseoSmile Crown Plus (Bego; VS), Crowntec (Saremco Dental; CR), GC Temp PRINT (GC Dental; TG), and NextDent C&B MFH (NextDent; ND)-were divided into four groups (n = 60 per group). Each group was further divided into three subgroups (n = 20) according to printing layer thickness (25, 50, and 100 μm). All specimens were subjected to thermocycling with coffee before measurements were taken with a spectroradiometer to calculate color differences. The Kubelka-Munk (K-M) absorption (K) and scattering coefficients (S), translucency parameters (TP), and surface roughness (Ra) values were calculated for each printing layer thickness and compared with those of the 2M2 shade tab (target). The data were analyzed using Mann-Whitney U test, the variance accounted for (VAF) coefficient by Cauchy-Schwarz, and post hoc comparisons using Tukey test (α ≤ .05). S (79% ≤ VAF ≤ 100%) and K (40.45% ≤ VAF ≤ 100%) spectral distribution depended on the wavelength. A 25-μm layer thickness resulted in no significant differences from the 2M2 shade for S (P > .230) and K (P > .200). VS showed significantly different S (P = .004) and K (P = .003) values from those of the shade tab with 50-μm layering thickness, whereas other materials did not show significant differences from the 2M2 shade for S (P > .280) and K (P > .301). The 100-μm layer thickness specimens had significantly different S and K values compared to the 2M2 shade tab (P < .004). TP values of resins with 100-μm layer thickness were significantly lower than resins in 25- and 50-μm layer thicknesses (P < .001). The Ra values of resins increased significantly with 100-μm layer thickness (P ≤ .001). All tested materials, except for VS, showed color properties similar to the target shade when 25- and 50-μm printing layer thicknesses were used. The translucency of resins tended toward an inverse relationship with printing layer thickness. The surface roughness of resins increased significantly with 100-μm layer thickness. However, all resins with a printing thickness of 25 μm showed better color properties and surface roughness.

Effect of ceramic type and thickness on the masking ability of chairside machinable all-ceramic crowns.

This study aimed to evaluate the influence of ceramic type and thickness on the masking ability and final aesthetic effects of chairside machinable all-ceramic crowns. Six kinds from three types chairside machinable ceramic materials (IPS e.max CAD HT/MT/LT, IPS Empress LT, and VITA Suprinity HT/T) in shade A2 were fabricated to slice specimens into 1.0, 1.5, and 2.0 mm-thick sections (n=10). The color parameters of the specimens against black and white tiles and four resin substrates (A2, A4, B3, and C4 shade) were measured with a spectrophotometer. The translucency parameter (TP) was calculated using color parameters measured over standard white and black backgrounds. The color differences (ΔE) were calculated between there substrate shades (A4, B3, C4 ) and A2 shade (control group). Two-way analysis of variance (ANOVA) was performed on the TP values. The two va-riables were ceramic type and ceramic thickness. Three-way ANOVA was used to determine the effects of ceramic materials, ceramic thickness, and substrate shades on the ΔE values, followed by Tukey test for multiple comparisons (α=0.05). Ceramic type, ceramic thickness, and substrate shade significantly affected the ΔE values (P<0.001). The L* and b* values of the specimens increased with increasing ceramic thickness, except in substrate A2, whereas the ΔE values decreased. The color difference of all 1.0 mm-thick specimens or all specimens over the substrates C4 shade exceeded the clinically acceptable threshold (ΔE>3.3). The masking ability of chairside machinable all-ceramic crowns is influenced by ceramic type and thickness, and ceramic material. The thickness of ceramic less than 2.0 mm cannot mask the gray shade abutment.

Translucency of chairside monolithic zirconias using different sintering ovens: An in vitro investigation

ObjectiveTo evaluate the translucency of several monolithic zirconias (MZ) processed in various sintering ovens designed for single-visit, chairside use. MethodsDiscs (n = 40) from zirconia blocks were fabricated for each MZ at manufacturer-recommended minimal thicknesses, as provided in each material's instructions for use: IPS e.max ZirCAD LT (ZLT); CEREC Zirconia+ (CZ+); 3M Chairside (3M); KATANA Zirconia (KT). Groups (n = 10) were sintered following manufacturer instructions for each oven: CEREC SpeedFire, Ivoclar CS4, Ivoclar CS6, and Ivoclar S2 (laboratory furnace control). Specimens were highly polished on one side and glazed on the other. Each side was measured with a spectrophotometer against white and black backgrounds to determine translucency parameter (TP) and contrast ratio (CR) values. Results for TP and CR for each material and oven combination were compared with a linear mixed model. Oven precision was evaluated using the Kruskall-Wallis test. ResultsGlazed specimens were more translucent than polished ones (p < 0.001). ZLT and CZ+ were more translucent than 3M and KT regardless of the sintering oven (p < 0.01). Several oven/material combinations reached or exceeded the S2 oven TP: CS4 with CZ+ and 3M; CS6 with ZLT and KT (p < 0.01). SpeedFire was significantly less precise (p < 0.05) and produced lower TP values for ZLT, CZ+, and KT (p < 0.01). Results for TP and CR were highly correlated. ConclusionsMZ surface finish, material thickness, and oven used all had a significant effect on translucency. Some chairside-oriented solutions produced results with translucency equal to conventionally processed zirconia. Clinical significanceThe translucency of a ceramic restoration is an important factor in determining its esthetics. Clinicians desiring the most esthetic outcomes with monolithic zirconia should be aware of the significant effects that surface finishing, material thickness, and the sintering oven used can have on restoration translucency.

Surface treatment, liquid, and aging effects on color and surface properties of monolithic ceramics.

The purpose of this study was to investigate the effects of surface treatments, liquids, and aging on color, translucency, and surface properties of monolithic ceramics. Lithium disilicate (LDS) and zirconia-reinforced lithium silicate (ZLS) ceramics (n = 135 each) were cut and divided into three groups [crystallization+glaze (single stage), crystallization-glaze (two stages), and crystallization-polish (two stages)]. One sample from each group was examined using scanning electron microscopy (SEM). Remaining samples were divided into four subgroups (distilled water, coffee, grape juice, and smoothie) (n = 11 each), stored for 12 d in the respective liquids, and thermally aged. One sample from each subgroup was analyzed using SEM. The color, gloss, and roughness values of the samples were analyzed after surface treatment (initial) and storage under different liquids+aging conditions. The initial data and both the aged data and data change values were analyzed using robust two- and three-way analyses of variance. The glazed groups exhibited smoother surfaces. Ceramic type and ceramic-surface treatment interactions affected the initial translucency parameter (TP) (P < .001) and the initial and aged roughness values (P ≤ .001). Surface treatment type affected the color change (P < .001), and ceramic type affected the aged TP values (P < .001). Type of ceramic, surface treatment, and their interactions affected both the initial and aged gloss (P ≤ .001) and TP change values (P ≤ .015). Surface treatment type and ceramic-surface treatment interactions affected the gloss change values (P ≤ .001). Although both ceramics and all surface treatments are clinically applicable, crystallization-glaze is recommended. When gloss and smoothness are important or when translucency is important, ZLS or LDS may be preferred, respectively.

Correlation of resin composite translucency and IOS accuracy: An in-vitro study.

Different restoration materials have different optical characteristics that influence the intraoral scanner's (IOS) image accuracy. The purpose of this in-vitro investigation was to investigate how composite translucency affected the accuracy of IOS. GC G-aenial Universal Injectable JE composite plates were used for the study at 3 thicknesses (1-2-3mm). A lab scanner (3Shape E1) obtained 1 reference scan, whereas IOS (Trios3) was used to conduct 10 experimental scans per group. After 3D superimposition, deviation values were used to assess the accuracy (trueness and precision) outcomes for the corresponding groups. Using an LS170 V2.0 colorimeter, the translucency parameter (TP) of the plates was determined from L*a*b* values of CIELAB color space. The composite translucency resulted in a decrease in the scale of digital impressions. The 1mm group had the largest scale reduction (0.02mm) significantly, followed by the 2mm and 3mm groups (0.01mm). No difference was found in mean precision. The colorimeter detects the L*a*b* values and showed that 1mm composite plate expressed the highest TP value, then 2mm and 3mm groups (28.90, 14.26 and 6.49 respectively). The thinner composite, the higher translucency and TP were highly positively correlated to IOS trueness of composite plates. Composite translucency has an impact on optical impression accuracy. In correlation, the optical impression becomes less accurate the more translucent the composite is. This implies that in the digital process, the dentist should specify the appropriate optical properties of composite materials concerning both their mechanical and aesthetic qualities. Key words:Accuracy, translucency, resin composite, digital dentistry, intraoral-scanner.

Evaluation of Color and Translucency of Stained and Glazed Monolithic Lithium Disilicates and Zirconia After Toothbrushing with Different Dentifrices and Thermocycling.

To evaluate changes in color and translucency of stained and glazed monolithic lithium disilicates and zirconia after toothbrushing with conventional or whitening dentifrices followed by thermocycling. Samples (n &#61; 20/material) from CAD/CAM (IPS e.max CAD [EC]) and pressable (IPS e.max Press [EP]) lithium disilicates and 5Y-PSZ zirconia (Prettau 4 Anterior [PA]) were prepared and received staining and glazing procedures. Aging was performed by toothbrushing with conventional (n &#61; 10) or whitening (n &#61; 10) dentifrices, followed by thermocycling simulating 5, 10, and 15 years. Color coordinates L*, a*, b*, , and C* and h° values were assessed with a spectrophotometer at baseline and after each aging period to calculate color changes (ΔE00), lightness (ΔL*), and translucency parameter (TP). Data were analyzed using three-way repeated measures ANOVA's followed by Sidak post-hoc test (α &#61; .05). When comparing the dentifrices, EC and EP produced the greatest ΔE00 after 15 years with the whitening dentifrice (P < .05). Regardless of the dentifrice, PA showed greater ΔE00 than EC after 10 years (P < .05). When comparing the aging periods, EC and PA did not show differences in ΔE00 for both dentifrices (P ≥ .05). EC and EP produced an increased ΔL* after 15 years in the whitening group (P < .05). In the whitening groups, the ΔL* values of PA differ (P < .005) from those of lithium disilicates. Regardless of the experimental group, the TP values followed the inequality: PA < EC < EP (P < .05). Overall, the color of stained and glazed monolithic lithium disilicates and zirconia changed under aging with greater effects for whitening dentifrice. Aging did not influence translucency.

Research Paper: Comparing the Translucency of Several Enamel and Universal- Shade Composite Resins

Introduction: Translucency is one of the important optical properties of tooth color materials and it is greatly affected by the thickness of material. This study concerns comparing the translucency parameter (TP) of five different composite resins in different thicknesses. Materials and Methods: Five brands of composite resins; Gradia (GC) ,Crystalline (Confi-dental) Vit-l-escence (Ultradent) in A2, and Herculite XRV (Kerr), Opallis (FGM) in enamel A2 (EA2) shades were selected to enroll the study. Color coordinates of each composite were determined at 0.5, 1, and 1.5 mm thicknesses on a white backing, the backing of material itself and a black backing were calculated by using a spectrophotometer to evaluate the translucency parameter (TP) of the study materials. The masking ability was also calculated from the specimens on the material itself and on black backing. The values under 2 were estimated as imperceptible. One-way ANOVA, T-test and Tukey HSD were employed for statistical analysis. Results: Opallis (EA2) showed the less TP values in all thicknesses in comparison to the other materials (p&lt; 0.05) but there was no statistically significant difference between TP values of Gradia and Opallis in 1.5 and 0.5 mm-thick. The masking ability values recorded for all specimens at different thicknesses, were in the range of perceptible. Conclusion: In this study, translucency of Opallis (EA2) and Gradia(A2) was less than the other enamel /universal shade composites. For this reason, it would be concluded that if the restoration thickness is ≤1.5mm, these enamel/universal shade composite resins cannot mask the black background color.

INVESTIGATION OF MICROSCOPIC STRUCTURE, TRANSLUCENCY PARAMETERS, AND FRACTURE TOUGHNESS OF TWO PRESSABLE LITHIUM DISILICATE GLASS-CERAMIC MATERIALS.

To investigate the microscopic structure and fracture toughness of two pressable glass-ceramics-GC Initial LiSi Press (LiSi) and IPS e.max Press (e.max)-with different levels of translucency. Two groups each of LiSi and e.max, with medium opacity and high translucency levels, were examined. The crystal morphology of acid-etched specimens was observed under a scanning electron microscope (SEM). Six specimens in each group were fabricated in a square shape (12 ' 12 ' 1.5 mm) to measure translucency parameters (TP) using a spectrophotometer. Ten bar-shaped specimens in each group with dimensions of 23 x 2 x 4 mm were used to determine the fracture toughness (KIc) by a surface crack in flexure (SCF) using a universal testing machine. One-way ANOVA and Scheffe post-hoc tests were used for statistical analysis. LiSi showed fine dense crystals 1 to 1.5 μm in size, while e.max showed long rod-shaped crystals 3 to 4 μm in size. The TP values of all specimens coincided with their translucency levels. There was no statistical difference in the KIc between different translucency for both ceramics (P < .05). However, the KIc of e.max was significantly higher than that of LiSi at both translucency levels. As a result of larger and longer crystals, e.max provided better crack deviation mechanism to resist the fracture. Within the limitations of this study, the translucency levels of both lithium disilicate ceramics did not affect the fracture toughness of the materials. The fracture toughness of e.max was statistically higher than LiSi.

Comparison of the translucency parameters and bond strength of 5Y-ZP zirconia, 3-YTZP zirconia, and lithium disilicate.

E-max is a more aesthetic material than traditional zirconia. In addition, the bond strength of traditional zirconia with adhesive cements is lower. There are not enough studies on how the aesthetic values and bond strength of 5-YZP, the new generation zirconia, compare to e-max and traditional zirconia. Can 5-YZP be an alternative to e-max in terms of aesthetics and bond strength? The aim of the study is to compare the translucency property and bonding ability of 5y-zp zirconias with previous generation zirconias and lithium disilicate. Two types of zirconia Katana UT and Katana HT for measuring translucency values; and using a type of lithium disilicate IPS e.max CAD LT, three groups were formed (n = 10). Translucency specimens were fabricated (n = 10). Their L*a*b* values were measured against a black-and-white background with a spectrophotometer, and DE00 was calculated. To perform micro-shear tests, a cylinder design was made from zirconia and IPS e.max CAD blocks (n = 20). After the samples were aged by thermal cycle, the micro-shear test was applied to specimens cemented to teeth extracted with two different adhesive cement systems. According to the results of one-way analysis of variance, a statistically significant difference was found between the translucency parameter (TP) values of the groups. According to Tukey's honestly significant difference (HSD) multiple comparisons, the values of the three groups are statistically different from each other. Although IPS e.max CAD group has the highest TP values, the Katana HT group has the lowest values. 5Y-PZ has a TP intermediate to those of 3Y-TZP and lithium disilicate. Long-term bond strength of 3Y-TZP and 5Y-ZP were similar to those of lithium disilicate. To be an alternative to glass ceramics in the anterior region, translucency and bond strength values need to be improved.

Effect of glycerin on the optical proprieties of PEEK

The aim of this study is to evaluate the optical proprieties of PEEK and the influence of a coupling medium (G-glycerin), by testing the hypothesis that glycerin can influence translucency. Eight standardized specimens were fabricated from CopraPeek (WhitePeaks Dental Solution, Germany) Medium A2 dentine 10 mm x 15 mm polished to 1.0 in thickness and Nexco Paste Dentine veneer material shade A3, with thicknesses of 0.5, 1.0 and 1.5 mm. Color and CIELAB coordinates were evaluated using Vita 0.5, 1.0 and 1.5 mm. Color and CIELAB coordinates were evaluated using Vita Easyshade. All evaluations were repeated using glycerin and the values were recorded. Translucency is the relative amount of light that passes through a unit thickness of a material. Translucency parameter (TP) and contrast ratio (CR) were calculated. Also the value of color change (∆E*) was calculated and statistical analysis was performed [1]. Expected results: The mean TP values of the studied samples were in the range of 1.22-3.81, which is lower than those reported for natural teeth [2][3][4]. The OP values of PEEK were recorded in the range of 0.78–3.11, also lower than those of natural teeth. Although mean translucency values were significantly different for each method (TP and CR), they were highly correlated (r2=0.70), even when G was used (r2=0.56). Conclusion: The coupling medium significantly influenced the mean values of ∆E and translucency. Clinical assessment of perceptibility and acceptability thresholds of translucency is needed

Translucency Parameters and Masking Abilities of Monolithic CAD/CAM Ceramics.

To compare the translucency parameters and masking abilities of different monolithic CAD/CAM ceramics placed on different-colored substructures. Square-shaped specimens (12 × 12 × 1.5 mm) were prepared from feldspathic (C), leucite (EMP), lithium disilicate (e.max), zirconiareinforced lithium silicate (VS), resin nanoceramic (LU), polymer-infiltrated ceramic (VE), hybrid nanoceramic (GC), monolithic zirconia (TZI), and composite resin (TC) blocks (n &#61; 10 per material). After mechanical polishing, the translucency parameter (TP) was calculated. Then, each ceramic specimen was measured on eight substructures, and the color difference between ND2 and each substrate was calculated with the CIEDE2000 formula. TP values were analyzed with one-way ANOVA and Games-Howell tests, and the color differences indicating masking ability were analyzed with two-way ANOVA and Tukey HSD tests. The highest TP was observed in TC, followed by LU, EMP, C,GC, e.max, VS, VE, and TZI. The ΔE00 color difference values of TZI, VS, and VE on all abutment colors, except for ND9, were below the acceptable threshold value. All monolithic ceramic materials used in the study masked the ND1 and ND3 substrates. The ND9, representing severely discolored or devitalized preparations, could not be masked by any monolithic CAD/CAM ceramics used in the study.