Translucency Of Ceramics Research Articles

Degree of conversion and microhardness of resin cements photoactivated through glass ceramic.

BackgroundTo assess whether glass-ceramic shade, thickness and translucency affect degree of conversion (DC) and Knoop microhardness (KHN) of resin cements photoactivated using light-emitting diode (LED) or quartz-tungsten-halogen (QTH) units. Material and MethodsGlass-ceramic blocks were cut (2, 3 and 4mm) and sintered. For DC FT Raman spectroscopy (n=3), film specimens of cements (RelyX ARC, U200, Veneer, C&B) were obtained. For KHN test (n=3), cements were inserted in cylindrical matrix and covered by polyester strip. Specimens were photoactivated (30s) using LED or QTH according to each group: direct photoactivation (DP), interposing ceramic specimens or no photoactivation (NP). Data were analysed by ANOVA and Tukey’s test, Kruskal-Wallis and Dunn’s tests (p<0.05). ResultsCeramic features had significant effect on DC of RelyX ARC, U200 and Veneer (p<0.0017). Light source had no effect (p=0.9512). C&B and Veneer had higher DC, followed by dual cements. NP dual cements showed the lowest DC. For KHN, ceramic shade (p=0.1717) and light source (p=0.1421) were not significant, but ceramic translucency, thickness and resin cement were significant (p=0.0001). KHN was higher for U200 followed by ARC, and lowest for Veneer. ConclusionsDC was affected by ceramic shade, translucency and thickness. KHN was dependent on ceramic translucency and thickness. Higher DC and KHN were achieved for dual-cured cements photoactivated through 2mm-thick low translucent or 3mm-thick high translucent glass-ceramic. Key words:Cementation, composite resin cements, dental curing lights, glass ceramics.

Effect of Simulated Gastric Acid on Optical Properties of Different Monolithic Ceramics

Objectives: The purpose of this study was to evaluate the effect of simulated gastric acid on the color and translucency of monolithic ceramics. Materials and methods: A total of forty ceramic disks from four ceramic materials (10 each) were cut with a final thickness of 1.0 mm by using Isomet saw from ceramic blocks of each material (Ceramil Zolid fx white {Z}, IPS e.max CAD {E} HT A3, Vita Suprinity {S} HT A3, and Cerasmart {C} HT A3). Zirconia disks then colored with A3 coloring liquid and sintered, while IPS e.max CAD and Vita Suprinity were crystallized according to manufacturer’s instruction. Spectrophotometer was used to evaluate color change (∆E) and translucency parameter (TP). L*a*b* color coordinates were determined over white and black backgrounds according to the CIE Lab 1976 color scale before and after immersion in simulated gastric acid (HCl) for 96 h at 37 °C incubator. The collected data were statistically analyzed using ANOVA followed by Tukey’s post-hoc test and the significance level was set at P≤0.05. Results: The highest color change was recorded for group C followed by group E, group S, and the least one is group Z. Translucency increased significantly (P˂0.05) after acid immersion for all materials except for group C. Conclusion: Zolid fx showed the greatest color stability after gastric acid immersion, while Cerasmart is the least one, however, all tested ceramics are within the clinically acceptable limit. Translucency increased after gastric acid immersion for all tested ceramics except for Cerasmart, it decreased.

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

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. 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 3W 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. 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. L and APA significantly affected the translucency and color properties of RMCs. APA was found more favorable than L. Clinicians should carefully use surface conditioning methods, considering their impact on the optical characteristics of RMCs, especially when the restoration is thin.

Optical and Mechanical Properties of Highly Translucent Dental Zirconia.

The aim was to evaluate the translucency, opalescence, and fluorescence of highly translucent zirconia, lithium disilicate, and bovine teeth. One mm-thick specimens of five monolithic zirconia systems, two glass-ceramics, and bovine enamel/dentin were investigated. A spectrophotometer (Ci7600) was used to measure the CIELab color coordinates, and the translucency and opalescence values were obtained. For evaluating the fluorescence emission, the differences in spectral reflectance by the UV component of illumination were calculated. The microstructures of ceramic specimens were examined with a scanning electron microscope and the chemical compositions were determined with an X-ray fluorescence spectrometer. Mechanical properties were appraised with three-point bending strength, indentation fracture toughness, and Vickers hardness. Data were analyzed using a one-way ANOVA, followed by Tukey’s multiple comparison test (α = 0.05). A higher yttria content (5 mol%) significantly improved the translucency of zirconia ceramics, while they were less translucent than lithium disilicate (p < 0.05). Lowering the alumina content below 0.05 wt.% enhanced the translucency (p < 0.05), but a small amount of alumina was still required to obtain full densification. 0.05 wt.% Fe was used to increase the chroma of zirconia specimens without compromising their mechanical properties. The Er-containing zirconia specimen showed a maximal fluorescence emission at 430 nm. The degree of opalescence was affected by the microstructures of ceramic materials. The microstructure, incorporation of a secondary phase, and sintering behavior can have a strong impact on the final mechanical and optical properties of dental ceramics. Addition of small amounts of metal oxides can affect the translucency, opalescence or fluorescence qualities of zirconia

Does ceramic translucency affect the degree of conversion of luting agents?

ObjectivesSolely light-activated luting agents have been suggested for cementing procedures with aesthetic rehabilitations, but questions remain regarding their curing potential under more opaque prosthesis. To determine the degree of carbon double bond (C=C) conversion (DC) of four categories of luting strategies when considering the interposition of lithium-disilicate ceramic laminates with different translucencies during the photo-activation procedures.Materials and methodsFour different luting strategies were considered: a dual-activated resin-based cement (control, RelyX ARC, 3M ESPE), a solely light-activated resin-based cement (RelyX Veneer, 3M ESPE), a flowable resin-based composite (Filtek Z350 XT Flow, 3M ESPE), and a pre-heated (68 °C for 30 min) regular resin-based composite (Filtek Z350 XT, 3M ESPE). The DC was determined by Fourier-transformed infrared spectroscopy (n = 6), 1 min after light-activation in two conditions: (a) with direct light exposure and (b) with light exposure with the interposition of lithium-disilicate disks (e.max Press, Ivoclar Vivadent) with 1.5 mm thickness with three translucent degrees: high translucency (HT), low translucency (LT), and medium opacity (MO). The translucency parameter (TP) formula was performed to quantitatively evaluate the ceramics’ translucencies using white (L* = 93.7, a* = 1.2, and b* = 0.8) and black (L* = 8.6, a* = − 0.7, and b* = − 1.5) backgrounds. The irradiance from the light curing unit (Bluephase G2, Ivoclar Vivadent) was calculated with a power meter (Ophir Optronics) with direct light exposure to the sensor and also with the interposition of the light ceramic discs. Degree of conversion data was submitted to two-way ANOVA and Tukey’s test (α = 0.05).ResultsTranslucency parameters values were 16.4, 13.4 and 12.6 for HT, LT and MO ceramics—respectively—and affected the percentage of light transmission. For all ceramic translucencies the highest DC values were observed for the dual-activated resin-based cement followed by the solely light-activated resin-based cement, the flowable composite and then by pre-heated regular composite. The ceramic’s translucency influenced the DC only for the pre-heated composite.ConclusionsThe effect of the ceramic translucency on the curing behavior was dependent on the luting strategy. The DC was only affected for the pre-heated composite, which demonstrates lower conversion with the increased ceramic opacity.

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.

Influence of thickness and translucency of lithium disilicate ceramic on degree of conversion of resinous materials.

BackgroundIn this study was assessed the degree of conversion (DC) of amine-free resin cements light cured through lithium disilicate-reinforced ceramics at different thicknesses and translucency. Material and MethodsSpecimens were divided into 21 groups (n = 5) according to luting agent used: Variolink Esthetic LC (Light shade), RelyX Ultimate (A1 shade), and Filtek Z350 XT Flow (A1 shade); the ceramic translucency: low (LT) and high (HT); and the ceramic thickness: no ceramic (control), 0.5 mm, 1 mm, and 2 mm. A Teflon mold with (5 x 5 x 0.5 mm) was used to standardize the cement and over it the ceramic block from each group was placed. Set was cured using a polywave LED light (1200 mW/cm2 - Bluephase G2) for 40 s. FTIR spectra of uncured and cured materials was obtained and DC calculated from the height of the peaks 1610 and 1640 cm-1. Data were submitted to ANOVA followed by Tukey’s test (α = 0.05). ResultsThere was a significant difference for luting agents (p< 0.0001) and translucency (p = 0.025), but not for thickness (p = 0.73). Dual amine-free RelyX Ultimate showed the lowest DC values and higher translucency promoted higher DC. ConclusionsDual amine-free cement showed the lowest monomer conversion and higher translucency ceramics promoted a higher DC. Key words:Ceramic, degree of conversion, resin cement, thickness, translucency.

Effect of Different Surface Finishing Procedures on the Color and Translucency of two CAD/CAM Monolithic Glass Ceramics

Purpose: The purpose of this study was to investigate the effects of different surface finishing procedures, storage solutions, and prophylactic polishing on the color and translucency parameters (TPs) of two machinable glass ceramics; lithium silicate glass-ceramic (Obsidian)and lithium disilicate reinforced glass-ceramic (IPS e-max CAD). Materials and Methods: Obsidian and e-max milling blocks were sectioned with a low speed cutting machineunder water cooling into square specimens (10×10×1 mm3)(N=60). The specimens were divided into 3 groups (n=10 each) according to the received surface treatment; finishing and polishing, glaze, and staining and glaze in accordance with manufacturers’ instructions. Then, each group was further subdivided into 2 storage subgroups, coffee and distilled water as a control (n =5 for each subgroup). Color and translucency values were measured in CIELAB color space with spectrophotometer at the initial stage, and following 18 days, and after fine-grit prophylactic polishing paste application. Color changes (ΔE) and translucency (ΔTPs) were calculated and statistically analyzed using One-way ANOVA for comparing surface treatment followed by Tukey’s pair-wise if showed significant. Student t-test was used within material type to show effect of staining. Multifactorial analysis of variance ANOVA was performed to detect significance between variables (material type, surface treatment, immersion solution and re-polish).Results: There was a statistically significant difference between the ΔE values of both immersion solutions as (p = water) for both ceramics tested. Obsidian and e-max, glaze procedure showed lower color change values than finishing and polishing and staining and glazing surface(p > 0.05) following coffee storage. It was found that re-polish decreased color change significantly for both tested ceramics. The translucency was affected according the monolithic CAD/CAM ceramic type. The translucency of the e-max was found to be higher than that of obsidian glass-ceramic. Colorant coffee solution decreased the translucency of both obsidian and e-max ceramics. According to the results of this study, mechanical polishing exhibited highest translucency than stained and glazed and glazed groups. The re-polishing procedure decreased translucency parameter non-significantly for both tested ceramics. Conclusions: Within the limitations of this study, the following conclusions could be drawn: Staining drinks as coffee had a negative effect on the color stability and translucency of both obsidian and e-max glass ceramic materials tested. Glaze procedure led to more color stability with respect to finishing and polishing and stained and glaze for both ceramics after 18 days coffee storage. Polishing paste led to a decrease in color changes for both ceramics tested. The translucency was affected according the monolithic CAD/CAM ceramic type. The translucency of the e-max lithium disilicate glass-ceramic was found to be higher than that of obsidian lithium silicate glass ceramic after different finishing procedure, after coffee storage and after re-polish. Finished and polished groups presented the highest translucency than stained and glazed and glazed for both ceramics tested. Re-polish decreased translucency parameters non-significantly for both tested ceramics.

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.

Factors affecting the translucency of monolithic zirconia ceramics: A review from materials science perspective.

The use of monolithic [yttria (Y2O3)-stabilized tetragonal zirconia (ZrO2) polycrystalline] (Y-TZP) ceramics to restore teeth is expanding in dentistry. However, there are still some problems about color matching and the translucency of these ceramics. The employment of Y-TZP ceramics in aesthetically critical regions is questionable due to the insufficient translucency and opacity of the restorations. The objective of this review was to assess the factors affecting the translucency of monolithic Y-TZP ceramics for a better understanding the relevant parameters in restorations. The translucency of polycrystalline ceramics is a complex phenomenon. Apprehending the translucency regarding ceramics requires their knowledge of physical, chemical and microstructural characteristics with the light interactions among them.

Trade-off between fracture resistance and translucency of zirconia and lithium-disilicate glass ceramics for monolithic restorations

High strength and translucency are generally not coincident in one restorative material and there is still a continuous development for a better balance between these two properties. Zirconia and lithium-disilicate glass-ceramics are currently the most popular alternatives for monolithic restorations. In this work, the mechanical properties and more important, the slow crack growth (SCG) resistance, which rules long-term durability, were thoroughly studied for three zirconia ceramics stabilized by 3, 4 and 5 mol% yttria in comparison to lithium-disilicate glass-ceramic. Translucency versus strength maps revealed that the more translucent zirconia compositions (i.e. with higher yttria contents) fill the gap between the standard 3 mol% yttria stabilized zirconia (3Y-TZP) and lithium-disilicate. Moreover, increasing yttria content did not always result in lower strength, as values for 3 mol% and 4 mol% yttria were the same. Independent on the yttria contents, all zirconia showed similar relative susceptibility to SCG under static and cyclic conditions and were significantly more SCG-resistant than lithium-disilicate glass ceramic. A concern with higher yttria contents (5 and 4 mol%) however could lie in the higher sensitivity to defects, resulting in a larger scatter in strength. Statement of SignificanceIn addition to the common investigations on the generally reported strength, toughness and translucency, V-KI diagrams (crack velocity versus stress-intensity factor) from fast fracture to threshold for three newly developed zirconia were directly measured by double torsion methods under static and cyclic loading conditions. The crack-growth mechanisms were analyzed in depth. Results were compared with another popular dental ceramic, namely lithium-disilicate glass-ceramic, revealing the pros and cons of polycrystalline and glass-ceramics in terms of long-term durability. This is the first time that V-KI curves are compared for the major ceramic and glass-ceramic used for dental restorations. Strength versus translucency maps for different CAD/CAM dental restorative materials were described, showing the current indication range for zirconia ceramics.

Effects of accelerated artificial aging on the translucency and color stability of monolithic ceramics with different surface treatments

Statement of problemDifferent surface finishing procedures can be applied to monolithic restorations. However, information is limited regarding the long-term performance of these procedures. PurposeThe purpose of this in vitro study was to evaluate the effect of aging on the translucency and color stability of monolithic ceramics with different surface finishing procedures. Material and methodsDisk-shaped (14×1.5 mm) specimens of monolithic zirconia (Zirkonzahn Prettau [ZZ]) and lithium disilicate glass-ceramic (IPS e.max Press [IPS]) were fabricated. The specimens were divided into 3 subgroups according to the surface treatments (n=9, G: glazing, R: rubber polishing system, and P: rubber polishing system followed by polishing paste). Color measurements were made by using a spectrophotometer before and after an ultraviolet aging process. L*, a*, and b* parameters were recorded. ΔE and translucency parameter (TP) values were calculated. One specimen from each subgroup was examined by scanning electron microscopy (×30 000). The data were statistically analyzed using the Mann-Whitney U, Kruskal-Wallis, and post hoc tests (α=.05). ResultsΔE values of group ZZ (5.03) exceeded the clinically acceptable level (3.5); however, the color change was not clinically perceptible for IPS (0.41). The ΔE value of the subgroup P was found to be higher than that of the others for ZZ (P<.001). The ΔE value was not affected by the surface treatment for IPS. Group IPS showed significantly higher translucency than the ZZ group (P<.001). TP values were not affected by the surface treatment in either material and decreased after aging. However, changes in the TP values were too slight to be clinically perceptible. ConclusionsLithium disilicate ceramic was found to be more esthetic than monolithic zirconia ceramic in terms of color stability and translucency.

Effect of ceramic translucency and luting cement shade on the color masking ability of laminate veneers

The aim of this study was to evaluate the effect of ceramic material types, degree of veneer translucency, and luting cement shades on masking the underlying dark dental substrate to achieve best esthetics. In this in vitro study, 56 specimens each of 0.5-mm thickness were fabricated from two esthetic veneer materials Vita Enamic and Vita Suprinity, with two different translucencies, i.e., HT and T. To simulate the color of a dark underlying dental structure, background discs with C3 shade were fabricated using resin composite. The ceramic specimens with varying translucencies were cemented on the dark background of the resin composite with A1 and opaque white shades of resin luting cement. Color difference (ΔE) values from a reference color (A1 shade) were calculated using a spectrophotometer. The results were then statistically analyzed using three-way ANOVA test (α = 0.05). The ΔE values of both ceramic systems were affected by both the degree of veneer translucency (P = 0.00) and the luting agent shade (P = 0.016). The use of an opaque luting agent and T translucency resulted in a decrease in the ΔE* values for all ceramics tested, regardless to the material type. Suprinity and Enamic showed similarity in the masking ability of dark substrate after cementation. None of the 0.5-mm veneers of the two ceramic systems could reach A1 shade without a detectable color difference after cementation. The change in degree of veneer translucency was more effective than the change in luting agent shade in masking the underlying dark substrate.

Computable translucency as a function of thickness in a multi-layered zirconia

Statement of problemDetermining the relationship between variable thicknesses and the translucency of dental ceramics is essential for optimizing esthetics in different clinical situations. PurposeThe purpose of this in vitro study was to analyze the relationship between layer thickness and translucency of 2 multi-layered monolithic zirconia materials and to develop an equation by which the grade of translucency can be calculated dependent on the materials' layer thicknesses in advance. Material and methodsTwo semisintered multi-layered zirconia blanks, namely KATANA Zirconia Super Translucent Multi-Layered Disk (Noritake Dental Supply Co, Ltd) and Zirconia Ultra Translucent Multi-Layered Disk (UTML) (Noritake Dental Supply Co, Ltd), were sectioned (N=96) to separate the 4 layers (n=12 per layer): enamel layer, transition layer 1, transition layer 2, body layer. All specimens were sintered in a furnace (M2 Plus; Thermo-Star) at 1500°C for 2 hours and automatically polished under water cooling up to P2400 for the thicknesses of 1.6, 1.3, 1.0, 0.7, and 0.4 mm. Transmittance of visible light was measured using a spectrophotometer (Lambda 35; Perkin Elmer). Data were analyzed using the Kolmogorov-Smirnov, 2-way ANOVA, and Scheffé post hoc tests (α=.01) and curve fitting. ResultsAnalyzing the fitting of the values of the 8 material groups to the linear, exponential, and logarithmic curves, 7 of the 8 groups (not UTML body layer) fitted the most (R-square value closer to 1.0) to the logarithmic curve. Constants were obtained from the distance to the x-axis and the curvature. ConclusionsThe methodology of this study provided the materials' specific constants a and b by analyzing the translucency behavior of KATANA Super Translucent Multi-Layered Disk and Ultra Translucent Multi-Layered Disk in different thicknesses, allowing further translucency calculation by applying the developed formula and the constants.

Additive colours approach for dental ceramics translucency characteristics made from Sumatra and Java natural sands

Translucency is one of dental ceramics desirable aesthetic characteristics, which can be used as an indirect restoration. Dental ceramics can also be made using Computed Aided Design/Computer Aided Manufacturing (CAD/CAM) unit that can create variety blocks as an ingot into a customized restoration. This paper presents the results of self-synthesized porcelain blocks generated from natural sand of Sumatera and Java Islands to promote national independency. This research aims to determine the translucency of dental ceramics made from Indonesia’s natural sand. Six samples each of two different synthesized temperatures, 1150 °C and 1200 °C, were made. To analyse translucency of the sample, their image was taken in bright light background in a black box, then additive green and blue colours histogram channel with range 0 (opaque) to 255 (transparent) were evaluated using Matlab R2015B. The result revealed that mean of green peaks on 1150 °C has an average translucency value of 41%, compared to 34% of blue peaks. Lower percentage of translucency, 31% and 25% on the green and blue channel respectively were attained in samples synthesized in 1200 °C. These suggest that 1150 °C is the optimum temperature for translucency for these ceramic samples from natural sands as they contain leucite crystals shown by the XRD analyses as a result of silica-undersaturated mixture indicated by the Electron Dispersive Spectroscopy. SEM (Scanning Electron Microscope) results show remnant of air pocket in the samples sintered at higher temperature.In conclusion, natural sand from Sumatera and Java can be considered as reliable, cheap basic material options in developing self-synthesized dental ceramics with a desirable translucency. These preliminary results indicate that better balance between strength and translucency could potentially be achieved by making nano-sized dental ceramics.

Effect of surface finishing on the colour stability and translucency of dental ceramics

BackgroundThe purpose of this study was to investigate the effects of staining solutions and surface finishing on the colour stability and translucency of hybrid ceramic (HC) and resin nanoceramic (RNC) materials.MethodsTwenty four groups consisting of 10 specimens (240 specimens in total) were created out of HC and RNC, including six groups to be stored in distilled water served as the controls groups. The Vita Enamic technical set, Shofu polishers, medium and fine rubber wheels and Sof-Lex polishing discs were used as polishing instruments. Cola, tea, and coffee were used as staining solutions. The colour differences (∆E*) and translucency parameter (TP) were evaluated by a spectrophotometer. Data were analysed by a One-way Analysis of Variance (ANOVA) and Mann-Whitney U test.ResultsThere was a statistically significant difference between the ∆E* values of the HC specimens in the coffee groups and the ∆E* values of the other HC groups (p < 0.05). The ∆E* values of the RNC specimens in the coffee and tea groups were not different from the specimens in the cola groups (p > 0.05). The TP values of the polished groups were higher than the Sof-Lex groups and the Shofu groups on both HC and RNC materials (p < 0.05).ConclusionsIncreased ∆E* values were observed in HC specimens stored in a coffee solution compared to the specimens stored in a tea or cola solution. Both of the RNC specimens stored in coffee and tea had higher ∆E* values than the RNC specimens stored in the cola. The TP values of both HC and RNC specimens stored in the coffee solution decreased.

Translucency of dental ceramics for monolithic restorations

Translucency of dental ceramics for monolithic restorations

Novel Translucent and Strong Submicron Alumina Ceramics for Dental Restorations

An ideal ceramic restorative material should possess excellent aesthetic and mechanical properties. We hypothesize that the high translucency and strength of polycrystalline ceramics can be achieved through microstructural tailoring. The aim of this study is to demonstrate the superior optical and mechanical properties of a new class of submicron grain-sized alumina ceramics relative to the current state-of-the-art dental ceramic materials. The translucency, the in-line transmission (TIT) in particular, of these submicron alumina ceramics has been examined with the Rayleigh-Gans-Debye light-scattering model. The theoretical predictions related very well with the measured TIT values. The translucency parameter (TP) and contrast ratio (CR) of the newly developed aluminas were measured with a reflectance spectrophotometer on a black-and-white background. For comparison, the TIT, TP, and CR values for a variety of dental ceramics, mostly measured in-house but also cited from the literature, were included. The flexural strength of the aluminas was determined with the 4-point bending test. Our findings have shown that for polycrystalline alumina ceramics, an average grain size <1 µm coupled with a porosity level <0.7% could yield translucency values (TIT, TP, CR) similar to those of the commercial high-translucency porcelains. These values are far superior to the high-translucency lithium disilicate glass-ceramic and zirconias, including the most translucent cubic-containing zirconias. The strength of these submicron grain-sized aluminas was significantly higher than that of the cubic-containing zirconia (e.g., Zpex Smile) and lithia-based glass-ceramics (e.g., IPS e.max CAD HT). A coarse-grained alumina could also reach a translucency level comparable to that of dental porcelain. However, the relatively low strength of this material has limited its clinical indications to structurally less demanding applications, such as orthodontic brackets. With a combined high strength and translucency, the newly developed submicron grain-sized alumina may be considered a suitable material for dental restorations.

The Effect of Lithium Disilicate Ceramic Thickness and Translucency on Shear Bond Strength of Light-cured Resin Cement

Introduction: To achieve acceptable clinical performance, a ceramic veneer must be bonded to enamel by well-polymerized resin cement. Among different factors, thickness and translucency of the ceramic may affect the resin cement polymerization. Thus, the current study evaluated the effect of the thickness and translucency of lithium disilicate ceramic on light-cured resin cement bond strength to enamel. Methods: In this laboratory study, 208 sound bovine incisors were equally divided into 16 groups (n = 13). The lithium disilicate ceramic cubes in four thicknesses (0.4, 0.6, 0.8 and 1 mm) with four translucencies (high and medium opaque, high and low translucent) were fabricated and bonded to prepared enamel surfaces using a light-cured translucent resin cement according to manufacturer recommendations. After 5000 cycles of thermocycling, the bonded specimens were placed in a universal testing machine and loaded to the point of fracture. To determine the mode of failure, each sample was observed under a stereomicroscope. Data were recorded and analyzed by Shapiro-Wilk test and two-way analysis of variance (ANOVA). Results: The ceramic thickness and translucency could not significantly affect shear bond strength (SBS) of resin cement to enamel (p = 0.17 and p = 0.097, respectively). The Adhesive and ceramic cohesive failures were reported as the maximum and minimum mode of failure, respectively. Conclusion: The SBS of the light-cured resin cement bonding to enamel and lithium disilicate ceramic was not affected by the translucency of ceramics having a thickness of less than 1 mm.

EFFECT OF HEATED COMPOSITE CEMENT AND WEAR WITH DIFFERENT OPPOSING SURFACES ON COLOR OF CAD/CAM CERAMIC OCCLUSAL VENEERS

Statement of problem: improvement and maintain color stability of ceramic restorations is necessary factor for long success of esthetic fixed Prosthodontic restorations. Posterior occlusal ceramic and hybrid ceramic veneers are widely used as a clinical restorative treatment to improve appearance and restore the lost enamel. The abrasiveness limitation of different ceramics materials and its effect on color stability of both enamel and different opposing occlusal restorative materials are very important when selecting as an esthetic restorative material. In addition, recently, composite resin has been used as luting cement for indirect aesthetic restorations. The flow of the pre-heating composite as luting agent improves the adaptation and facilitate the placement of the restoration. Therefore, the effect of heat on color stability of composite as luting agent and its reflection on the color of occlusal ceramic veneers restorations are neededObjectives: this study was to investigate the effect of heating of flowable composite as luting agent and the wear of occlusal veneer ceramic restoration with different opposing(enamel, e. max and v. enamic) on the color of e. max and vita enamic CAD/CAM posterior occlusal veneers ceramic restorations.Materials and Methods: 20 extracted human upper premolars were prepared for occlusal veneers were scanned and CAD-CAM restorations were milled using e max and vita enamic CAD/CAM blocks with the same milling parameters. CAD/CAM posterior ceramic occlusal veneers restorations were cemented using flowable composite material before and after heating. Wear of occlusal veneers using chewing simulator (ROBOTA) with different opposing: human enamel, e. max and v. enamic CAD/CAM discs was used. The effect of wear and flowable composite heating on color stability were measured and the data were tabulated and analyzed statistically.Results: Total effect of heating of composite cement; regardless to occlusal veneers restorations material groups or mechanical wear, it was found that composite resin cement heating affected color stability significantly (p=0.00095 heated composite cement (ΔE) mean value = 4.53). Total effect of mechanical wear; irrespective of occlusal veneer material groups or composite resin cement heating, it was found that mechanical wear affected color stability non-significantly (p=0.5776> 0.05) as indicated three way ANOVA test where ( After aging (ΔE) mean value = 5.38 ≥ before aging (ΔE) mean value = 5.09) Conclusions: selection of the occlusal veneers materials should consider wear properties because the occlusal wear rate varies according to the materials of the occlusal veneers restoration and opposing surfaces as well as the applied load. Moreover, for best aesthetic results, clinicians must be taken in considerations the color, translucency of ceramics and the effects of the luting agent on optical properties.