Influence of resin cement shade on the color and translucency of ceramic veneers

ABSTRACT Objective This in vitro study evaluated the effect of two different shades of resin cement (RC- A1 and A3) layer on color change, translucency parameter (TP), and chroma of low (LT) and high (HT) translucent reinforced lithium disilicate ceramic laminates. Material and Methods One dual-cured RC (Variolink II, A1- and A3-shade, Ivoclar Vivadent) was applied to 1-mm thick ceramic discs to create thin RC films (100 µm thick) under the ceramics. The RC was exposed to light from a LED curing unit. Color change (ΔE) of ceramic discs was measured according to CIEL*a*b* system with a standard illuminant D65 in reflectance mode in a spectrophotometer, operating in the light range of 360-740 nm, equipped with an integrating sphere. The color difference between black (B) and white (W) background readings was used for TP analysis, while chroma was calculated by the formula C*ab=(a*2+b*2)½. ΔE of 3.3 was set as the threshold of clinically unacceptable. The results were evaluated by two-way ANOVA followed by Tukey's post hoc test. Results HT ceramics showed higher ΔE and higher TP than LT ceramics. A3-shade RC promoted higher ΔE than A1-shade cement, regardless of the ceramic translucency. No significant difference in TP was noted between ceramic discs with A1- and those with A3-shade cement. Ceramic with underlying RC showed lower TP than discs without RC. HT ceramics showed lower chroma than LT ceramics, regardless of the resin cement shade. The presence of A3-shade RC resulted in higher chroma than the presence of A1-shade RC. Conclusions Darker underlying RC layer promoted more pronounced changes in ceramic translucency, chroma, and shade of high translucent ceramic veneers. These differences may not be clinically differentiable

The Effect of a 10% Carbamide Peroxide Bleaching Agent on the Microhardness of Four Types of Direct Resin-based Restorative Materials

SUMMARY Purpose This in vitro study was undertaken to evaluate the effect of a 10% carbamide peroxide bleaching agent on the microhardness of four types of direct resin-based restorative materials. Materials and Methods Thirty disk-shaped specimens (10.0 mm diameter × 2.0 mm depth) of each material, including a microhybrid resin composite (Z250), a nanofilled resin composite (Z350), a silorane-based low-shrink resin composite (P90), and a hybrid resin composite (Valux Plus), were fabricated and then polished with medium, fine, and superfine polishing discs. After being polished, specimens were cleaned with distilled water for 2 min in an ultrasonic bath to remove any surface debris and then stored in distilled water at 37°C for 24 hours. Specimens from each material were divided into three groups (n=10). One group was selected as a control group (nontreated with bleaching agent). The other two groups were treated with bleaching agent for 14 days (group A) and for 14 days followed by immersion in artificial saliva for 14 days (group B). The top surfaces of the specimens in the different groups were also subjected to the Vickers hardness test with a load of 300 g and 15-second dwell time. Data were analyzed with a one-way analysis of variance and Tukey's HSD test (α = 0.05). Results There was a general reduction of Vickers hardness numbers (VHN) values of treated groups compared with the control group for each material used, but this reduction was minimal, with no significant difference between groups in Z250, whereas the other three materials (Z350, P90, and Valux Plus) showed a significant reduction of VHN of treated groups compared with the control group. Conversely, the findings showed no significant difference between treated groups A and B in all materials used except P90. Conclusion A 10% carbamide peroxide bleaching agent had an adverse effect on the microhardness of nanofilled, silorane-based low-shrink, and hybrid types of resin-based composite materials compared with the microhybrid type. </jats:sec

Effect of Mold Type and Diameter on the Depth of Cure of Three Resin-Based Composites

SUMMARY Objective: To evaluate the effects of different mold materials, their diameters, and light-curing units on the mechanical properties of three resin-based composites (RBC). Methods and Materials: A conventional nano-filled resin composite (Filtek Supreme Ultra, 3M Oral Care, St Paul, MN, USA) and two bulk-fill composites materials, Tetric Evoceram Bulk fill (Ivoclar Vivadent, Schaan, Liechtenstein) and Aura Bulk Fill (SDI, Bayswater, VIC, Australia), were tested. A total of 240 specimens were fabricated using metal or white semitransparent Delrin molds that were 4 or 10 mm in diameter. The RBCs were light cured for 40 seconds on the high-power setting of either a monowave (DeepCure-S, 3M Oral Care) or polywave (Bluephase G2, Ivoclar Vivadent) light-emitting diode (LED) curing unit. The depth of cure was determined using a scraping test, according to the 2009 ISO 4049 test method. Data were analyzed using multivariate analysis of variance followed by Tukey multiple comparison test (p&amp;lt;0.05). Results: In general, when used for 40 seconds, both LED curing lights achieved the same depth of cure (p=0.157). However, the mold material and its diameter had a significant effect on the depth of cure of all three RBCs (p&amp;lt;0.0001). Conclusion: Curing with either the polywave or monowave LED curing light resulted in the same depth of cure in the composites. The greatest depth of cure was always achieved using the 10-mm-diameter Delrin mold. Of the three RBCs tested, both Tetric Bulk Fill and Aura achieved a 4-mm depth of cure when tested in the 10-mm-diameter metal mold. Tetric Bulk Fill was the most transparent and had the greatest depth of cure, and the conventional composite had the least depth of cure. Very little violet (&amp;lt;420 nm) light penetrated through 6 mm of any of the RBCs. </jats:sec

UV-VIS-NIR absorber to harvest energy for solar thermophotovoltaics

Ideal ultraviolet-visible-infrared (UV-VIS-NIR) absorbers with consistent performance at elevated temperatures and severe climate conditions are crucial to harvest energy for solar-thermophotovoltaic systems (STPVs). As solar energy promises to fulfill the power demands, its efficient utilization through high-performing light-absorbing devices is inevitable. The requirement of high-temperature durability makes conventional plasmonics an infeasible choice, and those highly thermostable refractory metals/their derivatives suitable ones. In this work, a lossy refractory plasmonic material i.e. Zirconium-Nitride-based subwavelength, ultra-broadband, wide-angle, polarization-insensitive, and free-space impedance-matched metasurface absorber in a three-level Pythagorean fractal structure is demonstrated. A comprehensive investigative study is conducted with the successful attainment of more than 90% absorption between ∼ 500–900 nm with a peak of more than 98% at 655 nm. The mean absorption for wideband (200–2500 nm) is 86.01% and it is 91.37% for visible range. The proposed study provides an efficient choice of meta-absorbers for realizing highly efficient STPVs

Effect of High Irradiance on Depth of Cure of a Conventional and a Bulk Fill Resin-based Composite

SUMMARY Objectives This study evaluated the effect of using three commercial light curing units (LCUs) delivering a range of irradiance values, but delivering similar radiant exposures on the depth of cure of two different resin-based composites (RBCs). Methods A conventional hybrid RBC (Z100 shade A2, 3M ESPE) or a bulk fill RBC (Tetric EvoCeram Bulk Fill shade IVA, Ivoclar Vivadent) was packed into a 10-mm deep semicircular metal mold with a 2-mm internal radius. The RBC was exposed to light from a plasma-arc-curing (PAC) light (Sapphire Plus, DenMat) for five seconds, a quartz-tungsten-halogen (QTH) light (Optilux 501, Kerr) for 40 seconds, or a light-emitting-diode (LED) light (S10, 3M ESPE) for 20 seconds and 40 seconds (control). The Knoop microhardness was then measured as soon as possible at the top surface and at three points every 0.5 mm down from the surface. For each RBC, a repeated measures analysis of variance (ANOVA) model was used to predict the Knoop hardness in a manner analogous to a standard regression model. This predicted value was used to determine at what depth the RBC reached 80% of the mean hardness achieved at the top surface with any light. Results The PAC light delivered an irradiance and radiant exposure of 7328 mW/cm2 and 36.6 J/cm2, respectively, to the RBCs; the QTH light delivered 936 mW/cm2 and 37.4 J/cm2 and in 20 seconds the LED light delivered 1825 mW/cm2 and 36.5 J/cm2. In 40 seconds, the control LED light delivered a radiant exposure of 73.0 J/cm2. For Z100, using 80% of the maximum hardness at the top surface as the criteria for adequate curing, all light exposure conditions achieved the 2.0-mm depth of cure claimed by the manufacturer. The LED light used for 40 seconds achieved the greatest depth of cure (5.0 mm), and the PAC light used for five seconds, the least (2.5 mm). Tetric EvoCeram Bulk Fill achieved a 3.5-mm depth of cure when the broad-spectrum QTH light was used for 40 seconds delivering 37.4 J/cm2. It required a 40-second exposure time with the narrow-spectrum LED, delivering approximately 73 J/cm2 to reach a depth of cure of 4 mm. Conclusions When delivering a similar radiant exposure of 37 J/cm2, the QTH (40 seconds) and LED (20 seconds) units achieved a greater depth of cure than the PAC (five seconds) light. For both resins, the greatest depth of cure was achieved when the LED light was used for 40 seconds delivering 73 J/cm2 (p&amp;lt;0.05). </jats:sec

Emission Characteristics and Effect of Battery Drain in “Budget” Curing Lights

SUMMARY Recently, “budget” dental light-emitting diode (LED)–based light-curing units (LCUs) have become available over the Internet. These LCUs claim equal features and performance compared to LCUs from major manufacturers, but at a lower cost. This study examined radiant power, spectral emission, beam irradiance profiles, effective emission ratios, and the ability of LCUs to provide sustained output values during the lifetime of a single, fully charged battery. Three examples of each budget LCU were purchased over the Internet (KY-L029A and KY-L036A, Foshan Keyuan Medical Equipment Co, and the Woodpecker LED.B, Guilin Woodpecker Medical Instrument Co). Major dental manufacturers provided three models: Elipar S10 and Paradigm (3M ESPE) and the Bluephase G2 (Ivoclar Vivadent). Radiant power emissions were measured using a laboratory-grade thermopile system, and the spectral emission was captured using a spectroradiometer system. Irradiance profiles at the tip end were measured using a modified laser beam profiler, and the proportion of optical tip area that delivered in excess of 400 mW/cm2 (termed the effective emission ratio) was displayed using calibrated beam profile images. Emitted power was monitored over sequential exposures from each LCU starting at a fully charged battery state. The results indicated that there was less than a 100-mW/cm2 difference between manufacturer-stated average tip end irradiance and the measured output. All the budget lights had smaller optical tip areas, and two demonstrated lower effective emission ratios than did the units from the major manufacturers. The budget lights showed discontinuous values of irradiance over their tip ends. One unit delivered extremely high output levels near the center of the light tip. Two of the budget lights were unable to maintain sustained and stable light output as the battery charge decreased with use, whereas those lights from the major manufacturers all provided a sustained light output for at least 100 exposures as well as visual and audible indications that the units required recharging.</jats:p

Trans-reflective tunable color filter using electro-optic material

This research presents designing a tunable trans-reflective color filter utilizing Barium Titanate (BTO) and optimizing its performance by applying an artificial intelligence (AI) based inverse design model. The AI-based color filter design process is efficient and minimizes design challenges. The AI model comprising two sub-blocks is trained using a dataset that correlates geometrical parameters, refractive index, and input voltage variations with desired color outputs to precisely control the color filter's performance. The first is the parametric optimization block (POB), which employs two deep neural networks (DNNs) in the forward and inverse directions to achieve the optimized geometry of the proposed meta-atoms. Once the optimal parameters are completed, the next block, i.e., voltage tuning block (VTB), is employed to map specific colors onto the refractive index and the applied voltage of the BTO layer. In this way, by changing the voltage of the BTO layer, we can leverage BTO's tunable optical properties, which allow for a broad range of vibrant and customizable colors. The optimized color filter demonstrates enhanced tunability and efficiency, opening up new possibilities for applications in displays and imaging devices