Composite Discs Research Articles

Pre-Heating of Low-Shrinkage Composite Resins: Effects on Color Stability and Surface Roughness.

Objectives: The present study aimed to investigate the effect of preheating on the color stability and surface roughness of a silorane-based composite resin. Materials and Methods: A total of 44 Filtek P90 composite resin disks, (10mm×1mm), were fabricated using plastic molds and were divided into two groups. In group 2, the composite resin syringes were placed in a thermostatically controlled water bath at 55‒60°C before preparing the disks. After polishing the samples with silicon carbide papers, they were stored in distilled water for 48 hours. Roughness and color parameters were then measured in two stages: immediately after retrieval from distilled water and after 40 days of storage in tea solution. Finally, the differences in roughness and color parameters were recorded. Independent samplet-test and regression analysis were used at a significance level of P<0.05. Results: Based on the findings of the present study, there was no significant difference among the mean ∆E values (P=0.4); however, a significant difference in mean surface roughness (P=0.01) was found between the two groups. Regression analysis showed a significant relationship between the study groups in terms of surface roughness and ΔE values​ (preheated: r2 = 0.73; non-preheated: r2= 0.76). Conclusion: Filtek P90 silorane-base composite showed ΔE>3.3 and surface roughness above 0.2µ under preheated and non-preheated conditions and discoloration increased following preheating.

The Effect of Using Composite Primers, Silane and Surface Roughening on the Shear Bond Strength of Metal Brackets bonded to Old Composites

Background: One of the effective factors in successful orthodontic treatment is the use of appropriate bond between the orthodontic bracket and surface of the composite restoration. The aim of this study was to evaluate the effect of using composite primers, silane, and surface roughening on the shear bond strength of metal brackets bonded to old composites. Methods: In this laboratory study, 90 composite disks (Z350 3M) measuring 4 by 6 mm were kept in distilled water for 1 week and subjected to 5000°C heating rotation (rpm). These samples were divided into 6 groups based on the use of composite primer, surface roughening, and silane as follows: Group 1 (Control): old composite+37 % acid etching, Group 2: Old composite+37% acid etching+20 s cure. Group 3: Old composite+37% acid etching+5 s air-drying, Group 4: Old composite+acid etching+rubbing, Group 5: Old composite+roughing with diamond bur, Group 6: Old composite+Acid etching+roughing with diamond bur metal brackets were attached to the specimens and the specimens were immersed in water and in a thermal rotation system of 5000 rpm for 1 week. The shear bond strength of the brackets was measured. Results: The highest and the lowest shear bond strength values were found in the fourth and control groups, respectively, indicating a significant difference across all groups (P=0.001). In this regard, the results of least significant difference (LSD) test also showed that the mean shear bond strength of orthodontic brackets in the control group was significantly lower than that observed in other experimental groups, but without significant difference across the pointed groups. Conclusions: The use of surface roughness, composite primer, and silane together do not have a cumulative effect on the increase of the bond strength between old composite and orthodontic brackets. However, the use of each alone can increase the shear bond strength.

The Effect of Type and Mode of Light Curing Units on Degree of Conversion of Bulk Fill Composites

Introduction: Adequate polymerization is a critical factor in obtaining optimal physical and mechanical properties and a satisfying clinical outcomes in composite restorations. The aim of this study was to evaluate the effect of type and mode of light curing units on degree of conversion (DC) of Bulk Fill composites (Xtra-fill andTetric N-Ceram Bulk Fill) compared to conventional composite (Tetric N-Ceram).&#x0D; Materials &amp; Methods: This in-vitro experimental study was conducted in Kerman and Tehran School of Dentistry in 2019. Number of 15 uncured composites and 45 composite discs were fabricated using the Teflon molds with a 4 mm thick and 10 mm diameter and light cured from the top using LED ramp, LED and QTH curing units for 20 seconds. Bulk Fill composites (Xtra-fill andTetric N-Ceram Bulk Fill) were placed with a 4mm_thick increment and conventional composite (Tetric N-Ceram) was placed incrementally (with 2 mm thickness in each layer). The degree of conversion of top and bottom surfaces of composites were measured using the Fourier Transform Infrared Spectroscopy (FTIR). The results were analyzed with Two-way ANOVA and Tukey̛ s test. The level of significance was set as p value &lt; 0.05.&#x0D; Results: In all samples, the DC value of top surfaces was significantly higher than the 4mm depth (p value &lt; 0.05). Overall, there were no significant difference between the DC value of tested composites (p value &gt; 0.05), But LED light in ramp mode showed significantly better results compared to LED and QTH light sources (p value &lt; 0.05). The type and mode of light cure units had no influence on DC of bulk fill composites (p value &gt; 0.05), but the DC of conventional composite with QTH and LED ramp was significantly higher than LED (p value &lt; 0.05).&#x0D; Conclusion: The results of this study showed that the DC value of bulk fill composites were not significantly affected by the type and mode of light cure units, and all investigated bulk fill composites obtained clinically acceptable degree of conversion at 4 mm depth.

Comparison of polymerization shrinkage of a new bulk-fill flowable composite with other composites: An in vitro study.

Since composites still face a critical problem called polymerization shrinkage and bulk-fill composites have reported acceptable results for this issue, this study aims to assess the polymerization shrinkage of a new bulk-fill flowable composite (G-aenial bulk injectable [GBI]) and compare it to other bulk-fill and conventional composites. In this in vitro study, 25 composite discs were fabricated using three bulk-fill and two conventional composites. They were bonded to a microscopic slide and were covered by a coverslip. This assembly was transferred to a linear variable differential transformer and composite samples were cured from underneath the slides. Dimensional changes formed in composite samples were recorded. Data were analyzed using analysis of variance followed by post hoc Tukey's and Dunnett's tests. The groups were significantly different regarding polymerization shrinkage. G-aenial bulk injectable and G-aenial universal flo showed significantly higher polymerization shrinkage than other composites at 30, 60, and 1800 s after light irradiation, while X-tra fil and Filtek Z250 showed the lowest polymerization shrinkage at the aforementioned time points. According to the results, the new composite had polymerization shrinkage similar to the conventional one. Bulk-fill composites reported similar or lower shrinkage to conventional composites.

Utilization of composite rupture discs in fluid process engineering

Chemie Ingenieur TechnikVolume 94, Issue 9 p. 1349-1349 Poster Utilization of composite rupture discs in fluid process engineering M. Hundt, Corresponding Author M. Hundt martin.hundt@huckauf.de Huckauf Ingenieure GmbH, Robert-Koch-Str. 22, 40764 Langenfeld, GermanyCorrespondence: M. Hundt (martin.hundt@huckauf.de), Huckauf Ingenieure GmbH, Robert-Koch-Str. 22, 40764 Langenfeld, GermanySearch for more papers by this author M. Hundt, Corresponding Author M. Hundt martin.hundt@huckauf.de Huckauf Ingenieure GmbH, Robert-Koch-Str. 22, 40764 Langenfeld, GermanyCorrespondence: M. Hundt (martin.hundt@huckauf.de), Huckauf Ingenieure GmbH, Robert-Koch-Str. 22, 40764 Langenfeld, GermanySearch for more papers by this author First published: 25 August 2022 https://doi.org/10.1002/cite.202255037AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume94, Issue9Special Issue: (Bio)Process Engineering – a Key to Sustainable Development: ProcessNet and DECHEMA-BioTechNet Jahrestagungen 2022 together with 13th ESBES SymposiumSeptember 2022Pages 1349-1349 RelatedInformation

Adhesion of auto-mixed and manual-mixed self-adhesive resin cements to dentin on exposure to long-term high-altitude pressure

PurposeThe purpose of this study is to test the shear-bond-strengths of auto-mixed and manual-mixed self-adhesive resin cement to dentin on long-term high-altitude pressure.Design/methodology/approachHuman molars were embedded in acrylic resin. Sixty composite resin discs were obtained. The composite resin discs were bonded to dentin using hand-mixed and auto-mixed self-adhesive resin cement. After cementation, the samples were stored in artificial saliva and divided into two subgroups (n = 30), hypobaric pressure and the atmospheric pressure group. The specimen underwent three pressure cycles per day for 100 days. The failure types were evaluated after debonding with scanning electron microscopy. The shear bond strength was tested with Universal Testing Machine. Analysis of variances/Tukey post hoc tests were used for statistical analysis. Groups were also evaluated by the Weibull modulus.FindingsRegardless of hypobaric pressure changes, the highest bond strength was examined in auto-mixed Panavia SA samples. A significant difference was found in both auto-mixed MaxCem EC and hand-mixed RelyX U200 group after exposure to hypobaric pressure compared to the control group.Originality/valueThe luting cement-type, mixing methods of cements and environmental pressure changes significantly influence the bond strengths. Dentists can use auto-mixed self-adhesive resins in patients likely to be exposed to hypobaric pressure.

DEAE-Dextran Coated AgNPs: A Highly Blendable Nanofiller Enhances Compressive Strength of Dental Resin Composites.

Micro-crack formation and resultant bacterial infiltration are major causes of secondary caries formation in dental resin-based composite restorations. Improving dental resin composites’ mechanical and biological properties using highly bendable nanoparticles (NPs) can resolve this issue. This study aims to develop novel Diethylaminoethyl (DEAE)-Dextran silver nanoparticles (AgNPs) and subsequently modify composite resins with these NPs to enhance their mechanical and antibacterial properties. DEAE-Dextran AgNPs were successfully synthesized using a chemical reduction method that was confirmed with the help of ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), Zeta potential, and energy-dispersive X-ray spectroscopy (EDS). Antibacterial activity of a composite disc with DEAE-Dextran AgNPs was tested against Streptococcus mutans, Enterococcus faecalis, and oral microcosm. The composite discs prepared with DEAE-Dextran AgNPs exhibited excellent antibacterial activity compared with composite resin reinforced by simple AgNPs (p < 0.05). Mechanical properties were significantly enhanced by adding DEAE-Dextran into composite resin (p < 0.05). Moreover, unlike AgNPs, DEAE-Dextran AgNPs were found to be less hemolytic. The results establish strong ground applications for DEAE-Dextran-modified dental composite resins in restorative dental applications.

Seismic Behavior of Resilient Rocking Steel Column Base

ABSTRACT A resilient rocking steel column base (RRSCB) installed with composite combination disc spring (CCDS) is proposed in this paper. The restoring force model and energy calculation formulae of the RRSCB are derived by the theoretical analyses and energy conservation law, respectively. A refined finite element model validated by the cyclic loading tests is established with the aid of ABAQUS to investigate the seismic performance of the RRSCB. The results indicate that the RRSCB possesses satisfactory self-centering capability and desirable energy dissipation capacity for the design displacement. The established restoring force model and energy calculation formulae can reasonably predict the hysteretic behavior of RRSCB under cyclic loading.

Assessment of Color Difference of Translucent Zirconia Substructure Veneered Using a Layering Technique with Two Different Veneering Thicknesses: An in-vitro study

Background and objectives. The introduction of zirconia to the dental field created a path for development of new designs and applications, but still, a minimum framework thickness of 0.5 mm with the remaining thickness of the restoration used for building the ceramic veneer was always recommended. This might have possibly affected the final shade of the restoration due to the whitish color of Y-TZP. This in vitro study was designed to assess the color difference of translucent zirconia substructure veneered using a traditional layering technique with two different veneering thicknesses. Methods. A total of twenty translucent Ice zirconia disc samples with standardized dimensions 12 mm in a diameter, 0.5mm in thickness were designed and constructed using zirkonzahn system. The samples were classified into two groups: Group I: (n = 10) veneered by 0.5 mm thickness layering technique using IPS emax Ceram dentin shade A2. Group II (n = 10) veneered by 1 mm thickness layering technique using IPS emax Ceram dentin shade A2. Twenty composite resin discs 12mm in diameter and 5mm in thickness in A3 shade, were fabricated to be bonded to ceramic specimens using Dual-curing translucent rely X Unicem automix Self-Adhesive Resin luting cement. Spectrophotometer was used to measure color parameters L*, a*, b* for all samples. ΔE values were measured to determine color differences between the specimens and the A2 VITA classical shade (target shade). ΔE values were compared with an acceptability threshold (ΔE=3.7). Independent t-test was used to analyze data (P&lt;0.05) in this study and was analyzed using (SPSS) software, version 22. Results. The results showed that veneering thicknesses had a significant effect on the mean (ΔE) Values at P ≤ 0.001. The 0.5 mm veneer thickness showed the higher significant mean color difference (∆E) than the 1.0 mm veneering thickness where the recorded mean (ΔE) Values were (4.15±1.31) (2.65±1.39) respectively at p ≤ 0.001. Conclusions. This study concluded that 1.0 mm veneer thickness was the optimum thickness regarding color matching.

A Comparative Evaluation of Wear of Enamel to Various Restorative Materials of Different Surface Finishes-An In Vitro Study

Aim:The aim of this study is to evaluate the effect of different surface finish of various restorative materials on the wear of opposing enamel.Objectives of the study:1.To compare the amount of enamel loss in experimental groups of various restorative materials at different intervals of masticatory cycles. 2.To compare and evaluate the most compatible finished or polished surface of the restorative material causing least enamel wear. Materials and Methods: A total of 90 samples were prepared for this study - 75 in disc form and 15 enamel antagonist and divided into 6 groups. Group 1 - Enamel vs Enamel antagonist, Group 2 - Enamel vs Fiber Reinforced Composite disc, Group 3 Enamel vs Autoglazed metal ceramic disc , Group 4 - Enamel vs Overglazed metal ceramic disc, Group 5 - Enamel vs Polished metal ceramic disc by polishing kit, and Group 6 - Enamel vs PEEK disc were fabricated. 105 extracted premolars were collected and randomly divided into six groups of 15 each and 15 for enamel antagonist. Each tooth sample was weighed before wear testing using electronic analytical balance of 0.0001 g accuracy. Occlusal surfaces of these teeth were then abraded against the substrates in a wear machine for a total of 10,000 cycles. Each tooth sample was weighed after 5000 cycles and after the total of 10,000 cycles, respectively, using the same balance. Differences in weight of tooth samples before and after wear testing were evaluated statistically using One-way analysis of variance and Tukey’s post hoc tests was used. Results: The values obtained for overall mean percentage weight loss after 10000 rotations in increasing order is observed: Group 1 (Enamel Vs Enamel 0.0043 ± 0.00) &lt; Group 6 (Enamel Vs PEEK disc 00.0131 ± 0.01) &lt; Group 2 (Enamel Vs Fiber reinforced composite 0.0258 ± 0.01) &lt; Group 5 (Enamel Vs Polished metal ceramic disc 0.0294 ± 0.00) &lt; Group 3 (Enamel Vs Autoglazed metal ceramic disc 0.0318 ± 0.01) &lt; Group 4 (Enamel Vs Overglazed ceramic disc 0.0451 ± 0.01). Conclusion:PEEK showed the least amount of enamel wear followed by Fiber reinforced composite. Fiber reinforced composite may cause less wear than dental ceramics. Enamel wear produced by polished metal ceramic disc is substantially less than autoglazed and over glazed metal ceramic disc. This study indicates that any potential damage to ceramic can directly affect enamel and suggests that porcelain should be polished instead of over glazed.&#x0D; Key Words: Fiber reinforced composite, Autoglazed, Overglazed, Polished surface, Wear, PEEK.

Using Kubelka-Munk reflectance theory to predict optimal pink composite thickness and shade with an opaqued PEEK background for a final gingival color: An in vitro study

ObjectivesThe aims of this study were to demonstrate and evaluate how Kubelka-Munk (K-M) reflectance theory is used to adjust the color of the opaqued PEEK backing and the color and thickness of the resin composite layers in different thicknesses in order to minimize the color difference from a target gingival color. MethodsPEEK specimens were opaqued with either a dark or a light opaquer. Composite resin layers in 3 different colors were fabricated in varying thicknesses. Reflectance of opaqued PEEK and composite layers was determined using a spectroradiometer. Kubelka–Munk (K-M) absorption (K) and scattering (S) coefficients were derived for each material and then K-M reflectance theory was then used to predict the reflectance of each composite disk as layered on each backing. The color of the opaqued PEEK backings alone and the color of 12 pink composite layers on opaqued PEEK backings was calculated for the CIE D65 Illuminant. Composite resins in 3 different color were then bonded to the opaqued PEEK specimens and color differences of these specimens from the theoretical colors were determined. ResultsThe ∆E00 values ranged from 0.45 to 1.29 units for the bonded pink specimens and the K-M theory. K-M theory was validated as a viable predictor of gingival color using pink composite bonded to opaqued PEEK background. SignificanceUsing K-M theory to predict the gingival color of pink composite bonded to opaqued PEEK eliminates the need to make many specimens of different thicknesses that would otherwise be required to find an acceptable color match.

The Effects of Fresh Detox Juices on Color Stability of Resin Adhesive Systems

The purpose of the present research was to assess the effect of three different fresh detox juices on the color stability of the resin composite with three different adhesive systems. Disc-shaped resin composite specimens were prepared. Composite discs were randomly divided into 3 subgroups according to the adhesive system (Adper EasyOne, BondForce, Clearfil QuickBond), adhesive system was applied to the upper surfaces of the composite discs according to the manufacturer s instructions. The first color measurements were made with a spectrophotometer after the composite discs were kept in water for 24 hours. Samples in each group were divided into 4 subgroups according to the immersion solution (n=10; brands, water). The samples, which were kept in respective detox juices, were kept for 10 minutes twice a day, at other times they were kept in distilled water. Second color measurements were performed 30 days later. Data were analyzed with two-way ANOVA and Tukey HSD tests. According to the two-way analysis of variance, the adhesive system does not affect the color change significantly (p=0.773), but the detox juices has a significant effect on the color change (p=0.01). Fresh detox juices may adversely affect the color stability of adhesive systems, regardless of their color, but this effect may not be expected to be clinically observable.

Barium titanate 3–3 piezoelectric composites fabricated using binder jet printing

This study details property measurements from 3–3 BaTiO 3 -epoxy composite discs, fabricated using binder jet printing and post-sinter epoxy infiltration. Binder jet printing is a highly scalable additive manufacturing technique that has the potential to produce transducers with non-conventional geometries and without expensive tooling. Piezoelectric ceramic-epoxy composites are useful for certain applications, such as biomedical imaging and underwater communications, but ordinarily require difficult fabrication processes. Density, dielectric, and piezoelectric property measurements from discs sintered at temperatures between 1200—1400 °C are presented. Measured samples had porosity as low as φ = 32.4 %, while having a piezoelectric coefficient, electromechanical coupling coefficient, and permittivity as high as d 33 = 110 pC/N, k p = 0.274 , and ε 33 T / ε 0 = 411 , respectively. Findings show a limitation to increasing sintering temperature to decrease porosity, and suggest a trade-off when selecting a sintering temperature between minimizing φ and maximizing k p . Measurements from the printed discs are compared to measurements from a disc fabricated using a traditional uniaxial pressing method.

The Effect of Composite Brushing with Different Types of Toothpaste on Stain Due to Immersion in Coffee, Tea and Cuko Pempek Water

ABSTRACTComposite is a tooth-colored filling material that can change color by extrinsic staining such as coffee, tea and cuko pempek. Abrasive toothpaste can reduce stains but increase surface roughness. This study aims to determine the effect of the type of toothpaste for brushing on the formation of stains caused by coffee, tea and cuko pempek. This research is a quasi-experimental with pre and post control group design. 39 composite discs with a diameter of 1 cm and a thickness of 5 mm were prepared and divided into several groups, 1 group of negative control without treatment, 3 groups of immersion. Each immersion group was divided into 4 brushing groups, namely without brushing, brushing without toothpaste, brushing with abrasive paste and brushing with non-abrasive paste. Pre and post treatment discs were photographed and color changes were assessed using the CIE L*a*b and E system. Friedman, Kruskall Wallis and Mann Whitney U non-parametric analysis test was used to compare color values and color differences within groups and between groups. Based on this study, it can be concluded that there were significant color changes before and after the soaking treatment with coffee, tea and cuko pempek. The color change in coffee was significantly greater than that of tea and cuko pempek. There was no significant difference in color change between tea and cuko pempek. Conclusion: Brushing with toothpaste Keywords: composite; coffee; tea; cuko pempek; CIE LAB

Thermo-mechanical behavior of a rotating FG-GRC circular disk with variable thickness considering GNP dispersion patterns

Thermo-mechanical behavior of rotating functionally graded graphene reinforced composite (FG-GRC) circular disks with variable thickness and fixed-free boundary have been investigated. Two types of graphene nanoplatelet (GNP) dispersion patterns, i.e. the randomly oriented pattern and aligned one, are considered and the composite mechanical properties are predicted based on the Halpin–Tsai micromechanical model. By dispersing the disk into mathematical parts with non-uniform grids, governing equations are solved utilizing differential quadrature method. In numerical examples, influences of the material types, component contents, geometric shapes and temperature environment are discussed.

Photomechanical Structures Based on Porous Alumina Templates Filled with 9-Methylanthracene Nanowires

9-Methylanthracene (9MA) undergoes a concerted [4 + 4] photodimerization in its crystal form that can be harnessed in order to generate photomechanical motions such as bending, twisting, and expansion. As described in this paper, 9MA nanowires were grown in anodic aluminum oxide (AAO) templates with the goal of using the crystal expansion to generate a net increase in the height of the composite disk. The growth conditions were optimized in order to raise the filling amount from 28% to 77% of the available volume in the porous AAO. A new experimental method for detecting motion, based on the analysis of data from a dynamically misaligned Michelson interferometer, was developed. Template bending was observed, showing that the photodimerization of the confined nanowires generated mechanical work, but no conclusive evidence for surface disruption or vertical translation was observed. Optical measurements, as well as atomic force and scanning electron microscopy, showed that incomplete filling, crystal orientation, and debris from template polishing likely prevented the observation of vertical actuation in these nanocrystal composites. This work highlights some of the practical challenges that are involved in creating photomechanical actuators using the organic–inorganic composite approach, with the two most significant being (1) the uniform filling of the porous template with the organic active material and (2) the removal of excess organic material from the template’s surface.

Terahertz-range plasmon and whispering gallery mode resonances in the plane wave scattering from thin microsize dielectric disk with graphene covers

We analyse the scattering and absorption of a terahertz-range plane wave by a thin circular dielectric disk with two graphene covers. Assuming that the thickness of the whole composite disk is much smaller than the free-space wavelength, we reduce the complexity of the problem with the aid of the generalized boundary conditions. This yields a set of singular integral equations for the effective electric and magnetic currents, induced on an equivalent zero-thickness disk. The adopted advanced numerical solution technique is a version of the method of analytical preconditioning, which uses weighted polynomials as expansion functions in the discretization of the integral equations. Then, the resulting matrix equation has Fredholm second-kind property that enables us to control the computational error by the matrix size and reduce it to the desired level. This accurate analysis reveals resonances on several types of natural modes, best understood via visualization of in-resonance near-fields. They are the plasmon-mode resonances of the graphene disk, perturbed by the presence of the dielectric filler, and the dielectric disk modes, perturbed by the graphene covers. Additionally, quasi-full disk transparency is observed if the transverse resonance condition is fulfilled. Special attention is paid to the tunability of the found effects with the aid of graphene's chemical potential.

Analytically predicting the burst pressure of composite rupture discs by considering nonlinear strain path

The composite rupture discs are a safety device that burst at the specified pressure and prevent overpressure and damage to equipment by releasing the fluid at high flow rates. The burst pressure is determined by the bulge formed and then slotted sheet metal. In the hydraulic bulge-forming stage, the sheet is subject to biaxial stress, and after slotting, it is subject to uniaxial tensile stress. Due to the change in the loading type, the sheet has a nonlinear strain path during the bulge-forming and burst test after slotting. In the nonlinear strain paths, the equivalent failure strain changes according to the strain path. In this paper, based on the FEM simulation results and experimental tests, the relationship between plastic failure strain in uniaxial tensile state and the maximum pre-strain due to bulge forming is investigated. According to the results of this paper, when the sheet sufficiently forms under hydraulic pressure, the maximum strain in hydraulic bulge-forming and the equivalent failure strain after slotting are equal. Based on this result, analytical relations were developed to predict the burst pressure of composite rupture discs. This relation estimates the burst pressure of composite rupture discs with an average error of about 13%.

Microhardness Evaluation of Microhybrid Versus Nanofilled Resin Composite After Exposure to Acidic Drinks.

ABSTRACTObjective:To investigate the effect of two acidic agents on microhardness of nanofilled and microhybrid resin composite materials.Materials and Methods:70 resin composite discs (10 mm diameter and 2 mm thick) were prepared from 2 resin composites (35 from each type), nanofilled (Z350XT) and microhybrid (Z250), 3M/ESPE. Ten discs (5 from each group) were used as control (tested at 1 h before immersion). Each group was divided into 3 subgroups (n = 10) according to the storage media: distilled water (control), box-type cola and orange juice. Each subgroup was further subdivided into 2 divisions (n = 5) according to microhardness testing at 24 h and 7days after immersions. Digital Vickers Microhardness Tester (FM-7, Future Tech, Tokyo, Japan) was used to measure surface microhardness with a Vickers diamond indenter. The surface of the specimens received a load of 200 g for 10 seconds. Three indentations not less than 1 mm from each other were placed on the surface of all specimens. Vickers hardness number (VHN) was calculated for each indentation Data were statistically analyzed using one- way ANOVA followed by Newman-keuls tests (P ≤ 0.05).Results:Orange juice showed statistically significantly the lowest VHN mean value (92.7) followed by the Cola group (95.15) then the water group (104.02) compared to the control group (117.4). Microhybrid composite groups showed statistically significant higher VHN mean value (108.1) than the nanofilled composite (100.2). The 7days groups showed statistically significant lower VHN mean value (97.3) than 24h groups (106.6).Conclusions:All storage media reduced hardness of resin composites with orange juice showing the highest reduction in hardness values. Microhybrid is more resistant to degradation than nanofilled composite. Over time, microhardness of resin composites decreased progressively.

Study on hydraulic characteristics and internal flow mechanism of composite blade disc pump

Abstract Disc pump is widely used in difficult-pump-medium transportation such as petroleum and chemical industry. Discontinuous blade impellers play an important role in the passability and energy efficiency of disk pump. The research of design and internal flow mechanism are particularly important. Based on the structural characteristics and the internal flow mechanism of the original model, the improved design of the blade structure is carried out. Through the experimental verification and the numerical analysis of multiple working conditions, the influence law of the new composite blade on the hydraulic characteristics and internal flow mechanism of the disc pump is obtained. The results show that the error of energy efficiency characteristics of simulation and experiment under different flow conditions is within 5%, and the accuracy of simulation results meets the requirements; The hydraulic characteristics of the improved model are about 5.8% higher than that of the original model. The driving force of the new composite blade is more sufficient and the flow field is improved more obviously; The low pressure is located in the center of the impeller and gradually increases to the outlet of the impeller. There is obvious energy and mass conversion between the bladed region and bladeless region. The research results can provide a reference for the structural design of disc pump composite blade and the analysis of internal flow mechanism.