OBJECTIVE: Flexural strength values of multilayer zirconia may vary depending upon the specimen dimension, layers distribution, especially the layer in maximum tension side, i.e., loading configuration. Although the previous studies have examined flexural strength of the separate layers in one zirconia disc, capturing flexural strength across all layers of multilayer zirconia is still challenging yet important for their clinical indications. The objective of this study aimed to evaluate the flexural strength of multilayer graded translucent zirconia by three loading configurations with the full thickness of layers. MATERIALS AND METHODS: Four types of zirconia materials were selected namely KATANA Yttria Multi Layered (KATANA YML, Kuraray Noritake), IPS e.max ZirCAD Prime (ZirCAD Prime, Ivoclar Vivadent), and Origin Beyond + Hybrid (Origin Beyond, B&D Dental Technologies) multilayer zirconia, as well as monolithic InCoris translucent zirconia (inCoris TZI, Dentsply Sirona). The bar specimens were prepared by sectioning the zirconia discs with diamond blade to get the dimensions of 31.0 mm x 4.6 mm x 11.0 mm for KATANA YML and Origin Beyond, 42.0 mm x 6.4 mm x 13.1 mm for ZirCAD Prime, and 31.0 mm x 4.2 mm x 10.0 mm for inCoris TZI. The specimens were sintered with a Zircar high temperature furnace by following the protocols of manufacturers accordingly. The four longitudinal surfaces of all bar specimens for all materials were polished with diamond discs in a sequence of 125, 70, 45, 15, and 6 mm, and down to 0.5 mm finish. All polished specimens were subjected to the annealing treatment at 1000 oC for 15 min before mechanical testing. The three-point bend testing with three loading configuration was performed for flexural strength on the Universal Testing Machine (Instron 5566A) with a loading rate of 0.5 mm/min. The fracture surfaces of these bar specimens were examined by a field emission scanning electron microscope. The yttria (Y2O3) and hafnia (HfO2) concentrations were analyzed by energy disperse spectroscopy on polished surfaces. RESULTS: The highest mean 3 point bending flexural strength for all layers direction was for inCoris TZI with 786.55 MPa, whereas the lowest for Origin Beyond with 505.36 MPa. The inCoris TZI had overall highest flexural strength with vertical (enamel or dentin layer in tension) of 845.18 MPa. ZirCAD Prime had overall highest flexural strength with the loading configuration of dentin layer in tension of 906.22 MPa while Origin Beyond had the lowest flexural strength of 686.79 MPa. Under the loading configuration of enamel layer in tension, the flexural strength of all three multilayer materials ZirCAD Prime, Origin Beyond and KATANA YML had no significant difference, having a strength value range of 498-504 MPa. The dentin layer had the lowest yttria concentration while the enamel had the largest one, and the transition layer was between them. The distribution of hafnia concentration of different layers for all multilayer materials was consistent. CONCLUSION: Within the limitations of this in vitro study, we can conclude that material, and loading configurations as well as the interaction between material and loading configurations had a significant effect on flexural strength of multilayer zirconia. ZirCAD Prime showed a significantly higher flexural strength than KATANA YML whereas Origin Beyond had the lowest flexural strength. The flexural strength of dentin layer in tension was significantly higher than all layers in tension, while the flexural strength of all layers was significantly higher than enamel layer in tension. The yttria concentration of multilayer zirconia gradually increased from dentin layer to enamel layer whereas the hafnia concentration was consistent across different layers. These findings in this study could enrich the knowledge of clinicians when selecting the multilayer zirconia materials in the clinical settings.

Aim: The aim of this study is to investigate if biaxial flexural strength for pressed glass ceramic with glazed, polished and grinded surface is affected by the acidic beverages Coca Cola and red wine. Material and method: 63 specimens were manufactured in IPS e.max Press®, divided into 6 test groups and one control group (KG) with 9 specimens in each group, in the dimensions 12 mm in diameter and in thickness, 1,8 mm without notch and 2,2 mm with notch. The specimens subdivided by different surface treatments; glazed surface (CCG, RVG), polished surface (CCP, RVP) and ground surface (CCS, RVS). Three groups underwent thermocycling for 970 cycles in 8°C Coca Cola® and three groups red wine at room temperature. Results: The results show significant difference between the groups with α=0,001. Biaxial flexural strength test showed that the CCS group had the highest mean value (340 MPa) and CCP the lowest mean value (214 MPa). CCS showed significant differences to all groups except RVP and RVS. Furthermore the RVP group showed no significant difference to any other group and RVS only towards CCP. Conclusion: Within the limitations of this in vitro study the following conclusions can be made; Acidic beverages do not affect the flexural strength for pressed lithium disilicate based glass ceramics. The flexural strength is affected by surface treatment, where grinding with sandpaper results in higher flexural strength. / Syfte: Syftet med föreliggande studie är att undersöka om den biaxiala böjhållfastheten på litiumdisilikatbaserad glaskeram som framställts genom pressteknik med tre olika ytbehandlingar (glansbränd yta eller för att efterlikna ocklusal inslipning eller abraderat slitage) påverkas av de sura dryckerna Coca Cola® och rödvin.Material och metod: 63 provkroppar tillverkades av IPS e.max Press®. Provkropparna delades in i 6 testgrupper, och en kontrollgrupp (KG), á 9 i varje, med måtten 12 mm i diameter och tjocklek 1,8 mm utan notch och 2,2 mm med notch. Provkropparna delades in utifrån olika ytbehandlingar, glansbränd (CCG, RVG), polerad (CCP, RVP) och slipad med sandpapper (CCS, RVS). 3 grupper genomgick termocykling i 970 cykler i 8°C Coca Cola®, och 3 grupper i rödvin i rumstemperatur, varvat med destillerat vatten i 37°C. Därefter utfördes biaxialt böjhållfasthetstest och resultaten analyserades med One-way ANOVA, Tukey’s test, signifikansnivå α= 0,05.Resultat: Resultaten visar att det finns signifikant skillnad mellan grupperna α=0,001. Det biaxiala böjhållfasthetstestet påvisade att gruppen CCS hade högst medelvärde (340 MPa) och CCP hade lägst medelvärde (214 MPa). CCS visade signifikant skillnad jämfört med samtliga grupper, förutom RVP och RVS. Vidare uppvisade RVP ingen signifikant skillnad jämfört med någon av de övriga grupperna och RVS endast mot CCP.Slutsats: Inom denna in vitro-studies begränsningar kan följande slutsatser dras; Sura drycker påverkar inte böjhållfastheten på litiumdisilikatbaserad glaskeram som framställts genom pressteknik. Hållfastheten påverkas beroende på ytbehandling. Genom att slipa ytan med slippapper resulterade det i högre biaxial böjhållfasthet.

BACKGROUND: Polymer-infiltrated zirconia ceramic, benefiting from the synergistic effect of the ceramic matrix providing strength and the polymer enhancing toughness, has the potential to mimic the structure of natural teeth in its optical and mechanical properties. OBJECTIVE: To determine the effect of additives and various sintering temperatures on the optical and mechanical properties of zirconia ceramic matrix composites. MATERIALS AND METHODS: Groups consisted of unmodified zirconia powder, and zirconia modified with porcelain and porogens to form the porous ceramic matrix. Three types of Tosoh zirconia powder, TZ-3YSB-E, Zpex, and Zpex Smile, were used to fabricate porous blocks. Zirconia powder and porcelain powder were ball-milled separately. Zirconia powder was dry pressed and then cold isostatic pressed. The blocks were sintered at 1000 and 1150 ºC and sectioned into discs (n=10). For zirconia with additives groups, 10% of Titankeramik and 5% of PEG8000 were mixed to zirconia powder using a high-speed mixer. The zirconia blocks were pressed and sintered at 1000, 1150, 1200 and 1300 ℃, and sectioned into discs (n=10). Porous discs were treated with a 10% wt solution of 10-MDP for 4 hours and then dried in a vacuum oven for 24 hours. TEGDMA-UDMA resin monomers were infiltrated into discs and cured at 90°C under pressure. Polymer-infiltrated ceramics specimens were polished to 1.5 mm in thickness. Optical properties were determined with an X-rite spectrophotometer. Biaxial flexural strength and Vickers indentation tests were performed using an Instron universal mechanical tester. Vickers hardness and indentation fracture toughness values were calculated by measuring the indent dimensions under FESEM, in addition to microstructure assessment. Statistical analyses were performed using computer software, Microsoft Excel 2016 and JMP Pro 15. RESULTS: This study revealed that the type of zirconia powder utilized for the fabrication of porous ceramics for polymer-infiltration structures did not significantly influence their optical properties. Mean values of fully sintered zirconia showed significantly higher biaxial flexural strength (628.5-1277.4 MPa) than polymer-infiltrated groups (105.4-433.6 MPa), with P-3Y1150 achieving the highest value. Higher pre-sintering temperature from 1000 ℃ to 1150 ℃ led to enhanced biaxial flexural strength for polymer-infiltrated pure zirconia specimens, with values rising from 126.5-158.2 MPa to 243.4-433.6 MPa. Adding porcelain and porogens did not significantly affect the optical or specific mechanical properties, such as biaxial flexural strength and Vickers hardness, despite increasing the sintering temperature to 1300 ℃. Nevertheless, a significant increase in indentation fracture toughness was noted with ZPTKPEG1200 (7.65±0.55 MPa·m1/2) and ZPTKPEG1300 (7.09±0.61 MPa·m1/2), values that were markedly higher than those in all control groups of fully sintered zirconia (p<0.001). Sintering temperature was found to be a key determinant in influencing the ceramic matrix's microstructure, porosity, and density, as well as the biaxial flexural strength, Vickers hardness, and indentation fracture toughness of polymer-infiltrated zirconia. While changes in temperature did not affect optical properties, and polymer infiltration did not enhance all attributes, it did substantially elevate the indentation fracture toughness in mixed zirconia samples with additives, offering a potential area for further research. CONCLUSION: The mechanical properties of polymer-infiltrated ceramics responded significantly to the sintering temperature and the type of zirconia powder utilized, most notably in the 3Y-TZSB-E group. A notable increased indentation fracture toughness was discernible when Zpex powder, mixed with additives, was subject to polymer infiltration and sintered at temperatures between 1200-1300 °C. Even though polymer infiltration and additive incorporation did not uniformly enhance all properties, a noticeable improvement in fracture toughness was observed. These findings open the door to future research, especially in potential applications of dental restorative materials that demand superior fracture toughness.

OBJECTIVES: This study examined mechanical, chemical and microstructural properties of multilayer zirconia materials that are composed of layers of different forms of zirconia with varying translucency. Their resistance to low temperature degradation and their properties were compared to each other, and to monolithic zirconia. METHODOLOGY: “ZirCAD Prime” from Ivoclar Vivadent, “AxZir XT Multilayer Dental Zirconia” from Axsys Dental Solutions, and “inCoris ZI” from Dentsply Sirona, were examined. Twenty specimens were created from each material, half of which were aged. Specimens were examined for the following: Three point bending flexural strength, grain size, microhardness, indentation fracture toughness, warp and elemental composition. RESULTS: inCoris ZI had significantly higher flexural strength than ZirCAD Prime, which in turn had significantly higher strength than AxZir XT. The flexural strength values were 1113.55MPa, 857.21MPa and 625.77MPa, respectively. Grain size patterns were noted in multilayer specimens; more translucent layers had significantly larger grain sizes. AxZir XT’s incisal most layer average grain size was 0.988μm, whereas ZirCAD Prime’s was 1.172μm. The dentin most layer of AxZir XT average grain size was 0.529μm whereas ZirCAD Prime’s was 0.470μm. Microhardness results showed few significant differences between layers. The highest microhardness was found in AxZir XT’s incisal most layer, after aging, with a value of 13.502 GPa. The lowest was found in the aged inCoris ZI specimen, with a value of 10.775 GPa. In the ZirCAD Prime, fracture toughness was highest in the dentin most layer with a value of 8.88 MPa m¹/², compared to its incisal most layer that had a value of 4.92 MPa m¹/². This pattern was not seen in AxZir XT, where the dentin most layer had a value of 8.36 MPa m¹/², and the incisal most layer had a value of 6.40 MPa m¹/². Hydrothermal aging had detrimental and significant impacts on fracture toughness of all materials. Elemental composition analysis revealed predictable levels of elements or molecules in ZirCAD Prime. and inCoris ZI, but not within the AxZir XT. 5Y levels were seen in ZirCAD Prime’s incisal layer, and 2.5-3Y in the dentin most layer. inCoris ZI had constant levels of 3Y, but AxZir XT had no distinct level of Yttria in its layers. CONCLUSIONS: 1. Flexural Strength of multilayer materials was significantly lower than monolithic zirconia. 2. Grain sizes appeared largest in translucent incisal-most layers, with significant differences between them and the opaque dentin-most layers. 3. The elemental composition analysis showed an expected level of 3 mol% Yttria in the inCoris ZI with varying amounts by layer in the ZirCAD Prime from 3Y (cervical) to 5Y (incisal), but there was no clear gradation in the AxZir XT. 4. Some significant differences were seen between the materials and their layers in the microhardness tests. inCoris ZI had significantly lower values than both ZirCAD Prime and AxZir XT. The highest values were found within AxZir Xt. 5. Fracture toughness was significantly higher in the dentin-most layer compared to the incisal most-layer of ZirCAD Prime but not in AxZir XT. 6. LTD significantly decreased some fracture toughness test values. inCoris ZI, AxZir XT’s 1st incisal layer and ZirCAD Prime’s 2nd transition layer had significant decreases in fracture toughness after aging. 7. LTD had no impact on flexural strength or microhardness values. 8. LTD significantly decreased grain size of inCoris ZI.

The commercial use of hemp fiber in the construction industry within the United States is non-existent. This lack of use is because of State and Federal laws forbidding the growth of hemp in the United States, which has led to a lack of research. Not having an established supply chain for hemp and coupled with limited research has put the United States behind other countries in finding viable options for these renewable resources. This is a study of the performance of raw hemp fibers and processed hemp twine in a cement past mixture subjected to tensile loading. Three water/cement ratios (0.66, 0.49, 0.42) were considered. Replacement of cement with fly ash is also part of the program to see if it affects the performance of the system. A detailed description of the method of applying the tensile load to the micro/macro fibers along with the fixture setup is part of this article. The results of this investigation show the hemp twine and fibers will bond to the cement matrix and they can carry higher tensile loads at higher w/c ratios. This study shows that 30 mm embedment length is best for hemp macro fibers and 20 mm embedment for hemp micro fibers. This study also includes a comparative investigation of the performance of hemp fibers to synthetic and steel fibers added to a concrete mix. This investigation examined the compressive strength of the fiber-reinforced concrete mixes, flexural capacity, ductility, flexural toughness and the effects the fibers have on Young’s modulus of elasticity. All fibers were introduced to the same mix design (w/c = 0.49) with replacement of 25% of cement with fly ash. Hemp micro fibers at the same dosing rate a synthetic micro fibers has a slightly higher toughness and equivalent flexural strength. Hemp macro fibers at a higher dosing rate as compared to synthetic fibers will have similar toughness and equivalent flexural strength. Steel fibers performed better than the synthetic and natural fibers at 28-day compressive strength.

No description available.

SAMMANFATTNING  Syfte  Syftet med studien var att undersöka huruvida färginfiltrering med effektfärg påverkar böjhållfastheten i flerskiktad zirkonia.  Material och metod Zirkoniamaterialet KATANA™ Zirconia YML, Kuraray Noritake användes i studien. Totalt framställdes 54 stycken provkroppar varav sex stycken utgjorde en pilotstudie för polering. Resterande 48 delades in i sex grupper (n = 8). Tre av grupperna frästes ut från Emalj och Body 1 (E-B1) och de resterande tre grupperna frästes ut från Body 2 och Body 3 (B2-B3). Två grupper, från de olika skikten, infiltrerades med Esthetic Colorant A plus (A), två grupper infiltrerades med Esthetic Colorant Opaque (O) samt två grupper utgjorde kontrollgrupper utan infiltrering (K). Provkropparna infiltrerades och sintrades enligt fabrikantens anvisningar. Därefter polerades de enligt ett poleringsschema och slutligen genomfördes ett biaxialt böjhållfasthetstest. Resultaten från samtliga grupper analyserades med One-way ANOVA, Tukey’s test, med en signifikansnivå på α = 0,05 med hjälp av statistikprogrammet SPSS.  Resultat Resultatet påvisade ingen signifikant skillnad i böjhållfastheten inom grupperna för de två skikten (E-B1A, E-B1O och E-B1K) samt (B2-B3A, B2-B3O och B2-B3K). Grupperna med skikten som inkluderade B2-B3 uppvisade signifikant högre böjhållfasthet oavsett infiltrering/kontroll än grupperna E-B1A, E-B1O och E-B1K.   Slutsats Böjhållfastheten i flerskiktad zirkonia påverkas inte av infiltrering med effektfärg. / ABSTRACT Purpose The purpose of this in vitro study was to investigate whether color infiltration with effect colors affect the biaxial flexural strength of multilayer zirconia.   Material and method The zirconia material KATANA™ Zirconia YML, Kuraray Noritake was used in the study. A total of 54 specimens were produced, of which six were part of a pilot study for polishing. The remaining 48 were divided into six groups (n=8). Three of the groups were milled of Enamel and Body 1 (E-B1) and the remaining three groups were milled of Body 2 and Body 3 (B2-B3). Two groups, from the different layers, were colored with Esthetic Colorant A plus (A), two groups were colored with Esthetic Colorant Opaque (O), while two groups served as control groups (K). The specimens were colored and sintered according to the manufacturer's instructions, polished according to a polishing schedule, and finally a biaxial flexural strength test was performed. The results were analyzed using One-way ANOVA, Tukey's test, with a significance level of α = 0.05 using the statistical software SPSS.   Results The results showed no significant difference in flexural strength within the groups for the two layers (E-B1A, E-B1O, and E-B1K) and (B2-B3A, B2-B3O, and B2-B3K). The groups with layers that included B2-B3 showed significantly higher flexural strength regardless of coloring/control than the groups E-B1A, E-B1O, and E-B1K.  Conclusion The flexural strength of multilayered zirconia is not affected by color infiltration with effect colors.

The purpose of this study was to investigate the influence an increase in strand strength and the effect the as-cast vertical location had on transfer length, development length, and flexural strength and to resolve the discrepancies regarding the definition of the top-bar/strand effect. Two types of test specimens were fabricated and tested investigating each respective item. The increase in strand strength was found to influence transfer length, development length, and flexural strength, while the as-cast vertical location was only found to influence transfer length, and in turn development length. Contrary to the historical definition, the top-bar/strand effect was found to be more dependent on the amount of concrete cast above the strand than the amount below it, with transfer lengths showing a steady increase with a decrease in the amount of concrete cast above the strand. As a result of the findings of this study, a new transfer length equation was proposed and a previously proposed flexural bond length equation was recommended for use in lieu of the current code provisions. The current equations for flexural strength were found to give adequate estimates for flexural strength, although a decrease in ductility was noted. / Ph. D.

Seismic-resistant steel eccentrically braced frames (EBFs) are designed so that that yielding during earthquake loading is restricted primarily to the ductile links. To achieve this behavior, all members other than the link are designed to be stronger than the link, i.e. to develop the capacity of the link. However, satisfying these capacity design requirements for the beam segment outside of the link can be difficult in the overall design process of an EBF. In some cases, it may be necessary to make significant changes to the configuration of the EBF in order to satisfy beam design requirements. If this discovery is made late in the design process, such changes can be costly. The overall goal of this research was to develop guidelines for preliminary design of EBFs that will result in configurations where the beam is likely to satisfy capacity design requirements. Simplified approximate equations were developed to predict the axial force and moment in the beam segment outside of the link when link ultimate strength is developed. These equations, although approximate, provided significant insight into variables that affect capacity design of the beam. These equations were then used to conduct an extensive series of parametric studies on a wide variety of EBF configurations. The results of these studies show that the most important variables affecting beam design are 1) the nondimensional link length, 2) the ratio of web area to total area for the wide flange section used for the beam and link, 3) the angle between the brace and the beam, and 4) the flexural stiffness of the brace relative to the beam. Recommendations are provided for selection of values for these variables in preliminary design. / text

A obtenção de cerâmicas de SiC pela sinterização com a presença de aditivos que promovam a formação de uma fase líquida (SFL) durante o processo tem sido uma forma adequada para garantir a menor temperatura de sinterização. Pelo fato de o SiC ser frágil, a busca por melhores propriedades mecânicas e avaliação correta das mesmas, para ser aplicado em ambientes agressivos, é contínua. Com base nisso, na primeira etapa, foram estudados, quanto à molhabilidade sobre o SiC, os sistemas AlN/Re2O3 (Re = Dy, Yb) para serem utilizados como aditivos. Os ângulos de contato medidos foram menores que 10° e considerados adequados para a SFL. O SiC sinterizado com esses aditivos permitiu produzir microestruturas diferentes com o aumento da temperatura. Na segunda etapa, foram sinterizadas amostras na forma de pastilhas em várias temperaturas, cujas condições que apresentaram os melhores resultados de massa específica real e densidade relativa foram tomadas como referência para a sinterização na forma de barras prismáticas. Na terceira etapa, essas amostras foram avaliadas quanto à sua tenacidade à fratura (KIC) pelo método da barra entalhada em V, dureza e resistência à flexão. O comportamento de KIC foi avaliado em função da profundidade e raio de curvatura dos entalhes. Os valores variaram entre 2,59 e 3,64 MPam1/2. Verificou-se que os valores de KIC confiáveis foram aqueles encontrados com pequeno raio de curvatura na ponta do entalhe. Quando o raio foi grande, o mesmo não manteve a singularidade da raiz quadrada da ponta do entalhe, e forneceu valores de KIC superestimados. Foram realizados testes para determinar KIC em ar atmosférico e em água, cujos resultados foram menores em água que em ar, com queda entre 2,56 e 11,26%. A maior resistência sob flexão determinada em 4 pontos foi de 482 MPa. Observou-se correlação direta do tamanho dos grãos nos valores de KIC, dureza e módulo de ruptura das cerâmicas de SiC. / Obtaining SiC ceramics by sintering in the presence of additives that promote a liquid phase formation (LPS) during the process has been a proper manner to ensure the lowest sintering temperature. Because SiC is brittle, an ongoing search for better mechanical properties and proper evaluation of these properties for application in aggressive environments maintained. Thus, in the first stage we studied AlN/Re2O3 systems (Re = Dy, Yb), as to their wettability on SiC, for use as additives. The measured contact angles were smaller than 10° and considered suitable for the LPS. The sintered SiC with these additives allowed the production of different microstructures with the increase in temperature. In the second stage, pellet-shaped samples were sintered at various temperatures, and the conditions showing the best density results were taken as reference for sintering prism-shaped bars. In the third stage, these samples were evaluated for toughness (KIC) by single edge V-notched beam method, hardness, and flexural strength. The behavior of KIC was assessed for notch depth and notch radius of curvature. Values ranged between 2.59 and 3.64 MPa/m1/2. The reliable values of KIC were those found with small radius of curvature at the notch tip. When the radius was large, it did not maintain the singularity of the square root of notch tip and provided overestimated KIC values. Tests were performed to determine KIC in atmospheric air and water, and results were lower in water than in air, dropping between 2.56 and 11.26%. The greatest strength under the 4-point bending test was 482 MPa. We observed a direct correlation of grains size in KIC values, hardness and bending strength of SiC ceramics.