Ultimate Tensile Strength Tests Research Articles

Investigation of the effect of Ni and Cu variant MOF-74 in the Polydimethylsiloxane (PDMS)-based Mixed Matrix Membranes (MMMs) for efficient gas separation applications.

Mixed matrix membranes (MMMs) containing metal-organic frameworks (MOFs) have been an emerging and promising membrane technology to contribute to different gas separation applications including carbon dioxide (CO2) and oxygen (O2) separation, because of their large surface areas and distinctive gas adsorption features. In this work, the fabrication process of Polydimethylsiloxane (PDMS)-based MMMs was reported, in which 0.5 to 2 wt.% of each type of (Cu, Ni)-based MOF-74 variants were incorporated into a PDMS matrix in order to achieve high CO2/N2, O2/N2, and CO2/O2 separation efficiency. These MMMs and their nanofillers (MOF-74) were extensively characterized using scanning electron microscopy (SEM) along with Energy Dispersive X-Ray (EDX) mapping, X-ray Diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), a single gas permeation testing system, and an ultimate tensile strength testing (UTS) unit in order to gain insight into their properties in relation to their gas separation performance. The 1 wt.% of both (Cu and Ni)-MOF-74@PDMS were selected as the most optimum MMMs due to their uniform morphology and enhanced tensile strength, which exhibited high CO2 permeabilities of 4432 Barrer (37.9% increase) and 4288 Barrer (33.5% increase), respectively. Furthermore, in the case of 1 wt.% Ni-MOF-74@PDMS, the CO2/N2, O2/N2, and CO2/O2 selectivities were also enhanced to 36.2 (141.6% increase), 3.2 (21.9% increase), and 11.25 (98.1% increase), respectively. While, in the case of 1 wt.% Cu-MOF-74@PDMS the CO2/N2 and O2/N2 selectivities showed an increment up-to 94.7 (531.5% increase) and 6.47 (145% increase), respectively, Whereas, at 0.5 wt.%, Cu-MOF-74@PDMS showed the best CO2/O2 selectivity of 25.26 (344.7% increase).

Noninvasive diagnostic method using optical coherence tomography detected a vulnerable dentin enamel junction created by phosphoric acid etching.

To investigate the influence of phosphoric acid etching on the dentin enamel junction (DEJ) using optical coherence tomography (OCT). Human teeth were assigned to four groups: 1. control, no additional treatment (CT); 2. The primer of "SE Bond2" was applied (SE), 3. "Enamel Conditioner" was applied (EC), 4. "K-etchant syringe" was applied (KE). After treatment, the DEJ was observed using a laser microscope (CLSM), OCT, and scanning electron microscopy (SEM). Additionally, an ultimate tensile strength (UTS) test at the DEJ was performed. No cracks were observed by CLSM. In contrast, cracks were observed all samples by SEM. Additionally, OCT revealed a white line along the DEJ in all KE specimens and some EC specimens. The UTS test showed a significant difference between CT and KE. This study found that phosphoric acid etching may cause excessive demineralization and weaken the DEJ. This fragility was observed using a non-invasive diagnostic method using OCT.

Sustainable development of Draksha- Beeja extract loaded gelatin and starch-based green and biodegradable mats for potential tissue engineering applications

Eco-friendly, cost-effective solutions can solve sustainable tissue engineering issues, including making natural, biodegradable, and non-toxic biomaterials. This study aims to assess Draksha Beeja supplements (Grape Seed Extract, INLIFE) loaded edible gelatin and potato starch-based mat in prospective tissue engineering applications. The fabricated mats were characterized physiochemically in detail using Scanning Electron Microscope, Fourier Transform Infrared Spectroscopy, Ultimate tensile strength Testing, Atomic Force Microscopy, and Thermogravimetry. They were also examined in-vitro and in-vivo for cytocompatibility and biocompatibility assessment. The hemocompatibility assay indicated no blood toxicity. In-vivo testing showed high biocompatibility and no toxic reactions. More than 80% cell viability was noted for all the 3 Mats. The mats degraded after 14 days, promoted cellular proliferation, and accelerated wound healing based on histological examinations. The Mats on in-vivo testing in rat models were found to have no allergic reaction or toxic effect. This work highlighted a new horizon using a natural product-based Mat for biomedical applications. The mats were biocompatible, ecologically safe, and had thermal and mechanical qualities, suggesting their use in tissue engineering applications, and can promote sustainable biomaterials.

Mechanical characterizations of the fabricated AA 6061 based composites reinforced with B4C particulates

Aluminium metrics based aluminium alloys have numerous applications in the field of manufacturing technology. The aluminium alloys having three platforms of industrial applications which are widely used in electronics goods, ground transportation and aerospace engineering. To enhance the mechanical performance of this aluminium alloys can be developed by reinforcing with ceramics such as SiC, MgO, Gr Al2O3 to achieve the desirable properties of the materials. The present study deals with the synthesis of AA 6061 based matrix composites were synthesized using stir casting route and reinforced the content of B4C/15% by weight along with varied particulate sizes were used. The enhancement in mechanical properties has been energizing in the base alloy subsequent to addition of B4C particulates in the composites. The micro-hardness, ultimate tensile strength tests and SEM analysis are to be performed in this study.

Linear Dimensional Change and Ultimate Tensile Strength of Polyamide Materials for Denture Bases.

The aim of the current study was to evaluate the dimensional changes and ultimate tensile strength in three polyamide materials for denture bases fabrication through injection molding, subjected to artificial aging and different storage conditions. A total of 333 test specimens fabricated from Biosens (BS; Perflex, Netanya, Israel), Bre.flex 2nd edition (BF; Bredent, Senden, Germany) and ThermoSens (TS; Vertex Dental B.V., Soesterberg, The Netherlands)—n = 111 per material—were equally divided into three groups (n = 37) based on different treatments and storage conditions. Test samples allocated to the “Control group” were not artificially aged and stored in water for 24 h. Both “Treatment 1 group” and “Treatment 2 group” were subjected to thermocycling, the former dehydrated and the latter stored in water between cycle-sets. Linear changes and ultimate tensile strength were measured and analyzed for storage condition and material influence on the outcome variables. A Welch ANOVA test with Games–Howell post-hoc analysis was used to compare the influence of treatments across different materials. Significant differences were found for all three included materials with p values ranging from <0.05 to <0.001 for linear dimensional changes. The magnitude of alterations varied and was large for BS (Perflex, Israel) (ω2 = 0.62) and BF (Bredent, Germany) (ω2 = 0.47) and small but significant for TS (Vertex Dental B.V., The Netherlands) (ω2 = 0.05). However, results seem to fall into clinically acceptable range. Significant differences were also observed for the ultimate tensile strength test with the same range of p-values. All three materials showed different initial ultimate tensile strengths and varying reaction to artificial aging and storage with the lowest alterations observed for BF (Bredent, Germany) (ω2 = 0.05). Within the limitation of this study, it can be concluded that all three materials show different dimensional and mechanical properties when subjected to artificial aging and different storage. Although linear dimensions show significant changes, they seem to be clinically irrelevant, whereas the change in ultimate tensile strength after only 6-month equivalent clinical use was substantial for BS (Perflex, Israel) and TS (Vertex Dental B.V., The Netherlands).

Incorporation of Arginine to Commercial Orthodontic Light-Cured Resin Cements-Physical, Adhesive, and Antibacterial Properties.

(1) Background: The amino acid arginine is now receiving great attention due to its potential anti-caries benefits. The purpose of this in vitro study was to evaluate the shear bond strength (SBS), ultimate tensile strength (UTS), and antimicrobial potential (CFU) of two arginine-containing orthodontic resin cements. (2) Methods: Forty bovine incisors were separated into four groups (n = 10): Orthocem, Orthocem + arginine (2.5 wt%), Transbond XT, and Transbond XT + arginine (2.5 wt%). The brackets were fixed to the flat surface of the enamel, and after 24 h the SBS was evaluated using the universal testing machine (Instron). For the UTS test, hourglass samples (n = 10) were made and tested in a mini-testing machine (OM-100, Odeme). For the antibacterial test (colony forming unit-CFU), six cement discs from each group were made and exposed to Streptococcus mutans UA159 biofilm for 7 days. The microbiological experiment was performed by serial and triplicate dilutions. The data from each test were statistically analyzed using a two-way ANOVA, followed by Tukey’s test (α = 0.05). (3) Results: The enamel SBS mean values of Transbond XT were statistically higher than those of Orthocem, both with and without arginine (p = 0.02033). There was no significant difference in the SBS mean values between the orthodontic resin cements, either with or without arginine (p = 0.29869). The UTS of the Transbond XT was statistically higher than the Orthocem, but the addition of arginine at 2.5 wt% did not influence the UTS for either resin cement. The Orthocem + arginine orthodontic resin cement was able to significantly reduce S. mutans growth, but no difference was observed for the Transbond XT (p = 0.03439). (4) Conclusion: The incorporation of arginine to commercial orthodontic resin cements may be an efficient preventive strategy to reduce bacterial growth without compromising their adhesive and mechanical properties.

Studies on mechanical behavior and morphology of alumina fibers reinforced with aluminium-4.5% copper alloy metal matrix composites

Present investigation aims at the development of Aluminium-4.5% Copper with Alumina fibers (Al2O3) material to form hybrid composite material through Squeeze Casting Process. Samples of 10, 20 and 30 wt% of Alumina Fibers in Aluminium-4.5% Copper matrix were prepared. The various tensile properties of the materials viz., ultimate tensile yield stress were evaluated utilizing a standard 40 ton Universal Tensile Machine of model UTM ZD the ultimate tensile strength tests were as per ASTM E8-82 guidelines. The tensile specimens of diameter 10 mm and gauge length 80 mm were machined from the cast specimens with the gauge length of the specimens parallel to the longitudinal axis of the castings. The ductility of the specimens was assessed in terms of percentage elongation and Yield stress. The corrosion test results are presented for both base material and with reinforced material. The corrosion rate decreased with the duration of immersion. Aluminum-4.5% copper and aluminum-4.5% copper with alumina fibers showed a weight loss intermediate between the two in the chosen corrosion medium. The hybrid composite (aluminum-4.5% copper with alumina fiber reinforcement) specimens showed better corrosion pitting resistance than the base specimens. Scanning electron microscopy analysis was used to study the morphology of the composite materials.

Ultimate Tensile Strengths of 3D Printed Carbon-fiber Reinforced Thermoplastics in Liquid Nitrogen

3D printed composites have potential to satisfy needs for lighter and more sophisticated materials for aerospace, medical, and other sectors. However, few mechanical property measurements of 3D printed parts at cryogenic temperatures are available. To address this need, this work performs ultimate tensile strength testing of 3D printed thermoplastics immersed in liquid nitrogen at approximately 77 K. Materials tested include carbon-fiber reinforced PETG and carbon-fiber reinforced Amphora AM1800 filament. The carbon-fiber reinforced PETG increased in ultimate tensile strength and modulus of elasticity by 49% and 43.2% from room temperature tests, respectively. The carbon-fiber reinforced Amphora AM1800 filament decreased in ultimate tensile strength by 29.9% from room-temperature.

Feasibility Study on the Application of Fabricated Multipurpose Food Packaging Plastic (MFPP) Liner as Alternative Landfill Liner Material in Sustainable Landfill Infrastructure Model

Multipurpose Food Packaging Plastic (MFPP) is one of the largest residential and commercial solid waste all over the world. BWP is categorized under Non-Biodegradable Plastic Waste (N-BPW). Due to its inability to degrade, this abundance of N-BPW caused space decrement in landfill. Many methods have been proposed for recycling of N-BPW such as incorporating N-BPW into road construction and added material in concrete production. In the present study, the feasibility of using MFPP as landfill liner material is studied through a series of laboratory testing in terms of mechanical and chemical characteristics. The liner sample was prepared in terms of a fabricated layer (combination of 60 layers (Sample A) and 80 layers (Sample B) of a single plastic). The fabricated layers were prepared by applying hot-pressing technique to increase the strength of the surface attachment between each of the layers. The prepared fabricated MFPP liners were tested for Ultimate Tensile Strength Test (UTS), Scanning Electron Microscopy (SEM) and X-Ray Distraction (XRD). The tested samples were then compared with the Conventional Geomembranes (GMs). Obtained results indicated that proposed fabricated MFPP Liner had 70% similar characteristics to GMs. In addition, the fabricated MFPP Liners have an ability to sustain maximum loading higher than Conventional GMs. These desirable characteristics indicated that the fabricated MFPP Liners has potential to be used as landfill liner material.

Influence of protease inhibitors on the degradation of sound, sclerotic and caries-affected demineralized dentin

The aim of this study was to evaluate influence of protease inhibitors on degradation of sound, sclerotic and caries-affected dentin. Thirty-nine molars were used, thirteen for each dentin condition. Three slices were obtained from each tooth, each one immersed in the following different solutions for 1 h: 1) artificial saliva; 2) 2% chlorhexidine; 3) 0.5% epigallocatechin-gallate (EGCG). After immersion, samples were subjected to enzymatic degradation challenge (collagenase from Clostridium histolyticum). Nanohardness (HIT) and elastic modulus (Er) were measured before and after enzymatic challenge, as well as the ultimate tensile strength (UTS). Results of UTS, HIT and Er tests were submitted to repeated measurements ANOVA and Tukey post-test (α = 0.05). Higher values of UTS were found for sound dentin in control (40.30 ± 21.38 MPa) and 0.5% EGCG (30.05 ± 19.67 MPa) groups. Before degradation, higher values of HIT (0.237 ± 0.062 GPa) and Er (5.58 ± 1.75 GPa) were found for 0.5% EGCG group in caries-affected dentin. After degradation, 2% chlorhexidine group had higher values of HIT and Er for sound (0.134 ± 0.020 GPa and 3.57 ± 0.40 GPa) and sclerotic (0.201 ± 0.048 GPa and 4.30 ± 0.56 GPa) dentin. The 2% chlorhexidine showed best effect increasing HIT and Er, mainly for sclerotic dentin, before/after enzymatic degradation. The 0.5% EGCG showed better effect on HIT and Er in caries-affected dentin, before enzymatic degradation.

Effect of Erbium Addition on the Microstructure and Mechanical Properties of Aluminium Alloy

The effect of rare earth metal erbium (Er) modification on the microstructure and mechanical properties of aluminium alloys (A380) were investigated using Optical Microscope (OM), Scanning Electronic Microscope (SEM) attached with Electron Dispersive Scanning (EDS), Vicker’s hardness test and Ultimate Tensile Test (UTS). The results show that the addition of Er reduces the size of the silicon particle and improve mechanical properties of the aluminium alloy. In addition, by adding 0.1 wt. % of Er, the mean area (μm2) and aspect ratio value decreased. The coarse plate like existed in the unmodified alloy transformed into fine particle and short rod. The mechanical properties were investigated by using tensile test and Vicker’s hardness test. The ultimate tensile strength test shows that the tensile and the elongation increased 1.32 % and 9.1 % with 0.1 wt. % Er content of the aluminium alloys, respectively. The hardness improved from the addition of 0.1% Er aluminium A380 alloy.

The Use of Different Photoinitiator Systems in Photopolymerizing Resin Cements Through Ceramic Veneers.

To evaluate the effect of different photoinitiator systems on photopolymerizing resin cements through ceramic veneers with different thickness on microshear bond strength (μSBS), flexural strength (FS), and ultimate tensile strength (UTS) and verify the light attenuation through these ceramic veneers. Four photopolymerizing experimental resin cements were produced with the same resin matrix and associated with four different photoinitiator systems: camphorquinone (CQ), diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), Ivocerin, and TPO + Ivocerin. Eighty disc-shaped ceramic veneers (IPS Empress Esthetic, Ivoclar Vivadent) were fabricated (10-mm diameter) in two different thicknesses: 0.7 and 1.5 mm. A previously characterized multiwave LED (Bluephase G2, Ivoclar Vivadent) was standardized for 40 seconds of photoactivation. Light transmittance through each ceramic veneer thickness (n=5) was measured using a spectrometer (USB 2000, Ocean Optics). The μSBS of each resin cement (n=15) to the ceramic veneer was evaluated using 0.5-mm cylinders with 0.7-mm diameters photoactivated through the different ceramic veneer thicknesses. Samples for FS and UTS tests were made either with or without ceramics veneers (0.7 and 1.5 mm) fixed to the light-curing tip. Data were submitted to two-way analysis of variance and the Tukey test (α=0.05). The multiwave LED emitted higher irradiance into the blue wavelength spectra than into the violet wavelength spectra (p=0.0001). Light transmittance through the ceramic veneers was reduced in a systematic manner based on thickness regardless of the wavelength spectra emitted from the multiwave LED (p=0.00037). The μSBS was reduced in a systematic manner based on thickness regardless of the photoinitiator system (p<0.05). However, resin cements with CQ and Ivocerin showed higher bond strength values in comparison to the resin cement with TPO regardless of the ceramic veneer thickness (p<0.05). The FS and UTS means decreased (p<0.05) with the interposition of 0.7- and 1.5-mm ceramic veneers for all resin cements. The resin cement containing only TPO showed the lowest FS and UTS means (p<0.05) for all ceramic veneers. The thickness of the ceramic veneers reduced the irradiance of the multiwave LED in all wavelength spectra. Ivocerin alone or associated with TPO showed to be an effective alternative photoinitiator to substitute for CQ. The resin cement containing only TPO had lower bond strength values in comparison to resin cements with CQ, Ivocerin, and Ivocerin + TPO.

Study on the Potential of Fabricated Non-Biodegradable Plastic Waste (N-BPW) Liner as Alternative to Conventional Geomembrane

This study investigates the potential application of Non-Biodegradable plastic waste (N-BPW) from household (plastic food packaging (PFP)) namely plastic snack packaging (PSP) and plastic bread packaging (PBP) as an alternative to conventional liner material in landfill. The samples were prepared into a single and fabricated layer. The fabricated layers were prepared by applying hot-pressing technique to joint between layers. Then the prepared liners were tested for its chemical and physical properties through Ultimate Tensile Strength Test (UTS) and Fourier Transforms Infrared Spectroscopy (FTIR). The tested samples were compared with conventional geomembrane. Obtained results from FTIR showed that proposed PFP had 70% similar characteristics to geomembrane. In addition, the fabricated samples can sustain high maximum load as compared to conventional geomembrane based on UTS. The proposed liners offer an option to the landfill operators in choosing a good reusable material at a lower cost, solved N-BPW landfilling problems and has great potential to promote as an alternative landfill liner.

Fatigue and Durability of Laminated Carbon Fibre Reinforced Polymer Straps for Bridge Suspenders.

Steel cables and suspenders in bridges are at high risk of corrosion-fatigue and in some cases of fretting-fatigue in their anchorages. These factors greatly limit the service stresses of a specific cable system and involve expensive protection measures. In order to investigate the above limitations, the fretting fatigue behaviour of pin-loaded carbon fibre reinforced polymer (CFRP) straps was studied as models for corrosion-resistant bridge suspenders. Two types of straps were tested: small model straps with a sacrificial CFRP ply and large full-scale straps. In a first phase, five fully laminated and carbon pin-loaded CFRP model straps were subjected to an ultimate tensile strength test. Thereafter, and in order to assess their durability, 20 model straps were subjected to a fretting fatigue test, which was successfully passed by 4 straps. An S-N curve was generated for a load ratio of 0.1 and a frequency of 10 Hz. In a second phase, one full-scale strap was tested for its ultimate tensile strength and two full-scale straps were fatigue-tested. The influence of fretting fatigue loading on the residual mechanical properties of the straps was also assessed, and although fretting fatigue represented an important limitation for laminated CFRP straps, it could be shown that the investigated CFRP tension members can compete with the well-established steel suspenders.

Thermal joining of thermoplastics to metals: Surface preparation of steel based on laser radiation and tungsten inert gas arc process

Laser-based joining is a potential key manufacturing process for realizing metal plastic hybrids. Therefore, surface preparation is essential to achieve a mechanical form fit. A new approach for surface preparation is based on a tungsten inert gas (TIG) arc process with anodic polarity. This TIG structure was characterized compared to fiber laser manufactured structures in cw and pw mode. The comparison of different preparations was based on pure ultimate tensile strength tests on spot joints. Finally, a transfer to overlap joints was successfully carried out and characterized by tensile shear tests using fiber reinforced plastics.

KARAKTERISTIK SIFAT MEKANIS DAN STRUKTUR MIKRO PROSES AUSTEMPER PADA BAJA KARBON S 45 C DAN S 60 C

Abstract: Steel is an iron-carbon alloys containing concentrations of other alloys having a different composition and treatment materials, steel properties can be changed by heat treatment. The heat treatment process serves to increase the strength of a steel material. The nature of the material can be turned into a more robust and resilient heat treatment process, if done properly and correctly. Austempering process is just one example of the heat treatment process at steel that aims to improve the mechanical properties of the steel S 45 C and S 60 C. austempering process performed on the steel S 45 C and S 60 C aims to increase the hardness and toughness of the steel. Austempering process is done by austenisasi advance with temperature 8500C and held for 60 minutes, after which the process is carried out with 3 election austempering temperature of 3500C, 4500C, 5500C and held for 30 minutes. The method used to test the results of austempering is tensile testing using ASTM A370- 12a, Vickers hardness test and microstructure observation using a digital microscope. In the test results tensile steel S 45 C and S 60 C values obtained an increase in ductility and toughness of 17.1 % on steel S 45 C and 17 % on steel S 60 C. This value is obtained from the calculation of ultimate tensile strength test specimens that have not been in austempering process with a specimen that has been in the process of austempering at 3500C , and the results of testing hardness of the steel S 45 C and S 60 C obtained hardness value of 44% increase in steel S 45 C and 46 % on steel S 60 C. value this is obtained from the calculation of the average value of the test specimen is not in the process of austempering with a specimen that has been in the process of austempering at 3500C .

Fretting Fatigue Behaviour of Pin-Loaded Thermoset Carbon-Fibre-Reinforced Polymer (CFRP) Straps.

This paper focuses on the fretting fatigue behaviour of pin-loaded carbon-fibre-reinforced polymer (CFRP) straps studied as models for rigging systems in sailing yachts, for suspenders of arch bridges and for pendent cables in cranes. Eight straps were subjected to an ultimate tensile strength test. In total, 26 straps were subjected to a fretting fatigue test, of which ten did not fail. An S–N curve was generated for a load ratio R of 0.1 and a frequency f of 10 Hz, showing a fatigue limit stress of the straps around the matrix fatigue limit, corresponding to 46% of the straps’ ultimate tensile strength (σUTS). The fatigue limit was defined as 3 million load cycles (N = 3 × 106), but tests were even conducted up to N = 11.09 × 106. Catastrophic failure of the straps was initiated in their vertex areas. Investigations on the residual strength and stiffness properties of straps tested around the fatigue limit stress (for N ≥ 1 × 106) showed little influence of the fatigue loading on these properties. Quasi-static finite element analyses (FEA) were conducted. The results obtained from the FEA are in good agreement with the experiments and demonstrate a fibre parallel stress concentration in the vertex area of factor 1.3, under the realistic assumption of a coefficient of friction (cof) between pin and strap of 0.5.

Effect of phytic acid etchant on the structural stability of demineralized dentine and dentine bonding

ObjectiveThis study examined the effect of phytic acid (IP6) in stabilizing the morphology of dentine collagen network and resin–dentine bonding. MethodsDentine beams were fully demineralized with 10% phosphoric acid (PA) or 1% IP6 (pH 1.2). PA-demineralized beams were divided into three groups: (a) no further treatment (control), (b) treatment with 5% glutaraldehyde (GA) for 1h and (c) treatment with 1% IP6 (pH 7) for 1h. IP6-demineralized beams received no further treatment. The beams were then subjected to ultimate tensile strength (UTS) testing. Dentine micromorphology evaluation was performed using a field-emission scanning electron microscope (FE-SEM). Dentine disks were etched with 35% PA for 15s or 1% IP6 for 30s. PA-etched dentine disks were divided into three groups as (a), (b) and (c) as for UTS testing, but the treatment with GA or IP6 was done in 1min. For microtensile bond strength (µTBS) testing, flat dentine surfaces etched with PA or IP6 were blot-dried (wet dentine) or air-dried for 10s (dry dentine) and bonded with an etch-and-rinse adhesive followed by composite build-up. ResultsIP6-demineralized dentine showed significantly higher UTS, when compared to PA-demineralized dentine. GA and IP6 significantly improved UTS of PA-demineralized dentine. FE-SEM observation revealed that dentine collagen network was preserved by GA and IP6. No significant difference in µTBS was found between the wet and dry IP6-etched dentine groups. ConclusionIP6 etching showed a structural stabilizing effect on demineralized dentine matrix and produced good resin–dentine bonding, regardless of dentine moistness or dryness.

Effect of flavonoids on the mechanical properties of demineralised dentine

ObjectivesThis study compared the effect of three flavonoids: proanthocyanidin, naringin and quercetin on the modulus of elasticity (MOE) and ultimate tensile strength (UTS) of demineralised dentine. MethodsThirty teeth were sectioned into 0.5mm×1.7mm×7mm beams for MOE measurement. Another 30 non-carious molars were sectioned into 0.5mm×0.5mm thick dentine beams for UTS testing. Demineralised specimens were divided into three groups according to treatments: 6.5% proanthocyanidin, 6.5% quercetin and 6.5% naringin. Specimens were kept in their respective solutions and tested at baseline, 10min, 30min, 1h and 4h. The MOE of each specimen was determined using a three-point bending test at a crosshead speed of 0.5mm/min. For UTS evaluation, each specimen was tested in tension until failure using a crosshead speed of 1mm/min. Means and standard deviation were calculated. Two-way ANOVA and Tukey test were used to evaluate the effect of flavonoid treatment and treatment duration on MOE and UTS. ResultsBoth MOE and UTS were significantly affected by flavonoid treatment (p<0.001) and treatment duration (p<0.001). Interaction of the two factors was significant for MOE (p<0.001), but not for UTS (p>0.05). Flavonoid treatment improved the mechanical properties of demineralised dentine in the order: proanthocyanidin>quercetin>naringin. It took a longer time for the flavonoids to produce a significant change in UTS, when compared to MOE. ConclusionProanthocyanidin was more effective than quercetin and naringin in improving biomechanical properties of dentine matrix, thereby enhancing preventive and reparative dental therapies. Clinical SignificanceDespite its larger molecular size, proanthocyanidin was more effective than quercetin and naringin, in enhancing the biomechanical properties of demineralised dentine.

Ultimate tensile strength and microhardness of glass ionomer materials

Objective: This study evaluated the ultimate tensile strength (UTS) and microhardness (µKH) of conventional (CO) and hybrid resin-modified glass ionomer (RM). Material and methods: Nine specimens to UTS and twelve for µKHN of glass ionomer materials were obtained using special molds. The materials were manipulated and CO groups were allowed to self-cure for five minutes and RM were subjected to light-activation as indicated by manufactures through a glass slide. All specimens were dark-stored in 100% relative humidity for 24h. For UTS test, specimens were tested in tension in a universal testing machine (crosshead speed of 1 mm/min) until failure. For µKHN test a Knoop diamond indenter was used to make five indentations in the upper/light irradiated surface of the specimens. UTS and µKHN data were submitted to one-way ANOVA, followed by Tukey’s test (?= 5%). Results: The results for UTS were: Ionomaster: 7.0 (±1.6)A; Maxxion R: 8.8 (±3.7)A Vidrion R: 8.8 (±3.9)A; ChemFil Rock: 10.7 (±4.6)AB; Vitremer: 13.1 (±3.3)BC; Vitrofil R: 14.9 (±7.8)CD; Ionoseal: 14.5 (±8.2)CD; Resiglass: 16.3 (±2.3)D. The results for µKH: Ionomaster: 24.3 (±6.6)B; Maxxion R: 17.7 (±4.7)A, Vidrion R: 31.0 (±9.4) B; ChemFil Rock: 31.1 (±8.5)B; Vitremer: 20.3 (±3.3)A; Vitrofil R: 16.5 (±5.1)A; Ionoseal: 13.1 (±8.5)A; Resiglass: 21.6 (±5.2)A. Conclusion: It was observed that the hybrid resin-modified ionomers generally have higher cohesive strength than conventional ones, but lower microhardness.