scholarly journals Effect of microwave disinfection on physical and mechanical properties of acrylic resins

2008 ◽  
Vol 19 (4) ◽  
pp. 348-353 ◽  
Author(s):  
Rafael Leonardo Xediek Consant ◽  
Erica Brenoe Vieira ◽  
Marcelo Ferraz Mesquita ◽  
Wilson Batista Mendes ◽  
João Neudenir Arioli-Filho
Keyword(s):  
Flexural Strength ◽  
Room Temperature ◽  
Physical And Mechanical Properties ◽  
Hardness Test ◽  
Knoop Hardness ◽  
Microwave Energy ◽  
Bending Test ◽  
Acrylic Resins ◽  
Strength Tests ◽  
The Impact

This study evaluated the effect of microwave energy on the hardness, impact strength and flexural strength of the Clássico, Onda-Cryl and QC-20 acrylic resins. Aluminum die were embedded in metallic or plastic flasks with type III dental stone, in accordance with the traditional packing technique. A mixing powder/liquid ratio was used according to the manufacturer's instructions. After polymerization in water batch at 74ºC for 9 h, boiling water for 20 min or microwave energy at 900 W for 10 min, the specimens were deflasked after flask cooling at room temperature, and submitted to finishing. Specimens non-disinfected and disinfected by microwave irradiation were submitted to hardness, impact and flexural strength tests. Each specimen was immersed in distilled water and disinfected in a microwave oven calibrated to 650 W for 3 min. Knoop hardness test was performed with 25 g load for 10 s, impact test was carried out using the Charpy system with 40 kpcm, and 3-point bending test with a crosshead speed of 0.5 mm/min until fracture. Data were submitted to statistical analysis by ANOVA and Tukey's test (?=0.05). Disinfection by microwave energy decreased the hardness of Clássico and Onda-Cryl acrylic resins, but no effect was observed on the impact and flexural strength of all tested resins.

scholarly journals Effect of repeated disinfections by microwave energy on the physical and mechanical properties of denture base acrylic resins

2009 ◽  
Vol 20 (2) ◽  
pp. 132-137 ◽  
Author(s):  
Rafael Leonardo Xediek Consani ◽  
Douglas Duenhas de Azevedo ◽  
Marcelo Ferraz Mesquita ◽  
Wilson Batista Mendes ◽  
Paulo César Saquy
Keyword(s):  
Mechanical Properties ◽  
Impact Strength ◽  
Flexural Strength ◽  
Physical And Mechanical Properties ◽  
Knoop Hardness ◽  
Microwave Energy ◽  
Bending Test ◽  
Denture Base ◽  
Acrylic Resins ◽  
The Impact

The present study evaluated the effect of repeated simulated microwave disinfection on physical and mechanical properties of Clássico, Onda-Cryl and QC-20 denture base acrylic resins. Aluminum patterns were included in metallic or plastic flasks with dental stone following the traditional packing method. The powder/liquid mixing ratio was established according to the manufacturer's instructions. After water-bath polymerization at 74ºC for 9 h, boiling water for 20 min or microwave energy at 900 W for 10 min, the specimens were deflasked after flask cooling and finished. Each specimen was immersed in 150 mL of distilled water and underwent 5 disinfection cycles in a microwave oven set at 650 W for 3 min. Non-disinfected and disinfected specimens were subjected to the following tets: Knoop hardness test was performed with 25 g load for 10 s, impact strength test was done using the Charpy system with 40 kpcm, and 3-point bending test (flexural strength) was performed at a crosshead speed of 0.5 mm/min until fracture. Data were analyzed statistically by ANOVA and Tukey's test (α= 0.05%). Repeated simulated microwave disinfections decreased the Knoop hardness of Clássico and Onda-Cryl resins and had no effect on the impact strength of QC-20. The flexural strength was similar for all tested resins.

scholarly journals Effect of Gamma Radiation and Endodontic Treatment on Mechanical Properties of Human and Bovine Root Dentin

2016 ◽  
Vol 27 (6) ◽  
pp. 670-674 ◽  
Author(s):  
Veridiana Resende Novais ◽  
Priscilla Barbosa Ferreira Soares ◽  
Carlla Martins Guimarães ◽  
Laís Rani Sales Oliveira Schliebe ◽  
Stella Sueli Lourenço Braga ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Flexural Strength ◽  
Gamma Radiation ◽  
Hardness Test ◽  
Knoop Hardness ◽  
Endodontic Treatment ◽  
Bending Test ◽  
Human Teeth ◽  
Significant Difference ◽  
Root Dentin

Abstract This study evaluated the effect of gamma radiation and endodontic treatment on the microhardness and flexural strength of human and bovine root dentin. Forty single-rooted human teeth and forty bovine incisor teeth were collected, cleaned and stored in distilled water at 4 °C. The human and bovine teeth were divided into 4 groups (n=10) resulting from the combination of two study factors: first, regarding the endodontic treatment in 2 levels: with or without endodontic treatment; and second, radiotherapy in two levels: with or without radiotherapy by 60 Gy of Co-60 gamma radiation fractioned into 2 Gy daily doses five days per week. Each tooth was longitudinally sectioned in two parts; one-half was used for the three-point bending test and the other for the Knoop hardness test (KHN). Data were analyzed by 3-way ANOVA and Tukey HSD test (α=0.05). No significant difference was found for flexural strength values. The human dentin had significantly higher KHN than the bovine. The endodontic treatment and radiotherapy resulted in significantly lower KHN irrespective of tooth origin. The results indicated that the radiotherapy had deleterious effects on the microhardness of human and bovine dentin and this effect is increased by the interaction with endodontic therapy. The endodontic treatment adds additional negative effect on the mechanical properties of radiated tooth dentin; the restorative protocols should be designed taking into account this effect.

scholarly journals Impact and Flexural Strength, and Fracture Morphology of Acrylic Resins With Impact Modifiers

2009 ◽  
Vol 3 (1) ◽  
pp. 137-143 ◽  
Author(s):  
Fernanda Faot ◽  
Leonardo H V Panza ◽  
Renata C M Rodrigues Garcia ◽  
Altair Antoninha Del Bel Cury
Keyword(s):  
Impact Strength ◽  
Flexural Strength ◽  
High Capacity ◽  
Young Modulus ◽  
Fracture Morphology ◽  
Mechanical Tests ◽  
Bending Test ◽  
Mean Values ◽  
Acrylic Resins ◽  
The Impact

Objectives:This study evaluated the impact and flexural strength and analyzed the fracture behavior of acrylic resins.Methods:Eighteen rectangular specimens were fabricated of Lucitone 550, QC 20 (both unreinforced acrylic resins), Impact 1500 (extra strength impact), Impact 2000 (high impact) according to the manufacturers’ instructions. The impact strength was evaluated in notched specimens (50x6x4mm) and flexural strength in unotched (64x10x3.3mm), using three-point bending test, as well as, stress at yield, Young modulus and displacement at yield. Fragments from mechanical tests were observed by SEM. Data from impact strength, stress at yield and displacement at yield were analyzed by 1-way ANOVA and Tukey test (α=0.05). Young modulus values were analyzed by One-way ANOVA and Dunnett T3 multiple comparisons test (α=0.05).Results:Mean values of impact strength and stress at yield values were higher (P<.005) for Impact 2000 while Young modulus was higher (P<.05) for Lucitone 550; Impact 1500 and Impact 2000 showed significant values (P<.05) in the displacement at yield. Impact fractures of the all acrylic resins were brittle. Bending fractures of Lucitone 550 and Impact 2000 were brittle, QC 20 fractures were ductile and Impact 1500 showed brittle (75%) and ductile (25%) fractures.Conclusion:Within the limitations of this study, the Impact 2000 showed improved mechanical properties with high capacity of stress absorption and energy dissipation before the fracture.

The Temperature Dependence of Yield Stress and Fracture Toughness in Unstabilized Zirconia Crystals

1986 ◽  
Vol 78 ◽  
Author(s):  
T. W. Coyle ◽  
R. P. Ingel ◽  
P. A. Willging
Keyword(s):  
Fracture Toughness ◽  
Flexural Strength ◽  
Temperature Dependence ◽  
Yield Stress ◽  
Test Temperature ◽  
Room Temperature ◽  
Single Edge ◽  
Melting Technique ◽  
Strength Tests ◽  
Edge Notch

ABSTRACTThe flexural strength and the single edge notch beam fracture toughness of undoped ZrO2 crystals, grown by the skull melting technique, were examined from room temperature to 1400°C. On heating the toughness increased with test temperature to a maximum of 4.0 MPajm at 1225°C then gradually decreased to 2.6 MPa/m. Upon cooling after a 20 minute hold at 1250°C an increase in toughness to 5 MPa/m was observed at 1200°C; upon cooling to lower temperatures Kic gradually diminished. The loaddeflection curves for the flexural strength tests showed marked nonlinearity before failure for samples tested on cooling. The temperature dependence of the apparent yield stress suggests that initial yielding occurs by slip above 1200°C but that from 1200°C to 1050°C the observed yielding is due to stress induced tetragonal to monoclinic transformation.

FLEXURAL PERFORMANCE OF RC BEAMS UNDER TROPICAL CLIMATE EFFECTS

2014 ◽  
Vol 1 (1) ◽  
Author(s):  
Nauwal Suki ◽  
Mohd Hisbany Mohd Hashim ◽  
Afidah Abu Bakar
Keyword(s):  
Flexural Strength ◽  
Room Temperature ◽  
Tropical Climate ◽  
The Other ◽  
Bending Test ◽  
Rc Beams ◽  
Near Surface ◽  
Climate Effects ◽  
Flexural Performance ◽  
Temperature Conditions

This study investigates the flexural performance of RC beams under the effects of a tropical climate. Effects from the tropical climate, such as heat and rain throughout the year, may cause deterioration to the surface of concrete. Concrete will gradually erode and may expose the steel inside the beam. If the steel is exposed, it may be oxidized, thus decreasing the strength of the RC structure. To avoid this situation from happening, the Near Surface Mounted (NSM) method of strengthening may be applied as an alternative. Three beams with the size of 125 mm x 300 mm x 1800 mm (width; height; length) were constructed for this study. The first one is a beam without strengthening, while the other two beams were strengthened with CFRP plate horizontally positioned on the tension zones, where one beam is placed under room temperature conditions, while the other is left to endure the conditions of the tropical climate for a period of 6 months. All three beams were then tested under a four-point bending test. Results show that the strengthened beam placed under room temperature conditions has 1% more flexural strength compared to the exposed beam. The exposed beam, however, has 21% more flexural strength compared to the control beam. Thus, NSM is proven to strengthen beams even in a tropical climate.

Analysis of Physical and Mechanical Properties of Backhoe’s Bucket Repairment with Cladding Methode

2020 ◽  
Vol 841 ◽  
pp. 254-258
Author(s):  
Yustiasih Purwaningrum ◽  
Muhammad Hafiz ◽  
Risky Suparyanto
Keyword(s):  
Mechanical Properties ◽  
Bending Strength ◽  
Welding Process ◽  
Physical And Mechanical Properties ◽  
Hardness Test ◽  
Raw Material ◽  
Bending Test ◽  
Basic Material ◽  
Test Results ◽  
Low Carbon

Buckets are the most important component in backhoe construction, the bucket functions as a digger and carrier component in an excavator. Due to the heavy working media of the excavator so that this component is the most easily damaged part, damage that often occurs is wear caused by friction arising so that the thickness of the bucket is reduced which can eventually cause cracks in the bucket and in continuous use can cause the bucket to crack and broken. Cladding method is done to shorten the time or simplify the repair process is to directly patch the damaged part with a welding layer and then do the grading using a grinding. This study aims to determine the physical and mechanical properties of the material from the cladding process when compared with the raw material, the variations used are raw material, cladding with filler welding, and cladding with plates. The welding process is carried out with GMAW (Gas Metal Arc Welding) and low carbon steel. Welding results will be tested tensile strength, bending strength , impact test, hardness test, chemical composition, and corrosion rate. From the hardness test results showed that the weld metal from plate variation has the highest hardness value of 443 VHN. From the results of tensile testing the basic material has the highest value with 359.08 MPa. From the bending test results the highest value obtained from filler verification with 494.01 Mpa and the highest impact price obtained from the plate variation cladding method with a value of 1.49 J / mm2

scholarly journals Study of Waste Plastic Mix Concrete with Plasticizer

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
Baboo Rai ◽  
S. Tabin Rushad ◽  
Bhavesh Kr ◽  
S. K. Duggal
Keyword(s):  
Compressive Strength ◽  
Flexural Strength ◽  
Strength Characteristic ◽  
Room Temperature ◽  
Waste Plastic ◽  
Strength Tests ◽  
Hardened Properties

The fresh and hardened properties of waste virgin plastic mix concrete have been studied (CUR Report 1991). A number of concrete mixes were prepared in which sand was partially replaced by waste plastic flakes in varying percentages by volume. Waste plastic mix concrete with and without superplasticizer was tested at room temperature. Forty-eight cube samples were moulded for compressive strength tests at three, seven, and twenty-eight days. Eight beams were also cast to study the flexural strength characteristic of waste plastic mix concrete. It was found that the reduction in workability and compressive strength, due to partially replacement of sand by waste plastic, is minimal and can be enhanced by addition of superplasticizer.

scholarly journals Influence of Microfibers Additive on the Self-healing Performance of Mass Concrete

2021 ◽  
Vol 39 (1A) ◽  
pp. 104-115
Author(s):  
Alaa Z. Dahesh ◽  
Farhad M. Othman ◽  
Alaa A. Abdul-hamead
Keyword(s):  
Mechanical Properties ◽  
Flexural Strength ◽  
Physical And Mechanical Properties ◽  
Sem Analysis ◽  
Mass Concrete ◽  
Self Healing ◽  
Mixture Ratio ◽  
Concrete Mixtures ◽  
Strength Tests ◽  
Positive Effect

Because cracks are the main problem of mass concrete, this paper investigates an experimental study on the effect of polypropylene microfiber (PPMFs) on self -repair behavior of mass concrete, through study the microstructure, workability, physical, and mechanical properties of mass concrete. PPMFs with a diameter of 18 µm add in different percentages (0, 0.5, 1 and 1.5) % of cement weight. Where the prepared mixture ratio was (1:2:4.8) and the water-cement ratio (W/C) was 0.4. Also, 0.6% of Superplasticizer (SP) % of cement weight to all concrete mixtures was added. In this study, an SEM analysis used to observe the effect of PPMFs on the microstructure of mass concrete, and compressive and flexural strength tests for study the mechanical properties of this. And referring to the analysis and discussion of the results, PPMFs used have changed the microstructure of mass concrete, and have an effective effect on improving compressive strength and flexural strength, and mechanism of sealing the cracks of concrete autogenously. Also, 1% PPMFs (% of cement weight) recorded as the highest addition, which has a positive effect on mass concrete properties to apply it in the construction field.

scholarly journals Evaluation the Effect of different Cooling Cycles on the Hardness Surface of the Conventional Feldspathic Zirconia

2021 ◽  
Vol 3 (3) ◽  
pp. 96-101
Author(s):  
Shahad Hazim Ali ◽  
Lateef Essa Alwan ◽  
Abdul Kareem J. Al-Azzawi
Keyword(s):  
Room Temperature ◽  
Cooling System ◽  
Surface Hardness ◽  
Hardness Test ◽  
Control Group ◽  
P Value ◽  
Residual Tensile Stress ◽  
Slow Cooling ◽  
Fast Cooling ◽  
The Impact

Cooling rate is the main fact in success and life span of all ceramic restoration through its effect on mechanical properties and producing a residual tensile stress, crack propagation and failure restorations. The goals of this study is to assess the impact of diverse cooling cycles (slow cooling – fast cooling) on the surface hardness of the Zirconia (VM9). A total of 30 conventional Y-TZP Zirconia (Vita VM9) disks were fabricated according manufacturers recommendation. The samples were partition into three categories depending on the cooling system. Each group consisted of ten specimens in diameter (2mm×10mm). Control group: samples are unescorted by any change. Fast cooling group: these specimens were fast cooled after second firing (910C0 -600C0) with opening Oven muffle 25% withholding time for 5 minute and remove from the furnace to cool at room temperature. Slow cooling group: specimens were slow cooled after second firing (910C0 -400C0) with opening Oven muffle 25% withholding time for 5 minute and remove from the furnace to cool at room temperature. Each specimen was subjected to hardness test in load 9.8N at 15s using Digital microvickers Hardness tester, Scanning electron microscope. The statistical analysis revealed that, the highest vickers hardness mean value was for the control group (690.57 ± 69.9563) and for second group (618.12± 53.6164) and for third group (631.75±65.3858), The facts were statistically examined by applying ANOVA test (P- value) testes which revealed significant differences(p=0.038) (p<0.05) among groups. Conclusion: The impact of cooling cycle on the hardness surface measurements of the Zirconia (Vita VM9) between the three groups was significant. The slow cooling shows a higher value of (VH) Hardness and recommended for Zirconia than the fast cooling.

scholarly journals Effect of Commercially Available Denture Adhesives on Microhardness of a Flexible Denture Base Material

2019 ◽  
Vol 7 (5) ◽  
pp. 862-868
Author(s):  
Eman Mostafa Ahmed Ibraheem ◽  
Hoda Gaafar Hassan Hammad
Keyword(s):  
Base Material ◽  
Hardness Test ◽  
Knoop Hardness ◽  
T Test ◽  
P Value ◽  
Distilled Water ◽  
Denture Base ◽  
Significant Difference ◽  
Denture Adhesives ◽  
The Impact

BACKGROUND: Various clinical cases of thermopress denture base materials necessitate the use of denture adhesives to achieve proper retention and stability of the removable prosthesis. Therefore; the microhardness of these flexible materials as surface property and its’ alterations due to the application of various denture adhesives are still crucial issues to be discussed. AIM: This study aimed to investigate the impact of two commercially available denture adhesives (DAs) on microhardness of a flexible denture base material. METHODS: A total of 30 duplicate disc specimens (DS) were fabricated from a thermoplastic injection moulded resin (TR). The obtained 30-disc specimens (DS) were stored in distilled water for seven days, and then their microhardness was measured using Knoop Hardness Test (KHN) under a 10 g load for 10 seconds. The denture adhesives were prepared, and 15 DS were immersed in Corega Super Cream, while the other 15 DS were soaked in Fitty Dent Cream. All DS were stored in distilled water at 37°C. After 30 days of immersion in DAs, microhardness of DS was again measured. T-test for paired observation was used to investigate any alterations in microhardness between the baseline and after 30 days of immersion in the DAs. Statistical analysis was performed with SPSS 20®, Graph Pad Prism® and Microsoft Excel 2016 with a significant level set at P ≤ 0.05. RESULTS: Student`s t-test had revealed a significant difference between both groups after application of denture adhesive as a P value < 0.05. The obtained results showed that DA material type, flexible denture base material and their surface interaction provoke a statistically significant outcome on the mean microhardness. CONCLUSIONS: DAs were found to affect the microhardness of thermoplastic injection moulded resin (TR); which may jeopardise the durability and serviceability of complete denture and patients’ acceptance and comfortability.

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