Mechanical and Surface Properties of Monolithic Zirconia

2018 ◽  
Vol 43 (3) ◽  
pp. E119-E128 ◽  
Author(s):  
LM Candido ◽  
LN Miotto ◽  
LMG Fais ◽  
PF Cesar ◽  
LAP Pinelli
Keyword(s):  
Grain Size ◽  
Flexural Strength ◽  
Weibull Modulus ◽  
Testing Machine ◽  
Fracture Pattern ◽  
Honestly Significant Difference ◽  
Significant Difference ◽  
Tukey Honestly Significant Difference ◽  
Monolithic Zirconia ◽  
Standard Deviations

SUMMARY Purpose: This study compared monolithic zirconia with conventional ones based on mean roughness (Ra), Vickers hardness (VHN), topography, transmittance, grain size, flexural strength (FS), Weibull modulus, and fractographic behavior. Methods and Materials: One monolithic (Prettau Zircon [PR group]) and two conventional (ICE Zirkon Transluzent [IZ group] and BloomZir [BL group]) zirconias were used. Specimens were tested using a profilometer, a microhardness tester, a scanning electron microscope, a spectrophotometer, and a Universal Testing Machine (EMIC DL 2000). Ra, VHN, grain size, and transmittance were analyzed using the Kruskal-Wallis test associated with Dunn test (α=0.05). FS was analyzed using one-way analysis of variance with the Tukey honestly significant difference test (α=0.05). Results: Means and standard deviations of roughness, after sintering (Ra, in μm) and VHN, were, respectively, 0.11 ± 0.01, 1452.16 ± 79.49, for the PR group; 0.12 ± 0.02, 1466.72 ± 91.76, for the IZ group; and 0.21 ± 0.08, 1516.06 ± 104.02, for the BL group. BL was statistically rougher (p<0.01) than PR and IZ. Hardness was statistically similar (p=0.30) for all groups. Means and standard deviations of FS (in MPa) were 846.65 ± 81.97 for the PR group, 808.88 ± 117.99 for the IZ group, and 771.81 ± 114.43 for the BL group, with no statistical difference (p>0.05). Weibull moduli were 12.47 for the PR group, 7.24 for the IZ group, and 6.31 for the BL group, with no statistical differences. The PR and BL groups had higher transmittance values and grain sizes than the IZ group (p<0.05). Although the BL group had some fractures that originated in the center of the tensile surface, fractographic analyses showed the same fracture pattern. Conclusions: All tested zirconia showed similar VHN, and the monolithic zirconia had similar roughness compared to one of the conventional zirconias. In addition, the monolithic zirconia showed similar flexural strength and Weibull modulus compared to the others even though its mean grain size was larger. The total transmittance of monolithic zirconia was higher than only one of the conventional zirconias tested.

scholarly journals Effect of post type on the fracture resistance of endodontically treated premolars

2018 ◽  
Vol 145 ◽  
pp. 04003
Author(s):  
Ekaterina Karteva ◽  
Neshka Manchorova ◽  
Dessislava Pashkouleva ◽  
Donka Keskinova ◽  
Stoyan Vladimirov
Keyword(s):  
Fracture Resistance ◽  
Survival Rates ◽  
Testing Machine ◽  
Endodontically Treated Teeth ◽  
Honestly Significant Difference ◽  
Significant Difference ◽  
Tukey Honestly Significant Difference ◽  
Root Fractures ◽  
Restoration Method ◽  
Resistance Rates

Endodontically treated teeth (ETT) are more susceptible to fracture during mastication. The aim of our study was to investigate the fracture resistance of premolars, restored with different techniques. Eighteen human premolars, extracted for orthodontic or periodontal reasons, were used. Mesio-occlusal cavities were prepared on all of them. They were divided into 3 groups according to the restoration method: with a cemented fiber post (FP), with a cemented metal post (MP) and without a post, but restored with a fiber reinforced composite core (FRC). After thermocycling, their fracture resistance was evaluated in a standard testing machine. The results were analyzed with one-way ANOVA and Tukey Honestly Significant Difference (HSD) tests (p<0.05). The fracture modes were also determined. The MP group showed the lowest fracture resistance rates and the highest number of unrestorable root fractures. In conclusion, teeth restored with FRC cores or FP show better survival rates than those restored with metal posts.

scholarly journals Effect of Cooling Rate during Glazing on the Mechanical and Optical Properties of Monolithic Zirconia with 3 mol% Yttria Content

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7474
Author(s):  
Mi-Hyang Cho ◽  
Hyo-Joung Seol
Keyword(s):  
Crystal Structure ◽  
Grain Size ◽  
Optical Properties ◽  
Flexural Strength ◽  
Cooling Rate ◽  
Weibull Modulus ◽  
Tetragonal Zirconia ◽  
General Cooling ◽  
Monolithic Zirconia ◽  
Tetragonal Zirconia Polycrystal

Glazing is the final heat treatment process in the manufacturing of a monolithic zirconia prosthesis. Herein, the effect of cooling rate during zirconia glazing was investigated. A 3 mol% yttria-stabilized tetragonal zirconia polycrystal was glazed at the general cooling rate suggested by the manufacturer, as well as at higher and lower cooling rates, and the differences in flexural strength, hardness, optical properties, and crystal structure were evaluated. A higher cooling rate did not affect the flexural strength, hardness, grain size, optical properties, or crystal structure; however, the Weibull modulus decreased by 1.3. A lower cooling rate did not affect the flexural strength, optical properties, or crystal structure; however, the Weibull characteristic strength increased by 26.7 MPa and the Weibull modulus increased by 0.9. The decrease in hardness and the increase in grain size were statistically significant; however, the numerical differences were negligible. This study revealed that a lower cooling rate provides more reliable flexural strength. Therefore, glazing can proceed at a general cooling rate, which takes 3–4 min; however, glazing at a lower cooling rate will provide a more consistent flexural strength if desired, despite being time-consuming.

scholarly journals Effect of heat polymerization conditions and microwave on the flexural strength of polymethyl methacrylate

2018 ◽  
Vol 12 (01) ◽  
pp. 116-119 ◽  
Author(s):  
Serhat Emre Ozkir ◽  
Burak Yilmaz ◽  
Server Mutluay Unal ◽  
Ahmet Culhaoglu ◽  
Isin Kurkcuoglu
Keyword(s):  
Flexural Strength ◽  
Polymethyl Methacrylate ◽  
Clinical Success ◽  
Honestly Significant Difference ◽  
Significant Difference ◽  
Tukey Honestly Significant Difference ◽  
Heat Polymerization ◽  
Pmma Resin ◽  
Polymerization Conditions ◽  
One Way Anova

ABSTRACT Objective: The objective of this study is the effect of different heat polymerization conditions on the strength of polymethyl methacrylate (PMMA) resin base is unknown. Distinguishing one method that provides improved mechanical properties may be beneficial to the clinical success of complete and partial dentures and overdentures. The purpose of this study was to evaluate the effect of different polymerization methods on the flexural strength of a dental PMMA resin. Materials and Methods: Forty PMMA specimens (64 mm × 10 mm × 4 mm) were prepared with 4 different polymerization methods (n = 10); heat polymerization at 74°C for 9 h, at 100°C for 40 min, and with 620 kPa pressure at 100°C for 20 min. The remaining group of specimens was microwave polymerized at 180 W for 6 min. All specimens were thermocycled at 5°C and 55°C for 5000 times. Three-point flexure test was used to measure the flexural strength of specimens. One-way ANOVA and Tukey Honestly Significant Difference were applied to analyze the differences in flexural strengths (⍺ = 0.05). Results: The flexural strength of heat-polymerized groups was similar. The flexural strength of microwave polymerized group was significantly different and lower than the other groups (P < 0.05). Conclusion: Polymerizing conventional heat-polymerizing PMMA resin with microwave energy resulted in a significant decrease in flexural strength. The results of this study suggest that clinicians may benefit from using heat polymerization when processing PMMA denture bases instead of microvawe polymerization when tested brand is used.

The Influence of Force Direction on the Fracture Pattern and Fracture Resistance of Canine Teeth in Dogs

2017 ◽  
Vol 34 (1) ◽  
pp. 8-17 ◽  
Author(s):  
Stephanie Goldschmidt ◽  
Catherine Zimmerman ◽  
Caitlyn Collins ◽  
Scott Hetzel ◽  
Heidi-Lynn Ploeg ◽  
...  
Keyword(s):  
Fracture Resistance ◽  
Ex Vivo ◽  
Testing Machine ◽  
Fracture Pattern ◽  
Hard Tissue ◽  
Canine Tooth ◽  
Cross Sectional ◽  
Significant Difference ◽  
Force Direction ◽  
Testing Group

Biomechanical studies of the elongated canine tooth of animals are few, and thus our understanding of mechanical and physical properties of animal teeth is limited. The objective of the present study was to evaluate the influence of force direction on fracture resistance and fracture pattern of canine teeth in an ex vivo dog cadaver model. Forty-five extracted canine teeth from laboratory beagle dogs were standardized by hard tissue volume and randomly distributed among 3 force direction groups. The teeth were secured within a universal testing machine and a load was applied at different directions based on testing group. The maximum force to fracture and the fracture pattern classification were recorded for each tooth. After correcting for hard tissue cross-sectional area in a multivariate analysis, no significant difference in the amount of force required for fracture was apparent between the different force direction groups. However, the influence of force direction on fracture pattern was significant. The results of this study may allow the clinician to educate clients on possible causal force directions in clinically fractured teeth and, thus, help prevent any contributing behavior in the future.

scholarly journals Technology and Process Design for Phenols Recovery from Industrial Chicory (Chicorium intybus) Leftovers

Molecules ◽  
2019 ◽  
Vol 24 (15) ◽  
pp. 2681 ◽  
Author(s):  
Camilla Maria Cova ◽  
Luisa Boffa ◽  
Marco Pistocchi ◽  
Silver Giorgini ◽  
Rafael Luque ◽  
...  
Keyword(s):  
Extraction Process ◽  
Ethanol Solution ◽  
Ultrasound Assisted Extraction ◽  
Mineral Salts ◽  
Primary And Secondary Metabolites ◽  
Assisted Extraction ◽  
Honestly Significant Difference ◽  
Significant Difference ◽  
Tukey Honestly Significant Difference ◽  
Post Hoc

Vegetal leftovers from the agro–food industry represent a huge source of primary and secondary metabolites, vitamin, mineral salts and soluble as well as insoluble fibers. Economic reports on the growth in the polyphenol market have driven us to focus our investigation on chicory (Chicorium intybus L.), which is one of the most popular horticultural plants in the world and a rich source of phenolic compounds. Ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE) and their simultaneous combination, using either ethanol/water or water alone (also sub-critical), have been investigated with the aim of designing a green and efficient extraction process. Higher total-polyphenol yields as well as dramatic reductions in extraction times and solvent consumption have been obtained under these conditions. ANOVA test for analyses of variance followed by the Tukey honestly significant difference (HSD) post-hoc test of multiple comparisons was used in the statistical analysis. MAE experiments performed with sub-critical water, and MW/US experiments with an ethanol solution have shown polyphenol recovery values of up to ~3 g of gallic acid equivalents (GAE) per kg of fresh material in only 15 min, while conventional extraction required 240 min to obtain the same result.

scholarly journals Effect of Reduced Occlusal Thickness with Two Margin Designs on Fracture Resistance of Monolithic Zirconia Crowns

2020 ◽  
Vol 14 (02) ◽  
pp. 245-249
Author(s):  
Haider Hasan Jasim ◽  
Meelad Basil Findakly ◽  
Nada Ali Mahdi ◽  
Mustafa Tariq Mutar
Keyword(s):  
Fracture Resistance ◽  
Testing Machine ◽  
Three Dimensional ◽  
Fracture Load ◽  
Anova Test ◽  
Optical Scanner ◽  
Nickel Chromium ◽  
Significant Difference ◽  
Zirconia Crowns ◽  
Monolithic Zirconia

Abstract Objectives The aim of this study was to compare the effects of two margin designs (shoulderless and slight chamfer) with two occlusal thicknesses on fracture resistance and failure mode of the monolithic zirconia crowns. Materials and Methods Forty nickel–chromium dies were duplicated from the previous two prepared teeth using a three-dimensional optical scanner. Nickel–chromium supporting dies were divided into two main groups (n = 20) according to the type of margin design: group A, slight chamfer margin design and group B, shoulderless margin design. These groups were further divided into two subgroups according to the occlusal thicknesses (0.5 and 1 mm). The digital imaging of each die was done using a three-dimensional optical scanner, then zirconia blocks were milled by 5-axis machine. The crowns were cleaned by alcohol, air dried, and cemented by resin cement. Next, the crowns were subjected to 500 hot and cold cycles (30 seconds for each cycle). The samples were subjected to a static load until failure using an electronic universal testing machine and fracture resistance was recorded in Newton (N). Statistical Analysis Data were analyzed using the test of normality (Shapiro–Wilk test) and two-way analysis of variance (ANOVA) test. Results  The highest mean fracture load was recorded by the shoulderless (1 mm occlusal thickness) subgroup (3,992.5 N), followed by shoulderless (0.5 mm occlusal thickness) subgroup (3,244.4 N), and the slight chamfer (1 mm occlusal thickness) subgroup (2,811 N). The lowest mean of fracture load was recorded by slight chamfer (0.5 mm occlusal thickness) subgroup (1,632.9 N). The two-way ANOVA test revealed a significant difference between the four subgroups. Regarding the fracture mode, the slight chamfer subgroups showed a severe fracture of the restoration while the shoulderless subgroups showed a fracture through the midline of the restoration. Conclusion Within the limitation of the comparative study, shoulderless margin design has a more favorable outcome than a slight chamfer design in all thicknesses. Although the restoration with reduced occlusal thickness has lower fracture resistance than 1 mm occlusal thickness, the 0.5 mm restorations still can tolerate occlusal forces.

scholarly journals Comparison of four monolithic zirconia materials with conventional ones: Contrast ratio, grain size, four-point flexural strength and two-body wear

2016 ◽  
Vol 59 ◽  
pp. 128-138 ◽  
Author(s):  
Bogna Stawarczyk ◽  
Kathrin Frevert ◽  
Andreas Ender ◽  
Malgorzata Roos ◽  
Beatrice Sener ◽  
...  
Keyword(s):  
Grain Size ◽  
Flexural Strength ◽  
Contrast Ratio ◽  
Monolithic Zirconia

Undeveloped semiconic posterosuperior ligament and susceptibility to avulsion of the C-7 spinal nerve in Erb palsy

2011 ◽  
Vol 7 (6) ◽  
pp. 676-680 ◽  
Author(s):  
Yi-gang Huang ◽  
Liang Chen ◽  
Yu-dong Gu ◽  
Guang-rong Yu
Keyword(s):  
Failure Load ◽  
Transverse Process ◽  
Biomechanical Properties ◽  
Spinal Nerve ◽  
Spinal Nerves ◽  
Honestly Significant Difference ◽  
Significant Difference ◽  
Tukey Honestly Significant Difference ◽  
Tension Testing ◽  
Histological Characteristics

Object In Erb palsy, the C-7 spinal nerve has been found to be more subject to avulsion than the C-5 and C-6 spinal nerves. This study investigated the morphological and biomechanical characteristics of the semiconic posterosuperior ligaments (SPLs) at the C-5, C-6, and C-7 spinal nerves in neonates. Methods Twenty-four brachial plexuses from 12 fresh neonate cadavers were used in this study. In 12 brachial plexuses from 6 cadavers, the following studies were performed with respect to the SPLs at the C-5, C-6, and C-7 spinal nerves: gross observation of morphological and histological characteristics; measurement of length, thickness, and width; and a semiquantitative analysis of collagen. In the other 6 cadavers, biomechanical tension testing was performed bilaterally on the C5–7 SPLs to assess the tensile strength of the ligaments. Results The C5–7 spinal nerves are fixed to the transverse process through the SPL, a structure not observed at the C-8 and T-1 spinal nerves. Except for the width of the SPL insertion on the spinal nerve, which was found to increase gradually from C-5 to C-7, there was no statistically significant difference in the dimensions of the C-5, C-6, and C-7 SPLs. The sectional area percentage of collagen was 51% ± 10% in SPLs for C-5, 51% ± 11% for C-6, and 41% ± 10% for C-7; and this percentage was significantly lower in SPLs for C-7 than for C-5 or C-6 (1-way ANOVA, F = 4.3, p = 0.02; Tukey honestly significant difference test, p = 0.04 and 0.04, respectively). Sharpey fibers were observed at the transverse process origin of the SPL at C-5 and C-6 but not at C-7. Biomechanical tension testing showed that the mean failure load was 6.6 ± 0.9 N for the C-5 SPL, 6.4 ± 1.0 N for the C-6 SPL, and 5.4 ± 0.9 N for the C-7 SPL, and the failure load was significantly lower in SPLs at C-7 than in those at C-5 or C-6 (1-way ANOVA, F = 5.1, p = 0.01; Tukey honestly significant difference, p = 0.01 and 0.048, respectively). Nine of 12 C-7 SPLs failed at their origin from the transverse process, while only 4 of 12 C-5 SPLs and 3 of 12 C-6 SPLs failed at the origin site. Conclusions These findings suggest that the lower density of collagen and absence of Sharpey fibers decrease the biomechanical properties of the C-7 SPL, and this may account for the higher frequency of avulsion of the C-7 spinal nerve (in comparison with the C-5 or C-6 nerve) in Erb palsy.

scholarly journals Influence of Light-curing Parameters on Biofilm Development and Flexural Strength of a Silorane-based Composite

2016 ◽  
Vol 41 (2) ◽  
pp. 219-227 ◽  
Author(s):  
E Brambilla ◽  
A Ionescu ◽  
G Cazzaniga ◽  
M Ottobelli
Keyword(s):  
Flexural Strength ◽  
Laser Scanning ◽  
Testing Machine ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Curing Time ◽  
Two Samples ◽  
Significant Difference ◽  
Light Curing ◽  
Biofilm Development

SUMMARYObjectives: The aim of this study was to evaluate the differences in biological and mechanical performances of a silorane-based and a methacrylate-based composite. Another aim was to assess the influence of light-curing time and light-curing intensity on in vitro biofilm formation and flexural strength of the two tested composites.Methods: Experiment 1: 432 specimens obtained from a silorane-based composite and from a standard methacrylate-based composite were divided into six groups and light-cured for 10, 20, 30, 40, 60, or 80 seconds, using one of two light-curing intensities, 400 mW/cm2 or 800 mW/cm2. At 24 hours, a monospecific Streptococcus mutans biofilm adherent to the surfaces of the samples was obtained. Then, a colorimetric technique (MTT assay) was used to evaluate the adherent viable biomass. Two samples per group were observed using confocal laser scanning microscopy. Analysis of variance (ANOVA) and Tukey tests were used to analyze the results (p&lt;0.05). Experiment 2: 192 bar-shaped specimens were obtained and light-cured as in the previous experiment. A three-point bend test using a universal testing machine was performed to obtain flexural strength values. ANOVA and Tukey tests were used to analyze the results (p&lt;0.05).Results: In experiment 1, a highly significant difference (p&lt;0.0001) in biofilm development was shown between silorane-based and methacrylate-based composites. In fact, the silorane-based composite exhibited better biological performance. Significant differences were also found between the two light-curing intensities (p&lt;0.018) and for curing times (p&lt;0.0001): silorane-based composite light-cured for 80 seconds at 800 mW/cm2 light-curing intensity showed the lowest biofilm development. In experiment 2, a significant difference in flexural strength (p&lt;0.0318) was only found between the different composites. Nevertheless, both resin composites showed flexural strength values in accordance with International Organization for Standardization guidelines even after 10 seconds of light-curing time.Conclusions: Silorane-based composite was less prone to biofilm development compared with a methacrylate-based composite. Acceptable flexural strength values for both composites were obtained after 10 seconds of light-curing time.

scholarly journals Effects of Denture Cleansers on Heat-Polymerized Acrylic Resin: A Five-Year-Simulated Period of Use

2015 ◽  
Vol 26 (4) ◽  
pp. 404-408 ◽  
Author(s):  
Carolina Noronha Ferraz Arruda ◽  
Danilo Balero Sorgini ◽  
Viviane de Cássia Oliveira ◽  
Ana Paula Macedo ◽  
Cláudia Helena Silva Lovato ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Flexural Strength ◽  
Testing Machine ◽  
Color Stability ◽  
Acrylic Resin ◽  
National Bureau ◽  
Alkaline Peroxide ◽  
Significant Difference ◽  
Bonferroni Test ◽  
Clinically Significant

<p>This study evaluated color stability, surface roughness and flexural strength of acrylic resin after immersion in alkaline peroxide and alkaline hypochlorite solutions, simulating a five-year-period of use. Sixty disc-shaped (16x4 mm) and 60 rectangular specimens (65x10x3.3 mm) were prepared from heat-polymerized acrylic resin (Lucitone 550) and assigned to 3 groups (n=20) of immersion (20 min): C1: distilled water; AP: warm water and one alkaline peroxide tablet; SH: 0.5% NaOCl solution. Color data (∆E) were determined by a colorimeter and also quantified according to the National Bureau of Standards units. A rugosimeter was used to measure roughness (μm) and the flexural strength (MPa) was measured using a universal testing machine. Data were evaluated by Kruskal-Wallis followed by Dunn tests (color stability and surface roughness) and by one-way ANOVA and Bonferroni test (flexural strength). For all tests was considered α=0.05. AP {0.79 (0.66;1.42)} caused color alteration significantly higher than C1 {0.45 (0.37;0.57)} and SH {0.34 (0.25;0.42)}. The mean ∆Ε values quantified by NBS were classified as "trace" for C1 (0.43) and SH (0.31) and "slight" for AP (0.96). SH {-0.015 (-0.023;0.003)} caused significantly higher ΔRa than the C1 {0.000 (-0.004;0.010)} and AP {0.000 (-0.009;0.008)} groups. There was no statistically significant difference among the solutions for flexural strength (C1: 84.62±16.00, AP: 85.63±12.99, SH: 84.22±14.72). It was concluded that immersion in alkaline peroxide and NaOCl solutions simulating a five-year of 20 min daily soaking did not cause clinically significant adverse effects on the heat-polymerized acrylic resin.</p>

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