scholarly journals Study of crystallization, microstructure and mechanical properties of lithium disilicate glass-ceramics as a function of the sintering temperature

2021 ◽  
Vol 24 (2) ◽  
Author(s):  
Dayana Campanelli de Morais ◽  
Matheus Ferreira Theotonio Santos ◽  
Tiago Moreira Bastos Campos ◽  
Eliandra De Sousa Trichês ◽  
Alexandre Luiz Souto Borges
Keyword(s):  
Mechanical Properties ◽  
Glass Ceramics ◽  
Lithium Disilicate ◽  
Scanning Calorimetry ◽  
Sem Images ◽  
Microstructure And Mechanical Properties ◽  
Group 3 ◽  
Group 2 ◽  
Contrast Group ◽  
Group 1

Objective: The purpose of the present study was to synthesize and characterize lithium disilicate glass-ceramics through the Li2 O-SiO2 system for determining the most satisfactory sintering parameter by evaluating the crystalline composition, microstructure and mechanical properties. Material and methods: The glass-ceramics were prepared from a glass precursor by means of the melting/cooling technique with a composition of 33.33 Li2 O and 66.67 SiO2 (mol.%). The specimens were compressed by the uniaxial pressing technique and three different thermal treatments were used for sintering: 850 °C (Group 1), 900 °C (Group 2), and 950 °C (Group 3), which were determined based on the differential scanning calorimetry (DSC) result. The glass-ceramics were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Archimedes method, microhardness and biaxial flexural strength analyses. Results: The results regarding XRD predominantly showed lithium disilicate phase for all the heat treatments performed. Moreover, grains with a needle form were more predominantly observed in the SEM images for Group 3, as well as a higher densification and consequently higher mechanical properties. In contrast, Group 1 presented the lowest mechanical properties and densification, as well as the highest porosity. Conclusion: The present study demonstrated how extremely important it is to follow the heat treatment recommended by the manufacturers of ceramics, including time and temperature, which possess direct effects in the crystalline phase formation, as well as in the material’s microstructure and mechanical properties.   Keywords Crystallization; Glass-ceramics; Lithium disilicate.

Assessing Burnout in Subgroups of Athletes Based on Gratitude and Perceived Coach-Athlete Relationship

2021 ◽  
pp. 003329412199183
Author(s):  
Mariya A. Yukhymenko-Lescroart ◽  
Jeffrey B. Ruser ◽  
Nicole T. Gabana ◽  
Jenelle N. Gilbert
Keyword(s):  
Protective Role ◽  
Three Dimensions ◽  
Intercollegiate Athletes ◽  
Male Athletes ◽  
Group 4 ◽  
Athlete Burnout ◽  
Group 3 ◽  
Group 2 ◽  
Contrast Group ◽  
Group 1

The purpose of this study was to examine distinct groups of athletes based on their gratitude and coach-athlete relationships (CAR) and to compare the groups on three dimensions of athlete burnout: sense of reduced accomplishment, emotional and physical exhaustion, and sport devaluation. Types of gratitude measured included general trait gratitude, general state gratitude, and sport state gratitude. Cluster analysis with 576 intercollegiate athletes showed four distinct groups: “ungrateful in life and sport, and disconnected from the coach” (Group 1), “highly grateful in life and sport, and well-connected with the coach” (Group 2), “generally less grateful in life, but connected with the coach” (Group 3), and “generally grateful in life, but disconnected from the coach” (Group 4). Group 1 reported the highest levels of burnout. In contrast, Group 2 reported the lowest levels of burnout. Athletes in Groups 3 and 4 (which were similar on sport state gratitude, but differed on other indicators) reported moderate levels of burnout, but Group 4 athletes were more burned out than Group 3 athletes. Specifically, both groups reported similar levels of devaluation; yet, Group 4 scored higher on reduced sense of accomplishment and emotional/physical exhaustion than Group 3. Examination of group composition revealed that male athletes were overrepresented in Group 2 and underrepresented in Group 4, and Group 1 athletes tended to identify as non-religious. Taken together, findings point to the protective role that gratitude and a positive CAR may play in athlete burnout prevention.

scholarly journals Influence of Body Mass Index on Mechanical Properties in People With Obesity

2021 ◽  
Author(s):  
Serkan Usgu ◽  
Engin Ramazanoğlu ◽  
Yavuz Yakut
Keyword(s):  
Mechanical Properties ◽  
Body Mass Index ◽  
Body Mass ◽  
The Other ◽  
Positive Correlation ◽  
Weak Positive Correlation ◽  
Group 3 ◽  
Group 2 ◽  
The Right ◽  
Group 1

Abstract Background: The study was to determine influence of body mass index on muscular mechanical properties in people with obesity.Methods: A total of 300 individuals (mean age: 27.31±7.21 years) were participated. The participants were assigned in groups base on BMI classification (Group 1 (BMI=18.50-24.99 kg/m2), Group 2 (BMI=25.00-29.99 kg/m2), and Group 3 (BMI≥30 kg/m2)). The biceps brachii (BB), biceps femoris (BF) were measured bilaterally using the "MyotonPRO" device. Results: All mechanical properties of the right and left BB muscle, left BF tone and stiffness were found significantly difference between groups (p<0.05). The bilateral BB tone in Group 3 was lower than the other two groups. The right BB stiffness of Group 2 was found to be higher compared to the other two groups (p<0.05). While the right and left BB elasticity was similar in Groups 2 and 3, it was lower compared to Group 1 (p<0.05). The left BF tone and stiffness of Group 3 were found to be significantly higher than Groups 1 and 2 (p<0.05).The right BB tone showed a weak negative correlation with BMI in females, and for left side in males. A weak positive correlation was found between the right and left BB elasticity and BMI in males and females. The left-right BF tone and left BF stiffness showed a weak positive correlation in males. Conclusions: The bilateral BB tone and elasticity decreased, and the left BF stiffness increased as BMI increased. Different mechanical properties were observed in sex comparasion base on BMI clasification. The BB and BF mechanical properties were affected more in males than females.

Influence of Sintering Conditions on Microstructural and Mechanical Properties of an Yttria Partially Stabilized Zirconia

2016 ◽  
Vol 881 ◽  
pp. 143-146
Author(s):  
Fabiana Ribeiro da Silva Schanuel ◽  
Wilson Acchar
Keyword(s):  
Mechanical Properties ◽  
Oral Cavity ◽  
Cost Benefit ◽  
Stabilized Zirconia ◽  
Group 3 ◽  
Yttria Partially Stabilized Zirconia ◽  
Sintering Conditions ◽  
Group 2 ◽  
The Cost ◽  
Group 1

The aim of this study was to evaluate the dependence of sintering conditions on mechanical properties and microstructure of zirconia stabilized by yttria. Commercial blocks of pre-sintered of zirconia stabilized (DeguDent Dentsply, Germany-Cercon) were investigated in this study. The blocks belonging to group 1 were sintered under the recommended conditions by the manufacturer (1350°C for 6 hours). The blocks of group 2 were sintered under 1500°C for 6 hours. The blocks of group 3 were sintered under 1350 C for 14.5 hours. The results indicated that the sintering conditions influenced the mechanical properties and microstructure of zirconia. The three sintering conditions analyzed in this study produces zirconia bodies with properties adequate to be used in clinical function. However, the decisive factor for change in the sintering conditions should be the cost/benefit during the prosthetical process and longevity of clinical material to perform its function in the oral cavity.

scholarly journals Effectiveness of a toothpaste and a serum containing calcium silicate on protecting the enamel after interproximal reduction against demineralization

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ascensión Vicente ◽  
Antonio J. Ortiz-Ruiz ◽  
Belén M. González-Paz ◽  
Yolanda Martínez-Beneyto ◽  
Luis Alberto Bravo-González
Keyword(s):  
Calcium Silicate ◽  
Control Group ◽  
Surface Microhardness ◽  
Sem Images ◽  
X Ray ◽  
Electron Scanning Microscopy ◽  
Group 3 ◽  
Group 2 ◽  
Enamel Reduction ◽  
Group 1

AbstractTo evaluate the effectiveness of a calcium silicate/phosphate fluoridated tooth paste and a serum compared with a toothpaste containing hydroxyapatite on protecting the enamel after interproximal reduction against demineralization. 3 sets of eleven incisors were created. The teeth underwent interproximal enamel reduction (IER) of 0.5 mm. Each set was allocated to one of three groups: (1) Brushing without toothpaste (control group); (2) Vitis toothpaste + Remin Pro; (3) Regenerate toothpaste + Regenerate Serum. The agents were applied three times a day and specimens subjected to demineralization cycles for 30 days. The weight percentages of calcium (Ca) and phosphorous (P) were quantified by X-ray microfluorescence spectroscopy. Surface microhardness measurements and electron scanning microscopy (SEM) observations were made. Ca data and the Ca/P ratio were significantly higher in Group 3 than the other groups (p < 0.017), while P was significantly lower in Group 3 (p < 0.017). No significant differences were found between Groups 1 and 2 (p > 0.017). Group 3 showed significantly higher microhardness values (p < 0.05) than Group 1. No significant differences were found for other comparisons between groups (p < 0.05). SEM images showed less demineralization in Group 3. The application of a calcium silicate/phosphate fluoridated tooth paste (Regenerate advance) and a dual serum (Regenerate advance enamel serum) protect the enamel with interproximal reduction against demineralization. Therefore, this treatment could be used to prevent the dissolution of hydroxyapatite after IER.

In-vivo evaluation of the effect of cyanoacrylate on prosthetic vascular graft infection – does cyanoacrylate increase the severity of infection?

VASA ◽  
2020 ◽  
Vol 49 (4) ◽  
pp. 281-284
Author(s):  
Atıf Yolgosteren ◽  
Gencehan Kumtepe ◽  
Melda Payaslioglu ◽  
Cuneyt Ozakin
Keyword(s):  
Vascular Graft ◽  
Graft Infection ◽  
Vascular Graft Infection ◽  
Group 4 ◽  
Significant Difference ◽  
Group 3 ◽  
Group 2 ◽  
Prosthetic Vascular Graft Infection ◽  
Group 1

Summary. Background: Prosthetic vascular graft infection (PVGI) is a complication with high mortality. Cyanoacrylate (CA) is an adhesive which has been used in a number of surgical procedures. In this in-vivo study, we aimed to evaluate the relationship between PVGI and CA. Materials and methods: Thirty-two rats were equally divided into four groups. Pouch was formed on back of rats until deep fascia. In group 1, vascular graft with polyethyleneterephthalate (PET) was placed into pouch. In group 2, MRSA strain with a density of 1 ml 0.5 MacFarland was injected into pouch. In group 3, 1 cm 2 vascular graft with PET piece was placed into pouch and MRSA strain with a density of 1 ml 0.5 MacFarland was injected. In group 4, 1 cm 2 vascular graft with PET piece impregnated with N-butyl cyanoacrylate-based adhesive was placed and MRSA strain with a density of 1 ml 0.5 MacFarland was injected. All rats were scarified in 96th hour, culture samples were taken where intervention was performed and were evaluated microbiologically. Bacteria reproducing in each group were numerically evaluated based on colony-forming unit (CFU/ml) and compared by taking their average. Results: MRSA reproduction of 0 CFU/ml in group 1, of 1410 CFU/ml in group 2, of 180 200 CFU/ml in group 3 and of 625 300 CFU/ml in group 4 was present. A statistically significant difference was present between group 1 and group 4 (p < 0.01), between group 2 and group 4 (p < 0.01), between group 3 and group 4 (p < 0.05). In terms of reproduction, no statistically significant difference was found in group 1, group 2, group 3 in themselves. Conclusions: We observed that the rate of infection increased in the cyanoacyrylate group where cyanoacrylate was used. We think that surgeon should be more careful in using CA in vascular surgery.

Abnormal Haemostasis and Blood Viscosity in Malignant Hypertension

1984 ◽  
Vol 52 (03) ◽  
pp. 253-255 ◽  
Author(s):  
C Isles ◽  
G D O Lowe ◽  
B M Rankin ◽  
C D Forbes ◽  
N Lucie ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Blood Viscosity ◽  
Renal Damage ◽  
Antithrombin Iii ◽  
Plasma Viscosity ◽  
Malignant Hypertension ◽  
Fibrin Deposition ◽  
Group 3 ◽  
Group 2 ◽  
Group 1

SummaryWe have previously shown abnormalities of haemostasis suggestive of intravascular coagulation in patients with malignant hypertension, a condition associated with retinopathy and renal fibrin deposition. To determine whether such abnormalities are specific to malignant hypertension, we have measured several haemostatic and haemorheological variables in 18 patients with malignant hypertension (Group 1), 18 matched healthy controls (Group 2), and 18 patients with non-malignant hypertension (Group 3) matched for renal pathology, blood pressure and serum creatinine with Group 1. Both Groups 1 and 3 had increased mean levels of fibrinogen, factor VIIIc, beta-thrombo- globulin, plasma viscosity and blood viscosity (corrected for haematocrit); and decreased mean levels of haematocrit, antithrombin III and platelet count. Mean levels of fast antiplasmin and alpha2-macroglobulin were elevated in Group 1 but not in Group 3. We conclude that most blood abnormalities are not specific to malignant hypertension; are also present in patients with non-malignant hypertension who have similar levels of blood pressure and renal damage; and might result from renal damage as well as promoting further renal damage by enhancing fibrin deposition. However increased levels of fibrinolytic inhibitors in malignant hypertension merit further investigation in relation to removal of renal fibrin.

Sign in / Sign up

Export Citation Format

Share Document