scholarly journals Determination of Hardness and Fracture Toughness of Y-TZP Manufactured by Digital Light Processing through the Indentation Technique

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Ziyu Mei ◽  
Yuqing Lu ◽  
Yuxin Lou ◽  
Ping Yu ◽  
Manlin Sun ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Tetragonal Zirconia ◽  
Milling Process ◽  
Control Group ◽  
Digital Light Processing ◽  
Hardness Values ◽  
3D Printing Technique ◽  
True Hardness ◽  
Tetragonal Zirconia Polycrystal

Objective. The purpose of the study was to determine the hardness and fracture toughness of dental yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) manufactured by digital light processing (DLP) technology to study its clinical prospects. Methods. The experimental group was DLP-manufactured zirconia, and the control group was milled zirconia. The hardness was investigated under a range of test loads (0.49 N, 0.98 N, 1.96 N, 4.90 N, 9.81 N, 29.42 N, 49.03 N, 98.07 N, and 196.1 N). Meyer’s law was applied to describe the indentation size effect (ISE). Meanwhile, the PSR model and MPSR model were utilized to generate true hardness values. The cracks were observed to be induced by indentation under loads above 49.03 N, while the cracks showed the radial-median type under the load of 196.1 N, under which the fracture toughness was calculated. Results. The true hardness of DLP-manufactured zirconia was 1189 HV based on the PSR model and 1193 HV based on the MPSR model, a bit lower than that of milled zirconia. The fracture toughness was 3.43 ± 0.29   MPa √ m , which showed no statistical difference with the milled zirconia. Conclusion. The dental zirconia manufactured by the DLP 3D printing technique is similar to that manufactured by the conventional milling process in hardness and fracture toughness, thus having a promising future of clinical use.

Effect of TiN Addition on Microstructure and Mechanical Properties of Zirconia Matrix Ceramic Tool Material

2004 ◽  
Vol 471-472 ◽  
pp. 321-325 ◽  
Author(s):  
Jing Sun ◽  
Chuan Zhen Huang ◽  
Han Lian Liu ◽  
Sui Lian Wang
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Flexural Strength ◽  
Monoclinic Phase ◽  
Tetragonal Zirconia ◽  
Tool Material ◽  
Strengthening Mechanisms ◽  
Microstructure And Mechanical Properties ◽  
Ceramic Tool Material ◽  
Tetragonal Zirconia Polycrystal

In this paper, 3mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) and TiN/3Y-TZP(adding TiN particles to 3Y-TZP) composites were fabricated by hot-pressing technique. Phase composition, microstructure and mechanical properties of the composites were investigated. It is shown that the flexural strength, fracture toughness and Vickers hardness of TiN/3Y-TZP was significantly improved by the addition of TiN particles compared with 3Y-TZP. The flexural strength of ZYT2 (20wt% TiN addition) is 1318 MPa. The fracture toughness of ZYT4 (40wt% TiN addition) is 16.8MPa·m1/2. The toughening and strengthening mechanisms were analyzed. The XRD results show that the additing of TiN can hinder the transformation from tetragonal phase to monoclinic phase of 3Y-TZP during fabrication process.

Laser-Assisted Milling of Zirconia with Systematically Determined Machining Conditions

2017 ◽  
Vol 11 (2) ◽  
pp. 258-269
Author(s):  
Toru Kizaki ◽  
◽  
Yusuke Ito ◽  
Naohiko Sugita ◽  
Mamoru Mitsuishi
Keyword(s):  
Fracture Toughness ◽  
Unique Feature ◽  
Elevated Temperatures ◽  
Thrust Force ◽  
Tetragonal Zirconia ◽  
Systematic Method ◽  
Processing Efficiency ◽  
Diamond Tools ◽  
Dental Restoratives ◽  
Tetragonal Zirconia Polycrystal

Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) is a promising material for dental restoratives. Although grinding or polishing with diamond tools is widely used to machine Y-TZP, the processing efficiency and cost of the process are problematic. In this study, we applied laser-assisted machining (LAM) to Y-TZP, in which non-diamond tools were used. Unlike LAM applied to other materials, decrease of the fracture toughness at elevated temperatures which is a unique feature of the Y-TZP was adopted as a key mechanism for machinability enhancement. In addition, a systematic method to determine the LAM conditions was proposed. In this study, we explain the LAM condition-determining method, which is based on numerical simulations of the temperature distribution. Secondly, the determining method was evaluated through a series of LAM experiments to obtain the appropriate LAM conditions. Using the determined conditions, LAM of Y-TZP was demonstrated to be effective; the thrust force was reduced by 51.3% and the tool wear was significantly reduced, while no cracks formed on the Y-TZP.

Sinterability of Alumina-Dispersed 3Y-TZP

2006 ◽  
Vol 317-318 ◽  
pp. 37-40
Author(s):  
Bum Rae Cho ◽  
Dong Guk Yeoum
Keyword(s):  
Fracture Toughness ◽  
Tetragonal Zirconia ◽  
Micro Hardness ◽  
Drying Method ◽  
Hardness Tester ◽  
Pinning Effect ◽  
High Relative Density ◽  
Al2o3 Particles ◽  
Vickers Micro Hardness ◽  
Tetragonal Zirconia Polycrystal

The effect of Al2O3 addition on sinterability of Tetragonal Zirconia Polycrystal powders including 3mol% Y2O3 (3Y-TZP) was investigated. Each 3Y-TZP powder dispersed with 0.3, 0.6, 0.9 and 1.2wt.% of Al2O3 was prepared by the spray-drying method. The prepared powders were pressed into a disk type and sintered at 1350, 1400, 1450 and 1500 for 2 hours in the air. Resultant microstructures and mechanical properties of specimens were investigated by using Vickers/Micro hardness Tester, FE-SEM and XRD. Most of the specimens showed high relative density over 99% and a higher fracture toughness than pure 3Y-TZP. Al2O3 particles dispersed in 3Y-TZP microstructure depressed grain growth of 3Y-TZP by the pinning effect. Increase in fracture toughness of 3Y-TZP was explained by the crack deflection due to dispersed Al2O3 particles.

scholarly journals Effect of Different Surface Treatments on Biaxial Flexural Strength of Yttria-stabilized Tetragonal Zirconia Polycrystal

2018 ◽  
Vol 19 (3) ◽  
pp. 318-323
Author(s):  
Teerthesh Jain ◽  
Amit Porwal ◽  
Sumanth Babu ◽  
Zahid A Khan ◽  
Chandeep Kaur ◽  
...  
Keyword(s):  
Low Temperature ◽  
Flexural Strength ◽  
Tetragonal Zirconia ◽  
Surface Treatments ◽  
Control Group ◽  
Significant Difference ◽  
Biaxial Flexural Strength ◽  
Computer Aided ◽  
The Impact ◽  
Tetragonal Zirconia Polycrystal

ABSTRACT Introduction Ceramics are widely applied in dentistry owing to their excellent mechanical and physical attributes. The most popular ceramics are Lava™, KaVo Everest, and Cercon. However, it is unclear whether or not a different surface treatment along with low-temperature aging and mechanical loading (ML) affects the physical properties of computer-aided design (CAD)/computer-aided manufacturing (CAM)-machined yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramic. Aim The objective of this research was to assess the impact of various surface treatments as air-particle abrasion, ML, low-temperature degradation (LTD), and their cumulative effects on biaxial flexural properties of Y-TZP. Materials and methods Totally, 50 specimens were fabricated by CAD–CAM machining from Cercon® and divided into five groups following different surface treatments as control (C), air-particle abrasion (Si), ML, LTD, and cumulative treatment (CT) group. Results were investigated by two-way analysis of variance (ANOVA) and Tukey honest significant difference (HSD) test. Results The highest biaxial flexural strength was observed in the Si group (950.2 ± 126.7 MPa), followed by the LTD group (861.3 ± 166.8 MPa), CT group (851.2 ± 126.5 MPa), and the least with ML (820 ± 110 MPa). A significant difference was observed in the two-way ANOVA test. X-ray diffraction (XRD) analysis showed that the control group consists of 100% tetragonal zirconia and the maximum amount of monoclinic phase was obtained after LTD. Conclusion No negative effect on biaxial flexural strength was observed; indeed, it increases the biaxial strength. Hence, these surface treatments can be done in routine clinical practice to improve the performance of ceramic restoration. How to cite this article Jain T, Porwal A, Babu S, Khan ZA, Kaur C, Jain RB. Effect of Different Surface Treatments on Biaxial Flexural Strength of Yttria-stabilized Tetragonal Zirconia Polycrystal. J Contemp Dent Pract 2018;19(3):318-323.

FRACTIONAL DETERMINATIONS OF URINARY 17-KETOSTEROIDS IN HYPEREMESIS GRAVIDARUM

1962 ◽  
Vol 41 (1) ◽  
pp. 123-128 ◽  
Author(s):  
Pentti A. Järvinen ◽  
Sykkö Pesonen ◽  
Pirkko Väänänen
Keyword(s):  
Hyperemesis Gravidarum ◽  
First Trimester ◽  
Control Group ◽  
Before And After ◽  
Daily Urine ◽  
First Trimester Of Pregnancy ◽  
The Difference

ABSTRACT The fractional determination of 17-ketosteroids in the daily urine was performed in nine cases of hyperemesis gravidarum and in four control cases, in the first trimester of pregnancy both before and after corticotrophin administration. The excretion of total 17-KS is similar in the two groups. Only in the hyperemesis group does the excretion of total 17-KS increase significantly after corticotrophin administration. The fractional determination reveals no difference between the two groups of patients with regard to the values of the fractions U (unidentified 17-KS), A (androsterone) and Rest (11-oxygenated 17-KS). The excretion of dehydroepiandrosterone is significantly higher in the hyperemesis group than in the control group. The excretion of androstanolone seems to be lower in the hyperemesis group than in the control group, but the difference is not statistically significant. The differences in the correlation between dehydroepiandrosterone and androstanolone in the two groups is significant. The high excretion of dehydroepiandrosterone and low excretion of androstanolone in cases of hyperemesis gravidarum is a sign of adrenal dysfunction.

Determination of clinical efficiency of deproteinized dialysate from blood of milk-fed calves after endoprosthetics in patients with ventral hernias

2020 ◽  
Vol 28 (3) ◽  
pp. 323-333
Author(s):  
Sergej V. Ivanov ◽  
Ilya S. Ivanov ◽  
Evgenij G. Obyedkov ◽  
Liliya P. Popova
Keyword(s):  
Abdominal Wall ◽  
Inflammatory Reaction ◽  
Inflammatory Process ◽  
Anterior Abdominal Wall ◽  
Dynamic Change ◽  
Main Group ◽  
Control Group ◽  
Surgical Department ◽  
Regeneration Stage

Aim. To study the influence of deproteinized dialysate from blood of milk-fed calves on the type of exudative discharge and dynamics of inflammatory reaction after hernia repair with plastics of the anterior abdominal wall with hernioendoprosthesis of polypropylene. Materials and Methods. The study involved 59 patients being on stationary treatment in the surgical department of Kursk Regional Clinical Hospital. Patients were hospitalized for the herniation of small or medium dimension. The patients were divided to two groups: the main (n=30) and control (n=29) groups. After endoprosthetics, the patients of the control group were given complex conservative treatment. The patients of the main group, besides standard treatment, were administered deproteinized dialysate from blood of milk-fed calves intravenously in drips 10 ml + 200 ml of 0.9% sodium chloride solution within 7 days. For cytological examination and determination of the type of cytograms, the traumatic discharge was collected and analyzed using the method of M.F. Kamaev and M.A. Palthsev. Results. Cytomorphometric examination was conducted on the third, fifth and seventh day after endoprosthetics with the aim of studying dynamic changes. Determination of cell composition and also of its changes characteristic of each studied period, was necessary for obtaining further information characterizing inflammatory process in the region of placement of the endoprosthesis. After endoprosthetics in patients who were administered hemodialysate, the inflammatory reaction was less pronounced than in patients who did not receive the preparation. This was associated with a more dynamic change of stages of the inflammatory process. In patients of the main group who received deproteinized dialysate, regenerative type of inflammation first appeared on the fifth day and made 6.9%; by the seventh day the share of patients with the regenerative type rose to 17.5%, while in the patients of the control group no regeneration stage was observed in both periods. Conclusion. Analysis of the efficiency of influence of hemodialysate on the inflammatory reaction in plastics of the anterior abdominal wall with polypropylene endoprosthesis evidences faster course of all stages of inflammation and reduction of its intensity by 10%.

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