Surface quality of yttria-stabilized tetragonal zirconia polycrystal in CAD/CAM milling, sintering, polishing and sandblasting processes

2017 ◽  
Vol 65 ◽  
pp. 102-116 ◽  
Author(s):  
Abdur-Rasheed Alao ◽  
Richard Stoll ◽  
Xiao-Fei Song ◽  
Takashi Miyazaki ◽  
Yasuhiro Hotta ◽  
...  
Keyword(s):  
Surface Quality ◽  
Tetragonal Zirconia ◽  
Cad Cam ◽  
Tetragonal Zirconia Polycrystal

Influence of CAD/CAM Grinding in the Performance of Sintered Dental Zirconia Framework

2012 ◽  
Vol 727-728 ◽  
pp. 1081-1084
Author(s):  
Carlos Nelson Elias ◽  
Andréa Mattos Melo ◽  
Claudinei dos Santos
Keyword(s):  
Mechanical Properties ◽  
High Speed ◽  
Surface Defects ◽  
Tetragonal Zirconia ◽  
Surface Cracks ◽  
Brittle Behavior ◽  
Dental Prostheses ◽  
Cad Cam ◽  
Ceramic Restorations ◽  
Tetragonal Zirconia Polycrystal

The brittle behavior of ceramics limits the use of these materials under conditions of cyclic loading, as is the case of fixed partial dentures. To improve toughness and biocompatibility of ceramics is necessary to employ powders with better purities, adjust the conditions of compaction and sintering, microstructure control and explore mechanisms for increasing the toughness. Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) is generally used for dental ceramic restorations. The zirconia framework is fabricated using the CAD/CAM system. The ceramic mechanical properties are determined by testing polished sample. Previous work did not analyze the influence of surface defects induced during dentures grinding. Ceramic restorations manufacturing are made with coarse grinding high-speed diamond rotatory cutting instruments. This process induces residual stresses and the high temperature induces surface cracks. Consequently, a lower strength and reliability of the material is observed. In this work the mechanical properties of yttria stabilized zirconia were determined with the use of samples of dental prostheses molded in patients and machined with the use of a dental laboratory CAD/CAM system. The results showed that the mechanical properties of pre-sintered blocks are different from prosthetics machined by CAD/CAM and sintered under the same conditions used in the laboratories of the prosthesis. The defects created during machining reduce the mechanical properties of zirconia.

Development of Y-TZP Pre-Sintered Blocks for CAD-CAM Machining of Dental Prostheses

2008 ◽  
Vol 591-593 ◽  
pp. 712-716 ◽  
Author(s):  
Roberta M.C. Sasahara ◽  
H.N. Yoshimura ◽  
Cátia Fredericci ◽  
Alberto Calasans ◽  
Paulo Francisco Cesar ◽  
...  
Keyword(s):  
Flexural Strength ◽  
Vickers Hardness ◽  
Empirical Equation ◽  
Tetragonal Zirconia ◽  
Linear Shrinkage ◽  
Dental Prostheses ◽  
Biaxial Flexural Strength ◽  
Cad Cam ◽  
Dental Applications ◽  
Tetragonal Zirconia Polycrystal

The aim of this work was to establish a route to produce pre-sintered blocks of Y-TZP (yttria stabilized tetragonal zirconia polycrystal) suitable to be machined in a commercial CADCAM system, used to manufacture crowns and bridge frameworks for dental applications. Two commercial Y-TZP powders were investigated. The powders were pressed with different compaction pressures (40 to 500 MPa) and pre-sintered at temperature ranging from 900 to 1100°C. Vickers hardness, biaxial flexural strength, and linear shrinkage could be correlated to the relative density of pre-sintered samples. Using an empirical equation, pre-sintered blocks with a pre-defined density could be prepared. The blocks withstood the machining in a CAD-CAM system, and the machined and sintered crowns presented good adaptation.

scholarly journals Thermal effects on zirconia substrate after Er,Cr:YSGG irradiation

2013 ◽  
Vol 42 (6) ◽  
pp. 439-443 ◽  
Author(s):  
Alessandra Cassoni ◽  
Pérsio Vasconcelos Miranda ◽  
José Augusto Rodrigues ◽  
Silvia Coelho de Lacerda Heluy ◽  
Alberto Blay ◽  
...  
Keyword(s):  
Thermal Effects ◽  
Initial Temperature ◽  
Tetragonal Zirconia ◽  
Temperature Gradients ◽  
Water Cooling ◽  
Porto Alegre ◽  
Cad Cam ◽  
Post Hoc ◽  
One Way Anova ◽  
Tetragonal Zirconia Polycrystal

OBJECTIVE: The objective of the present study was to investigate the thermal effects of Er,Cr:YSGG laser irradiation (1.5W/20Hz) on yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP). MATERIAL AND METHOD: Fifteen disks of Y-TZP (AS Technology TitaniumFIX, São José dos Campos, Brazil) with 5 mm diameter and 3 mm high standardized with CAD-CAM were used. The Y-TZP disks were randomized in three groups (n=5): Y-TZP-G1 = control (no laser treatment); Y-TZP-G2 = Y-TZP + Er,Cr:YSGG laser (air-water cooling proportion 80%/25%); Y-TZP-G3 = Y-TZP + Er,Cr:YSGG laser (air-water cooling proportion 80%/0%). A thermopar (SmartMether, Novus, Porto Alegre, RS, Brazil) was attached to a digital thermometer (SmartMether, Novus, Porto Alegre, RS, Brazil) fixed to the opposite irradiated surface. The temperature gradients (ΔT) were calculated (ΔT = Final Temperature - Initial Temperature) for each group. Values were statistically analyzed by one-way ANOVA at the 95% confidence level and compared by Tukey post-hoc test (α=0.05) for each material. One sample of each group was analyzed by confocal white light microscopy. RESULT: The ANOVA test showed significant differences for the factor "laser" (p<.001). The temperature gradients (ΔT value) showed the following results: Y-TZP-G1 = 0 ºC; Y-TZP-G2 = -1.4 ºC and Y-TZP-G3 = 21.4 ºC. The ΔT values (ºC) of the non-refrigerated group were higher than the refrigerated group. The roughness value (Ra) ranged from 4.50 to -33.65 µm. CONCLUSION: The water refrigeration for Er,Cr:YSGG irradiation is essential to avoid thermal increase in the Y-TZP.

scholarly journals Surface Roughness and Necessity of Manual Refinishing Requirements of CAD/CAM-Manufactured Titanium and Cobalt-Chrome Bars – A Pilot Study

2019 ◽  
Vol 13 (1) ◽  
pp. 316-326 ◽  
Author(s):  
Peter Gehrke ◽  
Jochen Dinkel ◽  
Carsten Fischer ◽  
Kai Schmenger ◽  
Robert Sader
Keyword(s):  
Surface Roughness ◽  
Soft Tissue ◽  
Surface Quality ◽  
Computer Aided Design ◽  
Clinical Results ◽  
Limited Information ◽  
Post Processing ◽  
Computer Aided ◽  
Cad Cam

Background: Due to their increased precision, CAD/CAM generated bars (Computer-Aided Design/ Computer-Aided Manufacturing) are increasingly utilized in implant prosthodontics. For optimal clinical results, surface morphology should promote the integration of soft tissue while minimizing plaque and bacterial retention. Objective: Despite their clinical use, only limited information on the biological and clinical surface quality of CAD/CAM milled bars is available. The aim of the study was therefore to characterize the surface topography of bars of different manufacturers based on the profilometric analysis and the need for manual post-processing in the laboratory. Methods: A custom mandibular edentulous cast with four anterior implants was used as a reference cast and reproduced eight times. On each reproduction cast, corresponding scan flags were positioned and digitized. Acrylic 3D printed bar frameworks were produced and sent to the respective production center along with the digital files of the CAD bars for milling. In the course of profilometric analysis, all bars were examined in three critical Regions of Interest (ROI): Transmucosal, labial, basal. Sa and Ra values of each construction were determined. To evaluate the necessary refinishing time eight dental technicians macroscopically evaluated the bars by performing a subjective visual inspection. Kruskal-Wallis H-tests and Tukey and Kramer's post hoc tests were applied to detect differences between the samples. Results: After profilometric examination, three specimens (Dentsply Sirona: ZDC; Straumann: ZST; CAMLOG: ZCC) demonstrated surface roughness values in the biological acceptable range (Sa 0.2-0.4 μm) in the transmucosal region and provided optimal conditions for a reliable soft tissue adaptation. The Ra measurements revealed values beyond the acceptable threshold in the transmucosal region for three bars (Straumann: ZST; Dentsply Sirona: ZDC; Amann Girrbach: LAC). Four bars (LAC: Amann Girrbach; ZBC: BEGO; Datron: LDC & LDT; Zirkonzahn: ZZC) needed undesirable extensive manual rework. The evaluation of quality and time for manual post-processing by dental technicians confirmed the measurement-based ranking of the bars. Conclusion: It is desirable to define a clear roughness threshold for the clinical acceptance of transmucosal CAD/CAM generated surfaces. Clinical studies with profilometric data could help to further improve the surface quality of CAD/CAM milled bars and reduce the need for manual reworking time and effort.

Schwingungsüberlagertes Axialformen/Superimposed Oscillated Axial Forming

2020 ◽  
Vol 110 (11-12) ◽  
pp. 838-843
Author(s):  
Philipp Müller ◽  
Bernd-Arno Behrens ◽  
Sven Hübner ◽  
Hendrik Vogt ◽  
Daniel Rosenbusch ◽  
...  
Keyword(s):  
Surface Quality ◽  
Economic Importance ◽  
Combined Effect ◽  
Wird Eine ◽  
Forming Force ◽  
Forming Process ◽  
Forming Technology ◽  
Great Economic Importance ◽  
Gear Geometry

Techniken zur Steigerung der Formgebungsgrenzen in der Umformtechnik sind von hoher wirtschaftlicher Bedeutung. In dieser Arbeit wird eine Schwingungsüberlagerung im Krafthauptfluss eines Axialformprozesses zur Ausprägung einer Verzahnungsgeometrie untersucht. Die Auswirkungen der Schwingung auf die erzielbare Ausfüllung der Zahnkavitäten werden analysiert sowie die Parameter Schmierung und Oberflächengüte der Halbzeuge in ihrer kombinierten Wirkung untersucht. Es konnte eine Reduzierung der mittleren Umformkraft sowie eine Erhöhung der Formfüllung festgestellt werden. Techniques for extending the production limits in forming technology are of great economic importance. In this research, a superimposed oscillation in the main force flow of an axial forming process to form an axial gear geometry is investigated. The effects of the superimposed oscillation on the achievable form-filling of the tooth cavities are analyzed and the parameters lubrication and surface quality of the semi-finished products are investigated in their combined effect. A reduction of the averaged forming force as well as an increase of the form-filling could be achieved.

Behavior of 3mol% yttria-stabilized tetragonal zirconia polycrystal film prepared by slurry spin coating

2009 ◽  
Vol 186 (1) ◽  
pp. 128-132 ◽  
Author(s):  
Kongfa Chen ◽  
Yanting Tian ◽  
Zhe Lü ◽  
Na Ai ◽  
Xiqiang Huang ◽  
...  
Keyword(s):  
Spin Coating ◽  
Tetragonal Zirconia ◽  
Tetragonal Zirconia Polycrystal

scholarly journals Face Grinding Surface Quality of High Volume Fraction SiCp/Al Composite Materials

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Xu Zhao ◽  
Yadong Gong ◽  
Guiqiang Liang ◽  
Ming Cai ◽  
Bing Han
Keyword(s):  
Friction Coefficient ◽  
Surface Morphology ◽  
Surface Quality ◽  
Volume Fraction ◽  
High Volume ◽  
Spindle Speed ◽  
High Volume Fraction ◽  
Machining Parameters ◽  
Al Composite

AbstractThe existing research on SiCp/Al composite machining mainly focuses on the machining parameters or surface morphology. However, the surface quality of SiCp/Al composites with a high volume fraction has not been extensively studied. In this study, 32 SiCp/Al specimens with a high volume fraction were prepared and their machining parameters measured. The surface quality of the specimens was then tested and the effect of the grinding parameters on the surface quality was analyzed. The grinding quality of the composite specimens was comprehensively analyzed taking the grinding force, friction coefficient, and roughness parameters as the evaluation standards. The best grinding parameters were obtained by analyzing the surface morphology. The results show that, a higher spindle speed should be chosen to obtain a better surface quality. The final surface quality is related to the friction coefficient, surface roughness, and fragmentation degree as well as the quantity and distribution of the defects. Lower feeding amount, lower grinding depth and appropriately higher spindle speed should be chosen to obtain better surface quality. Lower feeding amount, higher grinding depth and spindle speed should be chosen to balance grind efficiently and surface quality. This study proposes a systematic evaluation method, which can be used to guide the machining of SiCp/Al composites with a high volume fraction.

Simulation and Productive Practice of 60 Tons Huge Rectangular Ingot by Wind Cooling

2011 ◽  
Vol 233-235 ◽  
pp. 2714-2717
Author(s):  
Xin Gang Ai ◽  
Sheng Li Li ◽  
Dong Wei Zhang ◽  
Nan Lv ◽  
Jun Tao
Keyword(s):  
Mathematical Simulation ◽  
Surface Quality ◽  
Solidification Time ◽  
Special Method ◽  
Cooling Process ◽  
Heavy Plate ◽  
Simulation Results

Huge rectangular ingots becomes crying needs in the condition of lots of heavy plate mills more than 5m have been in operation. In this paper, a special method of wind cooling outside mould has been presented and applied to produce 60t rectangular ingot. Mathematical simulation results tell us that by wind cooling, the solidification time of the 60t ingot can be shortened by 67 minutes, internal soundness can be ensured. The wind cooling process can obviously improve microstructure and preventing skull patch by increasing the thickness of solidified shell. A 60 tons huge rectangular ingot is successfully produced by wind cooling, the surface quality of is very well and the internal soundness should be improved further.

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