Fretting fatigue wear behavior of Y-TZP dental ceramics processed by non-conventional microwave sintering

This is the peer reviewed version of the following article: PRESENDA-BARRERA, ALVARO, Salvador Moya, Mª Dolores, Vleugels, Jozef , Moreno, Rodrigo, Borrell Tomás, María Amparo. (2017). Fretting fatigue wear behavior of Y-TZP dental ceramics processed by non-conventional microwave sintering.Journal of the American Ceramic Society, 100, 5, 1842-1852. DOI: 10.1111/jace.14769, which has been published in final form at http://doi.org/10.1111/jace.14769. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving[EN] The fretting wear behavior of self-mated Y-TZP dental materials obtained by non-conventional microwave and conventional sintering has been investigated. Two 3Y-TZP materials, a widely utilized commercial dental ceramic (LAVA) and a lab-prepared 3Y-TZP powder based equivalent have been assessed. Relative density and mechanical properties as well as the grain size variations upon sintering have been evaluated. After exposure to selected gross slip regime fretting wear conditions, the wear tracks have been characterized allowing the measurement of the coefficient of friction, track profiles, and pit features. The results indicate thaT microwave sintering results in a similar fretting wear behavior as observed for conventional sintered 3YTZP, since the measured volumetric wear loss is of a comparable order of magnitude. Regarding the influence of the grain size, the analysis revealed that a large grain size (>300 nm) results in an increased wear volume and that a higher resistance to fretting wear is constrained to a midrange particle size. Since the fracture toughness of all investigated ceramic grades was comparable, the influence of the fracture toughness could not be assessed. Abrasive grooving, delamination and microcracking have been identified as major wear mechanisms inside the wear tracks for both conventional and microwave sintered 3Y-TZP. In general, microwave sintering can provide 3Y-TZP dental materials with a comparable fretting wear resistance as that observed for conventional sintering using lower dwell sintering temperatures and a shorter processing time.Spanish Ministry of Economy and Competitiveness MINECO, Grant/Award Number: MAT2015-67586-C3-R; Generalitat Valenciana, Grant/Award Number: GRI-SOLIA/2013/035, GV/2014/009; MINECO, Grant/Award Number: IJCI-2014-19839.Presenda-Barrera, A.; Salvador Moya, MD.; Vleugels, J.; Moreno, R.; Borrell Tomás, MA. (2017). Fretting fatigue wear behavior of Y-TZP dental ceramics processed by non-conventional microwave sintering. Journal of the American Ceramic Society. 100(5):1842-1852. https://doi.org/10.1111/jace.14769S18421852100

Effect of microwave sintering on microstructure and mechanical properties in Y-TZP materials used for dental applications

The aim of this work is to study the application of microwave sintering to consolidate yttria-stabilized zirconia polycrystalline (Y-TZP) ceramics commonly applied in dentistry, so as to obtain highly dense materials and fine microstructure with shorter sintering cycles. Three Y-TZP materials are considered: two commercially available for dental applications and one laboratory studied powder. Microwave sintering was carried out at 1200 and 1300 degrees C for 10 min and conventional sintering at 1300 and 1400 degrees C for 2 h. Relative density, Vickers hardness and fracture toughness values for sintered samples were determined. Microwave sintering results, generally, in improved mechanical properties of the materials in terms of hardness and fracture toughness compared to conventional sintering and, in some cases, at lower sintering temperatures. A finer grain microstructure (final grain size < 250 min) was obtained with microwave sintering for both commercial materials. Fracture toughness values differ significantly between sintering techniques and chosen parameters. These results suggest that microwave heating can be employed to sinter Y-TZP commercial ceramics for dental applications obtaining improving the mechanical properties of the materials with a very important time and energy consumption reduction. Crown Copyright (C) 2015 Published by Elsevier Ltd and Techna Group S.r.l. All rights reserved.The authors would like to thank the financial support received from Universidad Politecnica de Valencia under Project 5P20120677 and Ministerio de Economia y Competitividad (MINECO) and co-funded by ERDF (European Regional Development Funds) through the Project (IEC2012-37532-C02-01). A. Borrell acknowledges the Spanish Ministry of Science and Innovation for her Juan de la Cierva Contract (JCI-2011-10498) and the Generalitat Valenciana for the financial support under Project GV/2014/009. A. Presenda acknowledges the Generalitat Valenciana for his Santiago Grisolia program scholarship (GRISOLLV2013/035). The authors would also like to acknowledge Prof. Dr. M. F. Sold from the Faculty of Medicine and Odontology at the Universidad de Valencia for supplying the commercial materials.Presenda, Á.; Salvador Moya, MD.; Penaranda-Foix, FL.; Moreno, R.; Borrell Tomás, MA. (2015). Effect of microwave sintering on microstructure and mechanical properties in Y-TZP materials used for dental applications. Ceramics International. 41(5, Part B):7125-7132. https://doi.org/10.1016/j.ceramint.2015.02.025S71257132415, Part

Influence of cement thickness on resin-zirconia microtensile bond strength

PURPOSE: The aim of this study was to evaluate the influence of resin cement thickness on the microtensile bond strength between zirconium-oxide ceramic and resin cement. MATERIALS AND METHODS: Thirty-two freshly extracted molars were transversely sectioned at the deep dentin level and bonded to air-abraded zirconium oxide ceramic disks. The specimens were divided into 8 groups based on the experimental conditions (cement type: Rely X UniCem or Panavia F 2.0, cement thickness: 40 or 160 µm, storage: thermocycled or not). They were cut into microbeams and stored in 37℃ distilled water for 24 h. Microbeams of non-thermocycled specimens were submitted to a microtensile test, whereas those of thermocycled groups were thermally cycled for 18,000 times immediately before the microtensile test. Three-way ANOVA and Sheffe's post hoc tests were used for statistical analysis (α=95%). RESULTS: All failures occurred at the resin-zirconia interface. Thermocycled groups showed lower microtensile bond strength than non-thermocycled groups (P.05). The number of adhesive failures increased after thermocycling in all experimental conditions. No cohesive failure was observed in any experimental group. CONCLUSION: When resin cements of adhesive monomers are applied over air-abraded zirconia restorations, the degree of fit does not influence the resin-zirconia microtensile bond strength.ope

Masking Ability of Zirconia with and without Veneering Porcelain

Purpose : The present study compared changes in CIE L*a*b* color coordinates of substrates of different colors when covered with zirconium oxide discs (Procera) and with such discs if veneered with two shades of porcelain. Material and Methods : Forty background substrates were fabricated and divided into four groups depending on the color of the substrates: white, black, gray, and tooth‐colored (Vita shade A3). The initial color of the substrates was measured using a colorimeter. The color of the substrates covered with plain zirconium oxide discs and with zirconium oxide discs veneered with porcelains of two shades (Vita shade A1 and B4) was measured. The color difference between the substrates, the substrates covered with plain discs, and the substrates covered with veneered discs was calculated, and the data were statistically analyzed with one‐way ANOVA and multiple paired t ‐test. Results : For each group of substrates, the resulting colors were significantly different when the substrates were covered by either plain zirconium oxide discs or zirconium oxide discs veneered with Vita shade A1 or B4 porcelain. Conclusion : While zirconium oxide coping material alone has a degree of masking ability, the resulting color of a restoration can be further modified with the veneering porcelain.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/96301/1/j.1532-849X.2012.00915.x.pd