Masanao Inokoshi1, Fei Zhang2, Jan De Munck1, Shunsuke Minakuchi3, Ignace Naert1, Jozef Vleugels2, Bart Van Meerbeek1, Kim Vanmeensel4. 1. KU Leuven BIOMAT, Department of Oral Health Sciences, KU Leuven (University of Leuven) & Dentistry, University Hospitals Leuven, Kapucijnenvoer 7, blok a bus 7001, B-3000 Leuven, Belgium. 2. Department of Metallurgy and Materials Engineering (MTM), KU Leuven (University of Leuven), Kasteelpark Arenberg 44, B-3001 Heverlee (Leuven), Belgium. 3. Gerodontology and Oral Rehabilitation, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo, Tokyo 113-8549, Japan. 4. Department of Metallurgy and Materials Engineering (MTM), KU Leuven (University of Leuven), Kasteelpark Arenberg 44, B-3001 Heverlee (Leuven), Belgium. Electronic address: kim.vanmeensel@mtm.kuleuven.be.
Abstract
UNLABELLED: The effect of sintering conditions and concomitant microstructure of dental zirconia (ZrO2) ceramics on their low-temperature degradation (LTD) behavior remains unclear. OBJECTIVES: Therefore, their effect on LTD of dental ZrO2 ceramics was investigated. METHODS: Three commercial pre-sintered yttria-stabilized dental zirconia materials were sintered at three temperatures (1450°C, 1550°C and 1650°C) applying three dwell times (1, 2 and 4h). Grain size measurements and LTD tests were performed on polished sample surfaces. LTD tests were performed at 134°C in an autoclave. The amount of monoclinic ZrO2 on the exposed surface was measured by X-ray diffraction (XRD). RESULTS: Higher sintering temperatures and elongated dwell times increased the ZrO2 grain size. Simultaneously, a larger fraction of zirconia grains adopted a cubic crystal structure, resulting in a decreased yttria content in the remaining tetragonal grains. Both the larger grain sizes and the lower average stabilizer content made the tetragonal grains more susceptible to LTD. Overall, independent on the commercial dental zirconia grade tested, the specimens sintered at 1450°C for 1h combined good mechanical properties with the best resistance to LTD. SIGNIFICANCE: In general, increased sintering temperatures and times result in a higher sensitivity to low-temperature degradation of Y-TZP ceramics.
UNLABELLED: The effect of sintering conditions and concomitant microstructure of dental zirconia (ZrO2) ceramics on their low-temperature degradation (LTD) behavior remains unclear. OBJECTIVES: Therefore, their effect on LTD of dental ZrO2 ceramics was investigated. METHODS: Three commercial pre-sintered yttria-stabilized dental zirconia materials were sintered at three temperatures (1450°C, 1550°C and 1650°C) applying three dwell times (1, 2 and 4h). Grain size measurements and LTD tests were performed on polished sample surfaces. LTD tests were performed at 134°C in an autoclave. The amount of monoclinic ZrO2 on the exposed surface was measured by X-ray diffraction (XRD). RESULTS: Higher sintering temperatures and elongated dwell times increased the ZrO2 grain size. Simultaneously, a larger fraction of zirconia grains adopted a cubic crystal structure, resulting in a decreased yttria content in the remaining tetragonal grains. Both the larger grain sizes and the lower average stabilizer content made the tetragonal grains more susceptible to LTD. Overall, independent on the commercial dental zirconia grade tested, the specimens sintered at 1450°C for 1h combined good mechanical properties with the best resistance to LTD. SIGNIFICANCE: In general, increased sintering temperatures and times result in a higher sensitivity to low-temperature degradation of Y-TZP ceramics.
Authors: Taciana Emília Leite Vila-Nova; Isabelle Helena Gurgel de Carvalho; Dayanne Monielle Duarte Moura; André Ulisses Dantas Batista; Yu Zhang; Carlos Alberto Paskocimas; Marco Antonio Bottino; Rodrigo Othávio de Assunção E Souza Journal: Dent Mater Date: 2020-01-31 Impact factor: 5.304
Authors: Marina R Kaizer; Petra C Gierthmuehlen; Mateus Bf Dos Santos; Sergio S Cava; Yu Zhang Journal: Ceram Int Date: 2017-05-19 Impact factor: 4.527