José Eduardo Vasconcellos Amarante1, Marcos Venícius Soares Pereira2, Grace Mendonça De Souza3, Manuel Fellipe R Pais Alves4, Bruno Galvão Simba5, Claudinei Dos Santos6. 1. Fluminense Federal University, Faculty of Dentistry, Institute of Health of Nova Friburgo, Dr. Silvio Henrique Braune St, 22 - Downtown, Nova Friburgo, RJ, 28625-650, Brazil; Pontical Catholic University of Rio de Janeiro, Department of Chemical and Materials Engineering, PUC-Rio, Marques de São Vicente St 225, Gávea, Rio de Janeiro, RJ, 22453-901, Brazil. Electronic address: jeduardo@id.uff.br. 2. Pontical Catholic University of Rio de Janeiro, Department of Chemical and Materials Engineering, PUC-Rio, Marques de São Vicente St 225, Gávea, Rio de Janeiro, RJ, 22453-901, Brazil. Electronic address: marcospe@puc-rio.br. 3. University of Toronto, Faculty of Dentistry, 124 Edward St #539, Toronto, ON, M5G1G6, Canada. Electronic address: Grace.DeSouza@dentistry.utoronto.ca. 4. State University of Rio de Janeiro, Faculty of Technology, Presidente Dutra Highway, Km 298, Resende, RJ, 27537-000, Brazil. Electronic address: manuelalves@usp.br. 5. São Paulo State University, Faculty of Engineering of Guaratinguetá UNESP/FEG, Ariberto Pereira da Cunha Ave, 333 - Portal Das Colinas, Guaratinguetá, SP, 12516-410, Brazil. Electronic address: brgalvao@yahoo.com.br. 6. State University of Rio de Janeiro, Faculty of Technology, Presidente Dutra Highway, Km 298, Resende, RJ, 27537-000, Brazil. Electronic address: claudineisvr@gmail.com.
Abstract
OBJECTIVES: The aim of this study was to evaluate the effect of hydrothermal aging on the mechanical properties and translucency of dental zirconia with different levels of translucency. METHODS: Three different types of dental yttria-stabilized zirconia were used: 3Y-TZP (ZrO2 - 3 mol.% Y2O3) of medium opacity (designated Z3OP), 3Y-TZP of medium translucency (Z3MT), and 5Y-PSZ (ZrO2 - 5 mol.% Y2O3) of high translucency (Z5HT). A total of 120 specimens were sintered (n = 40 specimens/group). The control group (sintered→polished→heat-treated) and the aged group (sintered→polished→heat-treated→hydrothermally degraded at 134 °C, 2 bar, 5h) were characterized by relative density, quantitative phase analysis by X-ray diffraction using the Rietveld method, microstructural analysis by scanning electron microscopy, surface roughness and translucency. All groups were submitted to a biaxial flexural strength test. Data analysis using Kruskal-Wallis, Nemenyi (p-value = 0.05), and Weibull statistics were used. RESULTS: All sintered specimens presented full densification. After aging, an increase of the m-ZrO2 phase content was observed for the Z3OP group. On the other hand, Z3MT and Z5HT did not show any m-ZrO2 phase, indicating resistance to the hydrothermal degradation. Smaller grains were observed in the Z3MT group in relation to Z3OP group and the Z5HT group presented a bimodal grain distribution, where the largest grains were associated to cubic ZrO2. Z3OP exhibited a slight increase in roughness as a function of degradation, while the roughness remained statistically stable in the other groups. Translucency was little influenced by degradation, but considerably affected by increasing thickness. The Z5HT samples were the group with the highest translucency among the control groups. Z3OP exhibited the highest flexural strength, while being the most susceptible to hydrothermal degradation. The lowest values were presented by Z5HT in all groups, due to the high concentration of c-ZrO2 grains. CONCLUSION: Hydrothermal aging is less critical to the flexural strength of zirconia-based materials than the materials' composition and microstructure. Z5HT zirconia showed the highest translucency, however the measured difference is not visually perceptible. Z5HT was considered the most resistant to hydrothermal degradation.
OBJECTIVES: The aim of this study was to evaluate the effect of hydrothermal aging on the mechanical properties and translucency of dental zirconia with different levels of translucency. METHODS: Three different types of dental yttria-stabilized zirconia were used: 3Y-TZP (ZrO2 - 3 mol.% Y2O3) of medium opacity (designated Z3OP), 3Y-TZP of medium translucency (Z3MT), and 5Y-PSZ (ZrO2 - 5 mol.% Y2O3) of high translucency (Z5HT). A total of 120 specimens were sintered (n = 40 specimens/group). The control group (sintered→polished→heat-treated) and the aged group (sintered→polished→heat-treated→hydrothermally degraded at 134 °C, 2 bar, 5h) were characterized by relative density, quantitative phase analysis by X-ray diffraction using the Rietveld method, microstructural analysis by scanning electron microscopy, surface roughness and translucency. All groups were submitted to a biaxial flexural strength test. Data analysis using Kruskal-Wallis, Nemenyi (p-value = 0.05), and Weibull statistics were used. RESULTS: All sintered specimens presented full densification. After aging, an increase of the m-ZrO2 phase content was observed for the Z3OP group. On the other hand, Z3MT and Z5HT did not show any m-ZrO2 phase, indicating resistance to the hydrothermal degradation. Smaller grains were observed in the Z3MT group in relation to Z3OP group and the Z5HT group presented a bimodal grain distribution, where the largest grains were associated to cubic ZrO2. Z3OP exhibited a slight increase in roughness as a function of degradation, while the roughness remained statistically stable in the other groups. Translucency was little influenced by degradation, but considerably affected by increasing thickness. The Z5HT samples were the group with the highest translucency among the control groups. Z3OP exhibited the highest flexural strength, while being the most susceptible to hydrothermal degradation. The lowest values were presented by Z5HT in all groups, due to the high concentration of c-ZrO2 grains. CONCLUSION: Hydrothermal aging is less critical to the flexural strength of zirconia-based materials than the materials' composition and microstructure. Z5HT zirconia showed the highest translucency, however the measured difference is not visually perceptible. Z5HT was considered the most resistant to hydrothermal degradation.
Authors: Ana Lúcia Nascimento Oliveira; Carlos Nelson Elias; Heraldo Elias Salomão Dos Santos; Claudinei Dos Santos; Ronaldo Sergio de Biasi Journal: Int J Biomater Date: 2022-05-21