Efeito do envelhecimento hidrotérmico e mecânico na performance à fadiga de zircônias de alta translucidez
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Data
2021-07-07
Autores
Prado, Pedro Henrique Condé Oliveira
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O objetivo deste trabalho foi avaliar a resistência à fadiga e ciclos até a falha de 3 zircônias odontológicas após envelhecimento hidrotérmico isolado e um novo protocolo alternado. Discos de zircônia “Y”Z T (VITA), INCORIS “T”ZI (Dentsply Sirona) e “K”ATANA UTML (Noritake Kuraray) (N=135) – 1ª, 2ª e 3ª gerações, respectivamente –, foram divididos em 9 grupos (n=15), com 3 tratamentos para cada zircônia: CF – Controle, somente com fadiga mecânica; EF – Envelhecido em reator hidrotérmico a 134 ºC por 20 h + Fadiga; EFA: 4 passos de envelhecimentos de 5h alternados com fadiga. O teste de fadiga em flexão biaxial foi realizado com configuração de pistão sob 3 esferas, utilizando o método step-stress (carga inicial: 100 Mpa, step: 50 MPa/10.000 ciclos, frequência: 20 Hz). Os dados foram analisados através de teste Kaplan-Meir e Mantel-Cox com α=0,05, além da análise de Weibull. Discos fraturados foram analisados em estereomicroscópio, Microscopia Eletrônica de Varredura (MEV) e Difratômetro de Raios-X (DRX). O envelhecimento isolado com fadiga aumentou a resistência do grupo TEF (810 ± 76 MPa), enquanto diminuiu a do YEF (516 ± 38 MPa), o protocolo alternado aumentou a resistência apenas para a YZ T (730 ± 59 MPa). A KATANA UMTL não apresentou diferenças para ambos os tratamentos. Igualmente, foi a única a não sofrer transformação de fase T-M. O grupo TEF apresentou maior taxa sobrevivência à fadiga (147,000.00 ciclos). A origem de fratura para todos os espécimes deu-se no lado de tração em defeitos pré-existentes. Zircônias de 2ª geração possuem melhor comportamento mecânico e longevidade pós-envelhecimento e fadiga. Embora seja menos resistente, a KATANA UTML não sofreu degradação.
This study aimed to evaluate the fatigue strength and cycles for failure of 3 dental zirconias after isolated and a novel hydrothermal and mechanical fatigue cycling aging protocol. “Y”Z T (VITA), INCORIS “T”ZI (Dentsply Sirona) and “K”ATANA UTML (Noritake Kuraray) zirconia discs (N=135), were divided into 9 groups (n=15), according to 3 proposed treatments for each zirconia: CF (control – only mechanical fatigue cycling); AF (aging in hydrothermal reactor at 134°C for 20 h + mechanical fatigue cycling ); AFA (Alternating protocol: 4 steps of 5 h of hydrothermal aging intercalated with mechanical fatigue cycling). Mechanical fatigue aging was performed according to the step stress approach through biaxial flexural setup (piston-on-3-balls, initial strength: 100 MPa, step: 50 MPa/ci000, frequency: 20 Hz) until failure. Data were analyzed using KaplanMeier and Mantel-Cox test (α=0.05), in addition to Weibull analysis. Fractured discs were analyzed in stereomicroscope, Scanning Electron Microscopy and XRay Diffraction. Continuous hydrothermal and mechanical fatigue cycling decreased the fatigue strength of YAF group (516 ± 38 MPa), while the alternating protocol increased it (730 ± 59 MPa). KATANA UTML showed no differences for both treatments and did not undergo T-M phase transformation. The TAF group showed the highest fatigue strength (810 ± 76 MPa) and cycles for failure (147,000.00 cycles). The fracture origin for all specimens was on the tensile side in pre-existing defects. INCORIS TZI zirconia have higher fatigue strength after hydrothermal and mechanical fatigue aging. Although less resistant, KATANA UTML did not suffer chemical degradation.
This study aimed to evaluate the fatigue strength and cycles for failure of 3 dental zirconias after isolated and a novel hydrothermal and mechanical fatigue cycling aging protocol. “Y”Z T (VITA), INCORIS “T”ZI (Dentsply Sirona) and “K”ATANA UTML (Noritake Kuraray) zirconia discs (N=135), were divided into 9 groups (n=15), according to 3 proposed treatments for each zirconia: CF (control – only mechanical fatigue cycling); AF (aging in hydrothermal reactor at 134°C for 20 h + mechanical fatigue cycling ); AFA (Alternating protocol: 4 steps of 5 h of hydrothermal aging intercalated with mechanical fatigue cycling). Mechanical fatigue aging was performed according to the step stress approach through biaxial flexural setup (piston-on-3-balls, initial strength: 100 MPa, step: 50 MPa/ci000, frequency: 20 Hz) until failure. Data were analyzed using KaplanMeier and Mantel-Cox test (α=0.05), in addition to Weibull analysis. Fractured discs were analyzed in stereomicroscope, Scanning Electron Microscopy and XRay Diffraction. Continuous hydrothermal and mechanical fatigue cycling decreased the fatigue strength of YAF group (516 ± 38 MPa), while the alternating protocol increased it (730 ± 59 MPa). KATANA UTML showed no differences for both treatments and did not undergo T-M phase transformation. The TAF group showed the highest fatigue strength (810 ± 76 MPa) and cycles for failure (147,000.00 cycles). The fracture origin for all specimens was on the tensile side in pre-existing defects. INCORIS TZI zirconia have higher fatigue strength after hydrothermal and mechanical fatigue aging. Although less resistant, KATANA UTML did not suffer chemical degradation.
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Palavras-chave
Degradação, Cerâmicas odontológicas, Zircônia, Y-TZP, Fadiga, Degradation, Dental ceramics, Zirconia, Y-TZP, Fatigue