Efeito da caracterização extrínseca na microestrutura e na probabilidade de sobrevivência à fadiga de uma zircônia de alta translucidez
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Data
2021-08-06
Autores
Barreto, Larissa Araujo Lopes [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Este estudo avaliou a rugosidade superficial e a resistência à fadiga (probabilidade de sobrevivência) de zircônia polidas e caracterizadas com pigmentação extrínseca e/ou glaze. Blocos de zircônia de alta translucidez (YZ®HT, Vita Zanhfabrik, Bad Säckingen, Alemanha) foram usinados em forma de cilindro e fatiados em uma máquina de corte de precisão, com refrigeração constante em água. Os discos foram polidos com lixas de carbeto de silício de granulação crescente (#400, #600, #800, #1200) em máquina politriz semi-automática, e foi realizada limpeza em banho ultrassônico com álcool isopropílico durante 5 minutos. Desta forma, foram obtidos 60 discos com 12 mm de diâmetro e 1,2 mm de espessura, distribuídos aleatoriamente entre os Grupos: P-somente polimento, CG-caracterização e glaze, e G-somente glaze. Os tratamentos foram realizados após a sinterização, de acordo com as recomendações do fabricante. Foram realizadas leituras através de um rugosímetro de contato (Surftest SJ 400, Mitutoyo, Tóquio, Japão) para avaliar a rugosidade média da superfície. Os discos foram submetidos ao teste de flexão biaxial em uma máquina de testes universal, como velocidade constante (0,5 mm/min) até a falha (n=3), para determinar a carga média de fratura, a fim de estabelecer o perfil de carga do teste de fadiga. O perfil de carga usado iniciou em 120 N com acréscimo de 5% da carga inicial a cada step, em intervalos de 20.000 ciclos na frequência de 4Hz. O modo de fratura foi avaliado com o auxílio do estereomicroscópio. Os valores de rugosidade inicial foram analisados com teste ANOVA 1-fator e Teste de Tukey (95%), que mostraram que os três grupos possuem rugosidades médias estatisticamente diferentes, sendo o grupo CG o grupo com maiores valores. A análise de probabilidade de sobrevivência foi realizada com Kaplan-Meier e Mantel-Cox (Log-rank, 95%), indicando que o grupo G apresentou uma maior resistência à fadiga e um número maior de ciclos necessários para a fratura, sendo diferente estatisticamente dos outros grupos. Assim, é possível concluir que caracterização superficial altera o comportamento mecânico da zircônia de alta translucidez. A zircônia de alta translucidez somente polida possui menor resistência à fadiga do que o tratamento superficial com glaze, que promove maior probabilidade de sobrevivência a longo prazo.
This study evaluated the surface roughness and fatigue strength (probability of survival) of polished zirconia and characterized with extrinsic pigmentation and/or glaze. High translucency zirconia blocks (YZ® HT, Vita Zanhfabrik, Bad Säckingen, Germany) were machined in cylinder shape and sliced in a precision cutting machine, with constant water cooling. The discs were polished with silicon carbide sandpaper with decreasing grains (#400, #600, #800, #1200) in a semi-automatic polishing machine, and cleaning was carried out in an ultrasonic bath with isopropyl alcohol for 5 minutes. Thus, 60 discs with 12 mm in diameter and 1.2 mm in thickness were obtained, randomly distributed among the Groups: P-polishing only, CG-characterization and glaze, and G-glaze only. The treatments were performed after sintering, according to the manufacturer's recommendations. Readings were taken using a contact roughness meter (Surftest SJ 400, Mitutoyo, Tokyo, Japan) to assess the average surface roughness. The discs were submitted to the biaxial flexion test in a universal testing machine, at constant speed (0.5 mm/min) until failure (n=3), to determine the mean fracture load, in order to establish the loading profile for fatigue test. The load profile used started at 120 N with an addition of 5% of the initial load at each step, at intervals of 20,000 cycles at the frequency of 4Hz. The fracture mode was evaluated with the aid of a stereomicroscope. The initial roughness values were analyzed using the one-way ANOVA test and Tukey test (95%), which showed that the three groups have statistically different mean roughnesses, with the CG group being the group with the highest values. The survival probability analysis was performed with Kaplan-Meier and Mantel-Cox (Log-rank, 95%), indicating that group G presented greater fatigue resistance and a greater number of cycles were required for the fracture, being statistically different of the other groups. Thus, it is possible to conclude that surface characterization alters the mechanical behavior of high translucency zirconia. High translucency zirconia only polished has lower fatigue resistance than surface treated with glaze, which promotes a greater long-term probability of survival.
This study evaluated the surface roughness and fatigue strength (probability of survival) of polished zirconia and characterized with extrinsic pigmentation and/or glaze. High translucency zirconia blocks (YZ® HT, Vita Zanhfabrik, Bad Säckingen, Germany) were machined in cylinder shape and sliced in a precision cutting machine, with constant water cooling. The discs were polished with silicon carbide sandpaper with decreasing grains (#400, #600, #800, #1200) in a semi-automatic polishing machine, and cleaning was carried out in an ultrasonic bath with isopropyl alcohol for 5 minutes. Thus, 60 discs with 12 mm in diameter and 1.2 mm in thickness were obtained, randomly distributed among the Groups: P-polishing only, CG-characterization and glaze, and G-glaze only. The treatments were performed after sintering, according to the manufacturer's recommendations. Readings were taken using a contact roughness meter (Surftest SJ 400, Mitutoyo, Tokyo, Japan) to assess the average surface roughness. The discs were submitted to the biaxial flexion test in a universal testing machine, at constant speed (0.5 mm/min) until failure (n=3), to determine the mean fracture load, in order to establish the loading profile for fatigue test. The load profile used started at 120 N with an addition of 5% of the initial load at each step, at intervals of 20,000 cycles at the frequency of 4Hz. The fracture mode was evaluated with the aid of a stereomicroscope. The initial roughness values were analyzed using the one-way ANOVA test and Tukey test (95%), which showed that the three groups have statistically different mean roughnesses, with the CG group being the group with the highest values. The survival probability analysis was performed with Kaplan-Meier and Mantel-Cox (Log-rank, 95%), indicating that group G presented greater fatigue resistance and a greater number of cycles were required for the fracture, being statistically different of the other groups. Thus, it is possible to conclude that surface characterization alters the mechanical behavior of high translucency zirconia. High translucency zirconia only polished has lower fatigue resistance than surface treated with glaze, which promotes a greater long-term probability of survival.
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Palavras-chave
Cerâmicas, Materiais dentários, CAD-CAM, Fadiga, Ceramics, Dental materials, CAD-CAM, Fatigue