Distribuição de tensões e probabilidade de falha de coroas totais em zircônia tradicional, graduada e bioinspirada
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2018-06-08
Autores
Ramos, Gabriela Freitas
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Universidade Estadual Paulista (Unesp)
Resumo
O objetivo foi avaliar a probabilidade de falha de coroas de zircônia-porcelana com e sem infiltração de sílica (gradação) da zircônia, em disposição tradicional, graduada e bioinspirada, através da análise de Weibull e de elementos finitos pelo critério de Tensão Máxima Principal. Foram utilizados cem preparos anatômicos de primeiro molar superior (26) confeccionados em resina epóxi- Nema G10, que foram divididos em quatro grupos: Tradicional: infraestrutura em zircônia (Zircônia Convencional-Incoris ZI, Sirona, Brasil) e cobertura de porcelana (Cerâmica Feldspática-Cerec Blocs); Graduada: infraestrutura em zircônia infiltrada por sílica e cobertura de porcelana; Bioinspirada: infraestrutura em porcelana e cobertura com zircônia (Zircônia translúcida-Incoris TZI, Sirona, Brasil); e Bioinspirada Graduada: infraestrutura em porcelana e cobertura com zircônia infiltrada por sílica. A porção mais externa de todas as coroas foi revestida com uma camada glaze. A carga para fadiga deslizante foi de 100 N. Então os espécimes foram ciclados mecanicamente em um simulador de ciclos mastigatórios no qual uma ponta aplicadora fez 2.106 ciclos a uma frequência de 4 Hz. A cada 500.000 ciclos as coroas foram avaliadas quanto à presença de falhas (trincas, lascamentos ou descolamento entre porcelana e zircônia, fraturas catastróficas), em estereomicroscópio. Os tipos de falhas predominantes para as coroas Tradicional e Graduada foram delaminação e trincas, respectivamente. Os parâmetros de Weibull (beta e eta), com intervalo de confiança bilateral de 95% foram respectivamente: Tradicional - 1,29 e 0,23 E+07 ciclos; Graduada - 1,95 e 0,23 E+07 ciclos; Bioinspirada - 1,00 e 1,67 E+07 ciclos e Bioinspirada graduada - 1,00 1,67 E+07 ciclos. As coroas Tradicionais e Graduadas apresentaram maior susceptibilidade à falha por fadiga e as Bioinspiradas e Bioinspiradas graduadas não demonstraram susceptibilidade à fadiga. Ainda, através da Análise de elementos finitos, pôde-se verificar que as coroas bioinspiradas e bioinspiradas graduadas apresentaram a melhor distribuição de tensões tanto sobre a coroa quanto para a estrutura dentária. As diferentes configurações de restauração apresentaram diferentes probabilidades de falha após o ensaio de fadiga deslizante, sendo que as coroas Bioinspirada e Bioinspirada Graduada apresentam a menor probabilidade de falha e melhor distribuição de tensões, podendo ser consideradas restaurações mais duradouras em longo prazo.
The objective was to evaluate the failure probability of zirconia-porcelain crowns with and without silica infiltration (graded material) of the zirconia, using traditional, graded and bio-inspired design, through Weibull and finite element analysis by maximum principal stress. One hundred anatomical preparations of first upper molar were made of epoxy resin Nema G10 and divided into four groups: Traditional- zirconia (Conventional zirconia -Incoris ZI, Sirona, Brazil) and porcelain cover (Feldsphatic ceramic-Cerec Blocks); Graded- infrastructure in zirconia silica infiltrated and porcelain cover; Bioinspired- porcelain infrastructure and zirconia cover (Trasnlucent zirconia-Incoris TZI, Sirona, Brazil); and Graded Bioinspired- porcelain infrastructure and zirconia infiltrated by silica cover. The outermost portion of all crowns was coated with a glaze layer. The load for sliding fatigue was 100 N. Then the specimens were mechanically cycled in a masticatory cycle simulator for 2 x 106 cycles at 4 Hz of frequency. Every 500k cycles the crowns were evaluated in stereomicroscope for failures presence (cracks, chipping or detachment between porcelain and zirconia, or catastrophic fractures). The predominant failure types for the Traditional and Graded crowns were delamination and cracking, respectively. The Weibull parameters (beta and eta) with 95% bilateral confidence interval were respectively: Traditional - 1.29 and 0.23 E + 07 cycles; Graded - 1.95 and 0.23 E + 07 cycles; Bioinspired - 1,00 and 1,67 E + 07 cycles and Graded Bioinspired - 1,00 1,67 E + 07 cycles. The Traditional and Graded crowns presented greater susceptibility to failure due to fatigue and the Bioinspired and Graded Bioinspired crowns showed no susceptibility to fatigue. Also, through the finite elements analysis, it was verified that the Bioinspired and Graded Bioinspired crowns presented the best stress distribution on both crown and dental structure. The different restoration configurations presented different failure probabilities after the sliding fatigue test. Bioinspired and Graded Bioinspired crowns had the lowest failure probability and better stress distribution, which may be considered lasting restorations in the long term.
The objective was to evaluate the failure probability of zirconia-porcelain crowns with and without silica infiltration (graded material) of the zirconia, using traditional, graded and bio-inspired design, through Weibull and finite element analysis by maximum principal stress. One hundred anatomical preparations of first upper molar were made of epoxy resin Nema G10 and divided into four groups: Traditional- zirconia (Conventional zirconia -Incoris ZI, Sirona, Brazil) and porcelain cover (Feldsphatic ceramic-Cerec Blocks); Graded- infrastructure in zirconia silica infiltrated and porcelain cover; Bioinspired- porcelain infrastructure and zirconia cover (Trasnlucent zirconia-Incoris TZI, Sirona, Brazil); and Graded Bioinspired- porcelain infrastructure and zirconia infiltrated by silica cover. The outermost portion of all crowns was coated with a glaze layer. The load for sliding fatigue was 100 N. Then the specimens were mechanically cycled in a masticatory cycle simulator for 2 x 106 cycles at 4 Hz of frequency. Every 500k cycles the crowns were evaluated in stereomicroscope for failures presence (cracks, chipping or detachment between porcelain and zirconia, or catastrophic fractures). The predominant failure types for the Traditional and Graded crowns were delamination and cracking, respectively. The Weibull parameters (beta and eta) with 95% bilateral confidence interval were respectively: Traditional - 1.29 and 0.23 E + 07 cycles; Graded - 1.95 and 0.23 E + 07 cycles; Bioinspired - 1,00 and 1,67 E + 07 cycles and Graded Bioinspired - 1,00 1,67 E + 07 cycles. The Traditional and Graded crowns presented greater susceptibility to failure due to fatigue and the Bioinspired and Graded Bioinspired crowns showed no susceptibility to fatigue. Also, through the finite elements analysis, it was verified that the Bioinspired and Graded Bioinspired crowns presented the best stress distribution on both crown and dental structure. The different restoration configurations presented different failure probabilities after the sliding fatigue test. Bioinspired and Graded Bioinspired crowns had the lowest failure probability and better stress distribution, which may be considered lasting restorations in the long term.
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Palavras-chave
cerâmica, bioinspiração, Gradação, Ceramics, Bioinspiration, Graded materials