Comportamento sob fadiga de restaurações cerâmicas ultrafinas cimentadas adesivamente em preparos correspondentes aos dentes posteriores
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Data
2017-12-01
Autores
Abu-Izze, Fernanda de Oliveira
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Universidade Estadual Paulista (Unesp)
Resumo
A fim de investigar a vida em fadiga, modos de falha e distribuição de tensões de restaurações ultrafinas parciais, tipo tabletop, em diferentes cerâmicas, sessenta preparos padronizados foram confeccionados em resina epóxi G10 e foram cimentadas adesivamente restaurações cerâmicas de silicato de lítio reforçado com zircônia (ZLS, Vita Suprinity- Vita Zahnfabrik), ou restaurações de cerâmica híbrida (PIC, Vita Enamic- Vita Zahnfabrik), em 0,5 ou 1 mm de espessura. O mesmo protocolo de ciclagem foi aplicado para todos os espécimes, que consistiu em 5.000 ciclos a 200 N, seguidos de 450 N ciclos até a fratura dos espécimes ou a suspensão do teste após 1,5 x 106 ciclos. A carga axial foi realizada com uma freqüência de 4 Hz no equipamento Biocycle V2 (Biopdi, São Carlos, SP), com amostras imersas em água. A presença de falhas e/ou fraturas foi verificada a cada 2,5 x 105 ciclos e a análise de sobrevivência foi realizada com o número de ciclos em que cada espécime falhou. Os espécimes foram avaliados usando estereomicroscópio e microscopia eletrônica de varredura (MEV). Após a tabulação de dados, foram realizados Kaplan-Meier e Mantel-Cox (Teste Log Rank), seguindo de comparação múltipla aos pares, todos com nível de significância de 5% e análise de Weibull. Através da análise tridimensional de elementos finitos, a distribuição de tensões máximas principais (TMP) nas tabletop oclusais posteriores foram avaliados comparando diferentes tipos de substrato (G10, esmalte/dentina, esmalte), espessuras e materiais cerâmicos. As restaurações de silicato de lítio reforçadas com zircônia com 0,5 mm de espessura (ZLS.5) apresentaram menor resistência à fadiga em comparação com restaurações cerâmicas híbridas de 1,0mm (PIC1), e ambas foram similares a outras restaurações (PIC.5 e ZLS1); X2 = 11,2; df = 3; p = 0,0107 <0,05). Os grupos ZLS apresentaram defeitos aleatórios que culminaram com a fratura, ao passo que os grupos PIC apresentaram defeitos que aumentaram com a fadiga mecânica após algum tempo sob ciclagem. As imagens do estereomicroscópio mostram falhas radiais observadas devido à translucidez do material, não houve danos causados pelo aplicador de carga. A distribuição de TMP foi semelhante para os diferentes tipos de substrato, mas o maior módulo de elasticidade mostrou uma concentração de tensão ligeiramente menor. É favorável o uso de PIC em espessura delgada, com resistência à fadiga semelhante à restaurações de ZLS mais espessas.
To investigate the fatigue life, failure modes and stress distribution of partial ultrafine restorations for posterior teeth in different ceramics, sixty standard tabletop preparations in epoxy resin G10 received lithium silicate based zirconia reinforced (ZLS, Vita Suprinity- Vita Zahnfabrik), or hybrid ceramic (PIC, Vita Enamic- Vita Zahnfabrik), restorations in .5 or 1 mm thickness bonded using resin cement. The same cycling protocol was applied for all specimens that consisted of 5.000 cycles at 200 N followed by 450 N cycles until the specimens’ fracture or the suspension of the test after 1.5 x 106 cycles. Axial load was carried out with a 4 Hz frequency in Biocycle V2 equipment (Biopdi, São Carlos, SP), with samples immersed in water. Presence of cracks and/or fractures was checked with every 2,5 x 105 cycles and the survival analysis was performed using the number of cycles in which each specimen failed. All specimens were evaluated using stereomicroscope and scanning electron microscopy (SEM). After data tabulation, Kaplan-Meier and Mantel-Cox (Log Rank test) analysis were performed, followed by multiple pairwise comparison, all with a significance level of 5%, and Weibull analysis. Through tridimensional finite element analysis, stresses distribution and maximum principal stresses in the posterior occlusal veneers were evaluated comparing different types of substrate (G10, enamel/dentin, enamel), thicknesses and ceramic materials. Zirconium-reinforced lithium silicate restorations with 0.5 mm thickness (ZLS.5) showed lower fatigue strength compared to 1.0 mm hybrid ceramic restorations (PIC1), and both were similar to other restorations (PIC.5 and ZLS1) (Log-Rank test, X2 = 11.2; df = 3; p = 0.0107<0.05). ZLS groups presented random defects that culminated with the fracture, whereas PIC groups presented defects that increased with the mechanical fatigue after some time under cycling. Stereomicroscope images show radial cracks observed due to the translucency of the material, there was no damage caused by applicator. TMP distribution was similar for the different substrate types, but the highest modulus of elasticity showed slightly lower stress concentration. PIC is favorable to be used in thin thickness with similar fatigue strength to thicker ZLS restorations.
To investigate the fatigue life, failure modes and stress distribution of partial ultrafine restorations for posterior teeth in different ceramics, sixty standard tabletop preparations in epoxy resin G10 received lithium silicate based zirconia reinforced (ZLS, Vita Suprinity- Vita Zahnfabrik), or hybrid ceramic (PIC, Vita Enamic- Vita Zahnfabrik), restorations in .5 or 1 mm thickness bonded using resin cement. The same cycling protocol was applied for all specimens that consisted of 5.000 cycles at 200 N followed by 450 N cycles until the specimens’ fracture or the suspension of the test after 1.5 x 106 cycles. Axial load was carried out with a 4 Hz frequency in Biocycle V2 equipment (Biopdi, São Carlos, SP), with samples immersed in water. Presence of cracks and/or fractures was checked with every 2,5 x 105 cycles and the survival analysis was performed using the number of cycles in which each specimen failed. All specimens were evaluated using stereomicroscope and scanning electron microscopy (SEM). After data tabulation, Kaplan-Meier and Mantel-Cox (Log Rank test) analysis were performed, followed by multiple pairwise comparison, all with a significance level of 5%, and Weibull analysis. Through tridimensional finite element analysis, stresses distribution and maximum principal stresses in the posterior occlusal veneers were evaluated comparing different types of substrate (G10, enamel/dentin, enamel), thicknesses and ceramic materials. Zirconium-reinforced lithium silicate restorations with 0.5 mm thickness (ZLS.5) showed lower fatigue strength compared to 1.0 mm hybrid ceramic restorations (PIC1), and both were similar to other restorations (PIC.5 and ZLS1) (Log-Rank test, X2 = 11.2; df = 3; p = 0.0107<0.05). ZLS groups presented random defects that culminated with the fracture, whereas PIC groups presented defects that increased with the mechanical fatigue after some time under cycling. Stereomicroscope images show radial cracks observed due to the translucency of the material, there was no damage caused by applicator. TMP distribution was similar for the different substrate types, but the highest modulus of elasticity showed slightly lower stress concentration. PIC is favorable to be used in thin thickness with similar fatigue strength to thicker ZLS restorations.
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Palavras-chave
Ceramicas, Estresse mecãnico, Prótese dentária fixa, Teste de fadiga, Ceramics, Mechanical stress, Fixed dental prosthesis, Fatigue test