Effects of porcelain thickness on the flexural strength and crack propagation in a bilayered zirconia system

• Autor(a) principal: Figueiredo, Viviane Maria Goncalves de [UNESP]
• Data de Publicação: 2017
• Outros Autores: Braga Pereira, Sauna Maciel [UNESP], Bressiani, Eduardo [UNESP], Valera, Marcia Carneiro [UNESP], Bottino, Marco Antonio [UNESP], Zhang, Yu, Melo, Renata Marques de [UNESP]
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://dx.doi.org/10.1590/1678-7757-2015-0479; http://hdl.handle.net/11449/163425
• topic: Ceramics; Porcelain; Mechanical stress; Confocal microscopy

Objective: This study evaluated the influence of porcelain (VM9, VITA Zahnfabrik, Germany) thickness on the flexural strength and crack propagation in bilayered zirconia systems (YZ, VITA Zahnfabrik, Germany). Material and Methods: Thirty zirconia bars (20.0x4.0x1.0 mm) and six zirconia blocks (12.0x7.5x1.2 mm) were prepared and veneered with porcelain with different thickness: 1 mm, 2 mm, or 3 mm. The bars of each experimental group (n=10) were subjected to four-point flexural strength testing. In each ceramic block, a Vickers indentation was created under a load of 10 kgf for 10 seconds, for the propagation of cracks. Results: The results of flexural strength were evaluated by One-way ANOVA and Tukey's test, with a significance level of 5%. The factor thickness of the porcelain was statistically significant (p=0.001) and the 1-mm group presented the highest values of flexural strength. The cracks were predominant among the bending specimens with 1 and 2 mm of porcelain, and catastrophic failures were found in 50% of 3-mm-thick porcelain. After the indentation of blocks, the most severe defects were observed in blocks with 3-mm-thick porcelain. Conclusion: The smallest (1 mm) thickness of porcelain on the zirconia infrastructure presented higher values of flexural strength. Better resistance to defect propagation was observed near the porcelain/ zirconia interface for all groups. Higher flexural strength was found for a thinner porcelain layer in a bilayered zirconia system. The damage caused by a Vickers indentation near and far the interface with the zirconia shows that the stress profiles are different.