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See detailResidual stress profiles in veneering ceramic on Y-TZP, alumina and ZTA frameworks: Measurement by hole-drilling
Fukushima, K. A.; Sadoun, M. J.; Cesar, P. F. et al

in Dental materials (2013)

OBJECTIVES: The residual stress profile developed within the veneering ceramic during the manufacturing process is an important predicting factor in chipping failures, which constitute a well-known ... [more ▼]

OBJECTIVES: The residual stress profile developed within the veneering ceramic during the manufacturing process is an important predicting factor in chipping failures, which constitute a well-known problem with yttria-tetragonal-zirconia polycrystal (Y-TZP) based restorations. The objectives of this study are to measure and to compare the residual stress profile in the veneering ceramic layered on three different polycrystalline ceramic framework materials: Y-TZP, alumina polycrystal (AL) and zirconia toughened alumina (ZTA). METHODS: The stress profile was measured with the hole-drilling method in bilayered disk samples of 19mm diameter with a 0.7mm thick Y-TZP, AL or ZTA framework and a 1.5mm thick layer of the corresponding veneering ceramic. RESULTS: The AL samples exhibited increasing compressive stresses with depth, while compressive stresses switching into interior tensile stresses were measured in Y-TZP samples. ZTA samples exhibited compressive stress at the ceramic surface, decreasing with depth up to 0.6mm from the surface, and then becoming compressive again near the framework. SIGNIFICANCE: Y-TZP samples exhibited a less favorable stress profile than those of AL and ZTA samples. Results support the hypothesis of the occurrence of structural changes within the Y-TZP surface in contact with the veneering ceramic to explain the presence of tensile stresses. Even if the presence of Y-TZP in the alumina matrix seems to negatively affect the residual stress profiles in ZTA samples in comparison with AL samples, the registered profiles remain positive in terms of veneer fracture resistance. [less ▲]

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See detailInfluence of zirconia framework thickness on residual stress profile in veneering ceramic: Measurement by hole-drilling.
MAINJOT, Amélie ULg; Schajer, G. S.; Vanheusden, Alain ULg et al

in Dental Materials (2011)

OBJECTIVES: Framework design is reported to influence chipping in zirconia-based restorations, which is an important cause of failure of such restorations. Residual stress profile in the veneering ceramic ... [more ▼]

OBJECTIVES: Framework design is reported to influence chipping in zirconia-based restorations, which is an important cause of failure of such restorations. Residual stress profile in the veneering ceramic after the manufacturing process is an important predictive factor of the mechanical behavior of the material. The objective of this study is to investigate the influence of framework thickness on the stress profile measured in zirconia-based structures. METHODS: The stress profile was measured with the hole-drilling method in bilayered disc samples of 20mm diameter with a 1.5mm thick veneering ceramic layer. Six different framework thicknesses from 0.5mm to 3mm were studied. Two different cooling procedures were also investigated. RESULTS: Compressive stresses were observed in the surface, and tensile stresses in the depth of most of the samples. The slow cooling procedure was found to promote the development of interior tensile stresses, except for the sample with a 3mm thick framework. With the tempering procedure, samples with a 1.5mm thick framework exhibited the most favorable stress profile, while thicker and thinner frameworks exhibited respectively in surface or interior tensile stresses. Significance: The measurements performed highlight the importance of framework thickness, which determine the nature of stresses and can explain clinical failures encountered, especially with thin frameworks. The adequate ratio between veneering ceramic and zirconia is hard to define, restricting the range of indications of zirconia-based restorations until a better understanding of such a delicate veneering process is achieved. [less ▲]

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See detailInfluence of veneer thickness on residual stress profile in veneering ceramic: Measurement by hole-drilling.
MAINJOT, Amélie ULg; Schajer, G. S.; Vanheusden, Alain ULg et al

in Dental Materials (2011)

OBJECTIVES: The veneering process of frameworks induces residual stresses and can initiate cracks when combined with functional stresses. The stress distribution within the veneering ceramic as a function ... [more ▼]

OBJECTIVES: The veneering process of frameworks induces residual stresses and can initiate cracks when combined with functional stresses. The stress distribution within the veneering ceramic as a function of depth is a key factor influencing failure by chipping. This is a well-known problem with Yttria-tetragonal-zirconia-polycrystal based fixed partial dentures. The objective of this study is to investigate the influence of veneer thickness on the stress profile in zirconia- and metal-based structures. METHODS: The hole-drilling method, often used for engineering measurements, was adapted for use with veneering ceramic. The stress profile was measured in bilayered disc samples of 20mm diameter, with a 1mm thick zirconia or metal framework. Different veneering ceramic thicknesses were performed: 1mm, 1.5mm, 2mm, 2.5mm and 3mm. RESULTS: All samples exhibited the same type of stress vs. depth profile, starting with compressive at the ceramic surface, decreasing with depth up to 0.5-1.0mm from the surface, and then becoming compressive again near the framework, except for the 1.5mm-veneered zirconia samples which exhibited interior tensile stresses. Stresses in the surface of metal samples were not influenced by veneer thickness. Variation of interior stresses at 1.2mm from the surface in function of veneer thickness was inverted for metal and zirconia samples. SIGNIFICANCE: Veneer thickness influences in an opposite way the residual stress profile in metal- and in zirconia-based structures. A three-step approach and the hypothesis of the crystalline transformation are discussed to explain the less favorable residual stress development in zirconia samples. [less ▲]

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See detailResidual stress measurement in veneering ceramic by hole-drilling
Mainjot, Amélie ULg; Schajer, Gary; Vanheusden, Alain ULg et al

in Dental Materials (2011)

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See detailInfluence of veneer thickness on residual stresses in zirconia prostheses.
Mainjot, Amélie ULg; Schajer, Gary; Vanheusden, Alain ULg et al

in Dental Materials (2010)

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