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Brazilian Journal of Oral Sciences
Piracicaba Dental School - UNICAMP
EISSN:
Vol. 13, No. 2, 2014, pp. 124-128
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Bioline Code: os14024
Full paper language: English
Document type: Research Article
Document available free of charge
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Brazilian Journal of Oral Sciences, Vol. 13, No. 2, 2014, pp. 124-128
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Strength of 3Y-TZP and feldspathic porcelain subjected to different cooling methods
de Almeida-Júnior, Antonio Alves; Longhini, Diogo; Galvão, Beatriz Regalado; dos Santos, Claudinei & Adabo, Gelson Luis
Abstract
Aim: To investigate the effect of the cooling rate on flexural strength of monolayer and bilayer
porcelain/zirconia (Y-TZP) bars. Methods: Forty-five specimens were made for each design
group: (PM) monolithic specimens of veneer porcelain Vita VM9 (Vita, Germany); (ZM) monolithic
specimens of zirconia (ZiHP; ProtMat, Brazil); (PB) bilayer specimens zirconia/porcelain with
porcelain on lower surface; and (ZB) bilayer specimens porcelain/zirconia with zirconia on lower
surface. Each group was cooled by three different methods after porcelain sintering: slow –
specimens were cooled inside the turned-off furnace; normal – specimens were removed from the
furnace and cooled in air at room temperature; and fast – specimens were removed from the
furnace at 910°C and cooled by compressed air for 10 s. Specimens were polished and flexural
strength was measured in water at 37 °C (n=15). Maximum load at fracture was recorded, and
equations for simple (monolayer) and composite (bilayer) structures were used to calculate the
flexural strength. Results were analyzed using one-way ANOVA (p<0.05) and Tukey test separately
for each design. Results: The results of one-way ANOVA were statistically significant only for the
PB group. The post-hoc Tukey test showed the highest flexural strength for fast cooling and the
lowest for slow cooling; the normal cooling was statistically similar to both. Conclusions: Cooling
methods affected only the flexural strength of bilayer specimens with porcelain on low surface
(under tension) when the slow cooling method was used.
Keywords
dental porcelain; zirconium; material resistance
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