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Objective: The objective of this study was to compare the flexural strength of four dental computer-aided design and computer-aided manufacturing (CAD/CAM) glass-ceramics, i.e., lithium-disilicate-based (IPS e.max CAD; EMX), leucite-based (IPS Empress CAD; EMP) and two zirconia-reinforced lithium silicate glass-ceramics (CELTRA DUO; CD and VITA SUPRINITY; VS).
Materials and methods: Thirty bar-shaped specimens (1.5mm x 4mm x 18mm) were prepared for each material by cutting from rectangular blocks, and finishing their surfaces by glazing. All specimens were loaded to fracture at a crosshead speed of 0.5 mm/min using a three-point bending fixture mounted on a universal testing machine. The flexural strength values were calculated and statistically analyzed by one-way ANOVA and Dunnett T3 (α=0.05). The strength data of all groups were also analyzed using the Weibull Statistics.
Results: The result from a statistical analysis showed that VS (319±42MPa) had the highest flexural strength following by CD (278±49MPa) and then EMX (236±20MPa). EMP (157±14MPa) showed the lowest flexural strength. The Weibull moduli and the characteristic strength were 9.02 and 336.97 for VS, 6.55 and 298.87 for CD, 13.90 and 244.69 for EMX, 12.77 and 164.02 for EMP.
Conclusions: For CAD/CAM glass-ceramics examined in this study, the zirconia-reinforced lithium silicate glass-ceramics had higher flexural strength and characteristic strength than a lithium-disilicate-based and leucite-based glass-ceramics.
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