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Influence of Core‐Veneer Thickness Ratio on the Fracture Load and Failure Mode of Zirconia Crowns
Author(s) -
Soares Luciana Mara,
Soares Cristiano,
Miranda Milton Edson,
Basting Roberta Tarkany
Publication year - 2019
Publication title -
journal of prosthodontics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.902
H-Index - 60
eISSN - 1532-849X
pISSN - 1059-941X
DOI - 10.1111/jopr.12601
Subject(s) - veneer , materials science , core (optical fiber) , fracture (geology) , cubic zirconia , composite material , failure mode and effects analysis , ceramic
Purpose To evaluate the influence of different core‐veneer thickness (CVT) ratios on fracture loads and failure modes of zirconia crowns with or without thermomechanical cycling (TC). Materials and Methods Forty yttrium‐stabilized tetragonal zirconia polycrystalline (Y‐TZP) cores were veneered with a pressable ceramic and divided into four groups (n = 10): group 1 ‐ 1:3 CVT ratio (0.5‐mm core, 1.5‐mm veneer); group 2 ‐ 1:1 CVT ratio (1.0‐mm core, 1.0‐mm veneer); groups 3 and 4 ‐ identical to groups 1 and 2, respectively, except that they underwent TC (1,000,000 cycles with an 84‐N load applied at a 4‐Hz frequency, temperature cycling at 4°C, 37°C, and 55°C – 30 seconds each). Loads were applied axially to the central fossa of the crowns with a 1 mm/min crosshead speed at 200 N until failure. Results Two‐way ANOVA showed that the crowns with a 1:3 CVT ratio had a lower mean fracture load than crowns with a 1:1 CVT ratio (group 1 = 1666.4 ± 466.4 N; group 2 = 2156.6 ± 472.3 N). TC had no effect on the fracture load for crowns with the same CVT ratio. The failures observed for the crowns in groups 1, 3, and 4 were fractures within the veneering ceramic, which exposed the core. The failure severity of fractures for group 2 was less extensive, characterized by chipping within the ceramic veneer. Conclusion Crowns with a 1:1 CVT ratio had higher fracture load values and more conservative failures. TC had no effect on the fracture load of the ceramic crowns.