IADR Abstract Archives
Fracture-toughness of CAD/CAM Materials – Alternative loading-approach for compact tension test
Objectives: This study determined plane-strain fracture-toughness (KIC) of five different CAD/CAM materials used for crown fabrication, following an alternative innovative loading approach of compact tension test specimens.
Methods: Rectangular-shaped specimens were cut from CAD/CAM blocks (n=10): Vita-MarkII (Vident) (VMII), Lava-Ultimate (3M/ESPE) (LU), IPS-e.max-CAD (Ivoclar-Vivadent), crystallized and un-crystallized (E-max and E-max-U, respectively), Celtra Duo (Dentsply) fired and unfired (CD, CD-U, respectively) and Vita Enamic (Vident) (VE). Specimens were notched and pre-cracked with a thin diamond disc before testing. Instead of applying tensile loading through drilled holes, a specially-made wedge-shaped steel loading-bar was used to apply compressive load at the notch area in Instron Universal testing machine. The bar engaged the top ¼ of the notch before compressive load was applied at cross-head speed of 0.5 mm/min. Fracture load was recorded and KIC = P x Y2 / B x w ½ was calculated from
mathematical formula. Means and SDs were calculated and data statistically-analyzed with one-way ANOVA at 95% confidence level and Tukey’s tests.
Results: Means and SDs of KIC in MPa-m1/2 for E-max, E-max-U, LU, VMII, CD, CD-U and VE were: 1.88(0.62), 0.81(0.25), 0.85(0.21), 0.73(0.13), 2.65(0.32), 1.01(0.15) and 1.02(0.19), respectively. ANOVA revealed significant difference among means (p<.05). CD and E-max had significantly highest mean KIC values among groups, while VMII had lowest mean value.
Conclusions: Mean fracture toughness values of the five tested materials varied considerably, however, none of them reached mean fracture toughness of dentin (3.08 MPa-m1/2) previously reported. For E-max and CD firing the specimens significantly increased mean KIC. The modified test arrangement was found to be easy to follow and simplified specimen preparation process.
Methods: Rectangular-shaped specimens were cut from CAD/CAM blocks (n=10): Vita-MarkII (Vident) (VMII), Lava-Ultimate (3M/ESPE) (LU), IPS-e.max-CAD (Ivoclar-Vivadent), crystallized and un-crystallized (E-max and E-max-U, respectively), Celtra Duo (Dentsply) fired and unfired (CD, CD-U, respectively) and Vita Enamic (Vident) (VE). Specimens were notched and pre-cracked with a thin diamond disc before testing. Instead of applying tensile loading through drilled holes, a specially-made wedge-shaped steel loading-bar was used to apply compressive load at the notch area in Instron Universal testing machine. The bar engaged the top ¼ of the notch before compressive load was applied at cross-head speed of 0.5 mm/min. Fracture load was recorded and KIC = P x Y2 / B x w ½ was calculated from
mathematical formula. Means and SDs were calculated and data statistically-analyzed with one-way ANOVA at 95% confidence level and Tukey’s tests.
Results: Means and SDs of KIC in MPa-m1/2 for E-max, E-max-U, LU, VMII, CD, CD-U and VE were: 1.88(0.62), 0.81(0.25), 0.85(0.21), 0.73(0.13), 2.65(0.32), 1.01(0.15) and 1.02(0.19), respectively. ANOVA revealed significant difference among means (p<.05). CD and E-max had significantly highest mean KIC values among groups, while VMII had lowest mean value.
Conclusions: Mean fracture toughness values of the five tested materials varied considerably, however, none of them reached mean fracture toughness of dentin (3.08 MPa-m1/2) previously reported. For E-max and CD firing the specimens significantly increased mean KIC. The modified test arrangement was found to be easy to follow and simplified specimen preparation process.
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