IADR Abstract Archives
Fracture toughness, KIC, of Five CAD/CAM glass-ceramics
Objectives: To test the fracture toughness, KIC, of five commercial available CAD/CAM glass-ceramics
Methods: Fracture toughness was determined with the V-notched beam test according to ASTM C1421-10. Five groups (N=8) of CAD/CAM glass-ceramic materials were tested: Group 1: IPS Empress®CAD(leucite), Group 2: Vita Suprinity(lithium silicate), Group 3: Celtra Duo(lithium silicate/lithium disilicate), Group 4: Obsidian(lithium silicate), and Group 5: IPS e.max®CAD(lithium disilicate). Each material were sectioned into bars (3mm x 4mm x 17mm) using an IsoMet saw. Groups 2-5 were fired according to the manufacturer’s instructions. An initial 0.5mm V-notch was placed using a Diamet diamond saw at low speed. The V-notch was continued to a depth between 0.9 and 1.1 mm using a razor blade at a constant load using 6, 3, 1 µm diamond paste (DMT Diamond paste). The specimens were cleaned in ethanol for 10 minutes. The specimens were loaded to failure in a three-point testing fixture (span-15 mm) at a crosshead speed of 0.5 mm/min in an Instron testing machine. Notch depths were measured at three even spaced points at 50x using an optical microscope and averaged with no difference of 0.1 mm across the specimen. The relative V-notch depth was calculated (a/W~0.25). The precracked beam method was used to calculate fracture toughness (KIC):
KIC = g * [(Pf*Sx10-6)/(t*w3/2)] *[(3(a/w)1/2)/(2(1-a/w)3/2)]
g is {1.99-[(a/w)(1-a/w)]*[2.15-3.93(a/w)+2.7*(a/w)2]}/[1+2(a/w)]
Pf is failure load; s is span; t is thickness; w is width; and a is average V-notch depth.
Results: The fracture toughness, KIC (MPa●m0.5), for each group is: Group 1: 1.07±0.11; Group 2: 1.36±0.19; Group 3: 1.38±0.14; Group 4: 1.71±0.18; and Group 5: 2.11±0.18. Using ANOVA (p≤0.05), a statistical difference was found between all the groups except Groups 2 and 3.
Conclusions: Within the bounds of this study, Group 5 gave the highest fracture toughness while Group 1 gave the lowest fracture toughness.
Methods: Fracture toughness was determined with the V-notched beam test according to ASTM C1421-10. Five groups (N=8) of CAD/CAM glass-ceramic materials were tested: Group 1: IPS Empress®CAD(leucite), Group 2: Vita Suprinity(lithium silicate), Group 3: Celtra Duo(lithium silicate/lithium disilicate), Group 4: Obsidian(lithium silicate), and Group 5: IPS e.max®CAD(lithium disilicate). Each material were sectioned into bars (3mm x 4mm x 17mm) using an IsoMet saw. Groups 2-5 were fired according to the manufacturer’s instructions. An initial 0.5mm V-notch was placed using a Diamet diamond saw at low speed. The V-notch was continued to a depth between 0.9 and 1.1 mm using a razor blade at a constant load using 6, 3, 1 µm diamond paste (DMT Diamond paste). The specimens were cleaned in ethanol for 10 minutes. The specimens were loaded to failure in a three-point testing fixture (span-15 mm) at a crosshead speed of 0.5 mm/min in an Instron testing machine. Notch depths were measured at three even spaced points at 50x using an optical microscope and averaged with no difference of 0.1 mm across the specimen. The relative V-notch depth was calculated (a/W~0.25). The precracked beam method was used to calculate fracture toughness (KIC):
KIC = g * [(Pf*Sx10-6)/(t*w3/2)] *[(3(a/w)1/2)/(2(1-a/w)3/2)]
g is {1.99-[(a/w)(1-a/w)]*[2.15-3.93(a/w)+2.7*(a/w)2]}/[1+2(a/w)]
Pf is failure load; s is span; t is thickness; w is width; and a is average V-notch depth.
Results: The fracture toughness, KIC (MPa●m0.5), for each group is: Group 1: 1.07±0.11; Group 2: 1.36±0.19; Group 3: 1.38±0.14; Group 4: 1.71±0.18; and Group 5: 2.11±0.18. Using ANOVA (p≤0.05), a statistical difference was found between all the groups except Groups 2 and 3.
Conclusions: Within the bounds of this study, Group 5 gave the highest fracture toughness while Group 1 gave the lowest fracture toughness.