IADR Abstract Archives
Fracture Toughness of Chairside Dental Zirconias
Objectives: The objective of this study was to measure the fracture toughness of commercially available chairside zirconia using the Single Edge Precrack Beam method.
Methods: Six chairside zirconias were tested: KatanaTM STML (Group 1), 3MTM Chairside Zirconia (Group 2), IPS e.max® ZirCAD MT Multi (Group 3), CEREC® MTLTM Medi (Group 4), CEREC® Zirconia Plus (Group 5) and IPS e.max® ZirCAD LT (Group 6). Seven bars (36 mm x 4 mm x 3 mm after sintering) were cut using a Buehler diamond saw. Bars were individually sintered according to the manufacturer's instructions. Sintered bars were indented with 3 equally spaced indents across the center of the bar using 5 kg loads using a Marco Vickers Hardness Tester. Indented bars were loaded in an indentation precracking fixture as described in ASTM Standard C 1421 using an Instron Universal testing machine (33R4204) at a crosshead speed of 0.25 mm/min until a crack was heard or until 10 kN were obtained. The specimen was then backlit to examine for a crack. If no crack was observed, the specimen was loaded higher by 2.5 kN until a crack was observed. Precracked specimens were loaded in a 30 mm 3-point flexure loading fixture until failure at a cross-head speed of 1 mm/min. After fracture three equa-spaced measurements were made at 80x using an Olympus SZX12 optical microscope.
The fracture toughess was calculated using:
KIC=(PfS/bW3/2)f(a/W)
where
f(a/W)=(3/2)(a/W)1/2(1.964-2.837a/W+13.711a2/W2- 23.250a3/W3+24.129a4/W4)
where
Pf=Failure load(N), S=Support span(m), B=Thickness(m), W=Width(m) and a=Precrack length
The averages were then calculated with standard deviations.
Results: The means and standard deviations for all groups are given in Table 1. The values were analyzed using ANOVA and student t-tests determined differences. The IPS e.max ZirCAD LT had the highest statistical values followed by the CEREC Zircona Plus. 3M Chairside Zirconia, CEREC MTL and IPS e.max ZirCAD MT Multi were not statistically different. The Katana STML was statistically lower than all other materials.
Conclusions: Within the bounds of this study, IPS e.max ZirCAD had the highest mean fracture toughness followed by the CEREC Zirconia Plus. CEREC MTL, 3M Chairside and ZirCAD Mt Multi had values statistically the same around 3.8 MPa-m1/2. Katana STML was statistically lower than all the other tested zirconias.
Methods: Six chairside zirconias were tested: KatanaTM STML (Group 1), 3MTM Chairside Zirconia (Group 2), IPS e.max® ZirCAD MT Multi (Group 3), CEREC® MTLTM Medi (Group 4), CEREC® Zirconia Plus (Group 5) and IPS e.max® ZirCAD LT (Group 6). Seven bars (36 mm x 4 mm x 3 mm after sintering) were cut using a Buehler diamond saw. Bars were individually sintered according to the manufacturer's instructions. Sintered bars were indented with 3 equally spaced indents across the center of the bar using 5 kg loads using a Marco Vickers Hardness Tester. Indented bars were loaded in an indentation precracking fixture as described in ASTM Standard C 1421 using an Instron Universal testing machine (33R4204) at a crosshead speed of 0.25 mm/min until a crack was heard or until 10 kN were obtained. The specimen was then backlit to examine for a crack. If no crack was observed, the specimen was loaded higher by 2.5 kN until a crack was observed. Precracked specimens were loaded in a 30 mm 3-point flexure loading fixture until failure at a cross-head speed of 1 mm/min. After fracture three equa-spaced measurements were made at 80x using an Olympus SZX12 optical microscope.
The fracture toughess was calculated using:
KIC=(PfS/bW3/2)f(a/W)
where
f(a/W)=(3/2)(a/W)1/2(1.964-2.837a/W+13.711a2/W2- 23.250a3/W3+24.129a4/W4)
where
Pf=Failure load(N), S=Support span(m), B=Thickness(m), W=Width(m) and a=Precrack length
The averages were then calculated with standard deviations.
Results: The means and standard deviations for all groups are given in Table 1. The values were analyzed using ANOVA and student t-tests determined differences. The IPS e.max ZirCAD LT had the highest statistical values followed by the CEREC Zircona Plus. 3M Chairside Zirconia, CEREC MTL and IPS e.max ZirCAD MT Multi were not statistically different. The Katana STML was statistically lower than all other materials.
Conclusions: Within the bounds of this study, IPS e.max ZirCAD had the highest mean fracture toughness followed by the CEREC Zirconia Plus. CEREC MTL, 3M Chairside and ZirCAD Mt Multi had values statistically the same around 3.8 MPa-m1/2. Katana STML was statistically lower than all the other tested zirconias.