IADR Abstract Archives
Fracture Load of All-Ceramic Crowns With Varying Occlusal Thicknesses
Objectives: Newer translucent zirconia materials may have different minimum occlusal thickness requirements based on type of cement. The purpose of this study was to evaluate the effect of occlusal thickness and cement type on the fracture load of crowns made with two all-ceramic materials.
Methods: Eighty extracted maxillary human third molar teeth were divided into two groups and restored with crowns using cubic-containing (4Y-TZP) zirconia (Katana STML Kuraray) and lithium disilicate (IPS e.max CAD LT, Ivoclar Vivadent) (control). Teeth were prepared with 0.5 or 1.0mm occlusal reduction and scanned (Omnicam, Dentsply/Sirona). The crowns were designed and milled. Half the crowns of each occlusal thickness in each material group were cemented with RMGI and the other half with a resin cement according to their respective manufacturer’s recommendations. The specimens were stored for 24 hrs in 37°C distilled water, then subjected to thermocycling and cyclic loading. Each crown specimen was loaded to failure in a universal testing machine (Instron) with a stainless-steel rod at 90 degrees to the occlusal surface. Data were analyzed with T-tests and ANOVAs/Tukey post hoc tests (alpha=0.05).
Results: Significant differences between groups were found based on type of ceramic, thickness, and cement (p<0.05).
Conclusions: In general, the use of a resin cement approximately doubled the fracture load compared to the use of the glass ionomer cement at each occlusal thickness for both ceramic types. Increasing the occlusal thickness from 0.5 to 1.0mm approximately increased the fracture strength by one third per ceramic and cement type.
The views expressed are those of the authors and do not reflect the official views or policy of the United States Air Force, Department of Defense, or its Components.
Methods: Eighty extracted maxillary human third molar teeth were divided into two groups and restored with crowns using cubic-containing (4Y-TZP) zirconia (Katana STML Kuraray) and lithium disilicate (IPS e.max CAD LT, Ivoclar Vivadent) (control). Teeth were prepared with 0.5 or 1.0mm occlusal reduction and scanned (Omnicam, Dentsply/Sirona). The crowns were designed and milled. Half the crowns of each occlusal thickness in each material group were cemented with RMGI and the other half with a resin cement according to their respective manufacturer’s recommendations. The specimens were stored for 24 hrs in 37°C distilled water, then subjected to thermocycling and cyclic loading. Each crown specimen was loaded to failure in a universal testing machine (Instron) with a stainless-steel rod at 90 degrees to the occlusal surface. Data were analyzed with T-tests and ANOVAs/Tukey post hoc tests (alpha=0.05).
Results: Significant differences between groups were found based on type of ceramic, thickness, and cement (p<0.05).
Conclusions: In general, the use of a resin cement approximately doubled the fracture load compared to the use of the glass ionomer cement at each occlusal thickness for both ceramic types. Increasing the occlusal thickness from 0.5 to 1.0mm approximately increased the fracture strength by one third per ceramic and cement type.
The views expressed are those of the authors and do not reflect the official views or policy of the United States Air Force, Department of Defense, or its Components.
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