Title: 1411 - Fracture Strength of Monolithic CAD/CAM Crowns Made From Two Silicate Ceramics


Julian Conejo (Presenter)
University of Pennsylvania

Jackey Cheng, University of Pennsylvania
Rania El Madhoun, University of Pennsylvania
Mohammed Abdulateef, University of Pennsylvania
Francis Mante, University of Pennsylvania
Markus Blatz, University of Pennsylvania


Objectives: This in-vitro study measured and compared the fracture load of zirconia-reinforced lithium silicate after different processing methods and lithium disilicate crowns.

Methods: Twenty premolar crowns with identical dimensions and 1.0 mm occlusal thickness were fabricated with the Cerec CAD/CAM system (Dentsply Sirona, Image 1) from two materials: zirconia-reinforced lithium silicate (Celtra Duo, DentsplySirona) and lithium disilicate (IPS e.max CAD, Ivoclar Vivadent). Celtra Duo crowns were processed by either polishing only (group CD/P), firing in SpeedFire Furnace (DentsplySirona; group CD/SF), or firing in Programat Furnace (IvoclarVivadent; group CD/PR). IPS e.max CAD crowns (group e.max/PR) were crystalized in the Programat Furnace. All crowns were etched and silanized following manufacturers recommendations and cemented with Calibra UNIVERSAL (DentsplySirona} self-adhesive resin cement to 3-D printed resin dies (Image 2).
Specimens were exposed to a computer controlled thermal load using thermocycling (5000 cycles, 5°C and 55°C for 120 seconds each. Fracture load was measured with a universal testing machine (Instron Model 4204, Instron Corp, Norwood, Mass. USA) at a crosshead speed of 1.0 mm/min and a load cell capacity of 50 kN. The fracture load values [N] for the specimens were computed using standard formula. Data was analyzed with One-way ANOVA followed by Tukey multiple comparison tests. The statistical power with alpha p=0.05 was 0.99.

Results: The fracture load of e.max/PR crowns was significantly higher than all other groups. Fracture load values were not significantly different among the Celtra Duo Zirconia-reinforced Lithium Silicate groups with different processing methods (Image 3).

Conclusions: Lithium disilicate crowns have a higher fracture resistance than zirconia-reinforced lithium silicate. Different processing methods for zirconia-reinforced lithium silicate have no effect on load-at-facture fracture values.


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Disclosure Statement:
The submitter must disclose the names of the organizations with which any author have a relationship, the nature of the relationship, and the clinical or research area involved. The following is submitted: NONE