Purpose: To compare the load-to-failure values of different ceramic CAD/CAM implant crown materials with drilled screw-access holes with and without cyclic loading applied.
Materials and Methods: Forty zirconia abutments with a titanium base were pre-loaded onto implants to support maxillary right first premolar crowns milled from four different CAD/CAM ceramic materials (zirconia-reinforced lithium silicate, hybrid ceramic, lithium disilicate, and zirconia; n = 10 each). After cementing the crowns, the screw-access channels were prepared by drilling through the occlusal surfaces. Half of the specimens were subjected to cyclic loading for 5 million cycles at 2 Hz (n = 5/material). After cyclic loading, vertical loads were applied until failure. The load-to-failure values of all crowns were recorded and statistically analyzed. Two-way ANOVA was used with restricted maximum likelihood estimation and Tukey-Kramer adjustments (α = .05).
Results: During cyclic loading, the zirconia abutment under one lithium disilicate specimen cracked at 2 million cycles, and a zirconia-reinforced lithium silicate crown also fractured. Results for the load-to-failure test series showed statistical differences between the materials. Zirconia resulted in significantly higher failure loads when compared to the other materials (P < .001). Cyclic loading did not significantly affect the load-to-failure values.
Conclusion: Cyclic loading did not significantly influence the load to failure of any of the materials tested. Zirconia crowns with drilled screw access channels cemented on zirconia abutments with a titanium base had higher load-to-failure values compared to the other ceramic crown materials.
