Objectives: CAD/CAM Zr-abutments are commonly used in restorative cases. However, fracture of Zr-abutments are found. The aim of this study was to investigate the effect of static loading on various conditions using "Aadva™" (CAD/CAM processing system/ GC) Zr- abutment.
Methods: Three types of Aadva Zr abutments (#142, compatible with standard implant narrow/ GC Implant Aadva) were used in this study. Group1 - Three lengths (7.5mm/10mm/12mm); Group2 - Three angles (20˚/30˚/40˚); Group3 - Three eccentric distances (0mm/0.75mm/1.65mm). All samples were machined with Aadva GM-1000 milling machine, and then fired at 1500 degree C for 2h. These abutments were placed in standard implant narrow (GC Implant Aadva) using original abutment screw with 20N-cm force. They were mounted in metal tube to expose 3mm with conventional resin. Samples were tested according to flexural strength test at a crosshead speed of 1mm/min. All data were analyzed by multiple comparison and Tukey's test. In addition the stress distribution was analyzed by 3D-FEM.
Results: Flexural strength of all samples decreased with the increase of length, angle, and eccentric distance. In group1, flexural strength of 7.5mm length, 10mm length, and 12mm length were 332.58±14.30 MPa, 231.73±17.56 MPa, 219.25±12.54 MPa, respectively. Flexural strength of 10mm and 12mm length was significantly lower than 7.5mm length (p<0.01). There were similar tendencies in groups 2 and 3 as well. These results were also demonstrated by 3D-FEM.
Conclusions: It is suggested that flexural strength of Zr-abutment is depend on the length, angle, and eccentric distance. Therefore, when Zr-abutment is selected in clinical situations, it's necessary to consider shape and loading direction.