Fracture Strength and Stress Distribution Analyses of CAD/CAM Titanium and Zirconia Abutments Restored with Resin-Based Ceramic and Monolithic Zirconia Crowns

Purpose: The aim of this study was to evaluate the effect of two different crown and abutment types produced with CAD/CAM systems on the biomechanical behavior of implant-supported fixed restorations. Material and methods: Thirty-six titanium implants received either custom-made zirconia abutments cemented on a ti-base (Zi) or single-piece custom titanium abutment (Ti). Then, resin-based ceramic crowns (RBC) crowns were manufactured for half of each abutment type and monolithic zirconia crowns (MZ) were manufactured for the other half. Thus, 4 study groups were formed as follows: Zi-RBC, Zi-MZ, Ti-RBC, Ti-MZ. Fracture resistance of the groups was tested using a universal testing machine and the failure types were determined. The stress distribution on abutments and crowns was evaluated with finite element analysis (FEA) analysis. Results: Zirconia, as the abutment type, showed higher fracture strength for both crown types. Considering the crown material, monolithic zirconia showed higher fracture strength for both abutment types. None of the groups showed screw or implant deformation. Ti-RBC and Ti-MZ groups showed only crown failures while 22% of Group Zi-RBC and 44% of Group Zi-MZ showed abutment fractures in addition to crown fractures. FEA analysis did not show significant differences for crowns while differences were observed for abutments. Conclusion: Zirconia abutments cemented on titanium bases can be considered an acceptable alternative to titanium abutments. Monolithic zirconia may provide longer intraoral service than resin-based ceramic as the crown material considering its higher resistance to fracture.