Comparison of the microgap between titanium and modified zirconia abutments after cyclic loading: A pilot study Purpose: Dental implants have been a common treatment modality for the replacement of missing teeth. Dental abutment is the implant component that connects the implant fixture to the restoration. Many studies have evaluated the mechanical properties and biological behavior of titanium and zirconia abutments. Recently, a modified zirconia abutment, consisting of a titanium insert in the interface with the implant fixture, was developed. The purpose of this study is to compare the microgap between CAD/CAM titanium abutments and CAD/CAM modified zirconia abutments after cyclic loading at three different intervals. Materials and methods: Sixteen implant fixtures (Biomet 3i, Palm Beach Gardens, Florida) were used for this study. Sixteen CAD/CAM abutments of the same configuration were fabricated and attached to the fixtures according to the manufacturer recommended torque of 25Ncm. Eight of those were made from titanium and eight were the modified zirconia abutments. The implant-abutment assemblies were embedded in polymerizing resin and mounted at 30 degree angulation in the loading machine. They were assigned to 4 groups: the control group that was not loaded, Group 1 that was loaded for 100,000 cycles, Group 2 that was loaded for 250,000 cycles and Group 3 that was loaded for 500,000 cycles. After sectioning lengthwise, the implant-abutment assemblies were examined under Scanning Electron Microscopy and the microgap between the abutment and the fixture was measured. The difference in the microgap was compared using analysis of variance (α=95%). Results: No statistically significant difference was found in the microgap between the titanium and the modified zirconia abutments throughout the loading cycles (p>0.05). A statistically significant difference was found in the microgap between the zirconia part and the metal insert between control group and Group 3 (p