Title of Thesis: Enhancing Retention of Implant Crowns to Titanium Base Abutments Using Crown Modification Purpose: The connection between a titanium base and its ceramic restoration is crucial to the long-term success of the restoration and for minimizing prosthetic complications. One risk of this abutment system is debonding of the components. The purpose of the study is to investigate whether the addition of auxiliary retentive features, horizontal circumferential grooves, will significantly improve the retention of the zirconia restoration and titanium base interface. Materials and Methods: For this in-vitro study a total of 48 prefabricated titanium bases with 3D printed ceramic restorations were divided into four groups. The groups were a control group, a group with a coronally located groove, a group with an apically located groove, and a group with two grooves. A universal testing machine was used to measure the maximum force (N) required for removal. One way ANOVA and Tukey post-hoc comparisons were used for statistical analysis. Results: Across all groups, 4 specimen were lost to testing. The mean dislodgement force for the control group was 130.3 N (97.48N-163.3N). The mean dislodgement force for the coronal groove group was 81.82 N (52.54N-117.8N). The mean dislodgement force for the apical groove group was 60.91N (35.39N-127.2N) The mean dislodgement force for the two groove group was 141.1N (95.32N-237.4N). A significant difference was found between groups (P<0.0001). A significant difference was found between the control group and the apical and coronal groove groups (P = 0.0031, P<0.0001 respectively), but not between the control group and the two groove group (P = 0.84). No significant difference was found between the apical groove group and the coronal groove group (P=0.34) Conclusion: Horizontal, circumferential grooves worsen retention of 3D printed ceramic implant restorations cemented to NobelBiocare titanium abutments. Location and number of grooves does not significantly impact retention.