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Aim: This study aims to compare the retentive capacity of two attachment systems after manual thermocycling. Settings and Design: In vitro study and Comparative trail. Materials and Methods: An edentulous mandibular Polymethyl Methacrylate model was fabricated to receive the overdentures with the two attachment systems to be compared. Two dental implants were placed in the predetermined right and left mandibular canine regions of the model. A total number of eight overdentures, four per group, were fabricated over the two implants with two attachment systems to be compared; Bar and clip attachment system (Group-1) and Locator attachment system (Group-2). All the overdentures were subjected to 5000 alternating thermal cycles using manual thermocycling. Then the samples were subjected to 100 vertical pulls each in the anterior and posterior regions using a universal testing machine and the mean retentive forces were calculated for each sample in the anterior and posterior regions, respectively. Results: The mean retentive forces after 100 vertical pulls, were calculated and tabulated for each sample in the anterior and posterior regions separately. Then, the cumulative mean of the anterior and the posterior regions were calculated for each group. The cumulative mean retentive forces of both the attachment groups were-Group-1 (Bar and clip attachment system) = 27.87 N ± 4.01 and Group-2 (locator attachment system) = 18.85 N ± 2.50 with a P value of 0.021. This difference was found to be statistically significant. Conclusion: Within the limitations of the present in vitro study, the bar and clip attachment system offered better retention than the locator attachment system.