This study aimed to compare the difference in mechanical behavior between two types of female-part clips of the Stress-Free Implant Bar (SFI-Bar) system during simulation of insertion-removal cycles. Materials and Methods: A total of 10 samples simulating SFI-Bar-attachment-retained implant overdentures were fabricated and randomly divided into two groups (n = 5). One group used E-clips (Elitor alloy) as the female part of the SFI-Bar, and the other used T-clips (all titanium grade IV with red nylon inserts). A total of 14,000 insertionremoval cycles were carried out on each sample. Retentive forces from each cycle were recorded for analysis. Results: Significant differences were found between the two groups (P < .05). Conclusion: The retentive force of E-clips increased as the number of dislodging cycles increased, suggesting that some adjustment may be needed to lower this part's retentive force. T-clips with changeable nylon inserts were deformed after about 4,200 insertion-removal cycles, which interfered with insertion. This indicated that T-clips may need replacement after 2 to 3 years of clinical use.

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