Effect of Cyclic Dislodging on the Retention of Two Attachment Systems for Implant-supported Overdentures: An In Vitro Study.

PURPOSE: The aim of this study was to compare and evaluate the retention of two new attachment systems used for implant-supported overdentures subjected to insertion-removal cycles. MATERIALS AND METHODS: Twenty custom-manufactured polyvinyl chloride models mimicking implant-retained over-dentureresin blocks were fabricated and divided into two groups (n = 10): group 1 ('Kerator' attachment) and group 2 ('EMI' attachment). Each model received two parallel implants (JD evolution(R)) 20 mm apart and was subjected to cyclic retention forces of 10, 100, 1000, 5000, 10000 and 14600 cycles using a universal testing machine in a 0.9% sodium chloride water solution at 22 degrees C. Data were analyzed using one-way analysis of variance; the level of significance was set at a < 0.05. RESULTS: The 'Kerator' and 'EMI' attachment systems reported a significant decrease in retention (64 and 56.6% respectively) after 14600 insertion-removal cycles (p < 0.001). The 'EMI' attachment showed significant higher loss of retention than the 'Kerator' attachment all along the 14600 cycles (p < 0.05) except for cycles 100 and 5000 (p > 0.05). CONCLUSION: Within the limitations of this in vitro study, both attachments reported satisfactory retentive values during the 14600 cycles, the 'Kerator' attachment showed better retention than the new 'EMI' attachment. The initial retentive force of both attachments has gradually decreased. CLINICAL SIGNIFICANCE: Both attachment systems evaluated in this study can be used in clinical practice for implant-supported overdentures.