Retentive force variations of stud attachments for implant overdentures.

Implant overdentures are considered a standard treatment option by many practitioners, especially for edentulous mandibles. Stud attachments have been used extensively in the construction of these overdentures. In this study, the retentive forces of O-ring/ball and Locator overdenture attachments under various conditions in the mouth were investigated through pull-out tests. In dry testing, the retentive forces of the O-ring/ball attachment started higher than those of the Locator attachment but significantly decreased after 50 insertion-removal cycles (P = 0.014). The Locator attachment had no significant change in its retentive force over time (P = 0.328). In wet testing, a saliva substitute was applied to the stud attachments between cycles. The retentive force of the O-ring/ball attachment increased significantly in wet testing compared to dry testing (P < 0.0001). The retentive force of the Locator system during wet testing did not change significantly from that achieved during dry testing for the first 80 cycles, but then it increased to reach the same levels as the O-ring/ball system at 510 cycles (P < 0.05). Within the limitations of the present study, the results suggest that it is advisable to avoid using O-ring/ball attachments as anchors for implant overdentures in a dry mouth environment. In such cases, Locator attachment or metal-to-metal attachment components would be preferable as implant overdenture anchors. In a saliva-irrigated mouth, there is no significant difference between the retentive properties of the O-ring/ball and Locator attachments over 6-9 months' use.

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®) 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° 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.