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.
Keywords: attachments; overdentures; retentive force; xerostomia.