In vitro study of the insertion and disinsertion effect on retention of two attachment systems of an overdenture on two implants

Objective: Implant-supported overdentures are a valid treatment option for edentulous patients. The use of two mandibular implants is considered the minimum standard of care. This study evaluated the retentive force of two attachments and their respective connection systems in a mandibular implant-supported overdenture. Methods: Two acrylic blocks were prepared: two parallel implants set 22 mm apart were embedded in one of the blocks, while in the other were positioned the female systems for each attachment system tested (Dalbo Ball BTI® and Locator® with female components in both clear and pink nylon). A specific machine was designed to measure the retentive force of the attachments over the cycles applied. The speed of insertion/disinsertion was 0.5 Hz, applied constantly. Results: The clear nylon Locator® attachments registered the highest initial retention value (85.7 N), followed by the Dalbo-Ball® system (62.1 N) and pink nylon Locator® (49.6 N). After 5400 cycles, the mean force exerted was highest in the clear nylon Locator® attachments (42.3 N) followed by Dalbo-Ball® (34.3 N) and pink nylon Locator® (24.6 N). Conclusion: The initial retention force decreases over time for the attachment systems tested.