Locator retention: does variation in number and configuration matter?

This pilot study was designed to collect initial data on overdenture attachment retention in varying configurations of attachment location in an implant-retained mandibular overdenture. A clear acrylic model of a mandible with 6 numbered implants and Locator resilient abutments was used to simulate implant placement in a patient. A clear acrylic denture was fabricated with 6 Locator housings to match the implants in the model. Attachments were tested in 4 different configurations: 2 implants, 2 and 5 (T25); 4 implants, 2-5 (T2345); 4 implants, 1, 3, 4, and 6 (T1346); and 6 implants, 1-6 (T1-6). Clear nylon male inserts were used for each test. The mean overall retentive strength across all 20 pulls was 576.0 N for configuration T1-6, 354.9 N for configuration T1346, 350.7 N for configuration T2345, and 189.9 N for configuration T25. Mean retentive strength also stabilized after the 7th pull for all 4 configurations, resulting in nonsignificant declines in retentive strength within each specific configuration after 7 pulls. Configuration T1-6 exhibited the greatest retentive strength relative to all other configurations both initially and after repeated application of force. Configurations T1346 and T2345 had similar retentive strengths, and both had greater retentive strength than T25. However, despite these differences, all 4 configurations exhibited similar losses in retentive strength from the repeated application of force during the first 7 pulls until stabilization occurred shortly thereafter.