Influence of different lubricants on the retentive force of LOCATOR® attachments – anin vitropilot study

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The aim of this in vitro pilot study was to evaluate the influence of an artificial saliva (AS) lubricant on the retentive force of a stud-type attachment (LOCATOR®) for implant overdentures (IODs).


Twenty custom-made models simulating a two-IOD with parallel implant situation were fabricated using LOCATOR® attachments. The in vitro testing was carried out with an Instron® universal testing machine for a total of 10,000 insertion–removal cycles, for each model, in two different aqueous test mediums (Group 1: 0.9% sodium chloride solution (NaCl), n = 10; Group 2: AS, n = 10). Changes in the mean retentive force (F) were plotted against the cycle numbers #10, #100, #1000, #5000, and #10,000. Mixed regression models were applied for statistical analyses.


A mixed regression (not considering interactions) predicted, compared to cycle #10, higher retentive forces at cycles #100 (P < 0.0001), #1000 (P = 0.017), similar forces at #5000 (P = 0.277), and lower forces at #10,000 (P = 0.012); there was no overall effect of the medium (P = 0.159). A second statistical model, employing the interaction term “cycle##medium”, confirmed similarly the effect. Although the interaction term was significant at cycle #100 (p = 0.045), there was no significant difference between the two groups (P = 0.140).


In this in vitro pilot experiment, there was no difference in mean retentive forces of the LOCATOR® attachments when tested with either 0.9% NaCl or a Glandosane®-like artificial saliva lubricant. A larger scale study may still confirm the superiority of either lubricant for quasiclinical bench experiments.

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