Available online 25 November 2019
Statement of problem
The LOCATOR system has been widely used for 2-implant-retained mandibular overdentures (2-MOs), but the influence of different LOCATOR attachments on the stability of 2-MOs has not been assessed.
The purpose of this in vitro study was to investigate the stability of 2-MOs anchored by LOCATOR attachments with different retentive forces.
Material and methods
An edentulous mandibular test cast with 2 bone-level implants inserted in the left and right mandibular canine regions was used. Twelve overdentures were then fabricated and anchored on the cast, following the instructions of the LOCATOR system. By replacing inserts of the 12 overdentures, the stability of 3 groups of LOCATOR inserts with different retentive forces was evaluated: blue group, pink group, and transparent group. With artificial saliva used on the cast and overdentures, vertical forces of 40 N, 55 N, and 100 N were loaded on the occlusal surface of the left incisor, left canine, and left molar, respectively. Under each loading condition, the vertical displacements at the loading point and the vertical and horizontal displacements of overdentures at the right distal edge were measured at the same time. One-way ANOVA and the post hoc Tukey honestly significant difference (HSD) test were used to compare the stability of 2-MOs with different LOCATOR attachments (α=.05 for all tests).
When a force of 40 N was applied to the incisor, the largest vertical movement of the incisor loading point appeared in the blue group (P<.05), and the displacements of the pink group showed significant difference from those of the transparent group (P>.05). When 55 N was loaded on the canine, the blue group showed the largest vertical displacements of both the loading point and the right distal edge of the overdentures (P<.05). No significant difference was found in the vertical displacements between the pink group and the transparent group (P>.05). When a force of 100 N was loaded on the molar point, the transparent group indicated a smaller movement in the vertical direction at the edge of the overdentures than the blue group (P<.05) or the pink group (P<.05).
LOCATOR attachments with different retentive forces had a significant effect on the denture stability of 2-MOs. Compared with the blue inserts, the pink and transparent inserts can offer greater stability for 2-MOs and could therefore be suggested for clinical situations.
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