The Influence of Interimplant Divergence on the Retention Characteristics of Locator Attachments, a Laboratory Study

Purpose: The aim of the study was to assess the influence of interimplant divergence on retention of two Locator attachments before and after in vitro simulation of 3 to 5 years of use.

Materials And Methods: A hydraulic universal testing machine was used to measure the retention of two blue Locator attachments during 5500 seating and unseating cycles. Ten pairs of Locators were tested with interimplant divergences of 0°, 10°, and 20°. Scanning electron microscopy (SEM) was used to examine surface changes of the components. The results were tested with ANOVA and Bonferroni post hoc correction when normally distributed. Results that were not normally distributed were tested with Kruskal-Wallis one-way ANOVA by ranks.

Results: At the start of the experiment the 10° group showed significantly more retention than the 0° group, but no significant difference was found between the 0° and 20° groups or the 10° and 20° groups. After 5500 cycles, there was no significant difference in retention between any of the groups. The SEM images showed an approximately equal amount of wear in the nylon patrix inserts from all the groups.

Conclusions: The retention of Locator pairs was not impaired by interimplant divergence of up to 20°. Retention after 5500 removal cycles was less than the initial retention in all groups. The nylon Locator patrices showed wear defects of similar location, type, and magnitude in the SEM images, regardless of interimplant angulation.