The Effect of Attachment Pick-up Timing on the Retention of Locator Overdenture Posts

The aim of this study was to evaluate the effect of the timing of pick-ups of retentive attachments on locator overdenture post retention. Forty-eight acrylic resin models of edentulous mandibles were prepared. A post space with a depth of 6 mm was drilled into 96 extracted, single-rooted teeth. In each model, two prepared roots were mounted in the canine position with 22 mm between them. The models were assigned to experimental and control groups (24 in each group). For the experimental group, 24 acrylic denture bases were fabricated on the resin models. Locator root posts were then luted into the post spaces using self-adhesive resin cement (RelyX Unicem). Retentive attachment pick-up was performed at two different times, either 15 minutes or 24 hours after locator post cementation. For the control group, there was no attachment pick-up, and the test was performed at either 15 minutes or 24 hours after cementation. Three screw-eye metal hooks were fixed to each acrylic base at the identical tripodal location to facilitate engaging the denture base to the load cell. After attachment pick-up, three braided chains (17 cm long) connected the metallic hooks of the denture bases to the load cell of the universal testing machine. A three-point vertical pull was employed 20 times. The dislodging forces were applied until displacement or separation of the specimens occurred. For both groups, each root/ matrix specimen was vertically secured in the universal testing machine (Instron, Model 8500 Plus Dynamic Testing System). The force required to dislodge the locator post was determined using pneumatic grips that grasped the locator post head along its long axis. The data were statistically analyzed using two-way ANOVA and Student’s t-test. The retention of the locator posts that were dislodged 24 hours after cementation was significantly higher than that of those dislodged 15 minutes after cementation in both the control and experimental groups (P<.05). There was a statistically significant difference in terms of post retention between the control and experimental groups for the locator posts tested after 15 minutes (P=.02). There was no significant difference between the control and experimental groups when tested at 24 hours (P=.274). It can be concluded that there was a significant increase in the retention of locator posts cemented with self-adhesive resin cement (RelyX Unicem) at 24 hours after cementation compared to that after 15 minutes. Attachment pick-up had a significant influence on the retention of the locator post at 15 minutes.