Influence of implant angulation and cyclic dislodging on the retentive force of two different overdenture attachments – an <i>in vitro</i> study

<jats:title>Abstract</jats:title><jats:sec><jats:title>Objective</jats:title><jats:p>This <jats:italic>in vitro</jats:italic> study evaluated the influence of implant angulations on the retentive behavior of two overdenture attachments during cyclic dislodging.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>Models simulating a two‐implant overdenture situation were fabricated. They were divided into five groups based on their simulated implant angulations (Groups: 1 = 0°; 2 = 20°; 3 = 30°; 4 = 40°; and 5 = 60°; <jats:italic>n</jats:italic> = 90). Each group was further divided into two subgroups based on its attachment system (control attachment: <jats:styled-content style="fixed-case">LOCATOR</jats:styled-content><jats:sup>®</jats:sup>; test attachment: <jats:styled-content style="fixed-case">SFI</jats:styled-content>‐Anchor<jats:sup>®</jats:sup>) except for group 5 which had no <jats:styled-content style="fixed-case">LOCATOR</jats:styled-content><jats:sup>®</jats:sup> group. All models underwent 10,000 insertion–removal cycles in a wet environment. Mean retentive forces were recorded. <jats:styled-content style="fixed-case">ANOVA</jats:styled-content> and linear regression models were used for statistical analyses, and the level of significance was at <jats:italic>P </jats:italic><<jats:italic> </jats:italic>0.05.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>The <jats:styled-content style="fixed-case">ANOVA</jats:styled-content> model revealed an effect of dislodging cycles for both attachments (<jats:italic>P </jats:italic>=<jats:italic> </jats:italic>0.0070). The linear regression model with repeated measures revealed a significant effect of angulation within the <jats:styled-content style="fixed-case">LOCATOR</jats:styled-content><jats:sup>®</jats:sup> groups (0° vs. 20°: <jats:italic>P </jats:italic><<jats:italic> </jats:italic>0.0001; 0° vs. 30°: <jats:italic>P </jats:italic><<jats:italic> </jats:italic>0.0001; 0° vs. 40°: <jats:italic>P </jats:italic><<jats:italic> </jats:italic>0.0001), but was insignificant within the <jats:styled-content style="fixed-case">SFI</jats:styled-content>‐Anchor<jats:sup>®</jats:sup> groups (0° vs. 20°: <jats:italic>P </jats:italic>=<jats:italic> </jats:italic>0.544; 0° vs. 30°: <jats:italic>P </jats:italic>=<jats:italic> </jats:italic>0.134; 0° vs. 40°: <jats:italic>P </jats:italic>=<jats:italic> </jats:italic>0.254; 0° vs. 60°: <jats:italic>P </jats:italic>=<jats:italic> </jats:italic>0.979). It further revealed a significant increase in the retentive force between the <jats:styled-content style="fixed-case">LOCATOR</jats:styled-content><jats:sup>®</jats:sup> and the <jats:styled-content style="fixed-case">SFI</jats:styled-content>‐Anchor<jats:sup>®</jats:sup> (20°: <jats:italic>P </jats:italic>=<jats:italic> </jats:italic>0.041; 30°: <jats:italic>P </jats:italic><<jats:italic> </jats:italic>0.0001; 40°: <jats:italic>P </jats:italic><<jats:italic> </jats:italic>0.0001), although there was no significant difference between the attachments at 0° (<jats:italic>P </jats:italic>=<jats:italic> </jats:italic>0.623).</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>This study confirms that the retentive behavior of <jats:styled-content style="fixed-case">SFI</jats:styled-content>‐Anchor<jats:sup>®</jats:sup> is not influenced by implant axial inclination even at angulations of up to 60°. The <jats:styled-content style="fixed-case">SFI</jats:styled-content>‐Anchor<jats:sup>®</jats:sup> may therefore be particularly indicated for clinical situations with marked implant axial discrepancies.</jats:p></jats:sec>