Effect of Labial Implant Inclination on the Retention and Stability of Different Resilient Stud Attachments for Mandibular Implant Overdentures: An In Vitro Study

Purpose: This study evaluated the influence of labial implant inclination on the retention and stability of different resilient stud attachments for mandibular implant overdentures. Materials and Methods: Four identical mandibular edentulous acrylic resin models were fabricated. For each model, two implants were inserted at the canine areas with different degrees of labial inclination: 0, 10, 20, and 30 degrees. Four experimental overdentures were fabricated over the models and fitted to the implants using resilient stud attachments. Regular retentive inserts (extra-light, light, and medium retention) were used for all implant inclinations, and extended-range inserts (extra-light and medium retention) were used for 30-degree inclination only. Vertical (retention) and oblique (stability) dislodging forces (lateral, anterior, and posterior) were evaluated initially (initial retention) and after overdenture insertion and removal (final retention). Results: After repeated insertions and removals, 30-degree inclination recorded the highest retention and lateral stability, and 0 degrees recorded the highest posterior stability; 20 degrees showed the lowest retention, and 30 degrees recorded the lowest posterior stability. The highest stability and retention values were recorded with light and medium regular inserts, and the lowest values were noted with extra-light regular inserts. Conclusion: Within the limits of this study, moderate labial implant inclination (10 degrees and 20 degrees) was shown to negatively affect retention and anterior/lateral stability, and excessive implant inclination (30 degrees) to negatively affect posterior stability. When implants are inclined labially, it is recommended to use light and medium regular stud attachments to obtain high levels of retention and stability for two-implant-retained overdentures. Keywords: attachment, implant, inclination, Locator, overdenture, retention, stud