Effect of Distal Implant Inclination on Dislodging Forces of Different Locator Attachments Used for Mandibular Overdentures: An In Vitro Study

Purpose To evaluate the effect of distal implant inclination on axial and nonaxial retentive forces of different Locator attachments used to retain mandibular overdentures. Materials and methods Four duplicate mandibular edentulous acrylic models received 2 implants in the canine areas with 0 degrees, 5 degrees, 10 degrees, and 20 degrees distal inclinations. Experimental overdentures were connected to the implants with Locator extra light retention (Le), Locator light retention (Ll), and Locator medium retention (Lm). For the 20 degrees model, extended range Locator extra-light retention (Lee) and Locator medium retention (Lem) were used. Axial and nonaxial (anterior, posterior, lateral) retentive forces were measured initially and after 540 cycles of denture insertion and removal. Three-way mixed ANOVA was used to analyze axial and nonaxial retentive forces Results After wear simulation, 20 degrees angulation showed the highest axial retention for Le and Ll while 5 degrees showed the highest retention for Lm; 0 degrees and 5 degrees showed the highest anterior and posterior retention for Lm; 20 degrees showed the highest lateral retention for Le and Ll. For all implant inclinations, Lm showed the highest axial and nonaxial retention, and Le and Lee showed the lowest retention for 10 degrees and 20 degrees inclined implants, respectively. Conclusions Axial and nonaxial retention of Locator attachments for implant-retained overdentures are significantly affected by the degree of distal implant inclination and the type of nylon inserts. Lm is recommended to retain overdentures when implants have 5 degrees or 10 degrees distal inclination, and Le and Ll are recommended with 20 degrees inclination to maintain high axial and nonaxial retention after wear.