The initial retention of implant-supported removable partial dentures(ISRPD) is unknown. the purpose of this in vitro study was to compare maximum dislodging forces of distal extension mandibular ISRPD with three different clasp design. a stimulated class 1 partially edentulous mandible was prepared with two implant in the first molar regions and two metal ceramic on distal abutments. Fifteen bilateral distal extension frameworks was fabricated with three different clasp design (Akers, I bar clasp ,no clasp),each specimen was subjected to three type of retention pulls ( main ,unilateral ,posterior pulls) five time with universal testing machine.