Objective: to evaluate the effect of bar and clip attachment systems with different materials on retention forces for two implant supported mandibular over dentures after wear simulation. Materials and methods: An edentulous mandibular model was constructed incorporating 2 parallel implants placed in the canine regions. Attachments were embedded in ametal-reinforced experimental over denture designed to be dislodged from the model by a universaltesting machine. Tensile dislodging force was applied to the overdenture at a cross-head speed of 50 mm/min. Four over dentures were constructed for the attachment systems. The attachments evaluated were metal bar with clip from polyoxymethylene (POM), metal bar with clip from polyetheretherketon (PEEK), (PEEK) bar with (POM) clip and(PEEK) barwith (PEEK) clip. Peak loadto-dislodgement was measured. Retention strength values (N) were recorded initially and after 270, 540, 810 and 1080 cycles of insertion and removal simulating 0, 3, 6, 9 and 12 months of denture using repictively. Repeated measure ANOVA was used to compare between more than two groups for dependent samples while One-way ANOVA was used to compare between more than two groups for independent samples. The significance level was set at P ≤ 0.