Aim of the study: This in vitro study aimed to compare the retention  force for the maxillary overdentures retained with five dummy mini-dental implant with full coverage palatal overdenture versus palateless overdenture, with O-ring attachment, on model with V- shaped palatal vault. Materials and methods: Tranceparent prefabricated maxillary acrylic resin model was used for this study.Two mini-dental implants with O-ring attachment were  placed on canine region and another two implants were placed on second premolarregion, in addion to one implant was placed silently mesial to the right central area of the same model. One palatless implant retained overdenture, and one full coverage implant retained overdenture  were constructed on the model. Both of them, retention and cyclic fatigue tests of each overdenture was measured using BENDAO tools of the universal testing machine and average reading were calculated. Results: It was found that Conventional group, recorded higher retention means value (25.55 ± 2.17 N) than Palateless group (24.215 ± 3.64 N).And the cyclic fatigue test for the Conventionalgroup Showed that the retention decreased significantly with time as indicated by ANOVA test (p <0.05),and for Palatelessgroup it was found that the retention decreased significantly with time as indicated by ANOVA test (p <0.05).