Objectives: The aim of this study was the assessment and comparison of Oral Health-Related Quality of Life (OHRQoL) with maxillary and mandibular Dentures supported by four implants inserted according to ‘All-on-Four^® Concept (fixed dentures versus milled bar overdentures) Materials and methods: Six edentulous patients were selected, each patient received four implants in the maxilla and four implants in the mandible; two implants in canine area and two implants in second premolar area. Three patients received implant supported screw-retrained fixed prosthesis and the other three patients received a milled-bar overdenture. (Oral Health-Related Quality of Life) “OHRQoL" evaluation by OHIP-14 questionnaire consisted of 14-items divided into seven domains: functional limitation, physical pain, psychological discomfort, physical disability, psychological disability, social disability, and handicap. Results: Comparing OHIP scores for all questions (items) for all groups, there was a significant difference in all questions of OHIP between groups except question 12 (difficulty in doing jobs). Comparing OHIP scores for all domains and total OHIP score for all groups, there was a significant difference in all domains and in total OHIP score between groups. In multiple comparison between each 2 groups there was a significant difference between CD and FP and between CD and MB for all items, all domains and total OHIP score. However, no significant difference was noted between FP and MB for all items, all domains and total OHIP score