Mohammed M Fouad^A; Ashraf A Gebril^B; Khaled M zahran^{C A}Prof.of Removable Prosthodontic ,Faculty of Dentistry ,Mansoura University ^BAssis. Prof. of Removable Prosthodontic ,Faculty of Dentistry ,Mansoura University ^CClinical demonstrator,Department of Removable ProsthodonticFaculty of Dentistry ,Mansoura University Abstract: Background: Minimizing rotational movements of implant assisted mandibular complete overdenture and load transfer to the surrounding bone depends mainly on the design of attachment and manner of loading by overdenture. Purpose: This study was conducted to compare, radiographically, the effect of two different design concepts utilizing anterior bar for retaining mandibular implant assisted complete overdenture on peri-implant alveolar bone height changes. Materials and Methods:Ten healthy completely edentulous male patients were selected for this study. All patients were classified randomly according to the design concept of the anterior bar retaining the implant assisted mandibular complete overdenture as follow: Group (I): where their implant assisted overdentures were constructed to be retained by anterior cantilvered bar with bilateral balls, Group (II): where Their implant assisted overdentures were constructed to be retained by anterior standard bar and two ball attachments screwed into two posterior fixtures in the first molar areas.Immediately, six (T1) and twelve months (T2) after definitive loading, peri-implant marginal bone height changes were evaluated using periapical digital radiograph. Results :The results of this study revealed a significant difference in bone loss around canine implants between the six months intervals and twelve months interval after mandibular overdenture insertion. In spite of a non-significant difference in bone loss was found between the two groups during the first 6 months, group (I) had a higher significant bone loss around canine implants than group (II) after the second six months of overdenture insertion. At the end of twelve months after overdenture insertion the peri-implant bone loss in group (I) was significantly higher than bone loss in group two around canine implants. Conclusions: Within the limitations of this study, it is possible to conclude that the four-implant assisted mandibular complete overdentures retained by standard anterior bar and bilateral ball attachments screwed into posterior implants can be considered a better design concept than two-implant assisted mandibular complete overdentures retained by anterior cantilevered bar with distal ball attachments, regarding the preservation of peri-implant marginal alveolar bone height.