To compare in-vivo conventional 4 parallelimplant placement and bar attachment with cantilever supporting complete overdenture with All-on four configuration supporting fixed screw-retained denture in the term of crestal bone loss around implants Materials and methods:Twelve male patients with good health and firm mucosa were selected to participate in this study. Each patient received four implants in the canine and second premolar areas of the mandible. The patients were randomly classified according to posterior implants angulation into two equal groups,Group(A) received four parallel implants in the canine and second premolar areas, bar-clip attachment with cantilever retaining complete overdenture while Group(B) recievedTwo anterior parallel implants in the canine region and two posteriorly 30° tilted implants in the second premolar area supporting fixed screw retained prosthesis. Crestal bone loss around implants was measured for each patient by using cone beam computed tomography (CBCT) and evaluation made at T6 and T12 Results:Therewassignificantdifference during comparing Marginal bone loss at 6 months with that of 12 months at mesial, distal, buccal and palatal bone for Group (A)(P=0.01, 0.025, 0.0001 and 0.007 respectively) and Group (B) (P=0.03, 0.028, 0.007 and 0.001 respectively). Comparing the two groups, there was no statistical difference at 6 months or 12 months. Conclusion: Despite the limitations in this study, it can be denoted than both treatment options provide the same values of marginal bone loss Only the patient desire is still the contributing factor for choosing the type of restoration, if the patient desire fixed prosthesis with reduced extensions then treatment option used for group(B) (fixed detachable prosthesis screwed to four implants with the posterior implants tilted 30° posteriorly) however when access for oral hygiene measures is more important with patients that cant maintain hygiene with fixed prosthesis, then the selection of group (A) will be more appropriate.