Background: The all-on-4 concept presents an ideal solution that enables using four dental implants placed in the inter-foraminal region to retain a prosthesis. This study aimed to compare the implant survival and bone loss of axial versus tilted distal implants in screw-retained prosthesis.
Methods: 28 Patients were randomly assigned into two groups; each group received four inter-foraminal implants; Group 1: received two axially placed anterior implants and two axially placed posterior implants. Group 2: received two axially placed anterior implants and two distally inclined posterior implants. All patients received screw-retained implant prosthesis. After a follow-up period of 2 years, implant survival was evaluated. Bone loss was measured at 6, 12, and 24 months.
Results: No implant losses were observed in both groups, representing a survival rate of 100%. Regarding marginal bone loss, there was no significant difference between anterior implants at 6, 12, and 24 months, with p-value of 0.931, 0.684, and 0.846, respectively. In addition, there was no significant difference between posterior implants at 6, 12, and 24 months with a p-value of 0.834, 0.765, and 0.904, respectively. Comparing anterior and posterior implants in group 1 at 6, 12, and 24 months showed no significant difference with p-value of 0.500, 0.464, and 0.500, respectively, and there was no significant difference in group 2 at 6, 12, and 24 months, with p-value of 0.456, 0.433, and 0.392, respectively.
Conclusion: The angulation of distal implants in all-on-4 mandibular screw-retained prosthesis does not influence implant survival or peri-implant marginal bone loss (MBL).