Objectives: To assess the effect of three different diameters of ball/ socket attachments and inter-implant distances (IIDs) on the retention of 2 implants as compared with single implant retained mandibular overdentures.
Materials and Methods: Four transparent acrylic resin casts simulating a completely edentulous mandible were fabricated. The forces (N) needed to dislodge single and 2 implant retained mandibular overdentures were estimated by a universal testing machine. Four main groups were computed,12 subgroups; a single implant was placed in mid-line area with 3.5mm, 4mm and 4.5mmdiameter ball and socket attachments respectively and 2 implants with IIDs 25mm in the canine, 32mm in 1st premolar and 40mm in 2nd premolar regions connected to 3.5mm, 4mm and 4.5mm diameter ball/socket attachments respectively.
Results: Statistically significant differences were found between single implant with ball attachment diameters(3.5mm,4mmand 4.5mm), single implant at (4.5mm) and 2 implants at (3.5 mm) diameters, 2 implants with ball attachment diameters(3.5mm, 4mm and 4.5 mm) at (25mm and 32mm and 40mm) IIDs and (25mm and 32mm and 40mm) IIDs at (3.5mm and 4 mm)ball attachment diameters, P ≤ 0.05, but it was non-significant at 4.5mm ball attachment diameters, P > 0.05.The interactions between IIDs and the diameter of ball/ socket attachments were statistically non significant, P> 0.05.
Conclusion: Increasing both ball and socket attachment diameters and the inter-implant distances had positively influenced the retention of mandibular overdenture.