Objectives : To compare the influence of platform switched and matched implants on supporting structures of mandibular overdenture by measuring marginal bone loss (MBL) and soft tissue changes including probing depth and implant stability. Material and Methods: Twenty completely edentulous patients age 50-60 years were selected for this longitudinal study. Complete dentures were performed for all patients, they were divided randomly into 2 groups; 10 patients each. The first group obtained 2 platform switched implants while the second group obtained two platform matched implants (3.6 × 11.5 mm) in the canine areas of the mandible. Radiographic measures were performed every 12 months for 3 years while clinical measures were made every 6 months for 3 years for each group. Data was examined by student's t-test and paired t-test. Results: The mean age of patients was 54 ±3.3 years. No statistically significant difference was observed in MBL between mandibular overdentures supported by 2 platform switched and that supported by 2 platform matched implants (p≥0.05). Also, there were no statistically significant differences in pocket depth or implant mobility between two studied groups after 1, 2 and 3 years follow up (p≥0.05). Conclusions: Platform switching appears to not influence marginal bone loss around implants or soft tissue in two implants supported mandibular overdentures.

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.