Purpose: The aim was to compare the effect of using different number of implants (two and four implants) on marginal bone loss around implant in implant –bar supported mandibular overdenture.
Material and methods: Twelve edentulous patients were randomly divided into two groups. Group I received two implants-bar supported overdenture while group II received 4 Implants-bar supported overdenture. Fixtures were surgically inserted with its top level 0.5mm below the crestal bone level. Each patient was recalled two months after implant insertion for superstructure placement.
Crestal bone loss around the implants were measured on CBCT images taken at time of final prosthesis pick-up, 3 months, 6 months and 12 months after overdenture pickup. Repeated-measure ANOVA with Tukey post hoc test was used to compare between the two groups at the different time points.
Results: There was a significant main effect of time on bone resorption (p < 0.001). however, there was no significant main effect of group on bone resorption (p= 0.132). There was no significant interaction between time and group. Multiple comparisons showed a significant difference between the baseline and 12 month time point in each group (p=0.006 and p=0.041, respectively). Also, there was a significant difference in bone resorption between the two groups at 12 month time point (p=0.044).
Conclusion: Four implants-bar supported overdenture provided better preservation of marginal bone than two implants-bar supported overdenture. Therefore, its recommended for clinicians to consider the design of four implants-bar supported overdenture specially when the bone of jaw is compromised.