AIM: The purpose of this research was to examine the effect of locator attachment versus retention silicone lining material on the supporting structure and retention of a single midline implant supporting mandibular overdenture. METHODS: Sixteen patients with completely edentulous mandibles were selected for this study and divided into two groups. In all patients, a single implant was placed at midline area after cone-beam radiography was performed. Group I was retained with locator attachment, while Group II was retained with silicone material. Follow-up was carried out at denture insertion, 6 months and 12 months following insertion. Peri-implant bone loss as well as posterior bone loss was evaluated using cone-beam computerized tomography and retention was evaluated using force meter device and wire hook attaches to the prosthesis. RESULTS: There was a statistically significant difference in peri-implant bone loss between the two groups at the 2nd follow-up period and at the end of the study period (p ≤ 0.05). There was no statistically significant difference in posterior bone loss between the two studied groups (p ≤ 0.05) and regarding retention that there was no statistically significant difference between the two groups along the follow-up periods. CONCLUSION: From the results obtained from this study, it could be concluded that locator attachment showed lower peri-implant bone loss than retention silicone liner in the overall follow-up period with a statistically significant difference. This was attributed to the decrease in the effect of the resiliency of retention silicone liner over time and the more permanent effect of locator attachment.