Introduction: The conventional treatment for completely edentulous patients is complete denture. But patients can have substantial difficulties using their conventional complete dentures due to a lack of retention, support, and stability and the related compromise in chewing ability. Endosseous implants have been shown to be a valuable rehabilitation for these patients. To enhance retention and stability of denture, various overdenture attachments systems can be used for mandibular implant overdentures.
Aim of the study: The aim of this study is to evaluate the retention of the prosthesis with different implant number and different attachment systems.
Materials and Methods: The model was used in two groups according to the number of implants. Group A model with two loaded implants in the canine region. Group B model with four loaded implants in the canine region and in the second premolar region. Each group was divided into three subgroups with different attachment systems positioner, bar & ball. Retention of attachments was evaluated by universal testing machine.

Results: It was observed that there was statistically significant difference between the different attachment systems, as bar attachment showed higher retentive force value with mean = 101.47 ± 25.04 compared with locator attachment with mean =55.53 ± 15.98 and ball attachment with mean = 52.71 ± 12.56. P value ≤ 0.05.
Conclusion: bar attachment group showed favourable retentive force compared with locator and ball attachment, and four implants overdenture showed higher retentive force compared with two implants overdenture.
Keywords: Implant overdenture, Bar attachment, Ball attachment, Locator attachment