Purpose: This study aimed to assess the change in the maximum bite force of completely edentulous patients rehabilitated with thermoplastic acrylic complete denture after placement of single implant-retained mandibular overdentures. Materials and Methods: Sixteen completely edentulous patients with age ranged from 50-60 years were selected from removable prosthodontic clinics, faculty of dental medicine, Al-Azhar University. Each patient received a thermoplastic acrylic complete denture. Three months after a new denture placement, bite force was evaluated using an occlusal force meter (GM10, Nagano Keiki, Japan). Each patient received a mid-symphyseal single dental implant, 10 mm length and 3.7mm diameter (Dentis, Dalseo-gu, Daegu , Korea) placed at the midline of the mandibular alveolar ridge. Two weeks after overdenture placement, bite force was evaluated to assess the changes in bite force after a single implant placement. Results: Bite force was increased considerably after single implant placement. It was significantly higher than the bite force recorded with a conventional thermoplastic complete denture. Conclusion: It was concluded that using immediate loading single implant-retained mandibular overdentures resulted in considerable improvement of bite force in completely edentulous patients.Completely edentulous patients with complete dentures are experiencing various issues with their dentures, mostly regarding the mandibular denture, for example diminished stability and retention Codex : 08/21.