Nabil Heba¹, Radwa M. K. Emera ², Habib A³, Abdel fadeel E ^{4 1}Clinical Demonstrator of removable Prosthodontics, Faculty of Dentistry, Mansoura University, Egypt ²Lecturer of Removable Prosthodontics, Faculty of Dentistry, Mansoura University, Egypt. ³Professor of removable Prosthodontics Faculty of Dentistry, Mansoura University, Egypt ⁴Assistant Professor of Oral Surgery, Faculty of Dentistry, Mansoura University, Egypt Abstract: Purpose:This study was carried out to compare the effect of two different bar attachments, milled-in bar and joint bar, splinting four mini dental implants to assist mandibular complete overdenture, regarding posterior residual alveolar ridge and peri-implant tissue health. Materials and Methods:Six healthy completely edentulous male patients were selected for this study. All patients were scheduled to receive maxillary complete dentures opposed by 4-Mini implants-assisted mandibular complete overdentures. Patients were randomly classified into two equal groups according to the design of the bar attachment as follows: Group (I) : where each patient received mandibular milled bar attachment design ;and Group (II): received joint  bar attachments . Peri-implant tissue health was evaluated on three observational periods (T0), 6 months after loading (T6) and 12 months (T12) after insertion. Peri-implant tissue evaluation were recorded for each implant using standard scores. Proportional area measurements were used to determine changes in the mandibular posterior residual ridge bilaterally after 12 months of denture insertion using panoramic radiographs. Results:There was a statistically significant difference in mandibular posterior residual ridge resorption between the two types of bar attachments. No statically significant difference was found regarding peri-implant tissue health. Conclusions:Milled-in bar splinting mini dental implant assisting mandibular overdenture appear to be associated with reduced posterior mandibular alveolar ridge resorption when compared to joint bar retaining mandibular overdenture over a period of 1 year.