Khaled K. Khaled¹, Mohammed M.Fouad², Elsayed A. Abdel-khalek³and Mustafa A. Neamatallah^{4    1-Teaching assistant of Removable Prosthodontics, Faculty of Dentistry, Horus University, Egypt. 2-Professor of Removable Prosthodontics, Faculty of Dentistry, Mansoura University, Egypt. 3-Lecturer of Removable Prosthodontics, Faculty of Dentistry, Mansoura University,Egypt. 4-Associate Professor of Medical and Genetic Biochemistry, Faculty of Medicine, Mansoura University, Egypt.} Abstract: Background: Two implant assisted overdentures are affected by the resiliency of the mucosa and so the settlement period of mandibular complete denture may affect the preservation of immediately loaded implants. Aim: To compare between two different settling periods of mandibular complete denture before inserting the immediately loaded dental implants regarding the effect on the metabolic activity of the peri-implants tissues Materials and methods: Ten completely edentulous male patients of mean age 60 years participated in this study. All patients received conventional complete dentures. For all patients, After the setting period (2 weeks for group A and 4 weeks for group B), two single piece dental implants with ball attachment were inserted in the mandibular canine areas and then immediately loaded. The metabolic activity of peri-implant supporting structures was assessed by evaluating the Glycoseaminoglycans (GAG) and Condriotin 4 Sulphate (C4S) levels in the peri-implant sulcular fluid (PISF). Results Statistical analysis showed that (1) there were a highly statistical significant decrease (P ≤ 0.001) in the means of GAG and C4S levels for both groups during all intervals of study (2) It was revealed that, there was a statistically no significant difference for GAG levels in the PISF of both groups at all intervals of study (T= -.074, P=.942), (T=.997, P=.332) and (T= .938, P=.361)while for C4S, after both 2 days (T= 0.905, P=0.377) and 3 months (T= 0.933, P=0.363) anda more favorable bone reaction with a statistically significant decrease (P ≤ 0.05) of the C4S levelsin the PISF of the 4 weeks settling period group at the end of study (T=2.239 and P=0.038). Conclusion: A minimal 4 week settling period is more advantageous before inserting the immediately loaded implants used for assisting mandibular complete overdenture regarding the peri-implant tissue health. Recommendation: Further studies are recommended on more number of patients and using other methods of evaluation to determine the definite time of settling before inserting the immediately loaded implants used for assisting mandibular complete overdenture. Keywords: implant overdenture, immediate loading, denture settling, metabolic activity