Objectives: Assessment of post-operative pain, swelling and trismus at various time intervals; measurement of the periodontal health distal to mandibular second molar at various time intervals; measurement of bone density at the site of extraction. Subjects and Methods: 60 patients were divided into two groups; each group contains 30 patients. Group A: the extraction socket received fresh autologous PRF with plaster of paris (POP) immediately after removal of the impacted mandibular third molar tooth and before suturing of the mucoperiosteal flap. Group B: the extraction socket received the fresh autologous PRF alone immediately after removal of the impacted mandibular third molar and before suturing of the mucoperiosteal flap. Follow up and evaluation were done in both groups for pain, swelling, healing, trismus and bone density. Results: our results showed that Group A had a significant decrease in the post-operative complications pian, swelling and trismus compared to group B. It also showed that group A had a significant increase in both periodontal health and bone density compared to group B. Conclusion: The use of PRF with POP within sockets of extraction impacted third molars proved to be effective for patients in decreasing the post-operative complications pain, swelling and trismus as well as increasing the periodontal health and bone density after removal of impacted lower third molar tooth.