Effect of Leukocyte- and Platelet-Rich Fibrin on Peri-Implant Mucosal Thickness in Edentulous Patients Treated with Mandibular Implant-Retained Overdentures: A Randomized Controlled Trial

<b>Background/Objectives</b>: The maintenance of peri-implant soft tissue health is critical for the long-term success of implant therapy, particularly in edentulous patients rehabilitated with mandibular overdentures. Leukocyte- and platelet-rich fibrin (L-PRF) has been proposed as an autologous biomaterial to enhance peri-implant tissue quality. This randomized controlled clinical trial evaluated the effect of L-PRF on peri-implant mucosal thickness in edentulous patients treated with mandibular implant-retained overdentures. <b>Methods</b>: Edentulous patients received two interforaminal implants to retain a mandibular overdenture and were randomly assigned to a test group (L-PRF applied during surgery) or a control group (standard protocol without L-PRF). Clinical measurements of keratinized mucosal thickness and width were recorded at baseline, 12 weeks, and 24 weeks. Volumetric analyses of soft and hard tissue changes were performed using digital superimposition of STL models. The trial was conducted in accordance with the Declaration of Helsinki and approved by the Scientific Ethics Committee of the Aconcagua Health Service. All participants provided written informed consent. <b>Results</b>: A significant increase in keratinized mucosal thickness was observed in the L-PRF group at 12 and 24 weeks compared with baseline (<i>p</i> < 0.01). No significant differences were detected between the groups in soft tissue volume (<i>p</i> = 0.12) or bone volume (<i>p</i> = 0.45). Mucosal width remained stable in both groups throughout follow-up. <b>Conclusions</b>: The application of L-PRF at implant placement resulted in a significant gain in peri-implant mucosal thickness, suggesting a soft tissue modulating effect. Enhancing keratinized mucosal thickness during implant surgery may improve peri-implant tissue quality and support long-term stability of mandibular overdentures.