(A) Two weeks after implant insertion, a mid-labiolateral peri-implantitis lesion close to the previous radiolucent lesion of tooth 12 developed, and the implant showed percussion pain and slight mobility. (B) The labiolateral bone loss greater than 50% of the implant length was found. (C) Guided tissue regenerative procedures with xenograft, PepGen P-15 was packed around the peri-implant defect and covered by a piece of Bio-Mend, absorbable membrane. (D) Three weeks after the GBR procedure, the implant did not show any tenderness or mobility. The PepGen p-15 particulates appeared as radiopaque.