Twelve implants with peri-implantitis underwent reentry flap surgery in five patients 6 to 96 months postregenerative surgery. This was necessary for additional treatment or new treatment of adjacent or other implants in close proximity to the original implant. Clinical measurements of the original depth of bone lesions ranged from 3 to 12 mm. Bone fill occurred around all implants and ranged from 2 to 9 mm, representing 40% to 100% of the original defect depth. These direct bony measurements support radiographic and sounding data in a previous report that recorded a mean of over 3 mm of bone fill in the defects treated with the specific regenerative approach used in this study. The results of this clinical series are encouraging; however, histologic research is necessary to determine if reosseointegration occurred, with direct visual evidence suggesting new bone formation, and more multicenter studies are needed to verify the results. (Int J Periodontics Restorative Dent 2014;34:47-59. doi: 10.11607/prd.1904)