A

Three-walled intrabony defects retain the greatest amount of surrounding bone, giving superior blood supply, cell sources, and physical containment for a graft; consequently they show the highest levels of new bone and cementum formation compared with 2-wall, crater (2-wall), or hemiseptal (1-wall) defects [Kim et al., 2004, PMID 15068110; Ling & Lai, 1994, PMID 7982130].