Apicoectomy and retrograde filling. Oral Surgery Photos. 1) Upper left lateral incisor tooth shown with gum tissue reflected. 2) Initial penetration through cortical bone. 3) Tooth apex located. 4) Tooth root after sectioning off the apex. 5) Application of Mineral Trioxide Aggregate (MTA) retrograde filling material. 6) - 7) MTA in place. 8) Closure. Also see: Infection.