A structure that is involved in tooth formation. A bell shape two layer epithelial structure that descends toward the ceratobranchial 5 bone, enclosing the dental mesenchyme. At later times in tooth development the cells at the apex of the bell may be involved in enameloid formation. This structure remains at the base of the erupted tooth and is the source of replacement teeth. [ http://zfin.org/ZDB-PUB-001208-4 ORCiD:0000-0002-2244-7917 GOC:cvs ]