The dental root forms when the hard substances of the crown are almost completely developed. External and internal enamel epithelia come together and form the epithelial root sheath (vagina radicalis epithelialis). The number of epithelial columns corresponds to the number of roots. In the region of the future tip of the root, the end of the root sheath bends centrally and forms a diaphragm (diaphragma vaginae radicis) which contains an opening (porus) through which vessels and nerves from the mesenchymal environment enter the dental papilla. When the root sheath grows into the mesenchyme, odontoblasts arise from the mesenchyme of this region and produce root dentin. The epithelial root sheath later disintegrates.
Cementoblasts differentiate in the internal layer of the dental sac (lamina cementoblastica) that faces the tooth primordium. They produce cementum, which is laid down on the root dentin. The cementum meets the enamel at the tooth neck. The alveolar bone arises from the external layer of the dental sac (lamina osteoblastica). The periodontium  develops from the intermediate part (lamina periodontoblastica). Collagenous periodontal fibres (Sharpey fibres) connect the alveolar bone with the cementum.