Cementum
Main article: Cementum
Cementum is a specialized bony substance covering the root of a tooth.[13] It is approximately 45% inorganic material (mainly hydroxyapatite), 33% organic material (mainly collagen) and 22% water. Cementum is excreted by cementoblasts within the root of the tooth and is thickest at the root apex. Its coloration is yellowish and it is softer than either dentin or enamel. The principal role of cementum is to serve as a medium by which the periodontal ligaments can attach to the tooth for stability. At the cementoenamel junction, the cementum is acellular due to its lack of cellular components, and this acellular type covers at least ? of the root.[17] The more permeable form of cementum, cellular cementum, covers about ? of the root apex.[18]



Main article: Pulp (tooth)
The dental pulp is the central part of the tooth filled with soft connective tissue.[14] This tissue contains blood vessels and nerves that enter the tooth from a hole at the apex of the root.[19] Along the border between the dentin and the pulp are odontoblasts, which initiate the formation of dentin.[14] Other cells in the pulp include fibroblasts, preodontoblasts, macrophages and T lymphocytes.[20] The pulp is commonly called "the nerve" of the tooth.

Microdontia is a condition where teeth are smaller than the usual size, and macrodontia is where teeth are larger than the usual size. Microdontia of a single tooth is more likely to occur in a maxillary lateral incisor. The second most likely tooth to have microdontia are third molars. Macrodontia of all the teeth is known to occur in pituitary gigantism and pineal hyperplasia. It may also occur on one side of the face in cases of hemifacial hyperplasia.

Anodontia is the total lack of tooth development. Hyperdontia is the presence of a higher-than-normal number of teeth, where as Hypodontia is the lack of some teeth. Usually, hypodontia refers to the lack of development of one or more teeth, and oligodontia may be used to describe the absence of 6 or more teeth. Some systemic disorders which may result in hyperdontia include Apert syndrome, Cleidocranial dysostosis, Crouzon syndrome, Ehlers-Danlos syndrome, Gardner syndrome, and Sturge-Weber syndrome.[69] Some systemic disorders which may result in hypodontia include Crouzon syndrome, Ectodermal dysplasia, Ehlers-Danlos syndrome, and Gorlin syndrome.