The cells of cementum are the entrapped cementoblasts, the cementocytes. Illustrated dental embryology histology and anatomy pdf free download lacunae also have canaliculi or canals. Unlike those in bone, however, these canals in cementum do not contain nerves, nor do they radiate outward. Instead, the canals are oriented toward the periodontal ligament and contain cementocytic processes that exist to diffuse nutrients from the ligament because it is vascularized.
After the apposition of cementum in layers, the cementoblasts that do not become entrapped in cementum line up along the cemental surface along the length of the outer covering of the periodontal ligament. These cementoblasts can form subsequent layers of cementum if the tooth is injured. Three possible types of transitional interfaces may be present at the CEJ. The traditional view was that certain interfaces dominated in certain oral cavities. The CEJ may exhibit all of these interfaces in an individual’s oral cavity, and there is even considerable variation when one tooth is traced circumferentially. When the cementoid reaches the full thickness needed, the cementoid surrounding the cementocytes becomes mineralized, or matured, and is then considered cementum. It has the highest fluoride content of all mineralized tissue.
Cementum also is permeable to a variety of materials. It is formed continuously throughout life because a new layer of cementum is deposited to keep the attachment intact as the superficial layer of cementum ages. Cementum on the root ends surrounds the apical foramen and may extend slightly onto the inner wall of the pulp canal. Cementum is capable of repairing itself to a limited degree and is not resorbed under normal conditions.
When cementum is exposed through gingival recession, it quickly undergoes abrasion by mechanical friction because of its low mineral content and thinness. The exposure of the deeper dentin can lead to problems such as extrinsic staining and dentinal hypersensitivity. The incidence of cemental caries increases in older adults as gingival decline occurs from either trauma or periodontal illness. It is a chronic condition that forms a large, shallow lesion and slowly invades first the root’s cementum and then dentin to cause a chronic infection of the pulp. Because dental pain is a late finding, many lesions are not detected early, resulting in restorative obstacles and increased tooth loss. Cemental spurs can be found at or near the CEJ. These are symmetrical spheres of cementum attached to the cemental root surface, similar to enamel pearls.
Cemental spurs result from irregular deposition of cementum on the root. Teeth are increasingly utilized as a source of nuclear DNA to aid identification of human remains. DNA extraction and the results of genetic analysis from the tissue are extremely variable and to some extent unpredictable. However, the quantity of DNA available in dentin is affected by age and dental disease, whereas that in cementum is not. Illustrated Dental Embryology, Histology, and Anatomy, Bath-Balogh and Fehrenbach, Elsevier, 2011, page 170. University of Pennsylvania and Temple University.
Survival and recovery of DNA from ancient teeth and bones”. Dentine and cementum as sources of nuclear DNA for use in human identification”. This page was last edited on 11 January 2018, at 00:28. Unsourced material may be challenged and removed. The vitality of the dentin-pulp complex, both during health and after injury, depends on pulp cell activity and the signaling processes that regulate the cell’s behavior.
Pulps of two extracted, not fully developed wisdom teeth, photographed from below. The pulp is the neurovascular bundle central to each tooth, permanent or primary. It comprises a central pulp chamber, pulp horns and radicular canals. The large mass of pulp is contained within the pulp chamber, which is contained in and mimics the overall shape of the crown of the tooth. This is not uniform throughout the coronal pulp but progresses faster on the floor than on the roof or side walls. Radicular pulp canals extend down from the cervical region of the crown to the root apex. They are not always straight but vary in shape, size and number.
38cc and the mean volume of a single adult human pulp is 0. Accessory canals are pathways from the radicular pulp, extending laterally through the dentin to the periodontal tissue seen especially in the apical third of the root. Accessory canals are also called lateral canals, because they are usually located on the lateral surface of the roots of the teeth. The pulp has a background similar to that of dentin, because both are derived from the dental papilla of the tooth germ. During odontogenesis, when the dentin forms around the dental papilla, the innermost tissue is considered pulp. The central region of the coronal and radicular pulp contains large nerve trunks and blood vessels.
The nerve plexus of Raschkow is located central to the cell-rich zone. The plexus of Raschkow monitors painful sensations. By virtue of their peptide content they also play important functions in inflammatory events and subsequent tissue repair. There are two types of nerve fiber that mediate the sensation of pain: A-fibers conduct rapid and sharp pain sensations and belong to the myelinated group, whereas C-fibers are involved in dull aching pain and are thinner and unmyelinated. The A-fibers, mainly of the A-delta type, are preferentially located in the periphery of the pulp, where they are in close association with the odontoblasts and extend fibers to many but not all dentinal tubules.