Dental papilla

In embryology and prenatal development, the dental papilla is a condensation of ectomesenchymal cells called odontoblasts, seen in histologic sections of a developing tooth. It lies below a cellular aggregation known as the enamel organ. The dental papilla appears after 8–10 weeks intra uteral life. The dental papilla gives rise to the dentin and pulp of a tooth. In embryology and prenatal development, the dental papilla is a condensation of ectomesenchymal cells called odontoblasts, seen in histologic sections of a developing tooth. It lies below a cellular aggregation known as the enamel organ. The dental papilla appears after 8–10 weeks intra uteral life. The dental papilla gives rise to the dentin and pulp of a tooth. The enamel organ, dental papilla, and dental follicle together forms one unit, called the tooth germ. This is of importance because all the tissues of a tooth and its supporting structures form from these distinct cellular aggregations. Similar to dental follicle, the dental papilla has a very rich blood supply and provides nutrition to the enamel organ. Formation of dental papilla occurs in the Cap stage of Odontogenesis. The cap stage is the third stage of tooth development and occurs during the ninth or tenth week of prenatal development. Unequal proliferation of the tooth bud forms a three-dimensional cap shape. Overlying this cap structure is the ectomesenchyme, which is attached to the mesodermal tissue known as the dental papilla superiorly, and lies within the epithelial concavity. Various types of differentiation occur at this stage; such as cytodifferentiation, histodifferentiation and morphodifferentation. Histodifferentiation is the differentiation of different tissue types during the development of an embryo/ undifferentiated group of cells. Furthermore, morphogenesis is a predominant physiological process during the cap stage. This is due to formation of primordium of the tooth. The primordium contains each of the primordial tissue types, essential for the development of successive teeth. These primordial tissues together form the enamel organ, dental papilla and dental sac. Also during the cap stage is the formation of a depression within the deepest part of each tooth bud of the dental lamina. The dental lamina is a band of epithelial tissue which connects the developing tooth bud to the oral epithelium. The dental lamina eventually disintegrates into small clusters of epithelium and is reabsorbed. The dental lamina is first evidence of tooth development and begins at the sixth week in utero. This is responsible for the cap like structure of the enamel organ. It is important to note that enamel is an ectodermal product as it is originally derived from ectoderm which is the outermost of the three germ layers of the forming embryo. The other two are: the mesoderm and the endoderm. It gives rise to the nervous system, sense organs, outer layer of the skin, teeth and the membrane lining the oral cavity (mouth). A section of the ectomesenchyme (a group of tissue made up of neurocrest cells which are present in the initial development of an embryo. This forms the hard and soft tissues of the neck and skull), condenses into a mass within the concavity of the cap of the enamel organ. This mass is now considered the dental papilla. Note that dental papilla is originally derived from ectomesenchyme. Ectomesenchyme (type of mesenchyme) is derived from neural crest cells (NCCs). A basement membrane exists between the enamel organ and dental papilla which will be the site of the future dentinoenamel junction. The dentinoenamel junction is the surface at which the enamel and the dentin of the crown of a tooth are joined. The existing ectomesenchyme around the outside of the cap of the enamel organ then condenses into the dental sac. A basement membrane separate the enamel organ and the dental sac. The dental sac produces the periodontium in future development. The periodontium is the tissue that surrounds and supports the teeth. It includes the connective tissue and overlying keratinised membrane lining the oral cavity that surrounds the teeth, the periodontal ligament, cementum which provides a protective covering for the root surface and supporting alveolar bone