FINE STRUCTURES OF THE DENTAL PULP
The dental pulp is the soft tissue of the tooth, which develops from the connective tissue of the dental papilla. Within the crown, the chamber containing the dental pulp is called the pulp chamber. The pulp contains blood vessels and nerves that enter through the apical foramen. The coronal pulp is within the crown. Within the root is the radicular pulp.
Each person has a total of 52 pulp organs, 32 in the permanent and 20 in the primary teeth. The total volumes of all the permanent teeth organs is 0.38cc and the mean volume of a single adult human pulp is 0.02cc. Maxillary central incisor has shovel shaped coronal pulp with three short horns on the coronal roof and triangular in cross section. Cuspid has the longest pulp with elliptical cross section. Crowns of the teeth contain coronal pulp.
The coronal pulp has six surfaces: the occlusal, the mesial, the buccal, the lingual and the floor. Because of continuous deposition of dentin, the pulp becomes smaller with age. This is not uniform throughout the coronal pulp but progresses faster on the floor than on the roof or side walls. Radicular pulp is that pulp extending from the cervical region of the crown to the root apex. They are not always straight but vary in shape , size and number.
The radicular portion is continuous with the periapical tissues through the apical foramen or foramina. Apical foramen is the opening of the radicular pulp into the periapical connective tissue. The average size is 0.3 to 0.4 mm in diameter. There can be two or more foramina separated by a portion of dentin and cementum or by cementum only. Most infections spread through the apical foramen from the periapical tissue to the pulp or from the pulp to periapical tissue. 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.
Interrelationship of nerves and blood vessels can be studied in the dental pulp with little interference from other tissue elements. Pulp tissue contains numerous nerves and vessels of varying size suspended in a fibrous and sparsely cellular gelatinous matrix. Graf made a quantitative study of the types of nerves in the human dental pulp and reported that a pulp cross section contains approximately one thousand separate nerve fibers, varying between 1 and 10 in diameter. The maximum size of arterioles in dental pulp has been measured by Provenza, who reported diameters ranging up to 100. The adventitia of the arterioles, metaarterioles, and precapillaries were obliterated by dense bundles of nerve fibers and by the adjacent interstitial tissue.
Smooth nerval innervation by autonomic fibers is generally described by light microscopists as a plexus of unmyelinated nerves that terminate on the surface or within the sarcoplasm of the muscle fibers. Connection between the nervous and muscular elements in mammalian urinary bladder and in the ureters were examined with the electron microscope by Geaser. These neuromuscular structures consisted of simple contacts between the cytolemma of the smooth muscle and the lemnoblast of autonomic fibers. Smooth muscle tissue in these preparations was seen to be cellular and no evidence was obtained in support of a syncytial arrangement.
Electrophysiologic and pharmacologic data indicate the vasomotor rule of the autonomic fibres, but they do not indicate the morphologic basis for the vasodilator and vasoconstrictor mechanisms. Data have been collected in this laboratory which indicates the presence of sympathetic vasoconstrictor fibers in the mandibular nerve.
The present investigation utilizes the electron microscope for the study of structures in the dental pulp and particularly emphasizes the blood vessel nerve complex. The fine structure of nerve types was examined in an attempt to define the structures which mediate vasomotor tone.
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