The distribution of nerves in human primary teeth

Abstract

Human primary teeth in the stages of late root formation, mot completion and root resorption were impregnated with silver to allow study of the distribution of nerves in the pulp.Neural trunks composed of many individual, myelinated nerve fibers enter the apical foramen of primary teeth and pass in a coronal direction, often in close association with blood vessels. Neural trunks in the crowns of the teeth divide into smaller branches, which divide further into myelinated nerve fibers, which become interwoven to form the parietal layer (plexus of Raschkow). An occasional unmyelinated fiber leaves this zone and passes into the odontoblastic layer of cells where it appears to terminate with no specialized ending apparent. No nerves were seen to enter the predentin or dentin.As primary teeth begin to undergo root resorption, degenerative changes such as thickenings, varicosities and fragmentation appear in the nerves. The quantity of neural tissue also decreases. The greater the amount of resorption, the greater are the degenerative changes. In teeth in which the roots are almost completely resorbed, only a small number of nerves remain.The pattern of distribution of nerves in primary teeth is observed to be similar to that of permanent teeth. The density of the innervation of the primary teeth, however, is not found to be as great as that of permanent teeth.The innervation of human primary teeth has received little attention when compared to similar research on permanent teeth. The lack of interest in the distribution of pulpal nerves in the primary dentition may result from the belief that the pulps are similar to those of permanent teeth or that primary teeth are not a lasting component of the oral cavity. Clinicians have long been aware of a lower sensitivity to pain in primary teeth than in permanent teeth which may be due to differences in number and/or distribution of their neural components. Another area in which information is lacking involves changes in the neural tissue of the primary teeth during the period of root resorption (and exfoliation). The present investigation is concerned, therefore, with the distribution of nerves in primary teeth during stages of root formation, root completion, and root resorption.Bradlaw ('36) studied neural degenerative changes in both human and animal primary teeth using a variety of silver impregnation techniques. He observed these changes to occur prior to exfoliation in some teeth but not in others. Mohuiddin ('50) studied the primary and permanent teeth of the cat by means of both the Romanes' and Bielschowsky silver methods. The permanent and nonresorbing primary teeth exhibited patterns of innervation similar to those observed for human permanent teeth by Rapp, Avery and Rector ('51). All of these investigators observed neural fibers within the pulp to form arborizations or a parietal layer (plexus of Raschkow) adjacent to the dentin and then terminate between or among the odontoblasts. A few nerves were found in the predentin and dentin, but none were obse...

Comparative Gene Expression Analysis of the Human Periodontal Ligament in Deciduous and Permanent Teeth

“…ARPP21 is enriched in the caudate nucleus and cerebellar cortex, and regulates the effects of dopamine [74]. Although we were unable to determine the precise function of these genes, the up-regulation of genes related to neurological system processes in permanent PDL tissues is consistent with the degree of innervation being lower for deciduous incisors and canines than for permanent premolars [3], [75], [76].…”

Scaffold-free microtissues: differences from monolayer cultures and their potential in bone tissue engineering

“…However, historically, dentin hypersensitivity has been a useful term as it has described a distinct clinical entity familiar to the dental profession [13]. Some individuals also experience a vague dull, throbbing ache, persisting for variable periods of time after the stimulus has been removed [19]. Whilst this pain sensation could be part of the condition, it does not fit the definition, utilises C fibres in the innervation process and is highly likely to be due to pulpal inflammation, needing endodontic or exdontia management [10].…”

“…One of the early, and most obvious hypotheses, was that dentin was innervated and therefore nerves were directly triggered by the stimulus. Histological stain techniques later proved not to be totally specific for nerve fibres [19]. Later evidence from electron microscopy revealed that nerve fibres do penetrate the dentinal tubules but only for a very short distance into the inner dentin, and mainly over the pulpal horns [20].…”

Distinctive Genetic Activity Pattern of the Human Dental Pulp between Deciduous and Permanent Teeth

“…For example, deciduous teeth exhibit less pain sensitivity when compared with permanent teeth as a result of differences in the number and/or innervation of their neural components, such as the Raschkow plexus [1], [2]. Deciduous teeth are composed of a less dense network of myelinated fibers than permanent teeth, and nerve fibers are seldom found in the calcified tissues of deciduous teeth [3], possibly related to why these teeth are less sensitive in pulp sensitivity tests. In addition, transient coronal discoloration and pulp canal obliteration after dental trauma are more frequent in deciduous teeth than in permanent teeth [4].…”