Innervation teeth rudiments and milk teeth

Nervous elements teeth attract the attention of many researchers. And this is quite understandable, because they are the link that binds the tooth with the Central nervous system and through it with the entire body. It is through this regard, the teeth become an organic part of the whole. The study innervating apparatus of the tooth at all stages of its development from the moment of occurrence of tooth root to complete the formation of the roots) is of great interest for us, as only a clear understanding of the functions of this unit may shed light on many aspects of biology and pathology dental tissues.
The study nerves tooth germs in embryogenesis devoted quite a large number of works. They deal with human embryos and some mammals. However, obtained by different authors data is extremely contradictory.
One group of authors were able to identify elements in the beginnings of dental relatively late stages of embryo development (Wassermann, 1939; Benanome, 1950; Arwill, 1958; Bock, 1960, and others). On this basis, they conclude that the nervous system has no impact on the formation and differentiation teeth rudiments and histogenesis dental tissues.
Another group of authors (E. C. Malko, 1962; Bradlow, 1939; Branchini, 1942; Plackove, 1962, and others) showed nervous elements in the early stages of early tooth development.
If innervation tooth germs in the embryonic period, the data of different authors vary significantly, in respect of germs in the post-embryonic period and teeth after the eruption of the major differences is not observed.
By time of a birth of the child crown already formed. The development of the same root comes in the post-embryonic period.


Fig. 1. Large bundle of nerve fibers, branching at the top of the pulp of the germ of a canine in a child 4 months. Is characterized by a small number of branches of the nerve fibers to the periphery of the pulp. About. 10, OK. 2 (by A. I. Rukavishnikova, 1965).

Directly after birth in the pulp of a tooth germ of nerves is little, and nerve fibers (as in the dental papilla in the period of embryogenesis) are revealed mainly in its Central part and in the field of vertices, i.e. where there is particularly intense histogenesis. In the same side departments and cervical part (and in the molars, and also in the sphere of small horns) nerves much less. Starting from the 4th month after birth, the number of nerve fibers and their beams increases (Fig. 1), they gradually begin to appear in those parts of the pulp where there was none before. By the end of 6-7 month nervous plexus already well expressed in the lower sections of the pulp and in the sphere of small horns of rudiment of molar. However, especially thick and it becomes common to the 10th month.
Studying the innervation of the teeth, in the early post-embryonic period, A. I. Rukavishnikov (1965) noted that the best nerve plexus expressed "in the field of cutting edge pulp cutters, pulp rudiments of molar, i.e., where the processes of histogenesis tissues begin earlier and more intensively flow". Thus, the formation of subtotalling plexus follows the same sequence as the development of nerve fibers of the pulp.
Especially great interest is the development of nerve endings in the tooth, its receptors, i.e. the part of the analyzer through which irritation enters the Central nervous system. Nerve endings in the form of the finest forks nerve fibers were described by a number of authors (N. I. Sazisin, 1936; E. C. Malko, 1956; L. P. Madan, 1957, 1958; Plackova, 1962, and others) in the dental papilla at early stages of development teeth rudiments of a person in embryogenesis. In newborns nerve endings presented mustache and bushes of 3-4 branches that end either in the layer of odontoblasts, either directly under it. By the end of 4-10-th months (depending on the group of teeth) in parallel with the increasing complexity of parodontological plexus structure of bushes too complicated. Their ultimate twigs, repeatedly interacted with each other, most of them formed under a layer of odontoblasts extensive receptor field. A smaller part is located in the very layer odontoblasts and only some of them penetrate into presdentin. Part of the terminal branches of the same Bush may result in the connective tissue, and another part - on the wall of a blood vessel (the so-called vascular tissue receptors). In some cases, these twigs form around vessels kind of coupling.


Picture innervation of milk tooth with a fully formed by the roots is represented in the following form. Beams makalnyh nerve fibers together with blood vessels enter through the apical foramen. Heading along the long axis of the tooth, they are situated in the Central part of the pulp, giving the path of a number of branches. However, the most extensive branching begin from the place of their transition from root to crown the pulp where they repeatedly sharing, give a large number of branches peripheral departments crown pulp. Most of these branches forms under a layer of odontoblasts nerve plexus, is particularly well expressed in the field of the horns of the pulp. The terminal branches, representing one of the most common types of receptors and having a form of simple or complex bushes found in connective tissue, pulp, and in the layer of odontoblasts, and predestine. A slightly different picture seems innervation root pulp where parodontological plexus not present, and predestine nerve endings are not defined.
The question about the mechanism of dissolution of the roots of teeth and the role of the nervous system in this mechanism little coverage in the literature. Not sufficiently studied and morphological changes in dental tissues in different periods of root resorption.
For a more detailed study of this question together with Professor E. C. Ryzhkov and assistant N. A. Paceway (1969) undertook a study of milk teeth with completely resorbed roots (once the crown is kept fragments of periodontal or traction belt (slurry). Analysis of the obtained data has shown that in milk teeth in the period of root resorption may be of two kinds of change: primary and secondary. The primary concern are those (physiological) changes that are caused by resorption of hard tissue for purposes of elimination of the tooth. Resorption of dentin is a large multi-core cells odontoceti. In the place where they fit visible to the different size of the gaps. The process of resorption rarely goes through education "liquid dentin" (this reaction usually occurs where there is rapid resorption of dentin).
The very large increase in the area of liquid dentin visible education corruptable structures, and fails to mention that in the first place is melting inorganic part of the dentin, while the dentinal tubules in the form of tubes will stand above the line of melting. Resorption only in isolated cases is carried out by liquid dentin. Resorption of dentin often comes at the expense odontolyticus reaction.
In some cases, in the cavity of the tooth gets a fungus, and then growing mycelium takes part in the resolution of dentin.
From the lingual surfaces of gum under crown is podrazhanie epithelium, which, as it tries to tear tooth turning into a foreign body. Quite often in such teeth observe the formation of a thick layer of substitution dentin, which is often the nature of the phase. Simultaneously with the formation of substitution dentin is observed and the process of its resorption. In rare cases, it turns into osteodentin.
The secondary target those pathological processes, which are played in the pulp when resorption roots, when it becomes easily accessible to influence of harmful factors (pathogenic microbes, fungi, rotting food products and others). In most cases, these teeth occurs inflammatory process, which extends from the root to the top of the pulp.
The analysis of works of other authors involved in the study of the condition of the nervous elements in milk teeth in the period resorption roots, fully confirms our conclusions. So, I. E. Androsov (1968), who studied the innervation of milk teeth in the period mixed dentition, specifies: "In the crown pulp (resorption roots 1/2) no change is observed. Not changed and pulp upper part of the root. In a large number of investigated milk teeth with resorbed roots remaining pulp maintained their structure, except the zone of resorption and adjacent departments."