Neuroplasticity and Content of Structural Elements in the Axoplasm of the Trigeminal Nerve During the Eruption of Permanent Teeth in Humans

The aim of the presented study was to identify the features of the quantitative formation of axoplasmic organelles with a primary analysis of the components of the axonal cytoskeleton (microtubules and neurofilaments) of myelinated and non-myelinated nerve fibers in the dental pulp during the eruption of permanent teeth in humans. Material and methods. The neurovascular bundle of dental pulp was studied in children aged 5, 10 and 14 years. On ultramicrographs of pulp sections at a magnification of ×40000, the diameters of myelin and non-myelin conductors were measured; per 1 µm2 of axoplasm of nerve conductors, the density of axoplasmic organelles, the number of microtubules and neurofilaments were calculated. The reliability of differences between groups was assessed using multivariate analysis of variance (MANOVA), the significance of average values was assessed using the Tukey test, correlation analysis was carried out using the Pearson criterion. Results. The process of eruption of permanent teeth was accompanied by a gradual increase in the number of organelles per unit cross-sectional area of the nerve, regardless of its characteristics (myelinated or nonmyelinated fiber type). The highest density of organelles was observed in large-diameter fibers of both myelinated and non-myelinated conductors throughout the indicated segment of ontogenetic development. The presence of myelin in the nerve sheath correlates positively with microtubule saturation in fibers of large (r=0.267, p=0.001) and small (r=0.314, p=0.000) diameters, and negatively in fibers with medium diameter (r=-0.246, p=0.002). The proportion of neurofilaments represented among the axoplasmic organelles of the neuroplasm as a whole was especially high in myelinated and unmyelinated nerve fibers of small diameter, averaging up to 70%. The presence of the myelin sheath and fiber diameter are not associated with neurofilament density with the exception of medium-diameter fibers (r=0.195, p=0.001). Conclusion. The process of eruption of permanent teeth is accompanied by an increase in the number of organelles, cytoskeletal elements in the axoplasm of nerve fibers innervating the dental pulp, providing the morphological substrate of neuroplasticity, which must be taken into account, for example, in the process of dental implantation and dental prosthetics.

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