Morphological versus functional changes of pulpal nerves in inflammation
In addition to the transmission of nerve impulses, there is another, a much slower type of signaling between the nerve endings in peripheral tissues and soma neuron through axonal transport. This process is bidirectional, including both front-and retrograde transportation of various cytochemical alarm agents. It allows transmission of information about the state of the tissue around the nerve endings neuron soma (10). Damage to the nerve endings and other tissue components in the pulp and paper results in the metabolic activation of neurons in the trigeminal ganglion. as a result, various signaling molecules-receptors, mediators and modulators are synthesized and transported to the nerve endings in damaged tissue, where they participate in the regulation of inflammation and tissue repair (8, 10). In addition, profound morphological changes occur in the peripheral nerve endings (12). These changes regulated growth factors and other signal molecules activation during the process (8, 10).
It should also be noted that the action potential fire and transport signalling molecules in the Central nervous system, resulting in a discrete cytochemical changes of the second order of neurons in the brain stem (13), which may be associated with Central sensitization with increased nociceptive transmission of impulses in the trigeminal pain pathways.
Sensory neuropeptides, CGRP and substance P, present in the afferent nerves normal healthy tissues (8-12)seems to be confined to a fine caliber pain intermediary afferents (10, 18). He also pointed out that neuropeptides are located mainly in unmyelinated C-fibers and that some small A8-fiber CGRP immunoreactive (31, 35, 48).
Morphological changes shown to take place in response to injury and inflammation in intradental nerve endings include an increase in their neuropeptide content and germination of nerve endings (8, 9). As already mentioned, sensory neuropeptides are able to induce vasodilatation and increased permeability of the vascular wall (47, 48). Such vascular reactions are an integral part of the inflammatory reaction and are necessary to meet nutritional needs associated with increased metabolic activity in connection with tissue repair and healing. Described above structural neural responses probably important for tissue repair, because they allow a more effective regulatory function of nerve endings in the treatment process (11, 12; the Main literature 3.1). In addition, the time course of morphological changes in the nerve endings indicates that they are an integral part of the fabric of answers. They are obvious within a few days after the insult in the rat teeth and they disappear simultaneously with the restoration of tissues and resolution insult in cases of reversible (8, 9).
The experimental data concerning the functional correlates of morphological changes in the tooth pulp nociceptors, described above, are limited. Given the scale of the changes, they can have significant impact on the sensitivity of the teeth. Electrophysiological studies show that the receptive field of single intradental nerve fibers in the inflamed canine teeth wider than in uninflamed management (44) (Fig. 3.7). Such a change is correlated with the morphological results show, the germination of the axon terminals (8, 9). Along with the expansion, the overlap of the receptive field of single afferents in dentin increases, which increases the number of activated fibres by stimulation of a particular field in the dentin (Fig. 3.7). Accordingly, such changes may contribute to the increased sensitivity of dentin in inflamed teeth (42, 44). ..