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Abstract
Introduction
Mammalian tooth pulp is densely innervated by sensory nerves that are mostly C fibers and A delta fibers. However, there is evidence suggesting that many unmyelinated axons in the pulp are in fact parent meylinated axons. Immunohistochemical staining for neurofilament protein 200 kDa (NFP200) was performed to identify the demyelinated but parent myelinated axons.
Materials and Methods
The pulp was removed from healthy premolars and 3rd molars extracted from juveniles and adults undergoing orthodontic treatment, and immunohistochemical staining were applied with NPF200 antibodies, which specifically dye myelinated axons. The specimens underwent an electron microscopy examination with diaminobenzidine (DAB) immunostaining after observation and analysis by fluorescence and confocal laser scanning microscopy.
Results
The NPF200 immuno-positive axons in the radicular pulp areas were observed as bundles of many nerve fibers. Many small bundles were formed with fewer axons when firing to the coronal pulp areas and then reachrd a different direction. In the radicular pulp, unmyelinated axons and myelinated axons were present together. However, in the coronal pulp, unmyelinated axons were most common and NFP200 immuno-positive unmyelinated axons with a larger diameter than those in the radicular pulp were observed more frequently. On the other hand, most of the immuno-positive unmyelinated fibers were similar in size to that of typically well-known unmyelinated fibers.
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Fig. 1.
Immunofluorescence staining on human molar pulp showing the distribution of neurofilament protein (NFP) 200-immunopositive (+) nerves. A. NFP200+ nerves are densely appeared in subodontoblastic plexus (SOP) of Raschow of coronal pulp. B, C. NFP200+ nerve bundles C in root portion branch off and project to their termination sites. The scale bar is 50 μm in A-C.
Fig. 2.
Immunoperoxidase staining for electron microscopic observations on the neurofilament protein (NFP) 200-immunopositive nerves of human molar pulp. A, B. Many NFP200-immunopositive (+) nerves terminate in subodontoblastic plexus (SOP) of coronal pulp. Some nerves are also passing through odontoblast (OB) layer. C, D. Nerve bundles travel the root portion C and make branches before projecting to SOP of Raschow or OB layer. The scale bar is 100 μm in A and 50 μm in B-D.
Fig. 3.
Electron microscopic observations on the neurofilament protein (NFP) 200-immunopositive (+) nerves in root and crown portions. A. NFP200+ myelinated (arrows) and unmyelinated (arrowheads) nerves are frequently observed in root portion. B. Majority NFP200+ nerves are unmyelinated (arrowheads) in coronal pulp. The scale bar is 4 μm in A and 500 nm in B.
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