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. Conclusion: Myelinated fibers innervated to the dental pulp maintain their myelins in the radicular portion, but these fibers lost myelins in the coronal portion. After the loss of myelin, the size of the axoplasm also decreased.