Quantitation of nerve fibres in the primary and permanent canine and incisor teeth in man

Myelinated and unmyelinated nerve fibres were counted and myelinated axons were measured in juxta-apical cross-sections of human primary and permanent canines and incisors. Fully-developed human primary canines had significantly more myelinated axons than permanent canines, but the number of unmyelinated axons was similar. Permanent incisors had significantly more myelinated nerve fibres entering the apex than did primary incisors, but the number of unmyelinated nerve fibres was similar. Primary canines and incisors lost nerve fibres early during resorption; evidence of degenerating myelinated axons was scant. A significant linear correlation existed between numbers of myelinated and unmyelinated axons for primary incisors and canines. The myelinated axon circumference was similar for primary and permanent teeth. Permanent teeth tended to have smaller groups of unmyelinated axons.