Qualitative structural development of the feline inferior alveolar nerve.

The qualitative structural development of the inferior alveolar nerve was studied by electron microscopy in 56 pre- and postnatal kittens and 21 young and old adult cats. At 25 days post conception the nerve was composed of a bundle of small axons enclosed by primitive sheath cells. Three weeks later myelination had been initiated. Axons measuring 2-3 micrometers underwent local demyelination from 2 weeks before to 3 weeks after birth. This was accompanied and followed by nodalization of larger axons. A typical perineurium was first apparent in the newborn kitten. Six to eight weeks postnatally, the nerve appeared qualitatively mature, although axonal growth was far from completed. This coincides with achievement of a fully mature primary dentition shortly after the weanling period. Apart from a continued size growth, no changes were observed in the nerve during the transition from the primary to the permanent dentition. In the inferior alveolar nerve of old cats, axonal and perineurial changes co-existed with signs of dental attrition and pathology.