Purpose: This study investigated the changes in the inferior alveolar nerve
after mandibular lengthening with different rates of distraction.
Materials and Methods: Bilateral mandibular corticotomies were performed in
8 goats. The mandibles in 6 goats were lengthened 10 min using a custom-ma
de distractor with 2 different rates of distraction (1 mm/d [n = 3] and 2 m
m/d [n = 3]); the other 2 nondistracted mandibles served as a control. The
goats with distracted mandibles were killed at 2 weeks after completion of
distraction. The inferior alveolar nerve specimens from all animals were ha
rvested and processed for histologic and ultrastructural evaluation.
Results: The mandibles were lengthened successfully in the distracted anima
ls. Morphologic changes in the inferior alveolar nerves were observed when
compared with the nondistracted controls. Moreover, signs of nerve degenera
tion, such as demyelination, axonal swelling, axoplasmic darking, and decre
ase in the number of axons, were more extensive and prominent in those nerv
es distracted at a rate of 2 mm/d.
Conclusions: Degenerative changes in the inferior alveolar nerve occur afte
r mandibular lengthening by distraction osteogenesis. The distraction rate
of 1 mm/d appears to be tolerable and safe for the inferior alveolar nerve,
but rapid distraction may cause serious degeneration. (C) 2001 American As
sociation of Oral and Maxillofacial Surgeons.