Journal of Dental Research, Vol 74, 1850-1860, Copyright © 1995 by International & American Associations for Dental Research Online Journals
The re-innervation of the tongue and salivary glands after lingual nerve repair by stretch, sural nerve graft or frozen muscle graft
K. G. Smith and P. P. Robinson
Department of Oral and Maxillofacial Surgery, University of Sheffield, School of Clinical Denstistry, England.
The lingual nerve is sometimes injured during the surgical removal of
impacted third molar teeth and may require repair. Removal of the damaged
section of nerve prior to repair leaves a gap between the nerve ends, and
we have investigated methods of closing the gap. THe characteristics of
regenerated fibers in the chorda tympani have been recorded in cats 24
weeks after the removal of a segment of lingual nerve and repair of the
defect by three methods. The nerve gap was closed either by stretching the
nerve ends together and repairing under tension, or by the insertion of a
sural nerve graft or freeze-thawed muscle graft. The properties of
gustatory, thermosensitive, and mechanosensitive units and the return of
the vasomotor and secretomotor responses were investigated by
electrophysiological techniques and the data from each of the repair groups
compared with those obtained from a series of normal control animals. After
each method of repair, the integrated whole-nerve activity recorded from
the chorda tympani during gustatory or thermal stimulation of the tongue
was reduced when compared with controls, but there was little significant
difference between the repair groups. Recordings made from single units in
the chorda tympani revealed that conduction velocities were faster after
stretch repair than after sural nerve graft or frozen muscle graft. In
addition, 48% of the units had developed into principally gustatory units
after stretch repair, indicating a better level of recovery than in the
graft groups, which contained 33% and 32%, respectively. The secretomotor
responses were also significantly greater after stretch repair than in
either of the graft groups or the controls, but there was no difference in
the vasomotor responses. These results reveal that repair of a short gap in
the lingual nerve by stretching the ends together is followed by better
overall recovery than after grafting, but where a graft is used, a similar
level of recovery results from use of a frozen muscle graft or a sural
nerve graft.
