Page 10 - GP Fall 2020

nerve hook (Figure 9) and then with fine Discussion examination and a panoramic radiograph,
cotton thread (Figure 10) carefully without Nerve lateralization is defined as the lateral which avoids intensive radiation and cost-
excessive stretching. The same procedure reflection of the IAN without incisive nerve ly imaging studies as well as special ar-
3
Figure 9. A. transection. In this case, the IAN was de- mamentarium. This procedure claims the
Inferior flected laterally while implants were placed advantage of placing longer implants and
alveolar and then left to fall back in against the im- a greater number of implants in order to
neurovascular plants. improve the strength of the final prosthesis.
bundle held by
nerve hook. B. The first case of IAN repositioning was The use of short implants is a topic of de-
Mental nerve reported by Alling in 1977 to rehabilitate bate because of interocclusal distance and
and vessel. denture patients with severe atrophy. The an unsuitable prosthesis implant height re-
4
Figure 10. first report of mandibular nerve replace- lationship. 9
Inferior ment for the insertion of dental implants
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alveolar nerve appeared in 1987 by Jenson & Nock. They Compared to other bone augmentation pro-
held and carried out IANT where a corticotomy was cedures involving longer waiting periods
lateralized performed around the mental foramen and before implant placement, the presented
with cotton incisive nerve was transected to allow the technique involves simultaneous implant
thread. transposition of the mental and IAN more placement and utilization of the window
posteriorly. When first seeking guidance in of buccal cortical plate that was removed
was then performed on the contralateral regard to the amount of bone needed above earlier being used as autograft, further re-
side. Implants were placed lingual to the the mandibular canal when performing ducing the cost of the procedure and by re-
neurovascular bundle without engaging IANL, 3-5mm is suggested by Jensen et al quiring less allograft.
the inferior cortex and the the neurovas- who were the first to introduce guidelines
cular bundle was placed back in its usual regarding bone height in such procedures. 6 As we look into the disadvantages of the
position lateral to the implants. A mix of technique, mobilization of the nerve cre-
ates a complex biologic situation which
allograft (Figure 11) and autograft particles Kan et al recommended a minimum of
5mm of bone be present above the man- might interfere with the healing process
dibular canal in order to perform IANL. In of implants 10 so that it does not recover
7
addition to the above guidelines, the choice alveolar ridge anatomy. Apart from this, it
to perform IANL or IANT was based on weakens the mandible due to the combina-
the amount of stretching that is needed to tion of removal of the cortical defect and
mobilize the IAN. Stretching the nerve by implant placement making it susceptible to
10-17% of its original length can disrupt fracture. To avoid this we utilized cortical
the nerve fibers internally. In this case, the window of bone as autograft, along with
1
marginal crestal bone above the canal was allograft to make up the decrease in defect
Figure 11. Placement of allograft after 3-4mm and excessive stretching of IAN of bone and the patient was rehabilitated
placement of implant in cortical window was not required post-operatively to avoid with prosthesis after six months reducing
defect Neurosensory Disturbance (ND) associat- the possibility of undesirable force on the
were added between the implant and neuro- ed with IANT. This resulted in choosing mandible. Since 3-4mm of marginal crestal
bone was left above IAN, it helped in gain-
vascular bundle and then lateral to the bun- IANL as the procedure for the case. ing primary stability for implants.
dle. This was followed by the placement of
the lateral buccal cortical plate, which was The procedure involved vertical splitting In the presented case ND needs a special
removed earlier. Subsequently, allograft of the mandibular body as an alternative to mention as it is common with IANL. The
particles and a collagen membrane were IANL using piezoelectric surgery, followed duration and degree of ND has been direct-
placed and then the soft tissue was closed by bone expansion and insertion of special ly related to the amount of compression
using resorbable sutures. A post-operative conical implants even with residual bone and tension applied to the nerve during the
panoramic radiograph was taken after one height over the mandibular canal of be- procedure. Functional recovery depends
11
month (Figure 12) and two years (Figure tween 1.8-8 mm by Rodriguez J G and Eld- on the ability and speed of nerve fiber re-
8
13), respectively. ibany RM has been suggested in the litera-
ture. Their technique needs simple clinical generation, which varies between 1-3mm a
day. In this case, paresthesia was present
12
postoperatively up to 12 weeks followed
by improvement in sensation at the end of
18 weeks. Return to normal sensation hap-
pened at the end of 6 months.

Figure 12. One month post-op OPG. Figure 13. Two year post-op OPG.

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