The inferior alveolar nerve supply
sensation to the lower lip, chin, etc. In case of severely atrophic mandible
the nerve need to be reposition to make space for implant placement. But
sometimes, there can be postoperative numbness in the lower lip and chin
region. So, to help patient decide, the dental
professional can give a block before the procedure with a longer
acting local anesthetic like Marcaine (8-16 hrs), similar to the postoperative
anesthesia the patient may experience.
Before the procedure the Inferior
Alveolar Nerve (IAN) need to be assess radiographically to locate the mental
foramen. There are 2 nerve repositioning techniques: lateralization and
transposition. For both the procedures a crestal incision with releasing incisions
are made and the flap is reflected labially. Care to be taken during raising of
the flap to preserve the periosteum and neurovascular bundle.
Inferior Alveolar Nerve transposition (IANT)
A complete
osteotomy is done and a window is created to avoid damage to the inferior
alveolar nerve. For complete mobilisation, the incisive branch or the terminal
branch located about 5 mm away from the mental foramen is section.
IAN Lateralization (IANL)
For this procedure, a partial osteotomy is done distal to the mental
foramen and a window is made. Dissection or sectioning of the terminal branches
of the nerve or incisive nerve is not done thereby maintaining the integrity of
the incisive nerve.
Then, in both the procedures the nerve is
retracted away using a nerve hook and a gauze passing below the nerve and
dental implant place bicortically for primary stability. The nerve is then
reposition and is left to lie outside the mandibular canal. The gap between the
bone window and implants can be fill with bone grafts and a resorbable membrane
to prevent direct contact and finally suture.
The bone grafts can be taken from various
parts of the body like chin, palate, etc. If more volume of bone grafts are
require then it can be harvested from the hip, knee, etc as they give the best
results. Moreover, allograft (graft obtain from cadavers) can also be use to
increase bone volume as they are effective, safe and can stimulate new bone
formation.
The decision to use either Transposition
or Lateralization depend on the amount of stretching or mobilization of the
nerve but stretching 10% – 17% of the original length can cause internal damage
of the nerve fibers. So, Transposition is prefer over Lateralization in term of
less stretching and hence, produces lesser side effects.
Postoperative measures
Antibiotics, Analgesics and corticosteroids are
recommended. Moreover, using corticosteroids pre and post operatively helps
reduce symptoms like inflammation, etc.
Advantages Of Nerve Repositioning
- GOOD
PRIMARY IMPLANT STABILITY (BICORTICAL FIXATION)
- MORE
NUMBER OF IMPLANTS CAN BE PLACE (IMPROVE DENTURE STRENGTH)
- SIMULTANEOUS
IMPLANT PLACEMENT (REDUCING TREATMENT TIME)
- IMMEDIATE
LOADING POSSIBLE (IMPROVE MASTICATORY FUNCTION)
- IMPLANT SURVIVAL RATE IS SIMILAR TO CONVENTIONAL IMPLANT
Besides, it also increases occlusal force resistance, occlusal stability, chewing efficiency, TMJ and masticatory muscle balance, etc.
Disadvantages Of Nerve Repositioning
·
THE
PROCEDURE DAMAGE THE ALVEOLAR RIDGE ANATOMY
·
TEMPORARILY
WEAKENS THE LOWER JAW (DUE TO BONE REMOVAL)
·
POTENTIAL
RISK FOR OSTEOMYELITIS
·
PATIENTS
WITH BRUXISM OR POOR OCCLUSAL RELATIONSHIP CAN INCREASE THE CHANCE OF IMPLANT
FAILURE.
Conclusion
Inferior alveolar
nerve repositioning is a technique being use for around 2decades now with a
good success rate. Sometimes, it is the only approach to achieve a fixed
prosthesis in atrophic mandible. The technique is safe and has a high success
rate. With precise planning, this technique can be successfully use in implant
placement in edentulous atrophic mandible.
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