This document discusses nerve injuries that can occur following extraction of lower wisdom teeth. It begins by outlining the anatomy of the inferior alveolar nerve, lingual nerve, and buccal nerve that are at risk during extraction. It then discusses factors that can increase risk of nerve injury like impacted tooth position and age. The document details how to classify and monitor recovery from different types of nerve injuries. It concludes with approaches to minimize nerve injury risk like improved imaging and coronectomy technique.

1. Nerve affections
following
extractions of
lower wisdom
tooth
Ahmed reda

2. ABSTRACT
2
• Lower third molar extraction is a routinely latneD a yb erudecorp enod
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evren ralubidnam eht fo sehcnarb eht fo eno ot egamad tuoba gnirb.
• An in-depth knowledge on the anatomy of the nerve, correct diagnosis and
the usage of proper techniques will enable the clinician to carry out this
procedure without leaving post-operative complications.
• This presentation focuses mainly on the causes of peripheral nerve trauma
during the procedure and whatshould or can be done to prevent it.

3. • The surgical removal of lower third molars endangers both the
lingual and inferior alveolar nerves most commonly.
• Patients sustaining an injury to either of these nerves must be
managed correctly, and this requires a diagnosis of the injury type
and regular monitoring of the recovery of sensation.
• Surgical intervention for a damaged inferior alveolar nerve is not
usually indicated but may be undertaken: if the nerve is
completely divided and the severed ends are misaligned; if a
bony fragment has compressed the mandibular canal; or if the
patient suffers from persistent neuropathic pain.
• In contrast, after injury to the lingual nerve, if sensory testing
demonstrates no neural recovery, exploration of the injury site
and microsurgical repair of within 3–4 monthsthe damaged nerve
is indicated.
3

4. 4
Panoramic
radiograph
Here we see the lower wisdom teeth both
sides left and right impacted
horizontally.
To conform the relation of them to the
canal of course CBCT is required to
determine whether or not .

5. Affected
Nerves• Impacted mandibular third molar teeth are in close proximity to the lingual,
inferior alveolar, mylohyoid(Injury to the mylohyoid nerve is rare and is not
considered) and buccal nerves
• During surgical removal, each of these nerves is at risk of damage, but the most
troublesome complications result from inferior alveolar or lingual nerve injuries.
The majority of injuries result in transient sensory disturbance but, in some cases,
permanent paraesthesia (abnormal sensation), hypoaesthesia (reduced sensation)
or, even worse, some form of dysaesthesia (unpleasant abnormal sensation) can
occur
• These sensory disturbances can be troublesome causing problems with speech and
mastication and may adversely affect the patient’s quality of life.
5

6. Cross-section of the mandible
through the third molar showing
the inferior alveolar, lingual,
mylohyoid and long buccal nerves.6

7. INFERIOR ALVEOLAR NERVE
Morphology: The inferior alveolar nerve is morphologically unusual in that it travels a significant distance
within bone in the mandible. In the mandibular canal it is supported by the surrounding connective tissue and
other structures in the neurovascular bundle.
After injury
unless the nerve is displaced into the socket,
the severed nerve ends do not retract, but will
remain in apposition. Regeneration within the
canal will thus be unimpeded unless
obstructed by displaced fragments of bone
from the roof of the canal. Good recovery
after injury would therefore be expected.
• Many studies have reported the frequency
of nerve injury during the removal of third
molars (for review see Robinson) and most
indicate that inferior alveolar nerve function
is disturbed after 4–5% of procedures (range
1.3–7.8%). Most patients will regain normal
sensation within a few weeks or months
and less than 1% (range 0–2.2%) have a
persistent sensory disturbance.
7

8. Fiveradiographicsignssuggestingjuxtapositionofthe
mandibularcanaltothethirdmolarroots,asdescribedby
RoodandShehab1990.
5Signssignificantlyrelatedtonerveinjury:
A.Radiolucencyacrosstherootsofthethirdmolar;
B.Deviationofthemandibularcanal;
C.Interruptionofthewhitelineofthecanal.Signs
consideredtobeclinicallyimportant:
D.Deflectionofthethirdmolarrootsbythecanal;
E.Narrowingofthethirdmolarroot.
8
RoodandShehab1990

9. 9
ThewithdrawalofRoodandShehab
1990
• The same study failed to show that ‘narrowing of the
inferior alveolar canal’ and the ‘presence of a dark and
bifid apex’ were significant predictors of inferior
alveolar nerve injury; features that had previously been
considered important.
• Paradoxically, sensory disturbance may occur following
removal of teeth that show none of these features, and
may not occur even when there appears to be clear
evidence of a close relationship between the canal and
the tooth roots.

10. 10
1-Ahigherincidenceofinferioralveolarnerveinjuryhasbeen
reportedwiththirdmolarsthatarehorizontallyormesioangularly
impactedandhavecompletebonecover.
2-Onestudyhasalsodemonstratedthatincreasingageis
associatedwithahigherfrequencyofinferioralveolarnerveinjury
(14–24yearoldpatients1.2%;35–81year-oldpatients9.7%).
Other factors affecting

11. 11
LINGUAL NERVE
After injury
If sectioned, the cut nerve ends
retract apart and, if the adjacent
soft tissue is also distorted, the
nerve ends may become
misaligned and trapped or
constricted by scar tissue.
Difference
• Regeneration of axons across a gap
will be less successful than if the nerve
ends remain in apposition. In addition,
the presence of a range of functionally
distinct nerve fiber types in this nerve
(e.g. mechanosensitive,thermosensitive,
gustatory, vasomotor and secretomotor)
may make successful regeneration of the
axons back to the correct receptor/
effector and location less likely.
Morphology: very different from the inferior alveolar nerve. At the usual site of
injury (adjacent to the lower third molar) the nerve is covered with only a thin layer of
soft tissue and mucosa, rather than being in a bony canal.

12. 12
Factors affecting the injury
• There is a wide range in the reported frequency of lingual nerve injuries during third molar
removal, with 0.2–22% of patients reporting sensory disturbances in the early post-operative
period and 0– 2% a permanent disturbance (for review see Robinson 19971).
• There are several possible explanations for the wide range in incidence.
• First, the variation may reflect differences in the time interval between tooth removal and the
assessment of the sensory impairment; early assessments will report many transient sensory
changes that recover rapidly and completely, and which would be missed if assessment takes place
after a longer recovery period.
• Secondly, the incidence of nerve injury may depend upon whether the sensory deficit was
established objectively by the clinician or was based on a subjective patient assessment.
• Finally, it may reflect differing surgical techniques; several studies have shown that the raising
and retraction of a lingual mucoperiosteal flap is associated with an increased frequency of lingual
nerve damage. Two recent studies and a systematic review have concluded that raising and
retracting a lingual periosteal flap is not necessary and is best avoided.

13. 13
BUCCAL NERVE
As the nerve crosses the external oblique
ridge it is composed of between one and
five branches, the lowest of which may
be over 1 cm below the deepest
concavity of the ridge. Therefore, part or
all of the nerve is at risk when the distal
relieving incision is made during third
molar surgery.
Morphology: This nerve descends between the two parts of the lateral pterygoid muscle, medial to
the ramus of the mandible, and then passes laterally across the external oblique ridge distal to the
third molar, to supply the cheek. The sensory distribution is variable but includes the lower
posterior buccal sulcus and gingivae, and an area of cheek mucosa.
Small areas of sensory disturbance
may go unnoticed but a few patients
complain of complete anaesthesia of
the cheek; the incidence of this
complication has not been reported.

14. 14
Sunderland’s
classification
A. Conduction
block; B.
Transection of
the axon with
an intact
endoneurium;
C. Transection
of the nerve
fibre (axon and
endoneurial
sheath) inside
an intact
perineurium;
D. Transection
of nerve fibers
and
perineurium,
nerve trunk
continuity
being
maintained by
epineurial
tissue; E.
Transection of
the entire nerve
trunk. Modified
from
Sunderland.
CLASSIFICATION OF NERVE INJUR

15. 15
Seddon and Sunderland
• Compression injuries (type A) may occur during the elevation of a third molar with roots in close proximity to
the mandibular canal. Minor compression of the nerve, or first degree injuries, will give rise to a temporary
conduction block, which is referred to by Seddon19 as neurapraxia.
• More severe compression or crush injuries (Type B) cause the axon distal to the site of the injury to degenerate
(Wallerian degeneration) and recovery of sensation is dependent upon regeneration of the damaged axons.
Seddon19 refers to this second degree injury as axonotmesis.
• Stretch injuries could occur, for example, when raising a lingual mucoperiosteal flap, and could give rise to
rupture of the endoneurium and perineurium to produce third or fourth degree injuries (Type C and D),
respectively.
• Complete section of the nerve trunk or fifth degree injuries (Type E), referred to by Seddon19 as neurotmesis,
may occur if the inferior alveolar nerve penetrates the root of a third molar and is severed during tooth
removal.
• Many nerve injuries that do not fit neatly into this classification and are more complicated. For example, a
rotating bur may not only partially divide the lingual nerve but also stretch the nerve. Inflammation around the
nerve, caused by infection or foreign bodies, may also alter neural function and increase the pain experienced.

16. A diagrammatic representation of the cellular events
which follow axonal discontinuity of a myelinated
trigeminal nerve fibre.
A. Normal appearance.
B. Transection of the nerve fibre peripherally results in
distal fragmentation of the axon and the myelin. In the
proximal segment degeneration occurs to at least the
first node of Ranvier.
C. Schwann cells in the distal stump form the bands of
Büngner through which the axon sprouts regenerate.
D. The regenerated axon regains contact with the
periphery and matures, but a reduction in diameter
persists.
E. If the cut ends of the nerve are widely separated, it
is less likely that good recovery will occur and
abnormalities may persist. Sprouts may locate and
innervate inappropriate targets or, if no target organ is
located, axonal sprouts may persist as a neuroma.
Modified from Holland and Robinson.
16

17. 17
Temporary block of nerve conduction (1st
degree injury) may be accompanied by some
local thinning of the axons and segmental
demyelination, but these changes are
reversible.
Recovery of sensation normally occurs
within a few days of the surgical trauma,
although recovery may be slightly slower if
segmental demyelination takes place.
• The initial delay prior to regeneration, and the
success of axons in crossing the injury site, is
dependent upon the nature of the injury.
• Crush injuries will recover more rapidly than
section injuries as the endoneurial sheaths usually
remain intact and therefore the regenerating axons are
guided back to the correct receptor type at the correct
location.
• Recovery from crush injuries may take months and
may not be complete.
• In contrast, after nerve section injuries, the
regenerating axons enter the endoneurial
sheaths of the distal stump, apparently at
random, and may be guided to an inappropriate
receptor at a new location. This may give rise to
abnormalities in localization and the sensation
perceived in response to a particular stimulus.
• Recovery will progress for at least a year and
will never be complete.
SEQUELAE OF NERVE INJURY

18. 18
METHODS USEDTO MONITOR NERVE RECOVERY
Simple Sensory
Testing
• A standard protocol for
sensory testing does
• Needs quiet room with
both the patient and
examiner comfortable.
not exist
• the patient’s eyes
closed and the
detection of a stimulus
is indicated to the
examiner by the patient
raising a finger.
Light Touch
Sensation
• most commonly
tested by gently
applying a wisp of
cotton wool to the
skin or mucosa.
• difficult to apply
this stimulus in a
reproducible manner
• Von Frey hairs
making these
instruments with a
standard force of 20
mN (reproducibility
)
Pin prick
sensation
• performed
using a
dental probe
or needle
• A simple
device,
described by
Sunderland,
overcomes
this
difficulty
Two Point
Discrimination
• This test can
quickly be
performed if
pairs of blunt
probes with
different
separations
(2–20 mm)
are mounted
around a disc

19. 19
Approach towards minimizing
nerve injury
• Many ideas have been brought forward aiming to reduce nerve injury during the removal of the
mandibular third molar. A preoperative radiograph should be taken to assess the relationship of the
corresponding nerves and the tooth to be extracted. In high risk patients as mentioned earlier, the
anatomical position of the tooth lies very close the nerve. Thus, in such situations, the patient
should be informed prior about the condition and the complications the individual might face if a
nerve injury takes place.
• Magnetic Resonance Imaging (MRI) has several advantages over the conventional Radiographic
and CT imaging. The advantage of MRI is that it has a better soft tissue contrast resolution
without having to use ionizing radiation. Hence this method provides sufficient information on the
relationship of the IAN and the impacted third molar and can be used in young patients to prevent
radiation exposure.
• Cone Beam CT (CBCT) appears to be the gold standard for this procedure. Since this device is not
readily available in most places, it still remains as a poor source of obtaining the diagnosis for a
mandibular third molar extraction.

20. 20
• Coronectomy or lock removal surgical approach towards reducing
the risk of peripheral nerve injury. This was done by removing the mesial portion of the
anatomical crown of a fully erupted third molar. The objective of this procedure was to
create adequate space for the mesial migration of the third molar so that the extraction of
the third molar can be done with minimal invasion to the IAN.
• orthodonticappliance to move the impacted third molar distant to the IAN. This method was proven
to be successful. However, the orthodontic appliance which is positioned in a difficult area of the mouth may
cause trauma to the neighboring tissue. Furthermore, this technique is not only time consuming as it required
5months of active therapy and 3 months of stabilization but also not cost effective.
• Tracking of the inferior alveolar nerve

21. 21
(a) CBCT localizing IAN proximal to lower teeth (distant from nerve). (b) CBCT localizing
IAN proximal to lower teeth (proximal to nerve).

22. 22
Traced boundaries of the inferior alveolar nerve canal on reconstructed
panoramic views.

23. 23
Inferior alveolar nerve Lingual Nerve
• If accidentally divided at the time of surgery, repair is
indicated if the nerve ends do not remain in
apposition within the canal.
• ideally be performed at the same time as the tooth
removal
• if this is not possible the patient should be referred
urgently to an appropriate maxillofacial unit.
• If a sensory disturbance is first noted at review,
recovery should be monitored using the sensory tests
described above.
• Patients with paraesthesia in the distribution of the
inferior alveolar nerve (evoked by touching the lip or
chin) usually require no surgical intervention.
• complete anaesthesia postoperatively should be
evaluated radiographically to ensure that the roof of
the mandibular canal has not been displaced inferiorly
to create an obstruction to regeneration for removal of
the bony fragment
• A lingual nerve that is knowingly transected during
wisdom tooth removal should be immediately repaired
using epineurial sutures
• In the majority of patients, the injury is only discovered
post-operatively.
• At early review, the presence of some sensation in
response to stimulation of the tongue suggests that the
nerve is at least partially intact; no treatment is indicated
but sensory monitoring is required.
• the absence of progressive sensory recovery by 3–4
months post injury is an indication for surgical
exploration at an appropriate maxillofacial unit.
• If, at the time of surgery, the nerve is found to be intact
and of fairly uniform thickness but merely constricted by
scar tissue, it should be freed (external neurolysis)
and the wound closed.
• If a neuroma has developed, this can be seen as a marked
expansion at the site of the injury and must be excised,
together with the damaged segment of the nerve.
TREATMENT

24. 24
ADD A FOOTER

25. 1. IOSR Journal of Dental and Medical Sciences
(IOSR-JDMS) e-ISSN: 2279-0853, p-ISSN: 2279-
0861. Volume 13, Issue 1 Ver. VI. (Jan. 2014),
PP 98-102 www.iosrjournals.org
2. A. R. LOESCHER, K. G. SMITH AND P. P.
ROBINSON
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Referance

26. Thank You!
Ahmed Reda Abdel-Hameed M.
Intern 2018
Sinai University
Email
ahmed_pharaoh19@yahoo.com