|Inferior Dental (Alveolar) & Lingual
The (surgical) removal of lower wisdom teeth
(3rd molars) endangers both the lingual and
inferior alveolar nerves; as the removal of
(lower) potential number of patients sustaining
nerve damage is likewise high.
The majority of injuries result in transient sensory
disturbance but, in some cases, permanent abnormal
sensation (paræsthesia), reduced sensation
(hypoæsthesia) or, even worse, some form of unpleasant
abnormal sensation (dysæsthesia) can occur.
These sensory disturbances can be troublesome, causing
problems with speech and chewing and may adversely
affect the patient’s quality of life.
They also constitute one of the most frequent causes of
complaints and litigation.
As can be seen from the illustrations below, branches of
the Mandibular Nerve (the third and lowermost division of
the Trigeminal Nerve or the 5th Cranial Nerve) can be in
close proximity either to the roots of the wisdom teeth
(also the 2nd molars as well) or to either side of the tooth
The spontaneous recovery rate for nerve injuries related to lower wisdom
tooth (3rd molar) removal is quite variable ranging from 50% - 100% for both
the IAN and LN.
Incidence of Nerve-Damage relating to Wisdom Tooth Removal:
Inferior Alveolar Nerve. IAN function is disturbed in 4 – 5% of procedures (range
1.3 – 7.8%). Most patients will regain normal sensation within a few weeks or
months and < 1% (range 0 – 2.2%) have a persistent sensory disturbance.
A higher incidence of IAN injury has been reported with wisdom teeth that are
horizontally or mesio-angularly impacted and have complete bone cover.
One study has also demonstrated that increasing age is associated with a higher
frequency of IAN injury (14 – 24 year old patients 1.2%; 35 – 81 year-old patients,
Lingual Nerve. There is a wide range in the reported frequency of LN injuries
during lower wisdom tooth, with 0.2 – 22% of patients reporting sensory
disturbances in the early post-operative period and 0 – 2%, a permanent
A higher incidence of IAN injury has been reported with certain types of surgical
technique (using an 'elevator' to 'protect' the LN) together with deeply impacted
teeth when the surgery is consequently difficult, particularly if distal bone removal is
Most cases of nerve damage during wisdom tooth removal are not identified at the
time of lower wisdom teeth removal but in the post-operative period.
However, careful monitoring of sensory recovery over a three month period should
distinguish between these different types of injury.
Monitoring sensory recovery is undertaken by the application of stimuli to the 'numb'
area. Responses of the patient will indicate first the arrival of the regenerating
nerve ends and then subsequently the level of recovery.
However, the most sensitive indicator of a sensory abnormality is the patient’s own
subjective report, as minor sensory disturbances may not be detected by testing.
Simple Sensory Testing
A standard protocol for sensory testing does not exist and attempts to standardise
objective evaluation of nerve injuries have been unsuccessful.
Evaluation techniques are subjective or semi-objective at best.
Suggested techniques include:
The most desirable outcome after nerve injury is the spontaneous return of normal
The likelihood of this occurring depends on both the severity of the injury and the
Inferior Alveolar / Dental Nerve:
If a sensory disturbance is first noted at review, recovery should be monitored
using the sensory tests described above.
Patients with paræsthesia in the distribution of the IAN (evoked by touching the lip
or chin) usually require no surgical intervention.
Patients with complete anæsthesia post-operatively should be evaluated
radiographically (such as an OPG or a CT scan) to ensure that the roof of
the nerve canal has not been displaced downwards to create an
obstruction to nerve repair and regeneration. In the extremely rare event that this
has occurred, removal of the bony fragment would seem to be appropriate, without
Referral to an Oral & Maxillofacial surgeon familiar with this type of procedure or
a neurosurgeon or a micro-neurosurgeon is important. The patient should know
that full recovery may not be achieved even with surgery though some recovery
may occur even if surgical ‘decompression’ is not performed.
If, after 3 months after the injury, monitoring reveals little or no sensory recovery,
referral is again indicated. A further X-ray to assess the continuity of the IDN
canal is obtained and surgical exploration and ‘decompression’ of the nerve is
considered if the canal is disrupted, if there is very little recovery of sensation or if
there is significant dysæsthesia.
However, the results of surgery are variable and sometimes disappointing.
If the LN is knowingly cut during wisdom tooth removal, it should be immediately
This may not be possible in dental practice and immediate referral to an
appropriate experienced Oral & Maxillofacial surgeon is indicated. 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.
Complete anæsthesia could be caused by both a crush or cutting injury and so
surgical intervention is not indicated initially.
However, the absence of progressive sensory recovery by 3 – 4 months post-
injury is an indication for surgical exploration at an appropriate Oral & Maxillofacial
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. This is unusual however and more commonly
the nerve is found to have been cut.
If a neuroma has developed, this can be seen as a marked expansion at the site
of the injury and must be removed together with the damaged segment of
the nerve. A nerve graft is then used. The results of surgery are very variable;
some patients regain good sensation whilst others show little if any improvement.
One study showed a success rate of 80% and a recent prospective study has
shown that the majority of patients consider the surgery worthwhile. Surgery
should therefore be offered to all patients with LN injury who show few signs of
Useful Contact Addresses:
In the UK (at the moment, I can only find the details for England), there are
seemingly 2 major centres regarding 'dental nerve' injuries; these are based at the
King's Dental Institute, London and at the School of Clinical Dentistry, Sheffield.
If you want to contact them about being seen regarding your nerve injuries, they
can be emailed at the following email addresses; Professor Renton (King's) and
Professor Robinson (Sheffield).
University of Sheffield, School of Clinical Dentistry
BJOMS 1990. A method of assessment in cases of lingual nerve injury
BJOMS 1992. Experiences in Lingual Nerve Repair
BJOMS 1997. Protection of the Lingual Nerve during operations on the Mandibular
3rd Molar - a simple method
Australian Dental Journal 1997 - IAN damage following removal of mandibular 3rd
molar teeth - A prospective study using panoramic radiography
BDJ 2002. Lingual nerve injury subsequent to wisdom teeth removal — a 5-year
retrospective audit from a high street dental practice
Braz J Oral Sci 2003 - Evidence Based Means of Avoiding Lingual Nerve Injury
Dental Update 2003 - Nerve Damage and Third Molar Removal
JADA 2003 - Lingual Nerve Damage due to inferior alveolar nerve blocks - A
BJOMS 2004 - Current management of damage to the inferior alveolar and lingual
nerves as a result of removal of third molars
BJOMS 2005 - New method for the objective evaluation of injury to the lingual
nerve after operation on 3rd molars
BJOMS 2005 - Objective evaluation of iatrogenic lingual nerve injuries using jaw-
BJOMS 2005 - A randomised controlled clinical trial to compare the incidence of
injury to the IAN as a result of coronectomy & removal of mandibular 3rd molars
J Canad Dent Assoc 2005 - Iatrogenic Paresthesia in the Third Division of the
Trigeminal Nerve - 12 Years of Clinical Experience
JOMS 2005. Frequency of Trigeminal Nerve Injuries following 3rd Molar Removal
JOMS 2005. Diagnosis and Management of Trigeminal Nerve Injuries
JOMS 2005. Lingual Nerve Damage After Mandibular Third Molar Surgery - A
Randomized Clinical Trial
JOMS 2005. Panoramic Radiographic Findings as Predictors of Inferior Alveolar
Nerve Exposure Following 3rd Molar Extraction
JOMS 2005. The Effect of Injury and Protocols for Management
JOMS 2005. The Results of Nerve Repair and the Management of Nerve Injury–
BDJ 2006 - Simplifying the assessment of the recovery from surgical injury to the
JOMS 2006. Case Report. Traumatic Changes of the Inferior Alveolar Nerve &
Gasserian Ganglion After Removal of a Mandibular 3rd Molar - Report of a Case
JOMS 2006. Frequency & Evolution of Lingual Nerve Lesions Following Lower 3rd
JOMS 2006. Late Surgical Management of Lingual Nerve Injuries - Outcome
JOMS 2006. Etiology of Lingual Nerve Injuries in the 3rd Molar Region - A Cadaver
& Histologic Study
JOMS 2006. Outcome Assessment of Inferior Alveolar Nerve Microsurgery - A
JOMS 2007. Functional Sensory Recovery After Trigeminal Nerve Repair
CDAJ 2007 - Permanent Nerve damage from IAN Blocks - An Update to include
Cochrane Collaboration 2008 - Interventions for Iatrogenic IAN Injury (Protocol)
Oral Surgery 2008 - IAN decompression and neurolysis
J Oral Maxillofac Surg 2009. The Anatomic Structure of the Inferior Alveolar
Neurovascular Bundle in the 3rd Molar Region
Dental Update 2010. Prevention of Iatrogenic Inferior Alveolar Nerve Injuries in
Relation to Dental Procedures.
Oral Surgery 2010. Correlation of the radiological predictive factors of Inferior
Alveolar Nerve injury with Cone Beam Computed Tomography findings.
J Oral Maxillofac Surg 2010. Diagnostic Accuracy of Panoramic Radiography in
Determining Relationship Between Inferior Alveolar Nerve & Mandibular 3rd Molar.
J Oral Maxillofac Surg 2010. Retrospective Review of Microsurgical Repair of 222
Lingual Nerve Injuries.
BDJ 2010. Trigeminal Nerve injuries in relation to the local anaesthesia in
Faculty Dent J 2011. Minimising and managing nerve injuries in dental surgical
JOMS 2011. Correlation of Radiographic Signs, Inferior Dental Nerve Exposure &
Deficit in Third Molar Surgery
BJOMS 2011. Incidence of Inferior Alveolar & Lingual Nerve Paraesthesia
following Mandibular 3rd Molar extractions. A retrospective audit of 236 cases
BJOMS 2011. The incidence of radiographic signs indicating close proximity of
inferior dental canal to lower wisdom teeth on orthopantomograms
J Oral Maxillofac Surg 2011. Long-Term Outcome of Trigeminal Nerve Injuries
Related to Dental Treatment
BDJ 2013. UK dentists' experience of iatrogenic trigeminal nerve injuries in relation
to routine dental procedures - why, when & how often?
Cochrane Review 2014. Review. Interventions for Iatrogenic Inferior Alveolar &
Lingual Nerve Injury
The branches of the Mandibular Nerve that are of
significance to wisdom teeth removal, include the:
- Inferior Alveolar (or Inferior Dental) (IAN / IDN)
- Lingual (LN)
- Long Buccal (LB)
- Mylohyoid (MH)
- Mental (MN)
Hence, trauma to these nerves can result in either numbness, tingling, altered
sensation or a loss of taste (or a combination or progression of these symptoms).
Trauma, here, covers stretching, crushing or cutting of these nerves.
The degree of trauma will greatly determine the degree of numbness (and loss of
taste) and its duration. Trauma can be due to use of instruments to remove the
tooth, drills used to remove bone and 'elevators' used to 'protect' the LN.
Trauma to the LN & the IAN can also result from the injection of local anæsthetic
(some local anæsthetics have been found to cause prolonged numbness), fracture
of the Lingual Plate, jaw fractures, osteotomies for the correction of malocclusion
and the removal of pathology in proximity to the IAN or the LN (such as peeling a
dentigerous cyst out of its cavity).
As this is a well recognised complication of lower wisdom tooth removal, patients
need to be warned about the potential for numbness (temporary / permanent) prior
to surgery so that the patient can weigh up the pros & cons and the potential
consequences of the procedure and if needs be, opt for a different surgical
treatment (such as a coronectomy or operculectomy).
|showing the course
of the ID Canal in
relation to the root
tips of the lower
- Mapping out and photographing the area
Light touch is most commonly tested by gently
applying a wisp of cotton wool to the skin or lining
of the cheek or lips.
However, it is difficult to apply this stimulus in a
reproducible manner and the use of a cotton wool
wisp on moist oral mucosa is difficult.
Greater consistency and reproducibility can be
obtained using Von Frey hairs. Stimuli are applied
at random and the area of anaesthesia can be
stimulus is felt.
Testing pin prick threshold is often performed using a dental probe or needle but
reproducibility is poor.
Areas of anæsthesia can be mapped. If sensation is present within the affected
area on the injured side, then the pin prick sensation threshold is determined.
The probes are drawn a few millimetres across the surface, at a constant pressure
and the patient asked to indicate the point at which the sensation becomes sharp
rather than dull.
The pin prick sensation threshold is noted for a series of randomly chosen
points on both the 'injured' and the 'uninjured' side.
This test can quickly be performed if pairs of blunt
probes with different separations (2 – 20 mm) are
mounted around a disc.
The probes are applied at a series of fixed sites
chosen on the lips or tongue, depending on which
has been damaged.
The probes are drawn a few millimetres across
the surface, at a constant pressure and the
patient is asked whether one or two
points are felt.
two point discrimination threshold.
This threshold varies in different regions of the mouth (2 – 4 mm on the tongue and
lip, 8 – 10 mm on the skin over the lower border of the chin).
Cotton wool pledgets soaked in saline solution, sugar solution, vinegar or quinine
solution are drawn 1 – 2 cm across the side of the tongue and the patient asked to
indicate whether they taste salt, sweet, sour, bitter or no taste, before
Stimuli should be applied in random order, to each side of the tongue and rinsing
with tap water between tests.
Before the removal of the
mouth needs to be assessed
radiographically (i.e. X-rayed).
This, amongst other things, will show
whether the IAN canal is in proximity
to the wisdom tooth and there are
certain appearances on the OPG
that suggest the IAN canal is
intimate with the tooth.
Studies have shown that these
aren't always reliable and the
definitive information can be gained
with a Cone Beam CT scan (often
used for dental implants but rarely
for wisdom teeth).
|Last Updated 21st November 2014
|Alveolar (Dental) or Lingual Nerves during lower 3rd molar removal