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Endo tips    Better Endo    Endo abstracts    Endo discussions

A 21 year retrospective study of reports of paresthesia following local anesthetic administration
Nerve injuries following nerve blocking in the pterygomandibular space
The etiology of altered sensation in the inferior alveolar, lingual, and mental nerves as a result of dental treatment
Lingual nerve paresthesia following third molar surgery: a retrospective clinical study.
Dysesthesia and anesthesia of the mandibular nerve following dental treatment
Permanent nerve involvement resulting from inferior alveolar nerve blocks.
Potent analgesic effects of GDNF in neuropathic pain states
Burning mouth syndrome (BMS): controlled open trial of the efficacy of alpha-lipoic acid (thioctic acid) on symptomatology
Evaluation of precautions adopted by dental surgeon using local anaesthesia
The use of autogenous vein grafts for inferior alveolar and lingual nerve reconstruction


Evidence-based means of avoiding Lingual Nerve Injury following Mandibular Third Molar Extractions

Braz J Oral Sci. April/June 2003 - Vol. 2 - Number 5
George W. Bernard DDS, Ph D
Victor Mintz DDS, MS
Division of Oral Biology and Medicine
University of California, Los Angeles School of Dentistry
Received for publication: April 8, 2003
Accepted: May 20, 2003

Severe damage or severance of the lingual nerve can result 
in permanent numbness, loss of taste and dysthesia of the 
anterior two-thirds of the tongue on the side of the mandibular 
third molar extraction, causing a lifetime of distress. During 
third molar extractions the incidence of injury and severance 
to the lingual nerve is far too prevalent. According to Kurt 
Thoma’s textbook of Oral Surgery, third edition, injury to the 
lingual nerve is invariably caused by negligence.

Thoma states that in ordinary cases any injury to the lingual 
nerve is gross negligence1. In recent years many articles have 
been written to confirm the reason for this. Because there is 
enormous variation in the pathway of the lingual nerve, especially 
in the third molar area 2,3,4,5, oral surgeons from Thoma forward 
developed techniques for 3rd molar extractions which limited 
extractions to a buccal approach, thereby giving a wide surgical 
berth to most variations of the lingual nerve. These variations 
are listed as running from the crest of the lingual bone to below
the floor of the mouth. Sometimes one of the variations is the 
lingual nerve traversing the retromolar pad area2,4. Staying 
away from the lingual bone during extractions, and the retromolar 
pad for incisions will keep the surgeon away from the multiple 
pathways the lingual nerve might take. If the dentist is cognizant 
of the lingual nerve ariations, they will then know where to 
design the boundaries of the surgical field. If for some reason 
the dentist has no choice but to involve an area where the lingual 
nerve might be, then it is incumbent that the nerve be
carefully dissected, identified and gently retracted to protect 
its integrity. 

If this is not done, various degrees of parethesia, dysesthesia 
and anesthesia may result in the anterior two-thirds of the tongue, 
floor of the mouth and lingual gingiva. Severance of the lingual 
nerve will include a variable loss of taste because of the involvement 
of the chorda tympani nerve, which runs within the lingual nerve 
sheath7. Lingual nerve injury occurs by direct compression, incision 
or excision during third molar removal, periodontal surgery,
tumor removal and also in cases of trauma whenever procedures are 
performed in the retromolar area. Alling8 lists the following reasons 
for lingual nerve damage by quoting Mozsary and Middleton9, poor flap 
design, uncontrolled instrumentation or fracture of the lingual Plate. 
Poor flap design is an admission of lack of knowledge of anatomy of
the surgical area. Uncontrolled instrumentation demonstrates a lack 
of care and caution in performing the surgery and fracture of the 
lingual plate shows an abandonment of knowledge of proper technique. 
During the seventies and eighties some articles were written and 
published by oral surgeons, trying to justify lingual nerve injuries
resulting from the removal of impacted third molars. One author 
distributed a questionnaire to oral surgeons throughout the country, 
requesting reasons for how the lingual nerve could be injured. He got 
an enormous response in terms of numbers and eighteen causes for the 
damage, but no one described or explained how or why anesthesia
occurred, and of course no one admitted to negligence5. Other articles 
reported, paradoxically, that the anatomical variations in the course 
of the lingual nerve justified the injuries.

Several attempts were reported in regard to stretching and 
compression of the nerve while retracting the lingual
flap. Some articles assumed a trauma to the lingual nerve as 
a result of the anesthetic injections even the toxicity
of the Lidocaine as causes of damage to the nerve, but there 
were no substantiation of these claims by any reliable
scientific studies10. There have been numerous articles that 
deny negligence based upon the assumed damage caused by
penetration through or into the nerve by the injection needle. 
But in the Journal of the American Dental Association, Anthony 
Pogrel wrote Direct trauma from the needle seems unlikely because 
it is known that most cases of trauma resulting from needle 
contact resolve spontaneously. It is difficult to envision how 
needle trauma can damage the whole nerve10. Kraft and Hickel11 
reported that they gave 12,104 mandibular block injections 
without performing surgery and found there was not one case of 
complete permanent anesthesia. Of these cases, there were 18 
cases of temporary anesthesia of the lingual nerve, indicating 
penetration into the nerve sheath with complete healing
afterward. This was direct evidence that piercing the lingual 
nerve did not sever it11. They wrote block anesthesia
alone does not have a decisive impact on the incidence of 
lingual sensory disturbance in surgical third molar
removal. Because the buccal approach for extracting the 
lower 3rd molar is the method of choice in the United States,

current Oral Surgery textbooks and the guidelines of the 
American Association of Oral and maxillofacial Surgeons
(AAOMS) favor this procedure. The articles, which report 
on the various reasons as to how the lingual nerve can be
inadvertently damaged, are attempts to cover up negligence. 
None of those reasons are legitimate in terms of
justifying the damage that could occur during the operation, 
and are not within the standard of care. Technology and
instrumentation today has made the surgery significantly 
simpler than it was four decades ago when Thoma wrote his
book. Dental surgeons have education, training and experience. 
They have learned anatomy and other pertinent basic sciences, 
and should be fully conscious of the structures that are 
encountered in doing any procedure. No surgeon should ever 
attempt to perform an operation without the capability of 
doing it properly and successfully completing the task. 
Because current oral surgery textbooks and discourse in 
university classrooms favor the buccal approach in
the removal of impacted third molars, the external oblique 
ridge is used as a marker for the incision going distally
and buccally, and begins at the distobuccal angle of the 
second molar, bearing in mind that the ramus of the mandible
flares laterally and posteriorly. This portion of the incision 
is continuous with the vertical buccal release incision 
alongside the first or second molar. This usually allows the 
surgeon to gain adequate access to the lower wisdom teeth, 
impacted or not, and carefully manage the lingual flap which
might include the retromolar pad without endangering the 
lingual nerve. If a straight line is drawn through the central 
fossae of the premolars and the molars, and it is extended 
through the retromolar pad, this line would end on the lingual 
or medial surface of the ramus, almost exactly where the lingual 
nerve usually comes down between the medial surface of the 
mandible and the hyoglossus muscle on its way anteriorly and 
inferiorly through the lingual mucosa to the lateral border 
of the sub- mandibular gland and the floor of the mouth.

An incision directed in any of these areas could very likely 
cause a  severance of the lingual nerve. Obviously, the
lingual flap has to be carefully retracted with a safe type 
of  retractor when it is necessary to remove occlusal
bone covering an impacted mandibular third molar in order 
to  protect the flap, remove bone, section the tooth, and
elevate sectioned portions of the tooth. Uncontrolled 
instrumentation is negligence and is one of the causes of
damaging or severing the lingual nerve. Bone removal and 
tooth sectioning with a relatively high speed drill is
another cause of nerve damage and severance, especially
when the lingual bone is pierced or cut. Again, this can be
avoided with careful, adequate, deliberate retraction, 
controlled instrumentation and direct vision of the surgical
field. 

In summary, with the buccal approach under direct vision, 
proper incision, careful bone removal, management and
protection of the flap during drilling, and elevation 
of the tooth structure, the lingual nerve can be preserved
during the surgery of mandibular third molars. In addition, 
with the proper incision, there is properly positioned
tissue to permit safe placement of the sutures. Following 
the accepted technique of the buccal approach, using the
external oblique ridge as a marker and making a buccal 
incision with a full mucoperiostal flap, one can gain
sufficient access to the third molar, if it is partially 
or fully impacted. Variations of the course of the lingual
nerve made clear by anatomical dissections indicate that it
occasionally passes through the retromolar pad2,7. This
reinforces the obligatory use of the buccal incision. 
A new major surgical problem occurs when it is necessary to
remove bone covering the distocclusal portion of the tooth 
before removing the tooth. This requires great care in
gaining access to the area. The lingual flap has to be 
retracted to expose the bone to be removed by drilling or
chisel. It is of the utmost importance that this lingual 
flap be protected at all times by means of a properly placed
and designed retractor so that the lingual flap is not damaged 
or excessively compressed because this is an area
where the lingual nervemight be encountered. Pichler and 
Beirne report that the Various types of lingual retractors,
such as Howarth’s, Ward’s, Meade’s, Hovell’s and Rowe’s 
retractors have been used for this purpose. During Third
Molar extractions recently, attention has been focused on 
the safety of lingual flap retractors, with some studies
particularly critical of the narrowness of the Howarth’s 
periosteal elevator 12,13. Other articles have also shown
that though lingual nerve retraction during third molar 
removal may cause transient damage, it is not associated with
permanent damage, and it has been suggested that lingual 
nerve retraction should be used in the removal of third
molars when necessary. Because a periosteal elevator may 
not be a broad enough retractor to totally protect the
nerve, special retractors have been developed for this 
purpose10,14,15. Greenwood et al.16 showed that a broader
lingual retractor as compared to a Howarth’s elevator was 
much less likely to be associated with sensory loss. Most
oral surgeons and experienced dentists never sever the lingual 
nerve. They do not because they follow the rules of
proper extraction of 3rd molars, and therefore always 
practice within the standard of care.

References

1. Thoma KH. Oral Surgery. 3rd ed. Saint Louis: Mosby; 1969.
2. Keisselbach JE, Chamberlain JG. Clinical and anatomic 
   observations on the relationship of the lingual nerve to the
   mandibular third molar region. J Oral Maxillofac Surg. 1984;42: 565-7.
3. Pogrel MA, Renaut A, Schmitt B. Ammar,. Relationship of the 
   lingual nerve to the mandibular third molar region.
   J Oral Maxillofac Surg. 1997; 53: 134-7.
4. Behnia H, Kheradvar A, Shahrokhi M. An anatomic study of the 
   lingual nerve in the third molar region.
   J Oral Maxillofac Surg. 2000; 58: 649-51.
5. Miloro M, Halkias LE, Sloane HW, Chakeres DW. Assessment of the 
   lingual nerve in the third molar region using
   magnetic resonance imaging. J Oral Maxillofac Surg. 1997; 55: 134-7.
6. Peterson L, Ellie E, Hupp J, Tucker M. Contemporary oral 
   and maxillofacial surgery. 4th ed. Saint Louis: Mosby; 2003.
7. Pogrel MA, Kaban LB. Injuries to the interior alveolar and lingual 
   nerves. Calif Dent J. 1993; 21: 50-4.
8. Alling CC. Dysthesia of the lingual and inferior alveolar nerves 
   following third molar surgery. J Oral Surg. 1973; 31: 918-20.
9. Mozsary PG, Middleton RA. Microsurgical reconstruction of the 
   lingual nerve. J Oral Maxillofac Surg. 1984 ;42: 415-20.
10.Pogrel MA, Thambi SRI. Permanent nerve damage resulting from 
   inferior alveolar nerve blocks. J Am Dent Assoc. 2000;131: 901-7.
11.Kraft TC, Hickel R. Clinical investigation into the incidence 
   of direct damage to the lingual nerve caused by
   local anesthesia. J Craniomaxillofac Surg. 1994; 22: 294-6.
12.To EW, Chan FF. Lingual nerve retractor. Br J Oral Maxillofac 
   Surg. 1994; 32: 125-6.
13.Blackburn CW, Bramley PA. Lingual nerve damage associated 
   with the removal of third molars. Br Dent J. 1989; 167: 103-7.
14.Browne WG. Lingual flap retractor for surgery in third molar 
   area. Br J Oral Surg. 1982; 20: 151-2.
15.Dean Medical Instruments, Inc. 15502 Commerce Lane, Huntington 
   Beach CA, 92649, USA.
16. Greenwood M, Langton SG, Rood JP. A combination of broad and 
    narrow retractors for lingual nerve protection
    during lower third molar surgery. Br Oral Maxillofac Surg. 
	1996; 34: 143-57.

The course of the lingual nerve can be seen in the following illustrations:
From "Anatomy, A Regional Atlas of the Human Body", Carmine D. Clemente, 
printed by Lea & Febiger, 1975; Courtesy: Urban & Fischer Verlag

The Infratemporal Region and the Branches of the Mandibular Nerve

The Infratemporal Region and the Branches of the Mandibular Nerve

The Infratemporal Region and the Maxillary Artery

The Infratemporal Region and the Maxillary Artery

Nerves of the Nasal and Oral Cavities and the Otic Ganglion

Nerves of the Nasal and Oral Cavities and the Otic Ganglion
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