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Incidence of nerve damage following third molar removal: A West of Scotland Oral Surgery Research Group Study
Incidence of nerve damage following third molar removal: A West of Scotland Oral Surgery Research Group Study F. A. Carmichael,
I>. A.
McGowan
Department of Oral Surgery, Glasgow G2 3.12
Glasgow Dental Hospital and School,
.378 Sauchiehall
Street,
SUMMARY. A survey was carried out to record both initial and longterm effects on the lingual and inferior alveolar nerves following third molar removal. Light hundred and twenty five patients were included from eight West of Scotland Oral Surgery Units, and had 1339 third molars removed. Changes in sensation were recorded by direct questioning at 6 to 24 h and 7 to 10 days, and by postal questionnaire at 12-18 months. The incidence of lingual nerve damage was found to be 15% of operated sides at 6 to 24 hours, 10.7”10 at 7 to 10 days, and 0.6% after 1 year. The incidence of inferior alveolar nerve damage was 5.5% of operated sides at 6 to 24 h, 3.9% at 7 to 10 days, and 0.9% after 1 year. These results are proposed as an indication of the likely incidence of nerve damage complicating third molar removal in the general circumstances of current United Kingdom practice and are presented as a basis for discussion of patient information and current prudent practice. Since one in four patients suffered at least temporary sensory deficit, we believe the case for effective warning of all patients undergoing impacted third molar removal is overwhelming.
Inferior alveolar nerve. Damage to this nerve has been more widely studied. Again there is a wide range of reported incidenccs ranging from 0.4 to 5.5% (Table 2). These papers are not always clear as to whether patients or teeth are being referred to. An increase in incidence has been related to more deeply impacted teeth (Rud, 1970) and to less expertenced surgeons (Sisk et al., 1986).
INTRODUCTION The removal of mandibular third molars results in many unwanted scquelac like pain, swelling, bruising and trismus. While these are unfortunate for the patient they are perhaps not unexpected following minor oral surgery. The patient may however be dissatisfied if the surgery results in impaired sensation. particulary if no prior warning has been given. Damage to the lingual and inferior alveolar nerves is distressing and is also a source of complaint and. increasingly. of litigation against the surgeon.
Mylohyoid nerve. Mylohyoid nerve damage is rarely mentioned in the literature as it can be confused with inferior alveolar nerve damage. It gives an area of
Lingual nerve. The incidence of nerve damage following mandibular third molar surgery has been widely reported, with quite marked differences in figures between the various studies. It ranges from 0.6 to 22%. Obviously the criteria for inclusion, techniques used, method of testing and time span varies in these studies (Table 1). Schwartz (1973) in a survey of 2500 members of the American Society of Oral Surgeons found 66% of the respondents had experienced the problem of impaired lingual sensation. There were 41X cases of permanent impairment and 2399 of temporary. The reported time span for recovery ranged from 2 days to 10 years. Litigation resulted from 53 cases. Ailing (1986) also sent questionnaires to 103 Fellows of the American Association of Oral and Maxillofacial Surgeons. Of those who replied an incidence of lingual dysesthcsia of @.06% was reported and of those 13% were persistent.
‘Table I - Lingual nerve damage following mandibular
third molar
surgery Author Rlld Bruce Rood
<‘I al.
Rud
FI al.
Sisk et al. Mason Arx
Blackburn
78
No. ..-.
1970 1980 I983
718 teeth 1% 990 teeth I I ‘%, 1400 teeth 6.6% (decreased to 0% at 6 months) 334 teeth 2% (lingual split removed) 73 teeth 3’:‘” (lingual split rctaincd) 500 teeth 0.6% (dccreascd to 0.2% at h months) 359 teeth 0.8’%> 104~1 teeth I I .5x (decreased to 0.6%) 550 patients 22’Y0 (decreased to 0%) 1117 teeth II’X (decrcascd to 0.5% at 36 weeks)
1984
Goldberg
Von
Year .~
1985 1986 1988
Kr Simpson
1989
& Rramley
1989
Incidence
Incidence
Table 2 -
Inferior alveolar molar surgery
third Author
Year
Robinson Frank flowe & Rud
I940 1959
Van
GoI
Poyton
1960
I’)70 er nl.
1077 19x0
Bruce Rood
EI ul.
RUd
Goldhcrg
CI ol.
Sisk P/ ul.
Von Arx 84 Simpson
of ncrvc damage following third molar removal: ,Z West ncrv’c damage
NO.
--------___ 300 patients
300 teeth l3.55 teeth
following
mandibular
Incidence
I (3I!‘” 5 .3‘ %, 5.2% 2.2%
71Y (deep) teeth 162 (not deep) I .2‘Z 932 pts & teeth 1.4% (decreased to 0% at 4 months) 1337 teeth 4.49% (dccrcased to at Icast I’%, at 6 months) 765 patients 7 1‘ %, 990prs & tcetn 4.4% 1400 teeth 5.5% (dccrcased to 0.4% at 6 months) 334 teeth 3% (lingual split removed) 73 teeth 3% (lingual split retained) 500 teeth 0.60/u (decreased to 0% at 6 months) 843 teeth 0.4% (cxpericnccd operators) 3SY teeth 3 ,6% (less expcricnced operators) 550 patients 5% (decreased to 0%)
altered sensation at the point of the chin, if effected and most investigators do not ask specifically about this nerve. The aim of this study was to record the incidence of lingual, inferior alveolar and mylohyoid nerve deficit and to attempt to correlate the results with the type and degree of impaction and method of removal. This would assist in the decision as to how thorough we should be in warning prospective patients about their chances of sustaining nerve damage. The study was dclibcratcly planned to be simple in operation and to record the experience of a substantial group of patients undergoing surgery in the routine circumstancesofcurrenthospital practice. The oral surgeons in the West of Scotland have a wide variety of training backgrounds and there is no tradition of strict adherence to common operating protocols. The results of the survey should therefore be broadly representative of current British experience.
MATERIALS
AND METHODS
Records were completed for 825 consecutive patients who presented for third molar surgery in eight West of Scotland Oral Surgery Units. There was no case selection apart from the fact that the patients required removal of an impacted lower third molar. A total of 1339 teeth were removed during an s-month period. Roth local and general anacsthesia were used. All grades of staff including undergraduate students carried out the surgery. The surgeons were asked to complete a form which recorded the state of eruption. angulation and associated pathology. This was assessed both clinically and radiographically.
ofScotlandOral
Surgery Research
Group Study
7Y
Type of anaesthcsia. method of bone removal (chisel or bur) or simple elevation, use of a lingual flap retractor, division of tooth and suturing were recorded. The surgeons also noted whether the patients were warned preoperatively of possible sensory dcfici t . Assessment of postoperative deficit was carried out by standard questioning, for example: ‘Do you have normal feeling in your lip, tongue and at the point of the chin’?‘. If the tongue was affcctcd the questions were asked: ‘Is it completely affected on one side or just the tip?’ and ‘Is it numb, tingling or painful?‘. If the inferior alveolar nerve was affected the questions were asked: ‘1s it the lip or lip and chin which are affected?’ and ‘1s it numb, tingling or painful?‘. These enquiries took place at between 6 to 24 hours and at 7 to 10 days. The symptoms recorded were purely subjective and although sensory testing may have been carried out this was not required to bc recorded. At approximately 1 year (range 12 to I8 months) only the patients who had given a positive response at 7 to 10 days were sent a postal questionnaire cnquiring as to whether they still had a change in sensation of their lip or tongue. One hundred and thirty five patients of a possible 169 replied (80% response rate). The data were coded and analysed on the Glasgow University Computing Services ICI, 3980 using the SPSSX programme. Chi square tests were used to calculate probabilities for comparisons.
RESULTS Results were obtained from 825 patients (31.5 males and 5 10 females). There was no cast selection and a total of 1339 teeth were removed. Most of the patients were aged between I6 and 30 years. and 4% of teeth were recorded as being erupted. 48% partially erupted and 48% uncruptcd. Those teeth reported as uneruptcd were assessed radiographically and 33.6% were found to have just soft tissue cover. 13% incomplete bone cover and 53.4% complete bone cover. The commonest angulation was mcsioangular (40%), followed by vertical (29%). distoangular and horizontal (15% each). and 1% were transverse or classified as ‘other’. which included other aberrant positions. Most teeth were removed because of a history of pericoronitis (59%) although caries. periapical infection and the presence of a related cyst were also listed. One hundred and sixteen teeth were removed for ‘other’ reasons, presumably for orthodontic indications or as a contralateral symptomless tooth in a patient undcrgoing a general anacsthctic. The majority (82.5%) of the teeth were removed under general anaesthesia, the remainder under local anaesthesia or local anacsthcsia with sedation. Chisels were used to rcmovc bone in 58% of cases, drills in 31% and 1I % did not rcquirc bone removal. Lingual flap retraction was used in 71% of cases. A Howarth’s pcriostcal elevator was usually used. the frequency varying with the depth of impaction: in 23% of erupted
X0
British Journal of Oral and ~axillofacial
Surrerb
teeth, 64% of those partly erupted, 65% of those unerupted with only soft tissue cover. 90% of those unerupted with incomplete bone cover and 98% of those uneruptcd with complete bone cover. Division was required in 218 teeth and 1017 wounds were sutured. Preoperative warnings of possible ncrvc deficit ranged from 82 to 100%. This varied from hospital to hospital, the lowest frequency being at the Dental Ilospital and School. This may be due to the fact that simpler cases were being carried out there and surgeons were reluctant to raise the possibility of nerve damage when they believed it to be unlikely. It may also bc the cast that relatively junior members of staff trcatcd these patients without reference to a more senior colleague. Ihzgual
We found no significant difference between the USC of a chisel or bur (19.6% of those removed with a chisel being affected and 13.5% of those removed with a bur). There was a significant increase in the incidence of deficit if a lingual retractor was inserted (chi square p
nerve
At 6 to 24 h, 15% of operated sides demonstrated some anacsthcsia or paracsthesia of the tongue mostly affecting the tip. This is a misleadingly high figure, because if the patient complained of the tip being affected, the surgeon may not have been able to differentiate between the two sides and may have recorded both as being affected. At 7 to IO days. the percentage reduced to 10.7%. When the incidence was related to the state of eruption. teeth completely erupted were significantly less frequently associated with anacsthcsia or paraesthesia of the tongue. and those with complete bone cover significantly more often (chi square p
inferior alveolur nerve At 6 to 24 h, 5.5% of operated sides showed some anacsthesia or paraesthcsia of the lip or lip and chin. This reduced to 3.9% at 7 to 10 days. The incidence was significantly less in relation to erupted or partially erupted teeth and significantly more in those with complete bone cover (chi square p
l‘able 5 - Inferior alveolar ncrbe deficit at 7 to IO days and state of eruption of teeth Table 3of tecrh Slate
Lingual net-ve dclicit at 7 to IO days and state of eruption Slate of eruption
of eruption
Erupted Partly-cruptcd Unerupted Soft tissue cover lnconipletc bone cover Complete bone cover
Total No. of teeth
No.with deficit
54 63X
I 57
214 i3Y 8.3 ‘chi square
--__
?;
1.85 X.Y
23 45 16 p
10.7s 13.3 19.3
t
Significantly fewer cruptcd teeth and significantly more uncruptcd teeth with complete bone cover resulted in deficit.
Table 4 - I.ingual teeth
ncrvc &licit
of
.-
Total No. of teeth -. _ 386 52.3 IO5 205 13 ‘chi square p
Significantly fewer vertically horizontally and ‘other’ an+
No. with deficit _
‘/u ._
21 ix 22 36 4
anglctl teeth and significantly teeth resulted in d&it.
_ 5.4’ II.1 I I.2 17.6 30.X’
more
No. with dclicit
54 63X
0 I7
Table 6 - Inferior
alveolar
0 1.1’
nerve
deficit
at 7 to
4.2 3.x 15.7
teeth and bone cover
IO days
and
of teeth
Angulation -. -Vertical Mcsioanpular Disloangular I lorizontal Other
$+icantl!: horizontally
‘!d,
Y 214 33Y 13 x3 I.3 ‘chi square p
Significantly fewer erupted teeth and part-erupted significantly more unerupted teeth with complctc resulted in deficit.
angulation
Angularion -. Vertical Mcsioangular Distoanpular Horizontal Other
at 7 IO IO days and angulation
---.__---__
Erupted Parlly-erupted Unerupted Soft lissuc cover lncomplcte bone cover Complctc bone cover
Total No. of teeth
-
l-Vl;ll No. of teeth -
-
3% 523 IO5 205 I3 ‘chi square p
No. with deficit _
‘X _
IO 20 Is” I
fewer vcrticnlly antjcd teeth and significantly impacted teeth resulted in deficit
_ 2.6’ 3.Y 2.3 7.3 7.7
more
Incidence of nerve damage following third molar removal: A West of Scotland Oral Surgery Rcscarch Group Study
alveolar nerve was visualiscd at the time of operation and in six of the 12 cases the teeth were divided. Mylohyoid nerve Questioning was carried out with regard to deficit affecting the point of the chin. However this was imprecise and difficult. In the initial stages it was not possible to differentiate between mylohyoid and inferior alveolar damage and whether it was bilateral or unilateral. However our reported incidence was very small, only 20 of 1339 teeth. At 12 to 18 months, only one patient continued to have such a complaint.
DISCUSSION At a Consensus Development Conference on Removal of Third Molars in 1979 it- was rccommended that patients should be informed of potential surgical risks, including any permanent condition that has an incidence greater than 0.5% or any transitory condition that occurs with an incidence of 5% or more. In order that the patient can give fully informed consent they must be able to weigh up the risks of nerve damage against the possible consequences of retaining the teeth. This is especially so when unerupted teeth arc symptomless. The incidence of paraesthesia is significant, and it is advised that all patients should be warned of this possibility and this warning should be recorded clearly in the clinical notes (Collins, 1988). It would seem from our results that lingual nerve damage is more likely with deeper impactions, with horizontal impactions and with tooth division, all factors which make it more likely that the operator will insert a lingual flap retractor to protect the lingual nerve. It is suggested that the insertion of a lingual flap retractor can induce sensory deficit (Swanson, 1989). There was a marked reduction in the incidence of lingual anaesthcsia/paraesthesia from 6 to 24 h compared with 12 to 18 months. Perhaps most of those that resolved might be due to shielding from the insertion of the retractor and those persisting due to direct damage from the chisel or bur. Unfortunately the dilemma of whether oinot to insert a lingual retractor is unresolved. It should probably only be inserted if distolingual bone is being removed. In an attempt to minimisc trauma to the lingual tissues a modified distolingual splitting tcchuiquc has been used. Unfortunately in a series by Ifochwald et al. (1983) when 598 teeth were removed using this technique there was still a 4.3% incidence although all resolved in 5 months. The presence of ‘tingling’ is often used as a hopeful sign to reassure an anxious patient that all will be well. Unfortunately half of our patients with unresolved symptoms had reported tingling at 7 to 10 days. This finding is in agreement with Blackburn (1990). The greater incidence in those cases using general anaesthesia (Blackburn & Bramlcy, 1989) was probably because deeper, more difficult teeth were removed
81
under general anaesthesia. Endotrachcal anacsthesia itself has been implicated in lingual anacsthesia in non-oral operations (Jones, 1971). Due to the number of different units involved, it was not possible to monitor precisely when recovery occurred. Spontaneous recovery has been reported as being unlikely after 36 weeks (Blackburn & Bramlcy, 1989) although claims of recovery after 10 years have been recorded (Schwartz, 1973). We feel that after 1 year further recovery is unlikely. Inferior alveolar nerve damage is easier to predict by radiographic assessment (Rood & Shchab, 1990). It would appear from our results that although the initial incidence of inferior alveolar nerve damage is lower than that of the lingual nerve, recovery is less likely in the long-term (12 to 18 months). Simpson (1958) felt recovery was unlikely after 6 months. Anaesthesia of the point of the chin has been suggested as being due to neuropraxia of the anterior cutaneous nerve of the neck (Killcy & Kay. 1968) and to the mylohyoid nerve (Roberts & Harris, 1973). Roberts and Harris infiltrated local anaesthesia around the mylohyoid nerve and consistently found an area of submental analgesia. They suggested that it occurred during lower third molar removal due to neuropraxia of the mylohyoid nerve during lingual soft tissue retraction. We found a low incidence of long-term damage of 0.07% of operated sides. Overall no responding patient had more than one nerve affected in the long term. The overall long term incidence of any type of residual nerve damage was 1.6(X1of operated sides (2.5% of patients). Acknowledgements We acknowledge the help of all members of staff who completed the questionnaires and Mrs Ann Shaw who processed the data. ‘l‘he West of Scotland Oral Surgery Research Group includes the following:Mr A. Brewer, Miss F. Carmichael. Mr D. J. Crawford. Mr H. A. Critchlow, Mr A. El Attar. Mr T. R. Flood. Mr N. llammersley, Mr I. Hollingum, Mr N. E. Merchant. Mr J. McManncrs, Professor D. A. McGowan. Mr K. F. Moos. Mr 1). 1. Russell, Mr W. Smith. Mr 1.. F. Stasscn. Mr 1). Stcnhouse, Mr D. M. Still and Mr H. I’. Wright.
Keferences AllingIl1.C.C (19%). Dysesthesiaofthclingualandinfcrior alvcolarncrvcsfollowingthird molarsur~erv.Jo~~,7rnlu/
Orulmrd M~~xiNo/acicllS‘l;r~ery,44,454.
_’
.
R1ackburn.C. W.& I3ramlcv.l’. A. (1080). Lineualnervc damageassociatedwith‘thcrem’ovaloflon’erthirdmol;lrs.
British VctrralJournul,
167, 103.
t3lackburn.C. W.(lYY0).Amethodofasscssmcntincascsof lingual nerve injury. British JournulofOralatrd Muxillo~fkiul
Surgery. 28,238. Bruce. Ii. A.. Fredrickson. G. C. & Small. G. S. (1980). Age01 paticntsand morbidity associated with mandibular third molar surgery. Journulofri~eAmrrica,l I~cnrctlA.ssociarint~,
101,240. Collins. M. R.N. (lY8X). Paraesthesiafollowinglowerwisdom toothextraction. Jo~~rncrlofthe~Mediccrl~~)r~fet~e,lcc~ Uniotr. 4,
41. Frank.V.
H. (19.59). 1’aresthcsia:cvaluationof
ofOralSurgery.
16cascs.Journal
17,27.
Goldhcrg.M.II..Nemarich.A.N.&MarcoII,W.P.( Complic;~tions;~ftcrmandil~ularthirdmolarsurgcry: ticalanalysisofS(H)consccutiveprocedurcsinpri\,ate
1985). astatis-
82
British Journal of Oral and Maxillofacial
Surgery
I lochwald. D. A., Davis. W. H. KLMartin0ff.J. (1983). Modified distolingualsplittingtcchniqucforremovalofi~npactcd mandihularthirdmolars: Incidcnccofpostoperativc scquelac. OrulSurgery, Oral Medicine. Ornlt’aarhology, 56, 9. I~owc.G. L.&Poyton.H.G.( IYho). Prevcntionofdamagc to thcinfcriordentalncrvcdurin:!thcextractionofmandibular third molars. Bririvh IknralJournal, lW,35S. Jones,B.C.( 1Y71).I.ingualnen~cinjury:ncompkationof intubation. h’rirish JownalofAnaesrhesia. 43,730. Killcy.1I.C. & Kay. I.. W. (lY68).Postopcrativeanaesthesiaol thechin. Briri.vh MedicalJournal, 4.775. Kipp. D. P., Goldstein. H. fl. Xr Weiss. W. W. (I 080).Dysethesia alter mandibular third molarsurgery: a retrospective study antlanalysisof 1377surgicaI procedures.Journnlojrh~, Amcricun DentulAssociarion, 100, 185. Mason.I>. A.( lY88). I.ingualnervedamagcfollowin~lowcrthird molarsurgery. Inrernafio~~ulJo~rrnalofOrulu~~dMoxillofuciul Surgery, 17,290. NIH Consensus Development Confcrencc Summary (197’)). Kcmoval of Third Molars. Volume 2. Number I I. Ro1~crts.G. D.D.&llarris.M.( 1973).Neuropraxisofthc mylohyoid nerve and submental analgesia. fIrirish Jortrnalo/ OrulSurgcry, I I. I IO. Robinson,‘l‘. 0. ( lY40). Paresthesia: apostopcrativecomplication folloa~ingremovalofthcm;~ndibularthirdmolar.A~r~rricun Journulof Orlhodonrics, 2ti, 27X. Rood.J. P.(IYS3). Lingualsplittcchnique:damagetoinfcrior alveolarandlingu;~lnen~csdurin~rcmovalofimpacted mandibularthird molars. Bririvh DenralJournal, 154,402. Rood.J. P. &Shchad.B. A. (199O).‘l‘heradiologicalprcdiction ofinferioral\,eolarnervcinjuryduringthirdmolarsur~ery. British Journulof Orulund MaxillofacialSur~ery, 28,20. Rud, J. (1970). Thcsplit bone techniqucforrcmovalofimpactcd 28,4 IO. mandibular third molars. JoLcr,lcr/o,fOralSI1r~ery, Rud.J. (1984). Re-cvaluationofthclingualsplit-bone technique
forthercmovalofimpactcdmandihularthirdmolars.Journa~ ofOralund Mnxillofucial Surgery, 42,113. Schwartz, 1.. J. (1973). Lingual anaesthesia followingmandibular odontcctomy. Joun~c~lofOrolSurgery, 31,918. Simpson,II.~.(IY58).1njuricstotheinferiordcntalandmcntal OralSurgery, 16,3(x3. nerves./ournulof Sisk.A.L..I~ammcr,W.H.Shclton,D.W.&Joy,T;..D.(1986). Complicationsfollowingremovalofimpactcdthirdmol;~rs: thcrolcofthcexpcrienceofthesurgcon. JournolofOralund MaxillofacialSurgery, 44,8.55. Swanson. A. E. (1089). Rcmovingthemandibularthird molar: Journulof neurosensorydeficitsandconsequentlitigation. rhc~CanadicmJ)enmlAssociarion, 55,383. Vnn
TheAuthors F. A. Carmichael, BDS, FDSRCPS Lecturer
D. A. McGowan, MDS, YhD, FDSRCS, FFDRCS, FDSRCPS Professor. DepartmcntofOralSurgery. GlasgowDentalHospitalandSchool. 378SauchichallStrcct. GlasgowG23JZ Correspondenceandrequesrsforoffprjnts Carmicheal Paperrcceivcd 17Junc 1YY I Acceptcd2.S October 19Y1
toMissF.
A.
I>. A.
McGowan
Department of Oral Surgery, Glasgow G2 3.12
Glasgow Dental Hospital and School,
.378 Sauchiehall
Street,
SUMMARY. A survey was carried out to record both initial and longterm effects on the lingual and inferior alveolar nerves following third molar removal. Light hundred and twenty five patients were included from eight West of Scotland Oral Surgery Units, and had 1339 third molars removed. Changes in sensation were recorded by direct questioning at 6 to 24 h and 7 to 10 days, and by postal questionnaire at 12-18 months. The incidence of lingual nerve damage was found to be 15% of operated sides at 6 to 24 hours, 10.7”10 at 7 to 10 days, and 0.6% after 1 year. The incidence of inferior alveolar nerve damage was 5.5% of operated sides at 6 to 24 h, 3.9% at 7 to 10 days, and 0.9% after 1 year. These results are proposed as an indication of the likely incidence of nerve damage complicating third molar removal in the general circumstances of current United Kingdom practice and are presented as a basis for discussion of patient information and current prudent practice. Since one in four patients suffered at least temporary sensory deficit, we believe the case for effective warning of all patients undergoing impacted third molar removal is overwhelming.
Inferior alveolar nerve. Damage to this nerve has been more widely studied. Again there is a wide range of reported incidenccs ranging from 0.4 to 5.5% (Table 2). These papers are not always clear as to whether patients or teeth are being referred to. An increase in incidence has been related to more deeply impacted teeth (Rud, 1970) and to less expertenced surgeons (Sisk et al., 1986).
INTRODUCTION The removal of mandibular third molars results in many unwanted scquelac like pain, swelling, bruising and trismus. While these are unfortunate for the patient they are perhaps not unexpected following minor oral surgery. The patient may however be dissatisfied if the surgery results in impaired sensation. particulary if no prior warning has been given. Damage to the lingual and inferior alveolar nerves is distressing and is also a source of complaint and. increasingly. of litigation against the surgeon.
Mylohyoid nerve. Mylohyoid nerve damage is rarely mentioned in the literature as it can be confused with inferior alveolar nerve damage. It gives an area of
Lingual nerve. The incidence of nerve damage following mandibular third molar surgery has been widely reported, with quite marked differences in figures between the various studies. It ranges from 0.6 to 22%. Obviously the criteria for inclusion, techniques used, method of testing and time span varies in these studies (Table 1). Schwartz (1973) in a survey of 2500 members of the American Society of Oral Surgeons found 66% of the respondents had experienced the problem of impaired lingual sensation. There were 41X cases of permanent impairment and 2399 of temporary. The reported time span for recovery ranged from 2 days to 10 years. Litigation resulted from 53 cases. Ailing (1986) also sent questionnaires to 103 Fellows of the American Association of Oral and Maxillofacial Surgeons. Of those who replied an incidence of lingual dysesthcsia of @.06% was reported and of those 13% were persistent.
‘Table I - Lingual nerve damage following mandibular
third molar
surgery Author Rlld Bruce Rood
<‘I al.
Rud
FI al.
Sisk et al. Mason Arx
Blackburn
78
No. ..-.
1970 1980 I983
718 teeth 1% 990 teeth I I ‘%, 1400 teeth 6.6% (decreased to 0% at 6 months) 334 teeth 2% (lingual split removed) 73 teeth 3’:‘” (lingual split rctaincd) 500 teeth 0.6% (dccreascd to 0.2% at h months) 359 teeth 0.8’%> 104~1 teeth I I .5x (decreased to 0.6%) 550 patients 22’Y0 (decreased to 0%) 1117 teeth II’X (decrcascd to 0.5% at 36 weeks)
1984
Goldberg
Von
Year .~
1985 1986 1988
Kr Simpson
1989
& Rramley
1989
Incidence
Incidence
Table 2 -
Inferior alveolar molar surgery
third Author
Year
Robinson Frank flowe & Rud
I940 1959
Van
GoI
Poyton
1960
I’)70 er nl.
1077 19x0
Bruce Rood
EI ul.
RUd
Goldhcrg
CI ol.
Sisk P/ ul.
Von Arx 84 Simpson
of ncrvc damage following third molar removal: ,Z West ncrv’c damage
NO.
--------___ 300 patients
300 teeth l3.55 teeth
following
mandibular
Incidence
I (3I!‘” 5 .3‘ %, 5.2% 2.2%
71Y (deep) teeth 162 (not deep) I .2‘Z 932 pts & teeth 1.4% (decreased to 0% at 4 months) 1337 teeth 4.49% (dccrcased to at Icast I’%, at 6 months) 765 patients 7 1‘ %, 990prs & tcetn 4.4% 1400 teeth 5.5% (dccrcased to 0.4% at 6 months) 334 teeth 3% (lingual split removed) 73 teeth 3% (lingual split retained) 500 teeth 0.60/u (decreased to 0% at 6 months) 843 teeth 0.4% (cxpericnccd operators) 3SY teeth 3 ,6% (less expcricnced operators) 550 patients 5% (decreased to 0%)
altered sensation at the point of the chin, if effected and most investigators do not ask specifically about this nerve. The aim of this study was to record the incidence of lingual, inferior alveolar and mylohyoid nerve deficit and to attempt to correlate the results with the type and degree of impaction and method of removal. This would assist in the decision as to how thorough we should be in warning prospective patients about their chances of sustaining nerve damage. The study was dclibcratcly planned to be simple in operation and to record the experience of a substantial group of patients undergoing surgery in the routine circumstancesofcurrenthospital practice. The oral surgeons in the West of Scotland have a wide variety of training backgrounds and there is no tradition of strict adherence to common operating protocols. The results of the survey should therefore be broadly representative of current British experience.
MATERIALS
AND METHODS
Records were completed for 825 consecutive patients who presented for third molar surgery in eight West of Scotland Oral Surgery Units. There was no case selection apart from the fact that the patients required removal of an impacted lower third molar. A total of 1339 teeth were removed during an s-month period. Roth local and general anacsthesia were used. All grades of staff including undergraduate students carried out the surgery. The surgeons were asked to complete a form which recorded the state of eruption. angulation and associated pathology. This was assessed both clinically and radiographically.
ofScotlandOral
Surgery Research
Group Study
7Y
Type of anaesthcsia. method of bone removal (chisel or bur) or simple elevation, use of a lingual flap retractor, division of tooth and suturing were recorded. The surgeons also noted whether the patients were warned preoperatively of possible sensory dcfici t . Assessment of postoperative deficit was carried out by standard questioning, for example: ‘Do you have normal feeling in your lip, tongue and at the point of the chin’?‘. If the tongue was affcctcd the questions were asked: ‘Is it completely affected on one side or just the tip?’ and ‘Is it numb, tingling or painful?‘. If the inferior alveolar nerve was affected the questions were asked: ‘1s it the lip or lip and chin which are affected?’ and ‘1s it numb, tingling or painful?‘. These enquiries took place at between 6 to 24 hours and at 7 to 10 days. The symptoms recorded were purely subjective and although sensory testing may have been carried out this was not required to bc recorded. At approximately 1 year (range 12 to I8 months) only the patients who had given a positive response at 7 to 10 days were sent a postal questionnaire cnquiring as to whether they still had a change in sensation of their lip or tongue. One hundred and thirty five patients of a possible 169 replied (80% response rate). The data were coded and analysed on the Glasgow University Computing Services ICI, 3980 using the SPSSX programme. Chi square tests were used to calculate probabilities for comparisons.
RESULTS Results were obtained from 825 patients (31.5 males and 5 10 females). There was no cast selection and a total of 1339 teeth were removed. Most of the patients were aged between I6 and 30 years. and 4% of teeth were recorded as being erupted. 48% partially erupted and 48% uncruptcd. Those teeth reported as uneruptcd were assessed radiographically and 33.6% were found to have just soft tissue cover. 13% incomplete bone cover and 53.4% complete bone cover. The commonest angulation was mcsioangular (40%), followed by vertical (29%). distoangular and horizontal (15% each). and 1% were transverse or classified as ‘other’. which included other aberrant positions. Most teeth were removed because of a history of pericoronitis (59%) although caries. periapical infection and the presence of a related cyst were also listed. One hundred and sixteen teeth were removed for ‘other’ reasons, presumably for orthodontic indications or as a contralateral symptomless tooth in a patient undcrgoing a general anacsthctic. The majority (82.5%) of the teeth were removed under general anaesthesia, the remainder under local anaesthesia or local anacsthcsia with sedation. Chisels were used to rcmovc bone in 58% of cases, drills in 31% and 1I % did not rcquirc bone removal. Lingual flap retraction was used in 71% of cases. A Howarth’s pcriostcal elevator was usually used. the frequency varying with the depth of impaction: in 23% of erupted
X0
British Journal of Oral and ~axillofacial
Surrerb
teeth, 64% of those partly erupted, 65% of those unerupted with only soft tissue cover. 90% of those unerupted with incomplete bone cover and 98% of those uneruptcd with complete bone cover. Division was required in 218 teeth and 1017 wounds were sutured. Preoperative warnings of possible ncrvc deficit ranged from 82 to 100%. This varied from hospital to hospital, the lowest frequency being at the Dental Ilospital and School. This may be due to the fact that simpler cases were being carried out there and surgeons were reluctant to raise the possibility of nerve damage when they believed it to be unlikely. It may also bc the cast that relatively junior members of staff trcatcd these patients without reference to a more senior colleague. Ihzgual
We found no significant difference between the USC of a chisel or bur (19.6% of those removed with a chisel being affected and 13.5% of those removed with a bur). There was a significant increase in the incidence of deficit if a lingual retractor was inserted (chi square p
nerve
At 6 to 24 h, 15% of operated sides demonstrated some anacsthcsia or paracsthesia of the tongue mostly affecting the tip. This is a misleadingly high figure, because if the patient complained of the tip being affected, the surgeon may not have been able to differentiate between the two sides and may have recorded both as being affected. At 7 to IO days. the percentage reduced to 10.7%. When the incidence was related to the state of eruption. teeth completely erupted were significantly less frequently associated with anacsthcsia or paraesthesia of the tongue. and those with complete bone cover significantly more often (chi square p
inferior alveolur nerve At 6 to 24 h, 5.5% of operated sides showed some anacsthesia or paraesthcsia of the lip or lip and chin. This reduced to 3.9% at 7 to 10 days. The incidence was significantly less in relation to erupted or partially erupted teeth and significantly more in those with complete bone cover (chi square p
l‘able 5 - Inferior alveolar ncrbe deficit at 7 to IO days and state of eruption of teeth Table 3of tecrh Slate
Lingual net-ve dclicit at 7 to IO days and state of eruption Slate of eruption
of eruption
Erupted Partly-cruptcd Unerupted Soft tissue cover lnconipletc bone cover Complete bone cover
Total No. of teeth
No.with deficit
54 63X
I 57
214 i3Y 8.3 ‘chi square
--__
?;
1.85 X.Y
23 45 16 p
10.7s 13.3 19.3
t
Significantly fewer cruptcd teeth and significantly more uncruptcd teeth with complete bone cover resulted in deficit.
Table 4 - I.ingual teeth
ncrvc &licit
of
.-
Total No. of teeth -. _ 386 52.3 IO5 205 13 ‘chi square p
Significantly fewer vertically horizontally and ‘other’ an+
No. with deficit _
‘/u ._
21 ix 22 36 4
anglctl teeth and significantly teeth resulted in d&it.
_ 5.4’ II.1 I I.2 17.6 30.X’
more
No. with dclicit
54 63X
0 I7
Table 6 - Inferior
alveolar
0 1.1’
nerve
deficit
at 7 to
4.2 3.x 15.7
teeth and bone cover
IO days
and
of teeth
Angulation -. -Vertical Mcsioanpular Disloangular I lorizontal Other
$+icantl!: horizontally
‘!d,
Y 214 33Y 13 x3 I.3 ‘chi square p
Significantly fewer erupted teeth and part-erupted significantly more unerupted teeth with complctc resulted in deficit.
angulation
Angularion -. Vertical Mcsioangular Distoanpular Horizontal Other
at 7 IO IO days and angulation
---.__---__
Erupted Parlly-erupted Unerupted Soft lissuc cover lncomplcte bone cover Complctc bone cover
Total No. of teeth
-
l-Vl;ll No. of teeth -
-
3% 523 IO5 205 I3 ‘chi square p
No. with deficit _
‘X _
IO 20 Is” I
fewer vcrticnlly antjcd teeth and significantly impacted teeth resulted in deficit
_ 2.6’ 3.Y 2.3 7.3 7.7
more
Incidence of nerve damage following third molar removal: A West of Scotland Oral Surgery Rcscarch Group Study
alveolar nerve was visualiscd at the time of operation and in six of the 12 cases the teeth were divided. Mylohyoid nerve Questioning was carried out with regard to deficit affecting the point of the chin. However this was imprecise and difficult. In the initial stages it was not possible to differentiate between mylohyoid and inferior alveolar damage and whether it was bilateral or unilateral. However our reported incidence was very small, only 20 of 1339 teeth. At 12 to 18 months, only one patient continued to have such a complaint.
DISCUSSION At a Consensus Development Conference on Removal of Third Molars in 1979 it- was rccommended that patients should be informed of potential surgical risks, including any permanent condition that has an incidence greater than 0.5% or any transitory condition that occurs with an incidence of 5% or more. In order that the patient can give fully informed consent they must be able to weigh up the risks of nerve damage against the possible consequences of retaining the teeth. This is especially so when unerupted teeth arc symptomless. The incidence of paraesthesia is significant, and it is advised that all patients should be warned of this possibility and this warning should be recorded clearly in the clinical notes (Collins, 1988). It would seem from our results that lingual nerve damage is more likely with deeper impactions, with horizontal impactions and with tooth division, all factors which make it more likely that the operator will insert a lingual flap retractor to protect the lingual nerve. It is suggested that the insertion of a lingual flap retractor can induce sensory deficit (Swanson, 1989). There was a marked reduction in the incidence of lingual anaesthcsia/paraesthesia from 6 to 24 h compared with 12 to 18 months. Perhaps most of those that resolved might be due to shielding from the insertion of the retractor and those persisting due to direct damage from the chisel or bur. Unfortunately the dilemma of whether oinot to insert a lingual retractor is unresolved. It should probably only be inserted if distolingual bone is being removed. In an attempt to minimisc trauma to the lingual tissues a modified distolingual splitting tcchuiquc has been used. Unfortunately in a series by Ifochwald et al. (1983) when 598 teeth were removed using this technique there was still a 4.3% incidence although all resolved in 5 months. The presence of ‘tingling’ is often used as a hopeful sign to reassure an anxious patient that all will be well. Unfortunately half of our patients with unresolved symptoms had reported tingling at 7 to 10 days. This finding is in agreement with Blackburn (1990). The greater incidence in those cases using general anaesthesia (Blackburn & Bramlcy, 1989) was probably because deeper, more difficult teeth were removed
81
under general anaesthesia. Endotrachcal anacsthesia itself has been implicated in lingual anacsthesia in non-oral operations (Jones, 1971). Due to the number of different units involved, it was not possible to monitor precisely when recovery occurred. Spontaneous recovery has been reported as being unlikely after 36 weeks (Blackburn & Bramlcy, 1989) although claims of recovery after 10 years have been recorded (Schwartz, 1973). We feel that after 1 year further recovery is unlikely. Inferior alveolar nerve damage is easier to predict by radiographic assessment (Rood & Shchab, 1990). It would appear from our results that although the initial incidence of inferior alveolar nerve damage is lower than that of the lingual nerve, recovery is less likely in the long-term (12 to 18 months). Simpson (1958) felt recovery was unlikely after 6 months. Anaesthesia of the point of the chin has been suggested as being due to neuropraxia of the anterior cutaneous nerve of the neck (Killcy & Kay. 1968) and to the mylohyoid nerve (Roberts & Harris, 1973). Roberts and Harris infiltrated local anaesthesia around the mylohyoid nerve and consistently found an area of submental analgesia. They suggested that it occurred during lower third molar removal due to neuropraxia of the mylohyoid nerve during lingual soft tissue retraction. We found a low incidence of long-term damage of 0.07% of operated sides. Overall no responding patient had more than one nerve affected in the long term. The overall long term incidence of any type of residual nerve damage was 1.6(X1of operated sides (2.5% of patients). Acknowledgements We acknowledge the help of all members of staff who completed the questionnaires and Mrs Ann Shaw who processed the data. ‘l‘he West of Scotland Oral Surgery Research Group includes the following:Mr A. Brewer, Miss F. Carmichael. Mr D. J. Crawford. Mr H. A. Critchlow, Mr A. El Attar. Mr T. R. Flood. Mr N. llammersley, Mr I. Hollingum, Mr N. E. Merchant. Mr J. McManncrs, Professor D. A. McGowan. Mr K. F. Moos. Mr 1). 1. Russell, Mr W. Smith. Mr 1.. F. Stasscn. Mr 1). Stcnhouse, Mr D. M. Still and Mr H. I’. Wright.
Keferences AllingIl1.C.C (19%). Dysesthesiaofthclingualandinfcrior alvcolarncrvcsfollowingthird molarsur~erv.Jo~~,7rnlu/
Orulmrd M~~xiNo/acicllS‘l;r~ery,44,454.
_’
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R1ackburn.C. W.& I3ramlcv.l’. A. (1080). Lineualnervc damageassociatedwith‘thcrem’ovaloflon’erthirdmol;lrs.
British VctrralJournul,
167, 103.
t3lackburn.C. W.(lYY0).Amethodofasscssmcntincascsof lingual nerve injury. British JournulofOralatrd Muxillo~fkiul
Surgery. 28,238. Bruce. Ii. A.. Fredrickson. G. C. & Small. G. S. (1980). Age01 paticntsand morbidity associated with mandibular third molar surgery. Journulofri~eAmrrica,l I~cnrctlA.ssociarint~,
101,240. Collins. M. R.N. (lY8X). Paraesthesiafollowinglowerwisdom toothextraction. Jo~~rncrlofthe~Mediccrl~~)r~fet~e,lcc~ Uniotr. 4,
41. Frank.V.
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Goldhcrg.M.II..Nemarich.A.N.&MarcoII,W.P.( Complic;~tions;~ftcrmandil~ularthirdmolarsurgcry: ticalanalysisofS(H)consccutiveprocedurcsinpri\,ate
1985). astatis-
82
British Journal of Oral and Maxillofacial
Surgery
I lochwald. D. A., Davis. W. H. KLMartin0ff.J. (1983). Modified distolingualsplittingtcchniqucforremovalofi~npactcd mandihularthirdmolars: Incidcnccofpostoperativc scquelac. OrulSurgery, Oral Medicine. Ornlt’aarhology, 56, 9. I~owc.G. L.&Poyton.H.G.( IYho). Prevcntionofdamagc to thcinfcriordentalncrvcdurin:!thcextractionofmandibular third molars. Bririvh IknralJournal, lW,35S. Jones,B.C.( 1Y71).I.ingualnen~cinjury:ncompkationof intubation. h’rirish JownalofAnaesrhesia. 43,730. Killcy.1I.C. & Kay. I.. W. (lY68).Postopcrativeanaesthesiaol thechin. Briri.vh MedicalJournal, 4.775. Kipp. D. P., Goldstein. H. fl. Xr Weiss. W. W. (I 080).Dysethesia alter mandibular third molarsurgery: a retrospective study antlanalysisof 1377surgicaI procedures.Journnlojrh~, Amcricun DentulAssociarion, 100, 185. Mason.I>. A.( lY88). I.ingualnervedamagcfollowin~lowcrthird molarsurgery. Inrernafio~~ulJo~rrnalofOrulu~~dMoxillofuciul Surgery, 17,290. NIH Consensus Development Confcrencc Summary (197’)). Kcmoval of Third Molars. Volume 2. Number I I. Ro1~crts.G. D.D.&llarris.M.( 1973).Neuropraxisofthc mylohyoid nerve and submental analgesia. fIrirish Jortrnalo/ OrulSurgcry, I I. I IO. Robinson,‘l‘. 0. ( lY40). Paresthesia: apostopcrativecomplication folloa~ingremovalofthcm;~ndibularthirdmolar.A~r~rricun Journulof Orlhodonrics, 2ti, 27X. Rood.J. P.(IYS3). Lingualsplittcchnique:damagetoinfcrior alveolarandlingu;~lnen~csdurin~rcmovalofimpacted mandibularthird molars. Bririvh DenralJournal, 154,402. Rood.J. P. &Shchad.B. A. (199O).‘l‘heradiologicalprcdiction ofinferioral\,eolarnervcinjuryduringthirdmolarsur~ery. British Journulof Orulund MaxillofacialSur~ery, 28,20. Rud, J. (1970). Thcsplit bone techniqucforrcmovalofimpactcd 28,4 IO. mandibular third molars. JoLcr,lcr/o,fOralSI1r~ery, Rud.J. (1984). Re-cvaluationofthclingualsplit-bone technique
forthercmovalofimpactcdmandihularthirdmolars.Journa~ ofOralund Mnxillofucial Surgery, 42,113. Schwartz, 1.. J. (1973). Lingual anaesthesia followingmandibular odontcctomy. Joun~c~lofOrolSurgery, 31,918. Simpson,II.~.(IY58).1njuricstotheinferiordcntalandmcntal OralSurgery, 16,3(x3. nerves./ournulof Sisk.A.L..I~ammcr,W.H.Shclton,D.W.&Joy,T;..D.(1986). Complicationsfollowingremovalofimpactcdthirdmol;~rs: thcrolcofthcexpcrienceofthesurgcon. JournolofOralund MaxillofacialSurgery, 44,8.55. Swanson. A. E. (1089). Rcmovingthemandibularthird molar: Journulof neurosensorydeficitsandconsequentlitigation. rhc~CanadicmJ)enmlAssociarion, 55,383. Vnn
TheAuthors F. A. Carmichael, BDS, FDSRCPS Lecturer
D. A. McGowan, MDS, YhD, FDSRCS, FFDRCS, FDSRCPS Professor. DepartmcntofOralSurgery. GlasgowDentalHospitalandSchool. 378SauchichallStrcct. GlasgowG23JZ Correspondenceandrequesrsforoffprjnts Carmicheal Paperrcceivcd 17Junc 1YY I Acceptcd2.S October 19Y1
toMissF.
A.