YIJOM-2847; No of Pages 5
Int. J. Oral Maxillofac. Surg. 2014; xxx: xxx–xxx http://dx.doi.org/10.1016/j.ijom.2014.01.013, available online at http://www.sciencedirect.com
Clinical Paper Oral Surgery
Assessment of lingual nerve injury using different surgical variables for mandibular third molar surgery: a clinical study
S. Yadav1, A. Verma2, A. Sachdeva3 1
Department of Dentistry, BPS Government Medical College, Khanpur Kalan, Sonepat, Haryana, India; 2Department of Oral and Maxillofacial Surgery, PDM Dental College, Bahadurgarh, Haryana, India; 3Department of Oral and Maxillofacial Surgery, IP Dental College, Ghaziabad, Uttar Pradesh, India
S. Yadav, A. Verma, A. Sachdeva: Assessment of lingual nerve injury using different surgical variables for mandibular third molar surgery: a clinical study. Int. J. Oral Maxillofac. Surg. 2014; xxx: xxx–xxx. # 2014 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. Abstract. The objective of this study was to investigate the incidence of sensory impairment of the lingual nerves following lower third molar removal and to compare the outcome with various operative variables. A total of 1200 mandibular third molars were removed under local anaesthesia. Predictor variables were categorized as lingual flap retraction, tooth sectioning, and buccal guttering. The outcome variable was the presence or absence of lingual nerve impairment. Different operative techniques were performed to identify independent predictors. Of the 1200 patients, 67 (5.6%) experienced transient sensory impairment at the 1week follow-up. In all cases this resolved completely during the study period, except for four (0.3%) patients who suffered permanent impairment of lingual nerve function. Factors that predicted lingual nerve injury were lingual flap retraction, tooth sectioning, and buccal guttering. The incidence of lingual nerve injury was greater when combinations of these operative variables were used.
Accepted for publication 27 January 2014
Impacted mandibular third molar teeth are in close proximity to the lingual, inferior alveolar, mylohyoid, and buccal nerves. The most serious and often discussed postoperative complication that arises from third molar surgery is trigeminal nerve injury, specifically with involvement of either the lingual or inferior alveolar nerve. The majority of injuries result in transient sensory disturbances, but in some cases permanent paraesthesia (abnormal sensation), hypoaesthesia (reduced sensation), or, even worse, some form of dysaesthesia (unpleasant abnormal sensation)
those carried out for the management of trauma, cysts, tumours, and pre-prosthetic problems, orthognathic surgery, damage caused by the use of instruments, and most commonly removal of the third molars. Indirect injury to the nerves can also be a result of physiological phenomena, including pressure from hematomas and postsurgical edema.1 The overall risk of lingual nerve injury associated with third molar removal ranges from 0.2% (permanent disturbance) to 22% (sensory disturbances in the early postoperative period).2,3 The
0901-5027/000001+05 $36.00/0
can occur. Sensory loss lasting longer than 6 months is mostly permanent. The subsequent distorted sensory sensation can result in significant impairment in speech and chewing, and taste loss from the ipsilateral anterior segment of the tongue, which has a negative impact on socializing and the patient’s psychological wellbeing. These nerves can be damaged as a result of direct or indirect forces. Due to the anatomical location of the nerve, direct trauma to the lingual nerve may occur during various surgical procedures, e.g.
Key words: lingual nerve; sensory impairment; third molars.
# 2014 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Yadav S, et al. Assessment of lingual nerve injury using different surgical variables for mandibular third molar surgery: a clinical study, Int J Oral Maxillofac Surg (2014), http://dx.doi.org/10.1016/j.ijom.2014.01.013
YIJOM-2847; No of Pages 5
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Yadav et al.
reported rate of permanent lingual nerve injury is generally in the range of 0–2%. This study sought to identify the incidence of lingual nerve damage following the removal of mandibular third molars. Materials and methods
The present prospective hospital-based study included 1200 patients who underwent the removal of mandibular third molar teeth under local anaesthesia; both male and female patients were included, and they ranged in age from 18 to 45 years. The study design was quasi-experimental. Patients with any neurological disorder were excluded from the study as they might have unfairly influenced the outcome. The third molar on only one side was removed for each patient. All mandibular third molar surgeries were performed by a senior surgeon with more than 5 years of experience. Ethical clearance was obtained for this clinical study. Prior to surgery, a panoramic and intraoral peri-apical radiograph was taken. Assessment of the impacted tooth was done for determination of the angulation and of the position of the tooth in relation to the ramus of the mandible and the second molar (based on Winter’s classification and the Pell and Gregory classification4; Table 1). Mandibular third molar teeth with a class III relation and position C depth were not included in the study. Prior to the procedure, the patients were informed of the possible outcome in their own language and written consent was obtained. At 1 week following surgery (at the time of suture removal), the patient was questioned regarding any alteration in sensation and underwent a clinical examination.
Statistical analysis
The statistical analysis was performed using SPSS version 17 software (SPSS
Inc., Chicago, IL, USA). The x2 test of significance was used for qualitative data and the P-value calculated; P < 0.05 was considered significant and P < 0.001 as highly significant. For the analysis, impairment of the lingual nerve was considered the dependant variable. We determined the significance of overall temporary and permanent lingual nerve impairment at 1 week and at 6 months following the surgery. The significance of different operative variables in relation to lingual nerve impairment, including buccal guttering, tooth sectioning, and lingual flap retraction, was also determined.
Surgical procedure
The choice of surgical procedure was made after proper clinical and radiographic assessment of the impacted tooth regarding position, depth, and any other surgical difficulty. Three surgeons were involved in this study, all having more than 5 years of surgical experience. The surgical procedure planned for each patient was also discussed among the surgeons. The buccal approach with a trapezoidal mucoperiosteal flap was used in all cases. All procedures were performed with the same surgical instruments under local anaesthesia (2% lidocaine hydrochloride with adrenaline 1:80,000) using inferior alveolar nerve block and local tissue infiltration. Different surgical techniques were used for removal of the tooth, including buccal flap and elevation; buccal guttering with or without lingual flap retraction; and buccal guttering with tooth sectioning with or without lingual flap retraction. A buccal mucoperiosteal flap was employed. Buccal guttering was performed with a straight fissure bur in a straight hand piece under normal saline irrigation. For tooth sectioning, a round and straight fissure bur was used. A
Table 1. Number of patients according to the classifications of Pell and Gregory and Winter. Variables
No. of patients
Percentage
Angulation (Winter’s classification) Mesioangular Horizontal Vertical Distoangular
558 252 96 294
46.5% 21% 8% 24.5%
Pell and Gregory classification IA IB II A II B
108 210 630 252
9% 17.5% 52.5% 21%
Degree of impaction Soft tissue impaction Partial bony impaction Total bony impaction
216 882 102
18% 73.5% 8.5%
Howarth periosteal elevator was carefully used to retract the lingual flap as and when required, and was not pushed deep down. Elevators and extraction forceps were used to deliver the tooth from the socket. After removal of the third molar, the socket was inspected and irrigated with normal saline and the flap repositioned and sutured with a 3–0 silk suture. A gauze pack was pressed against the surgical site for the patient to bite on. The surgical sites of all patients were reviewed 7 days after the operation by an independent observer. All patients were asked to report any subjective alteration in lingual sensation; sensory deficits were also identified by clinical examination, carried out bilaterally. Tactile perception of the following stimuli was assessed: light touch sensation using a wisp of cotton wool, pin prick with the point of a dental probe, and two-point discrimination.5–7 Any positive results were recorded; these patients were seen again on a monthly basis for about 6 months. The incidence of lingual nerve impairment at 1 week postoperatively (temporary) and at 6 months postoperatively (permanent) was related to the different surgical techniques used for the third molar removal. Various operative variables such as buccal guttering, tooth sectioning, and lingual flap retraction were also assessed for their relation to lingual nerve impairment. Results
Tables 2 and 3 show the lingual nerve sensory impairment related to the different surgical procedures at the 1-week and 6month postoperative follow-ups, respectively. The overall incidence of temporary lingual nerve impairment at the 1-week follow-up was 5.6% (67/1200 patients), which was highly significant (P < 0.001). Lingual nerve impairment at the 1-week follow-up was higher in patients for whom buccal guttering, lingual flap retraction, and tooth sectioning were done (11.9%; 44/368) compared to patients in whom buccal guttering and lingual flap retraction were done (5.1%; 13/256). The overall incidence of permanent sensory impairment of the lingual nerve at the 6-month follow-up was 0.3% (4/ 1200 patients), which was not significant (P = 0.85). Permanent lingual nerve impairment was seen in two of the 368 patients (0.5%) who underwent the buccal guttering, lingual flap retraction, and tooth sectioning technique. No incidence of
Please cite this article in press as: Yadav S, et al. Assessment of lingual nerve injury using different surgical variables for mandibular third molar surgery: a clinical study, Int J Oral Maxillofac Surg (2014), http://dx.doi.org/10.1016/j.ijom.2014.01.013
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Lingual nerve injury in third molar surgery
3
Table 2. Incidence of sensory impairment of the lingual nerve at the 1-week follow-up. No. of patients operated on
Different surgical techniques used Buccal flap and elevation Buccal flap, buccal guttering, and elevation Buccal flap, buccal guttering, tooth sectioning, and elevation Buccal flap, buccal guttering, lingual flap retraction, and elevation Buccal flap, buccal guttering, lingual flap retraction, tooth sectioning, and elevation
Sensory impairment after 1 week
78 173 325 256 368
0 1 9 13 44
Percentage (%) 0% 0.6% 2.8% 5.1% 11.9%
Table 3. Incidence of sensory impairment of the lingual nerve at the 6-month follow-up. No. of patients operated on
Different surgical techniques used Buccal flap and elevation Buccal flap, buccal guttering, and elevation Buccal flap, buccal guttering, tooth sectioning, and elevation Buccal flap, buccal guttering, lingual flap retraction, and elevation Buccal flap, buccal guttering, lingual flap retraction, tooth sectioning, and elevation
Sensory impairment after 6 months
78 173 325 256 368
0 0 1 1 2
Percentage (%) 0% 0% 0.3% 0.4% 0.5%
Table 4. Operative variables and their relationship with lingual nerve impairment. Lingual nerve impairment after 1 week
Lingual nerve impairment after 6 months
Operative variables
No. of patients (%)
Buccal guttering Done Not done
1122 (93.5%) 78 (6.5%)
67 (6.0%) 0 (0%)
4 (0.3%) 0 (0%)
Tooth sectioning Done Not done
693 (57.7%) 507 (42.3%)
53 (7.6%) 14 (2.8%)
3 (0.4%) 1 (0.2%)
Lingual flap retraction Done Not done
624 (52%) 576 (48%)
57 (9.1%) 10 (1.7%)
3 (0.5%) 1 (0.2%)
nerve injury was observed in patients who were treated with the buccal flap and elevation of the tooth technique, or the buccal flap, buccal guttering, and elevation technique. Only one out of 325 patients (0.3%) for whom the technique of buccal flap, buccal guttering, and tooth sectioning was done showed permanent nerve impairment, and only one out of 256 patients (0.4%) who were treated with the buccal flap, buccal guttering, and lingual flap retraction technique had permanent nerve impairment. Table 4 shows the relationships of the various operative variables with the incidence of lingual nerve injury. Lingual nerve impairment at the 1-week followup was highly significant (P < 0.001) for patients in whom lingual flap retraction (9.1%) and tooth sectioning (7.6%) were done. The majority of the lingual nerve injuries recovered within 3–4 weeks postoperatively. The incidence of permanent lingual nerve impairment was 0.5% (P = 0.356) when lingual flap retraction was considered and 0.4% (P = 0.484) when tooth sectioning was considered – results that are non-significant.
Discussion
The lingual nerve is morphologically very different from the inferior alveolar nerve. Adjacent to the lower third molar, the nerve is covered by a thin layer of soft tissue and mucosa, which is why the chances of lingual nerve injury are greater during surgical removal of the tooth. A study by Miloro et al. precisely documented the in situ location of the lingual nerve in the third molar region using magnetic resonance imaging (MRI) and reconfirmed the relatively vulnerable position of this structure during third molar surgery.8 Mandibular third molar surgery accounts for a significant proportion of iatrogenic injury to the lingual nerve.7,9 Sensory impairment following this surgery is probably the most significant morbidity,10 but this is largely preventable if the potential risk is anticipated and the surgical procedure adapted accordingly. There is no convincing evidence regarding a relationship between age, sex, or race and the incidence of nerve injury.2,5,11–13 The surgical removal of horizontal, mesioangular, and distoangular impacted
teeth is more likely to result in nerve injury, probably because of the increased surgical manipulation and exposure required to remove such teeth.2,11,13 Many studies have concluded that there is high risk of injury to the lingual nerve from mechanical injury due to chisels, burs, or elevators, tooth sectioning, and lingual flap retraction.2,11,13 In the present study we observed temporary lingual nerve injury in 7.6% of cases and permanent injury in 0.4% of cases when tooth sectioning was considered. The great inconsistencies in outcomes reported in previous studies may be the result of differences in the operative techniques used and surgical skill rather than the anatomical position of the tooth.2,5,14 Renton and McGurk reported that the difficulty of the extraction was also a strong predictor of temporary and permanent lingual nerve injury.13 Lingual nerve damage is particularly associated with deeply impacted teeth when the surgery is moderately difficult, particularly if distal bone removal is required.15,16 Different surgical techniques for mandibular third molar removal have been felt
Please cite this article in press as: Yadav S, et al. Assessment of lingual nerve injury using different surgical variables for mandibular third molar surgery: a clinical study, Int J Oral Maxillofac Surg (2014), http://dx.doi.org/10.1016/j.ijom.2014.01.013
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to potentially affect the frequency of lingual nerve damage. The ‘lingual splitbone technique’ is considered to result in a higher frequency of nerve disturbances than the ‘buccal approach’. An incidence of 12.8% temporary lingual nerve impairment was reported when using the lingual split technique and only 2.3% when using a bur.14 In the present study we used the buccal guttering technique with a bur, resulting in an incidence of 6% lingual nerve impairment. The results of studies comparing the incidence of lingual nerve injury during surgery utilizing bone removal with burs or chisels are unclear.15,16 One study found improved results (0.6–6.9% temporary and 0.3–0.8% permanent) when the buccal approach was used. They concluded that avoidance of the use of a lingual flap was an important factor in reducing temporary lingual nerve damage.17 The reported incidence of lingual nerve impairment after third molar removal varies widely, ranging from 0% to 23% for temporary damage and 0–2% for permanent damage.2,14–20 Our study results are in concordance with those of the studies performed previously. In this study, the overall incidence of temporary lingual nerve impairment was determined to be 5.6%; the overall incidence of permanent lingual nerve impairment was determined to be 0.3%. The prevalence of postoperative lingual sensory impairment in our study compares favourably with the data from previous studies.2,11,13,21 We believe that temporary sensory impairment usually subsides within a 6-month period; longer impairment may be regarded as permanent.5,12,21,22 Lingual flap retraction is a controversial issue. Whereas some discourage its use,20,23,24 others advocate it.5,25 It is possible that the elevation of a lingual mucoperiosteal flap when chisels are utilized is of more importance than the method of bone removal itself. The decision to use this technique during surgery was mostly made for horizontal, followed by distoangular impactions, and with certain operative variables, like tooth sectioning, bone removal, and long operations. Careful lingual retraction in selected cases has been shown to improve surgical access, and this could be responsible for the protection of the lingual nerve against permanent damage.25,26 Few studies have reported a lower incidence of permanent lingual nerve injury with the use of lingual flaps.14,19 The unjustified use of retraction is responsible for a high prevalence of tem-
porary sensory impairment.21,24 Several studies have shown that the raising and retraction of a lingual mucoperiosteal flap is associated with an increased frequency of lingual nerve damage.15,16 A few studies and reviews have concluded that raising and retracting a lingual periosteal flap is not necessary20 and is best avoided.17,21 A study on mandibular third molar surgery without lingual flap retraction showed a higher prevalence of temporary and permanent lingual nerve damage (6.5% and 1%, respectively).11 Lingual retraction per se was the strongest predictor of developing temporary postoperative hypoesthesia, presumably due to a stretch-type injury from the retractor. In this study, 85% of the patients who suffered sensory impairment had undergone lingual tissue retraction. Various publications5,23,25 have reported temporary lingual nerve deficits of 2.1–9.1% with lingual retraction, which corresponds to the result of 9.1% found in our study in cases where lingual flap retraction was done. There are various operative variables and factors associated with lingual nerve impairment. When these operative variables are compared individually, the results are almost the same, however when these factors are used in combination, the incidence of nerve damage increases.In conclusion, there remains debate regarding the aetiology, incidence, and outcome of neurological damage during third molar surgery despite the many studies published in the literature. Ostectomy of the bone distal to the third molar, tooth sectioning, and retraction of the lingual flap for accessibility increase the risk of lingual nerve damage. Despite technological advances, permanent nerve injury may still occur, and it is important that patients are informed of this prior to surgery. It is inappropriate to compare the results reported by different clinicians using different methods and different sample sizes with different assessments and analyses. In spite of these drawbacks, it appears that the surgical skill of the operator is of great importance. Skill, coupled with anatomical, dental, and patient factors, will ultimately determine the potential for lingual nerve injury. According to the Pell and Gregory classification of impacted mandibular third molars, we did not include patients with class III relation and position C depth in the present study. A future study may be designed to include all types of impacted mandibular third molars, including class III and position C, for the assessment of lingual nerve injury.
Funding
None. Competing interests
None. Ethical approval
Ethical clearance was obtained from the Research and Ethics Committee of BPS Government Medical College. Patient consent
Not required. References 1. Cade TA. Paresthesia of the inferior alveolar nerve following the extraction of the mandibular third molars: a literature review of its causes, treatment, and prognosis. Mil Med 1992;157:389–92. 2. Valmaseda-Castello´n E, Berini-Ayte´s L, Gay-Escoda C. Lingual nerve damage after third lower molar surgical extraction. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2000;90:567–73. 3. Bataineh AB. Sensory nerve impairment following mandibular third molar surgery. J Oral Maxillofac Surg 2001;59:1012–7. 4. Garcı´a GA, Sampedro FG, Rey JG, Vila PG, Martin MS. Pell-Gregory classification is unreliable as a predictor of difficulty in extracting impacted lower third molars. Br J Oral Maxillofac Surg 2000;38:585–7. 5. Gu¨licher D, Gerlach KL. Sensory impairment of the lingual and inferior alveolar nerves following removal of impacted mandibular third molars. Int J Oral Maxillofac Surg 2001;30:306–12. 6. Rehman K, Webster K, Dover MS. Links between anaesthetic modality and nerve damage during lower third molar surgery. Br Dent J 2002;193:43–5. 7. Hillerup S, Stoltze K. Lingual nerve injury in third molar surgery. 1. Observations on recovery of sensation with spontaneous healing. Int J Oral Maxillofac Surg 2007;36:884–9. 8. Miloro M, Halkias LE, Slone 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. 9. Hillerup S. Iatrogenic injury to the inferior alveolar nerve: etiology, signs and symptoms, and observations on recovery. Int J Oral Maxillofac Surg 2008;37:704–9. 10. Visintini E, Angerame D, Costantinides F, Maglione M. Peripheral neurological damage following lower third molar removal: a preliminary clinical study. Minerva Stomatol 2007;56:319–26.
Please cite this article in press as: Yadav S, et al. Assessment of lingual nerve injury using different surgical variables for mandibular third molar surgery: a clinical study, Int J Oral Maxillofac Surg (2014), http://dx.doi.org/10.1016/j.ijom.2014.01.013
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Lingual nerve injury in third molar surgery 11. Jerjes W, Swinson B, Moles DR, El-Maaytah M, Banu B, Upile T, Kumar M, Al Khawalde M, Vourvachis M, Hadi H, Kumar S, Hopper C. Permanent sensory nerve impairment following third molar surgery: a prospective study. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2006;102:e1–7. 12. Queral-Godoy E, Figueiredo R, ValmasedaCastello´n E, Berini-Ayte´s L, Gay-Escoda C. Frequency and evolution of lingual nerve lesions following lower third molar extraction. J Oral Maxillofac Surg 2006;64:402–7. 13. Renton T, McGurk M. Evaluation of factors predictive of lingual nerve injury in third molar surgery. Br J Oral Maxillofac Surg 2001;39:423–8. 14. Rood JP. Permanent damage to inferior alveolar and lingual nerves during the removal of impacted mandibular third molars. Comparison of two methods of bone removal. Br Dent J 1992;172:108–10. 15. Mason DA. Lingual nerve damage following lower third molar surgery. Int J Oral Maxillofac Surg 1988;17:290–4. 16. Blackburn CW, Bramley PA. Lingual nerve damage associated with the removal of lower third molars. Br Dent J 1989;167:103–7.
17. Robinson PP, Smith KG. Lingual nerve damage during third molar removal. A comparison of two surgical methods. Br Dent J 1996;180:456–61. 18. Wofford DT, Miller RI. Prospective study of dysaesthesia following odontectomy of impacted mandibular molars. J Oral Maxillofac Surg 1987;45:15–9. 19. Walters H. Reducing lingual nerve damage in third molar surgery: a clinical audit of 1350 cases. Br Dent J 1995;178:140–4. 20. Gargallo-Albiol J, Buenechea-Imaz R, GayEscoda C. Lingual nerve protection during the surgical removal of lower third molar. A prospective randomised study. Int J Oral Maxillofac Surg 2000;29:268–71. 21. Pichler W, Beirne OR. Lingual flap retraction and prevention of lingual nerve damage associated with third molar surgery: a systematic review of the literature. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2001;91:395–401. 22. Robinson PP, Loescher AR, Yates JM, Smith KG. Current management of damage to the inferior alveolar and lingual nerves as a result of removal of third molars. Br J Oral Maxillofac Surg 2004;42:285–92.
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23. Gomes AC, Vasconcelos BC, deOliveira e Silva ED, da Silva LC. Lingual nerve damage after mandibular third molar surgery: a randomized clinical trial. J Oral Maxillofac Surg 2005;639:1443–6. 24. Shepherd JP. Lingual nerve retraction increases the risk of temporary lingual nerve damage during mandibular third molar surgery. Evid Based Dent 2006;7:47. 25. Pogrel MA, Goldman KE. Lingual flap retraction for third molar removal. J Oral Maxillofac Surg 2004;62:1125–30. 26. Gibbons AJ, Moss CE. Lingual flap retraction in third molar surgery. J Oral Maxillofac Surg 2007;65:364.
Address: Sunil Yadav Department of Dentistry BPS Government Medical College for Women Khanpur Kalan Sonepat Haryana India Tel: +91 9818998838 E-mail: [email protected]
Please cite this article in press as: Yadav S, et al. Assessment of lingual nerve injury using different surgical variables for mandibular third molar surgery: a clinical study, Int J Oral Maxillofac Surg (2014), http://dx.doi.org/10.1016/j.ijom.2014.01.013
Int. J. Oral Maxillofac. Surg. 2014; xxx: xxx–xxx http://dx.doi.org/10.1016/j.ijom.2014.01.013, available online at http://www.sciencedirect.com
Clinical Paper Oral Surgery
Assessment of lingual nerve injury using different surgical variables for mandibular third molar surgery: a clinical study
S. Yadav1, A. Verma2, A. Sachdeva3 1
Department of Dentistry, BPS Government Medical College, Khanpur Kalan, Sonepat, Haryana, India; 2Department of Oral and Maxillofacial Surgery, PDM Dental College, Bahadurgarh, Haryana, India; 3Department of Oral and Maxillofacial Surgery, IP Dental College, Ghaziabad, Uttar Pradesh, India
S. Yadav, A. Verma, A. Sachdeva: Assessment of lingual nerve injury using different surgical variables for mandibular third molar surgery: a clinical study. Int. J. Oral Maxillofac. Surg. 2014; xxx: xxx–xxx. # 2014 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. Abstract. The objective of this study was to investigate the incidence of sensory impairment of the lingual nerves following lower third molar removal and to compare the outcome with various operative variables. A total of 1200 mandibular third molars were removed under local anaesthesia. Predictor variables were categorized as lingual flap retraction, tooth sectioning, and buccal guttering. The outcome variable was the presence or absence of lingual nerve impairment. Different operative techniques were performed to identify independent predictors. Of the 1200 patients, 67 (5.6%) experienced transient sensory impairment at the 1week follow-up. In all cases this resolved completely during the study period, except for four (0.3%) patients who suffered permanent impairment of lingual nerve function. Factors that predicted lingual nerve injury were lingual flap retraction, tooth sectioning, and buccal guttering. The incidence of lingual nerve injury was greater when combinations of these operative variables were used.
Accepted for publication 27 January 2014
Impacted mandibular third molar teeth are in close proximity to the lingual, inferior alveolar, mylohyoid, and buccal nerves. The most serious and often discussed postoperative complication that arises from third molar surgery is trigeminal nerve injury, specifically with involvement of either the lingual or inferior alveolar nerve. The majority of injuries result in transient sensory disturbances, but in some cases permanent paraesthesia (abnormal sensation), hypoaesthesia (reduced sensation), or, even worse, some form of dysaesthesia (unpleasant abnormal sensation)
those carried out for the management of trauma, cysts, tumours, and pre-prosthetic problems, orthognathic surgery, damage caused by the use of instruments, and most commonly removal of the third molars. Indirect injury to the nerves can also be a result of physiological phenomena, including pressure from hematomas and postsurgical edema.1 The overall risk of lingual nerve injury associated with third molar removal ranges from 0.2% (permanent disturbance) to 22% (sensory disturbances in the early postoperative period).2,3 The
0901-5027/000001+05 $36.00/0
can occur. Sensory loss lasting longer than 6 months is mostly permanent. The subsequent distorted sensory sensation can result in significant impairment in speech and chewing, and taste loss from the ipsilateral anterior segment of the tongue, which has a negative impact on socializing and the patient’s psychological wellbeing. These nerves can be damaged as a result of direct or indirect forces. Due to the anatomical location of the nerve, direct trauma to the lingual nerve may occur during various surgical procedures, e.g.
Key words: lingual nerve; sensory impairment; third molars.
# 2014 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Yadav S, et al. Assessment of lingual nerve injury using different surgical variables for mandibular third molar surgery: a clinical study, Int J Oral Maxillofac Surg (2014), http://dx.doi.org/10.1016/j.ijom.2014.01.013
YIJOM-2847; No of Pages 5
2
Yadav et al.
reported rate of permanent lingual nerve injury is generally in the range of 0–2%. This study sought to identify the incidence of lingual nerve damage following the removal of mandibular third molars. Materials and methods
The present prospective hospital-based study included 1200 patients who underwent the removal of mandibular third molar teeth under local anaesthesia; both male and female patients were included, and they ranged in age from 18 to 45 years. The study design was quasi-experimental. Patients with any neurological disorder were excluded from the study as they might have unfairly influenced the outcome. The third molar on only one side was removed for each patient. All mandibular third molar surgeries were performed by a senior surgeon with more than 5 years of experience. Ethical clearance was obtained for this clinical study. Prior to surgery, a panoramic and intraoral peri-apical radiograph was taken. Assessment of the impacted tooth was done for determination of the angulation and of the position of the tooth in relation to the ramus of the mandible and the second molar (based on Winter’s classification and the Pell and Gregory classification4; Table 1). Mandibular third molar teeth with a class III relation and position C depth were not included in the study. Prior to the procedure, the patients were informed of the possible outcome in their own language and written consent was obtained. At 1 week following surgery (at the time of suture removal), the patient was questioned regarding any alteration in sensation and underwent a clinical examination.
Statistical analysis
The statistical analysis was performed using SPSS version 17 software (SPSS
Inc., Chicago, IL, USA). The x2 test of significance was used for qualitative data and the P-value calculated; P < 0.05 was considered significant and P < 0.001 as highly significant. For the analysis, impairment of the lingual nerve was considered the dependant variable. We determined the significance of overall temporary and permanent lingual nerve impairment at 1 week and at 6 months following the surgery. The significance of different operative variables in relation to lingual nerve impairment, including buccal guttering, tooth sectioning, and lingual flap retraction, was also determined.
Surgical procedure
The choice of surgical procedure was made after proper clinical and radiographic assessment of the impacted tooth regarding position, depth, and any other surgical difficulty. Three surgeons were involved in this study, all having more than 5 years of surgical experience. The surgical procedure planned for each patient was also discussed among the surgeons. The buccal approach with a trapezoidal mucoperiosteal flap was used in all cases. All procedures were performed with the same surgical instruments under local anaesthesia (2% lidocaine hydrochloride with adrenaline 1:80,000) using inferior alveolar nerve block and local tissue infiltration. Different surgical techniques were used for removal of the tooth, including buccal flap and elevation; buccal guttering with or without lingual flap retraction; and buccal guttering with tooth sectioning with or without lingual flap retraction. A buccal mucoperiosteal flap was employed. Buccal guttering was performed with a straight fissure bur in a straight hand piece under normal saline irrigation. For tooth sectioning, a round and straight fissure bur was used. A
Table 1. Number of patients according to the classifications of Pell and Gregory and Winter. Variables
No. of patients
Percentage
Angulation (Winter’s classification) Mesioangular Horizontal Vertical Distoangular
558 252 96 294
46.5% 21% 8% 24.5%
Pell and Gregory classification IA IB II A II B
108 210 630 252
9% 17.5% 52.5% 21%
Degree of impaction Soft tissue impaction Partial bony impaction Total bony impaction
216 882 102
18% 73.5% 8.5%
Howarth periosteal elevator was carefully used to retract the lingual flap as and when required, and was not pushed deep down. Elevators and extraction forceps were used to deliver the tooth from the socket. After removal of the third molar, the socket was inspected and irrigated with normal saline and the flap repositioned and sutured with a 3–0 silk suture. A gauze pack was pressed against the surgical site for the patient to bite on. The surgical sites of all patients were reviewed 7 days after the operation by an independent observer. All patients were asked to report any subjective alteration in lingual sensation; sensory deficits were also identified by clinical examination, carried out bilaterally. Tactile perception of the following stimuli was assessed: light touch sensation using a wisp of cotton wool, pin prick with the point of a dental probe, and two-point discrimination.5–7 Any positive results were recorded; these patients were seen again on a monthly basis for about 6 months. The incidence of lingual nerve impairment at 1 week postoperatively (temporary) and at 6 months postoperatively (permanent) was related to the different surgical techniques used for the third molar removal. Various operative variables such as buccal guttering, tooth sectioning, and lingual flap retraction were also assessed for their relation to lingual nerve impairment. Results
Tables 2 and 3 show the lingual nerve sensory impairment related to the different surgical procedures at the 1-week and 6month postoperative follow-ups, respectively. The overall incidence of temporary lingual nerve impairment at the 1-week follow-up was 5.6% (67/1200 patients), which was highly significant (P < 0.001). Lingual nerve impairment at the 1-week follow-up was higher in patients for whom buccal guttering, lingual flap retraction, and tooth sectioning were done (11.9%; 44/368) compared to patients in whom buccal guttering and lingual flap retraction were done (5.1%; 13/256). The overall incidence of permanent sensory impairment of the lingual nerve at the 6-month follow-up was 0.3% (4/ 1200 patients), which was not significant (P = 0.85). Permanent lingual nerve impairment was seen in two of the 368 patients (0.5%) who underwent the buccal guttering, lingual flap retraction, and tooth sectioning technique. No incidence of
Please cite this article in press as: Yadav S, et al. Assessment of lingual nerve injury using different surgical variables for mandibular third molar surgery: a clinical study, Int J Oral Maxillofac Surg (2014), http://dx.doi.org/10.1016/j.ijom.2014.01.013
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Lingual nerve injury in third molar surgery
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Table 2. Incidence of sensory impairment of the lingual nerve at the 1-week follow-up. No. of patients operated on
Different surgical techniques used Buccal flap and elevation Buccal flap, buccal guttering, and elevation Buccal flap, buccal guttering, tooth sectioning, and elevation Buccal flap, buccal guttering, lingual flap retraction, and elevation Buccal flap, buccal guttering, lingual flap retraction, tooth sectioning, and elevation
Sensory impairment after 1 week
78 173 325 256 368
0 1 9 13 44
Percentage (%) 0% 0.6% 2.8% 5.1% 11.9%
Table 3. Incidence of sensory impairment of the lingual nerve at the 6-month follow-up. No. of patients operated on
Different surgical techniques used Buccal flap and elevation Buccal flap, buccal guttering, and elevation Buccal flap, buccal guttering, tooth sectioning, and elevation Buccal flap, buccal guttering, lingual flap retraction, and elevation Buccal flap, buccal guttering, lingual flap retraction, tooth sectioning, and elevation
Sensory impairment after 6 months
78 173 325 256 368
0 0 1 1 2
Percentage (%) 0% 0% 0.3% 0.4% 0.5%
Table 4. Operative variables and their relationship with lingual nerve impairment. Lingual nerve impairment after 1 week
Lingual nerve impairment after 6 months
Operative variables
No. of patients (%)
Buccal guttering Done Not done
1122 (93.5%) 78 (6.5%)
67 (6.0%) 0 (0%)
4 (0.3%) 0 (0%)
Tooth sectioning Done Not done
693 (57.7%) 507 (42.3%)
53 (7.6%) 14 (2.8%)
3 (0.4%) 1 (0.2%)
Lingual flap retraction Done Not done
624 (52%) 576 (48%)
57 (9.1%) 10 (1.7%)
3 (0.5%) 1 (0.2%)
nerve injury was observed in patients who were treated with the buccal flap and elevation of the tooth technique, or the buccal flap, buccal guttering, and elevation technique. Only one out of 325 patients (0.3%) for whom the technique of buccal flap, buccal guttering, and tooth sectioning was done showed permanent nerve impairment, and only one out of 256 patients (0.4%) who were treated with the buccal flap, buccal guttering, and lingual flap retraction technique had permanent nerve impairment. Table 4 shows the relationships of the various operative variables with the incidence of lingual nerve injury. Lingual nerve impairment at the 1-week followup was highly significant (P < 0.001) for patients in whom lingual flap retraction (9.1%) and tooth sectioning (7.6%) were done. The majority of the lingual nerve injuries recovered within 3–4 weeks postoperatively. The incidence of permanent lingual nerve impairment was 0.5% (P = 0.356) when lingual flap retraction was considered and 0.4% (P = 0.484) when tooth sectioning was considered – results that are non-significant.
Discussion
The lingual nerve is morphologically very different from the inferior alveolar nerve. Adjacent to the lower third molar, the nerve is covered by a thin layer of soft tissue and mucosa, which is why the chances of lingual nerve injury are greater during surgical removal of the tooth. A study by Miloro et al. precisely documented the in situ location of the lingual nerve in the third molar region using magnetic resonance imaging (MRI) and reconfirmed the relatively vulnerable position of this structure during third molar surgery.8 Mandibular third molar surgery accounts for a significant proportion of iatrogenic injury to the lingual nerve.7,9 Sensory impairment following this surgery is probably the most significant morbidity,10 but this is largely preventable if the potential risk is anticipated and the surgical procedure adapted accordingly. There is no convincing evidence regarding a relationship between age, sex, or race and the incidence of nerve injury.2,5,11–13 The surgical removal of horizontal, mesioangular, and distoangular impacted
teeth is more likely to result in nerve injury, probably because of the increased surgical manipulation and exposure required to remove such teeth.2,11,13 Many studies have concluded that there is high risk of injury to the lingual nerve from mechanical injury due to chisels, burs, or elevators, tooth sectioning, and lingual flap retraction.2,11,13 In the present study we observed temporary lingual nerve injury in 7.6% of cases and permanent injury in 0.4% of cases when tooth sectioning was considered. The great inconsistencies in outcomes reported in previous studies may be the result of differences in the operative techniques used and surgical skill rather than the anatomical position of the tooth.2,5,14 Renton and McGurk reported that the difficulty of the extraction was also a strong predictor of temporary and permanent lingual nerve injury.13 Lingual nerve damage is particularly associated with deeply impacted teeth when the surgery is moderately difficult, particularly if distal bone removal is required.15,16 Different surgical techniques for mandibular third molar removal have been felt
Please cite this article in press as: Yadav S, et al. Assessment of lingual nerve injury using different surgical variables for mandibular third molar surgery: a clinical study, Int J Oral Maxillofac Surg (2014), http://dx.doi.org/10.1016/j.ijom.2014.01.013
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Yadav et al.
to potentially affect the frequency of lingual nerve damage. The ‘lingual splitbone technique’ is considered to result in a higher frequency of nerve disturbances than the ‘buccal approach’. An incidence of 12.8% temporary lingual nerve impairment was reported when using the lingual split technique and only 2.3% when using a bur.14 In the present study we used the buccal guttering technique with a bur, resulting in an incidence of 6% lingual nerve impairment. The results of studies comparing the incidence of lingual nerve injury during surgery utilizing bone removal with burs or chisels are unclear.15,16 One study found improved results (0.6–6.9% temporary and 0.3–0.8% permanent) when the buccal approach was used. They concluded that avoidance of the use of a lingual flap was an important factor in reducing temporary lingual nerve damage.17 The reported incidence of lingual nerve impairment after third molar removal varies widely, ranging from 0% to 23% for temporary damage and 0–2% for permanent damage.2,14–20 Our study results are in concordance with those of the studies performed previously. In this study, the overall incidence of temporary lingual nerve impairment was determined to be 5.6%; the overall incidence of permanent lingual nerve impairment was determined to be 0.3%. The prevalence of postoperative lingual sensory impairment in our study compares favourably with the data from previous studies.2,11,13,21 We believe that temporary sensory impairment usually subsides within a 6-month period; longer impairment may be regarded as permanent.5,12,21,22 Lingual flap retraction is a controversial issue. Whereas some discourage its use,20,23,24 others advocate it.5,25 It is possible that the elevation of a lingual mucoperiosteal flap when chisels are utilized is of more importance than the method of bone removal itself. The decision to use this technique during surgery was mostly made for horizontal, followed by distoangular impactions, and with certain operative variables, like tooth sectioning, bone removal, and long operations. Careful lingual retraction in selected cases has been shown to improve surgical access, and this could be responsible for the protection of the lingual nerve against permanent damage.25,26 Few studies have reported a lower incidence of permanent lingual nerve injury with the use of lingual flaps.14,19 The unjustified use of retraction is responsible for a high prevalence of tem-
porary sensory impairment.21,24 Several studies have shown that the raising and retraction of a lingual mucoperiosteal flap is associated with an increased frequency of lingual nerve damage.15,16 A few studies and reviews have concluded that raising and retracting a lingual periosteal flap is not necessary20 and is best avoided.17,21 A study on mandibular third molar surgery without lingual flap retraction showed a higher prevalence of temporary and permanent lingual nerve damage (6.5% and 1%, respectively).11 Lingual retraction per se was the strongest predictor of developing temporary postoperative hypoesthesia, presumably due to a stretch-type injury from the retractor. In this study, 85% of the patients who suffered sensory impairment had undergone lingual tissue retraction. Various publications5,23,25 have reported temporary lingual nerve deficits of 2.1–9.1% with lingual retraction, which corresponds to the result of 9.1% found in our study in cases where lingual flap retraction was done. There are various operative variables and factors associated with lingual nerve impairment. When these operative variables are compared individually, the results are almost the same, however when these factors are used in combination, the incidence of nerve damage increases.In conclusion, there remains debate regarding the aetiology, incidence, and outcome of neurological damage during third molar surgery despite the many studies published in the literature. Ostectomy of the bone distal to the third molar, tooth sectioning, and retraction of the lingual flap for accessibility increase the risk of lingual nerve damage. Despite technological advances, permanent nerve injury may still occur, and it is important that patients are informed of this prior to surgery. It is inappropriate to compare the results reported by different clinicians using different methods and different sample sizes with different assessments and analyses. In spite of these drawbacks, it appears that the surgical skill of the operator is of great importance. Skill, coupled with anatomical, dental, and patient factors, will ultimately determine the potential for lingual nerve injury. According to the Pell and Gregory classification of impacted mandibular third molars, we did not include patients with class III relation and position C depth in the present study. A future study may be designed to include all types of impacted mandibular third molars, including class III and position C, for the assessment of lingual nerve injury.
Funding
None. Competing interests
None. Ethical approval
Ethical clearance was obtained from the Research and Ethics Committee of BPS Government Medical College. Patient consent
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Address: Sunil Yadav Department of Dentistry BPS Government Medical College for Women Khanpur Kalan Sonepat Haryana India Tel: +91 9818998838 E-mail: [email protected]
Please cite this article in press as: Yadav S, et al. Assessment of lingual nerve injury using different surgical variables for mandibular third molar surgery: a clinical study, Int J Oral Maxillofac Surg (2014), http://dx.doi.org/10.1016/j.ijom.2014.01.013
