|Year : 2014 | Volume
| Issue : 3 | Page : 176-179
Labial sensory impairment following extraction of impacted mandibular third molars
Surekha Gontu1, Somuri Vijay Anand2, Chitturi Srinivasa Vara Prasad3, Prathigudupu Raja Satish2, Kuchimanchi Phani Kumar2, Meka Sridhar2
1 Department of Oral and Maxillofacial Surgery, Government Dental College, Vijayawada, Andhra Pradesh, India
2 Department of Oral and Maxillofacial Surgery, SIBAR Institute of Dental Sciences, Guntur, Andhra Pradesh, India
3 Department of Oral and Maxillofacial Surgery, Darshan Dental College, Udaipur, Rajasthan, India
|Date of Web Publication||17-Sep-2014|
Department of Oral and Maxillofacial Surgery, Government Dental College, Vijayawada, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
Introduction: The purpose of this study was a prospective investigation into the occurrence of impairment of labial sensation after surgical removal of impacted third molars.
Aims and Objectives: The aim of this study was to determine the incidence of postoperative sensory impairment of inferior alveolar nerve (IAN) after extraction of impacted mandibular third molars.
Materials and Methods: The study sample consisted of 200 patients who were indicated for removal of impacted mandibular third molars. Extraction of the impacted tooth was done by using surgical bur technique. Postoperatively, patients were evaluated for impairment of labial sensation. Objective evaluation of IAN was carried out using light touch sensation, tactile discrimination, pain awareness, and two point discrimination.
Results: Of 200 subjects, only two patients showed neurosensory deficit in relation to IAN.
Conclusion: The main cause of neurosensory impairment was due to variables associated with tooth position, degree of impaction, operator skill and also depth of impaction and age of the patient.
Keywords: Inferior alveolar nerve paresthesia, neurosensory impairment, paresthesia after impacted third molar removal, third molar impaction
|How to cite this article:|
Gontu S, Anand SV, Prasad CV, Satish PR, Kumar KP, Sridhar M. Labial sensory impairment following extraction of impacted mandibular third molars. J NTR Univ Health Sci 2014;3:176-9
|How to cite this URL:|
Gontu S, Anand SV, Prasad CV, Satish PR, Kumar KP, Sridhar M. Labial sensory impairment following extraction of impacted mandibular third molars. J NTR Univ Health Sci [serial online] 2014 [cited 2020 Apr 1];3:176-9. Available from: http://www.jdrntruhs.org/text.asp?2014/3/3/176/140937
| Introduction|| |
Injury to the inferior alveolar nerve (IAN) and the lingual nerve is characteristic complication following the removal of impacted lower third molars.  Nerve injury may result from compression, stretching or complete sectioning of the nerve caused by bone fragments or iatrogenic damage due to instrumentation. In the majority of cases, altered sensation is a transitory phenomenon. 
Inferior alveolar nerve and lingual nerve damage is a well-recognized complication of removal of lower third molars. The incidence of immediate impairment of the IAN after third molar surgery has been reported in the region of 4-5% and permanent disturbance less than 1%.  A permanent alteration of lingual sensation following third molar surgery is a frequent occurrence with the incidence of as many as one in 200 procedures. 
This prospective study was conducted on patients, undergoing surgical removal of impacted lower third molars and the incidence of postoperative neurosensory impairment (NSI) involving IAN was assessed.
| Materials And Methods|| |
A sample of 200 patients was randomly selected from the total number of patients undergoing surgical removal of lower third molar. The mean follow-up after surgery was 6 months.
Standard draping procedure was carried out. Local anesthesia was achieved by blocking the IAN, lingual nerve and long buccal nerve using 2% lignocaine with 1:80,000 adrenaline. Either Ward's incision or modified Ward's incision was placed. Once the flap was reflected bone removal was carried out using a surgical bur (S. S. White no. 701). Subsequently, tooth was elevated and then removed. Impacted third molar was sectioned using a surgical bur and then the tooth was removed in fragments. Socket was curetted to remove any remnants and debris. The sharp edges of the socket were trimmed with a bone file. The socket was then thoroughly irrigated with normal saline and betadine. The soft-tissue flap was approximated and primary closure achieved. Finally a gauze pressure pack was placed and postoperative instructions were given. Alteration in IAN sensation was tested according to standard clinical neurosensory tests, which comprised of subjective and objective evaluation after 1 week period.
Subjective evaluation was carried out by questioning patients about any alteration in neurosensory perception in the area of innervation of IAN. They were evaluated for reduced sensation, anesthesia and altered sensation, paresthesia or dysesthesia. Objective evaluation was performed only when the patient gave a positive response in the subjective evaluation. Objective evaluation of IAN was carried out using the following tests: Light touch sensation, tactile discrimination, pain awareness, and two point discrimination.
| Results|| |
Of the 200 patients, two cases of NSI were seen in the age group 31-35 years [Table 1]. The incidence of NSI among female subjects is 1.3888% (1 in 128) and among male subjects it is 0.78125% (1 in 72). Right sided tooth (1.089%) with partially visible crowns (1.190%) and without caries (1.063%) showed a higher incidence of NSI [Table 2]. NSI was seen in the teeth with two roots, which are either conical or curved in shape [Table 3]. Out of two cases of NSI, the level of the root in one case was above the IAN canal and in another case at the level of inferior alveolar canal. Buccal flap reflection + ostectomy + odontectomy + lingual flap retraction showed more frequency of NSI [Table 4].
In the study group, out of 24 patients with distoangular impaction, 1 (4.166%) showed NSI, and out of 104 patients with mesioangular impaction 1 (0.961%) patient had NSI. Patients with horizontally or vertically impacted teeth had no NSI [Table 5]. 88 patients having retromolar space larger than the mesiodistal diameter of crown showed no NSI evident, whereas 112 patients having retromolar space smaller than the mesiodistal diameter of the crown, 2 (14.28%) patients had NSI evident [Table 5].
| Discussion|| |
One of the major complications that may occur after the extraction of impacted mandibular third molars is damage to the inferior alveolar and lingual nerves caused by the trauma suffered during and after surgical removal. Trauma could be iatrogenic or due to the anatomical position of the impacted tooth in relation to the IAN.
The rate of these neurological complications, according to the surveys, varies from 0.5% to 1% of permanent damages and from 5% to 7% of temporary damages. A study done by Checchi et al. on "removing high-risk impacted mandibular third molar" stated that there is a 30% incidence of temporary risk increases when there is a true relationship between an impacted molar and the mandibular canal.  In our study also there is a higher incidence of NSI when the mandibular molar roots reaching the nerve canal.
According to Osborn et al. the incidence of neurosensory deficit increased in patients over 35 years of age, whereas patients younger than 26 years rarely presented postoperative NSI.  Bataineh stated that the incidence of IAN impairment increased from 0.4% in the age group of 20-29 years to 3.5% in those aged above 40 years, and that IAN paresthesia occurred more frequently in older aged patients where there is surgical removal of bone and root splitting was done.  In our study also there was an increase of NSI above 35 years of age.
This positive correlation may be related to increased bone density, complete root formation and diminished wound healing capacities. ,,,,, Bui et al. showed that increased age is associated with complete root formation and hence chances of complications are more. 
Gender was often cited as a risk factor for complications. Many studies have reported increased complications among females associated with oral contraceptive use.  In our study, out of 128 males only one patient had NSI and out 72 females one patient had paresthesia of the lower lip indicating high incidence in females.
The teeth with radiographic evidence of completely developed roots, deep impaction and roots with vertical proximity to the nerve canal were significantly correlated with sensory loss of the IAN. ,,, In this study, on radiographic examination of the study group, two out of the 192 patients with developed roots, had NSI. Partially developed roots in eight patients showed no NSI. The removal of the teeth with completely developed roots involved injury to the IAN with a higher probability than the removal of the tooth germ did. Possible causes for neurosensory deficit disclose a close anatomic relationship between the third molar roots and mandibular canal - particularly if the roots are believe to surround the nerve and in elder age patients. 
The deep impaction of the tooth and the radiographic superimposition of the roots and the canal both contributed to postoperative sensory loss. According to Gülicher and Gerlach, position of the mandibular canal and its relationship to the roots was found to be factors of distinct importance for the incidence of loss of labial sensation. 
However, Valmaseda-Castellσn et al. in their study stated that only deflection of the mandibular canal was associated with IAN injury and it constituted a predictive clue. The distance between the roots and the IAN can also be indicative of a close relationship.  The teeth with radiographic evidence of completely developed roots, deep impaction and roots with vertical proximity to the nerve canal were significantly correlated with sensory loss of the IAN. ,,,
According to some studies the duration of the surgical procedure could also indirectly be a reflection of its difficulty, although surgical time also depends on the manual skill of the surgeon and on the choice of a proper tooth removal strategy. 
Among the surgical procedure carried out in our study, in 56 patients raising of buccal flap, ostectomy and lingual flap retraction was carried out, and in 16 patients raising of buccal flap, ostectomy and odontectomy was carried out. In both of these groups no NSI was evident. In remaining 128 patients raising of a buccal flap, ostectomy, odontectomy and lingual flap retraction was carried out. Among these, two patients had NSI.
The surgical instrumentation had an influence on the incidence of the nerve damage. The necessity of sectioning the tooth several times, the use of rotating instruments in the depth of the socket and the intra-operative opening of the mandibular canal frequently led to sensory loss. 
Fielding AF et al. stated that mesioangular impactions are the most common of all impacted teeth (43%) and have the highest incidence of lingual paresthesia (30.6%) associated with the removal. The second most cited type of impaction resulting in lingual paresthesia was the distoangular impaction (19.6%). 
In our study, the surgical removal of a distoangularlly impacted tooth with a Pederson difficulty score of 8 and a mesioangular impacted molar with a Pederson difficulty score of 6 but with roots reaching the nerve canal showed paresthesia of the IAN. Surgical removal of vertically and horizontally impacted tooth showed no neurosensory deficit.
Both the patients who had NSI were managed with medical intervention only. The sensory sensations gradually improved and returned back to normal over a period of 8 months.
| Conclusion|| |
Modern dentistry is practiced with an emphasis on preventive care. However, this principle is not always applied to the treatment of impacted third molars.
The removal of mandibular third molars may cause intra-operative and postoperative complications. Age-related complications should be an area of concern to the practitioner. This study emphasis the significant relationship of age, angulation of the impacted tooth, proximity of the roots to the inferior alveolar canal, and the surgical procedure involving usage of the rotary surgical burs to the persistence of NSI after surgical extraction of impacted mandibular third molars.
| References|| |
|1.||Gülicher 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. |
|2.||Greenwood M, Corbett IP. Observations on the exploration and external neurolysis of injured inferior alveolar nerves. Int J Oral Maxillofac Surg 2005;34:252-6. |
|3.||Blackburn CW. Experiences in lingual nerve repair. Br J Oral Maxillofac Surg 1992;30:72-7. |
|4.||Checchi L, Alessandri Bonetti G, Pelliccioni GA. Removing high-risk impacted mandibular third molars: A surgical-orthodontic approach. J Am Dent Assoc 1996;127:1214-7. |
|5.||Osborn TP, Frederickson G Jr, Small IA, Torgerson TS. A prospective study of complications related to mandibular third molar surgery. J Oral Maxillofac Surg 1985;43:767-9. |
|6.||Bataineh AB. Sensory nerve impairment following mandibular third molar surgery. J Oral Maxillofac Surg 2001;59:1012-7. |
|7.||Bruce RA, Frederickson GC, Small GS. Age of patients and morbidity associated with mandibular third molar surgery. J Am Dent Assoc 1980;101:240-5. |
|8.||Valmaseda-Castellón E, Berini-Aytés L, Gay-Escoda C. Inferior alveolar nerve damage after lower third molar surgical extraction: A prospective study of 1117 surgical extractions. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2001;92:377-83. |
|9.||Robert RC, Bacchetti P, Pogrel MA. Frequency of trigeminal nerve injuries following third molar removal. J Oral Maxillofac Surg 2005;63:732-5. |
|10.||Gomes AC, Vasconcelos BC, de Oliveira e Silva ED, da Silva LC. Lingual nerve damage after mandibular third molar surgery: A randomized clinical trial. J Oral Maxillofac Surg 2005;63:1443-6. |
|11.||Rood JP, Shehab BA. The radiological prediction of inferior alveolar nerve injury during third molar surgery. Br J Oral Maxillofac Surg 1990;28:20-5. |
|12.||Bui CH, Seldin EB, Dodson TB. Types, frequencies, and risk factors for complications after third molar extraction. J Oral Maxillofac Surg 2003;61:1379-89. |
|13.||Carmichael FA, McGowan DA. Incidence of nerve damage following third molar removal: A west of Scotland oral surgery research group study. Br J Oral Maxillofac Surg 1992;30:78-82. |
|14.||Fielding AF, Rachiele DP, Frazier G. Lingual nerve paresthesia following third molar surgery: A retrospective clinical study. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1997;84:345-8. |
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]