|Year : 2014 | Volume
| Issue : 1 | Page : 6-10
Sensory nerve paresthesia following third molar surgery: Effectiveness of an evidence based protocol
Mohanavalli Singaram, Venkesana Balakrishnaraja Krishnakumararaja, Sasikala Balasubramaniam, Elavenil Paneerselvam, Poornima Poornima, Gayathri Gopi
Department of Oral and Maxillofacial Surgery, SRM Dental College, Ramapuram, Chennai, Tamil Nadu, India
|Date of Web Publication||19-Mar-2014|
40/8, Venus Apartments, Kamaraj Nagar, 3rd Street, Choolaimedu, Chennai - 600 094, Tamil Nadu
Objective: To assess the incidence of inferior alveolar and lingual nerve paresthesia following third molar surgeries and to assess the effectiveness of a set departmental protocol for reducing the incidence of these paresthesia. Study Design: The study included 110 patients who underwent surgery for third molar removal. All cases followed a protocol which included using a standard Ward's incision, raising a lingual flap, use of minimal ostectomy and tooth sectioning in all cases. A standardized data form was used to record the patient's age, sex, Pederson's difficulty index, distance between the root apices and inferior alveolar canal, the length of the "redline" and operating time. Results: Postoperative inferior alveolar nerve paresthesia occurred in five cases (4.5%) and lingual nerve paresthesia occurred in one case (0.9%). Paresthesia was significantly related to the duration of the surgical procedure, but unrelated to the other variables recorded. Conclusion: The current protocol followed appears to be effective in reducing the incidence of inferior alveolar and lingual nerve paresthesia to an acceptable level even in the presence of high risk factors.
Keywords: Impacted third molar, inferior alveolar nerve, lingual nerve, paresthesia
|How to cite this article:|
Singaram M, Krishnakumararaja VB, Balasubramaniam S, Paneerselvam E, Poornima P, Gopi G. Sensory nerve paresthesia following third molar surgery: Effectiveness of an evidence based protocol. SRM J Res Dent Sci 2014;5:6-10
|How to cite this URL:|
Singaram M, Krishnakumararaja VB, Balasubramaniam S, Paneerselvam E, Poornima P, Gopi G. Sensory nerve paresthesia following third molar surgery: Effectiveness of an evidence based protocol. SRM J Res Dent Sci [serial online] 2014 [cited 2019 Aug 18];5:6-10. Available from: http://www.srmjrds.in/text.asp?2014/5/1/6/129055
| Introduction|| |
Impacted teeth are extremely common in the South Indian population, with incidence of 41.2%.  The removal of impacted third molars is therefore one of the most commonly performed oral surgical procedures, especially in teaching institutions. The most distressing complication of third molar removal is lingual and inferior alveolar nerve damage, which may lead to temporary or permanent paresthesia. The incidence of such paresthesia varies in literature, from 0 to 23% for lingual nerve to 0.4-13.4% for inferior alveolar nerve.  Of the several factors implicated in paresthesia, some are avoidable and some are not. One factor that cannot be avoided in a teaching institution is inexperience of the surgeon. We therefore decided to develop a protocol based on previous literature reports that would minimize the nerve damage due to other avoidable factors.
The aim of our study was to assess the effectiveness of our department protocol in preventing inferior alveolar and lingual nerve paresthesia. The hypothesis was that this protocol would reduce the incidence of paresthesia when compared to previous literature reports.
| Materials and Methods|| |
The patients included in this study were those who had been referred to the Department of Maxillofacial Surgery of our institution for removal of symptomatic third molars. Patients with systemic diseases, and in whom the impacted teeth were associated with pathological lesions, were excluded. All patients were evaluated with an orthopantomogram prior to the procedure.
In all the patients, the surgical procedure was carried out by post graduate students. All patients were informed that they would be evaluated for study purposes and written consent form was obtained. Local anesthesia was given using inferior alveolar nerve block only after testing for positive aspiration. The incision used was Ward's or modified Ward's incision. A buccal mucoperiosteal flap was raised and retracted using an Austin's retractor. A lingual mucoperiosteal flap was also raised and retracted using a Molt's periosteal elevator. Ostectomy was done using sterile handpieces and saline irrigation. Tooth sectioning was carried out in all cases. After retrieval of the tooth, wound closure was carried out using 3-0 silk sutures.
A standardized data form was used to record the patient's age, sex, and Pederson's difficulty index based on Winter's and Pell and Gregory classifications. The distance between the root apices and inferior alveolar canal, and the length of the "redline" was also determined. After completion of the procedure, the operating time was also noted.
Patients were followed up after 24 hours and 7 days. Patients were specifically questioned about sensory changes in the lower lip, chin and tongue on the treated side. If the patients described any positive symptoms, testing of the affected area was done using a sharp dental probe. Two point discrimination, pin prick, touch and pressure tests were carried out. Affected patients were placed on multivitamins (Neurobion forte) and reviewed every week until recovery.
Statistical analysis was done using Pearson's Chi-square test. Each of the factors recorded on the data form was analyzed for significance in relation to lingual and inferior alveolar nerve paresthesia.
| Results|| |
A total of 110 patients were included in the study out of which 56 were male (50.1%) and 54 female (40.9%). The age ranged from 18 to 67 years (mean 29.4 years). Most of the patients were in the age group of 20-30. According to the Pederson's index, 34 cases (30.9%) were classified as slightly difficult, 52 (47.3%) as moderately difficult and 24 (21.8%) as very difficult. The redline measurement was <5 mm in 61 cases (55.4%) and greater than 5 mm in 49 cases (44.5%). In most of the cases, the mesial root tip was close to the canal. The distance was positive in 14 cases (12.7%), null in 19 cases (17.2%), close in 55 cases (50%) and well away in 22 cases (20%). The distance of the distal root tip from the canal was positive in eight cases (7.3%), null in 34 cases (30.9%), close in 34 cases (30.9%) and well away in 34 cases (30.9%). The duration of the surgical procedure ranged from 15 to 120 min, the average operating time being 43.7 min.
Postoperative inferior alveolar nerve paresthesia occurred in five cases (4.5%) and lingual nerve paresthesia occurred in one case (0.9%). Statistical analyses revealed that the paresthesia was unrelated to age, the difficulty index, redline and distance of root tips from the nerve canal [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]. However, the incidence of paresthesia appeared to be directly related to the duration of the surgical procedure [Figure 6]. The results of the Chi-square analysis are tabulated in [Table 1].
|Figure 4: Influence of distance between mesial root tip and canal on nerve paresthesia|
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|Figure 5: Influence of distance between distal root tip and canal on nerve paresthesia|
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In all cases, sensory nerve paresthesia was transient and resolved within a period of 2 weeks. All patients with paresthesia were followed up for 6 months. These patients showed no discomfort in the region of nerve impairment after resolution of numbness at 2 weeks.
| Discussion|| |
Sensory nerve impairment is a serious complication of third molar surgery. Whether temporary or permanent, it is stressful for the patient and may form grounds for litigation.  The etiology of nerve impairment is multifactorial and several factors have been implicated in previous studies. These include non-modifiable factors such as degree of impaction, , relationship of the root apices to the inferior alveolar canal,  and anatomical variations in the lingual nerve course. , Modifiable factors include experience of the operator, ostectomy, retraction of the lingual flap and tooth sectioning. , The experience of the operator has been a significant risk factor for both inferior alveolar and lingual nerve paresthesias, especially permanent sensory loss. , In a teaching institution, the inexperience of the operator is a factor that cannot be avoided. It is therefore essential to provide an evidence based protocol taking into account all the other modifiable factors in order to reduce the incidence of nerve paresthesia.
The non-modifiable factors which pose a risk of injury to the inferior alveolar nerve and lingual nerve have been described by several authors. Black  and Miura et al.  in their respective studies showed that nerve injury was more common among older patients. In the present study, although very few patients presented in the older age group, this factor was unrelated to nerve damage. The type and degree of impaction has been related to nerve injuries. Wofford and Miller stated that dysesthesia was more common in complete bony and mesioangular impactions. Carmichael and McGowan retrospectively analyzed 815 patients and concluded that paresthesia was more common in completely bony and horizontal impactions. Jerjes et al.  stated that cases recorded as "very difficult" in the Pederson index were 95% more likely to develop permanent paresthesia. Leung and Cheung  reviewed several prospective studies and stated that unerupted teeth and distoangular impactions were associated with high risk of lingual nerve paresthesia. In the present study, however, none of these parameters were significantly associated with inferior alveolar or lingual nerve paresthesia.
Modifiable factors such as ostectomy and tooth sectioning are also thought to influence inferior alveolar nerve injuries. Although tooth sectioning has not been significant in reducing paresthesia in certain studies,  it was theorized that tooth sectioning would reduce the amount of ostectomy performed and would also reduce compression on the nerve canal by elevators. The method of ostectomy appears to have an effect on inferior alveolar nerve paresthesia. Rood et al.  compared bone removal using a chisel and removal using surgical drills, and stated that using a surgical drill produced a higher incidence of permanent inferior alveolar nerve damage. However, the use of chisel, especially in the lingual split technique, increases the risk of lingual nerve paresthesia and hence was not followed in the current protocol.
With regard to lingual nerve paresthesia, the most controversial modifiable risk factor has been the raising of a lingual flap. The lingual nerve has a wide degree of anatomic variation, and has been found to lie above the bony alveolar crest. The surgeon cannot therefore rely on the lingual alveolar plate to protect the nerve and hence some authors advocate intentionally raising the flap and protecting the nerve using a retractor. ,,. However, others have argued that retracting the flap has resulted in an increased incidence of paresthesia Pichler and Beirne  analyzed eight such studies in a systematic review of the literature. The authors concluded that the use of lingual nerve retractor may associated with increased incidence of temporary nerve damage but is neither protective nor detrimental with regard to permanent nerve damage. It has been recommended that with experience, raising the lingual flap may be avoided. However, in the case of inexperienced surgeons, it would be better to intentionally raise the flap and protect the nerve by retraction to avoid inadvertent damage. Therefore our current protocol is to raise a lingual flap and protect the nerve, and this has resulted in an extremely low incidence of paresthesia (0.9%) when compared to previous studies. Appiah-Anane and Appiah-Anane  have reported that the type of incision also determines the risk of lingual nerve damage and most authors advocate a buccally directed incision extending towards the external oblique ridge. In the current study, Ward's incision and a buccal approach was used in all cases.
The only factor of significance in the current study was the duration of the surgical procedure performed. In all cases of paresthesia, the duration was above 90 min. This is in agreement with the studies carried out in 1117 patients by Valmaseda-Castellón et al. It is theorized that longer duration would result in more postoperative swelling and hematoma which, by compressing on the nerve, might have contributed to temporary paresthesia.
In the current study, the incidence of inferior alveolar nerve paresthesia was 4.5% and lingual nerve paresthesia was 0.9%. In both cases, paresthesia was temporary and complete recovered within 2 weeks. There was no incidence of permanent paresthesia. In previous literature reports, the incidence of inferior alveolar nerve paresthesia ranges from 0.4% to 13.4% (mean 4.5%) and lingual nerve paresthesia ranges from 0 to 23% (mean 6.7%). Hence in following the current protocol, the incidence of nerve paresthesia is reduced even in the presence of several risk factors including inexperience of the surgeons.
| Conclusion|| |
Even in the presence of non-modifiable risk factors for paresthesia, it is possible to reduce the complication rates to a minimum using an evidence based protocol. Using a standard Ward's incision, raising a lingual flap, use of minimal ostectomy and tooth sectioning in all cases appears to reduce the incidence of postoperative lingual and inferior alveolar nerve paresthesias.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]