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Oral Surgery: Lingual Nerve Damage During Removal of Mandibular Third Molars: A Comparison of Two Surgical Methods

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By: David K. Lam, DDS and Howard I. Holmes, DDS, Dip OMFS
2002-05-01
ABSTRACT

Lingual nerve injury is a serious neurological complication, which can result from a number of reasons, including performing oral and maxillofacial surgical procedures. One of the controversial areas that exist, in relationship to this problem, is that regarding the relative merits of different surgical techniques for the removal of third molars in reducing or avoiding lingual nerve somatosensory disturbances. The purpose of this paper is to review the anatomy of the lingual nerve in the third molar region. Additionally to compare two popular techniques of removing mandibular third molars, namely, the lingual split-bone and the buccal approach, in relationship to the incidence of a lingual nerve sensory disturbance and those factors that appear to be most associated with its development.

Injury to the lingual nerve can be one of the most serious complications that can arise from the performance of a number of oral and maxillofacial surgery procedures. Due to this nerve's variable anatomical location, it may be iatrogenically traumatized, during various surgical procedures carried out for the management of trauma, oncologic, salivary gland problems, pre-prosthetic problems or third molar removal. As well, local anesthetic injections themselves may lead to either transient or permanent dysfunction1,2 (Fig.1). The surgical removal of mandibular third molars is by far the most common culprit, usually representing over 75% of the patients who are afflicted with this problem.1 The subsequent distorted somatosensory sensation, be it anesthesia or paraesthesia can result in significant impairment in speech, chewing, taste, sleep, work or socializing (Figs. 2a & b). If dysesthesia results, not uncommonly a chronic neuropathic pain syndrome further compromises the patient (Fig.3). In 1973, Schwartz3 distributed questionnaires to oral surgeons regarding the presence of lingual nerve anesthesia after removal of mandibular third molars. Of the 1,291 respondents, 2,399 cases of temporary lingual nerve dysesthesia and 418 cases of permanent anesthesia were reported. Fifty-three of these cases were involved in litigation. Although these reported figures could not indicate the incidence of lingual nerve damage, they do reveal the scope of the problem.

The incidence of lingual nerve disturbance after third molar removal has been reported to vary widely from 0% to 23% (Table 1). Temporary disturbances, are by far more common, however; permanent problems have been reported up to only an incidence of 2%.15 Different surgical techniques for mandibular third molar removal have been felt to potentially affect the frequency of lingual nerve damage. The "Lingual Split-Bone Technique" is considered to result in a higher frequency of lingual nerve disturbances than the "Buccal Approach." The lingual Split-bone technique was first developed in the United Kingdom (UK), where practices were largely hospital based and the use of chisels and osteotomes predominated. A purely lingual approach had been described by Warwick James. Sir William Kelsey Fry, as later described by Ward in 1956,26 developed the buccal approach in conjunction with the lingual split. This technique involves the reflection of tissues buccally, distally and lingually in order to expose the bone and tooth from all aspects. A periosteal elevator, usually a Howarth's, is placed between the lingual periosteum and the lingual plate of bone. Chisels are used for socket saucerization and the tooth delivered distolingually. Ward has stated the advantages of this technique when the tooth is in lingual version, are speed, elimination of dead space and better healing.26 The primary goal of using a lingual flap retractor is to protect the lingual nerve during bone removal and tooth elevation. In contrast, a buccal approach which avoided disturbance of lingual tissues by not retracting a lingual flap was developed for office based practices in North America (USA) by such early pioneers as G.B. Winter. Bone and tooth are removed using a drill from a buccal direction. The goal in both techniques is the same, namely, to minimize the incidence of lingual nerve injury during mandibular third molar removal. Not uncommonly in our present era some surgeons employ the "buccal approach," however additionally elevate the lingual tissue in hopes of decreasing damage to the nerve. Clearly, a surgical technique based on a sound knowledge of the anatomic variations in the position of the lingual nerve and a clear assessment of the literature as it relates to the various described techniques is necessary to avoid iatrogenic injury. Hence, the purpose of this paper is to:

1. Review the anatomy of the lingual nerve in the third molar region.

2. Compare the incidence of nerve injury with the existing techniques of removing lower third molars, (the lingual split-bone and the conventional buccal approach with or without lingual flap elevation).

3. Ascertain variables with respect to the techniques that may be responsible for the nerve injuries which occur such that appropriate recommendations for their avoidance might be suggested.

ANATOMY OF THE LINGUAL NERVE IN THE THIRD MOLAR REGION

Although in most textbooks the anatomy of the lingual nerve is consistently described as having a standard pathway, such is not the case. Mozsary clearly depicted that the close relationship of the nerve to the medial aspect of the mandible in the third molar region does not always exist40 (Figs. 4-6). More importantly the position of the lingual nerve in the mandibular third molar region is now recognized to be highly variable (Fig.7). The mean horizontal distance of the nerve from the lingual plate having been reported to range from 0.58 mm27 to 3.45 mm.28,29 The nerve has been shown to contact the lingual plate directly from 22% to 62%27 of the time. The mean vertical distance of the lingual nerve below the alveolar crest has similarly been demonstrated to be from 2.28 mm27 to 8.32 mm...28,29 Additionally, the nerve can be found above the lingual crest in 4.6%27 to 17.6%27 of cases and lie within the retromolar tissues in 0-15%27,30 (Fig. 8).

Kiesselbach and Chamberlain were the first to present quantitative data on the position of the lingual nerve in the mandibular third molar area.27 The position of the lingual nerve was measured in 34 cadaver dissections and 256 cases of third molar extraction cases. The average horizontal distance of the nerve from the lingual plate was 0.58 ± 0.90 mm and the nerve contacted the lingual plate of the third molar in 62% of the cases. The average vertical distance of the lingual nerve was 2.28 ± 1.96 mm below the alveolar crest. In 17.6% of the dissections, however, the nerve was found at the level of the alveolar crest or higher and even in the retromolar tissues. Of the 256 extraction cases, the nerve was visualized above the lingual plate of the third molar region in 4.6% of the cases. Furthermore, 8.8% of the dissections showed 0.5mm. thick flat nerves, thus demonstrating that a 25 gauge needle-also 0.5mm thick-could seriously damage the lingual nerve during anesthetic injections.27

Although Kiesselbach and Chamberlain27 reported for the first time, the lingual nerve may lie more superiorly above bone in the third molar region and as a result, the surgeon cannot always depend on the lingual plate to serve as protection, their study design was limited. Their study population, sample size, and methods may have introduced confounding variables. The study population was one with unknown histories (age, presence of teeth, prior facial or dental surgery, history of facial trauma or disorders), small in size, and the possibility of iatrogenic nerve displacement during the cadaveric fixation process and surgical dissection (e.g. tongue retraction may displace the nerve) may have impacted on the reliability of their results.

Pogrel and his associates28,29 attempted to overcome some of the limitations of Kiesselbach and Chamberlain27 by describing the anatomical relationship of the lingual nerve in the third molar region using a reproducible landmark on the mandible. They bisected 20 cadaveric heads (40 sides) sagittally and the lingual nerve was identified but not dissected freely, to avoid disturbing the underlying structures. The anterior border of the retromolar pad was used as a reproducible landmark for measurements. The lingual nerve was demonstrated to be at risk during surgery on the mandibular lingual side since it had a close relationship to the mandibular lingual plate in the molar and retromolar area for a mean distance of more than 27 mm.29 The mean vertical distance of the lingual nerve was found to be 8.32 mm (SD = 4.05 mm)28,29 inferior to the lingual crest and the mean horizontal distance of the lingual nerve to the lingual plate was 3.45 mm (SD = 1.48mm).28,29 In one case, however, the nerve was level with the crest and in two cases, it was found superior to the lingual plate. It is in this 7.5% of cases, where the lingual nerve is at or above the lingual crest, the nerve is at risk for injury during any surgery on the lingual side of the mandible or retromolar area. Pogrel et al. also demonstrated that the position of the nerve on the right side of the mandible bore no statistical relationship to the position of the nerve on the left side.28,29 Pogrel's study overcame some of the problems found in the Kiesselbach and Chamberlain study.27 The authors noted the presence or absence of teeth and performed more careful surgical dissection; but the small sample size, poor cadaver histories, and possible iatrogenic nerve displacement during cadaveric fixation and dissection still existed. In this study also the presence or absence of teeth in the retromolar area had no statistical relationship on the nerves position or relationship to the crest of the lingual plate. Holzle, who more recently evaluated the lingual nerve's anatomical relationships, in cadaveric edentulous and atrophic mandibles came to a similar conclusion, suggesting that loss of muscle tone and connective tissue tension with advancing age results in the nerve descending into the floor of the mouth such that it's position relative to the lingual crest remains unchanged.38 Additionally Holzle defined that the distance from the distal releasing incision in the retromolar triangle was a mean of 4.41 mm. (+/- 1.44 mm.).

Behnia et al.30 further avoided some of the previous problems associated with cadaveric dissections and clinical observations by studying 669 nerves from 430 fresh cadavers. This study eliminated some confounding variables by using an adequate sample size and a better cadaver demographic history. The cadaver age and sex were noted, and obligatory inclusion criteria included the presence of at least one mandibular third molar and the absence of any history of dental/facial surgery. Any cadavers with a history of chronic diseases or tissue degeneration, which could change the shape of the face were, also excluded. The mean vertical distance of the nerve was 3.01 ± 0.42 mm inferior to the lingual crest with 14.05% of the cases above the lingual crest and 0.15% of the cases had the nerve in the retromolar pad region. The mean horizontal distance of the nerve to lingual plate was 2.06 ± 1.10 mm and 22.27% of the time, the nerve was in direct contact with the lingual plate. These findings differ markedly from those reported by both Pogrel et al.28,29 and Kisselbach and Chamberlain27 most likely due to the small sample size and possible fixation artifact of the former studies. The use of fresh cadavers avoided inaccuracies caused by cadaveric fixation artifact but the normal anatomic relationships may still be affected by the loss of vascularity and early onset of tissue degeneration/necrosis.31 Furthermore, the use of surgical clips in an attempt to prevent nerve dissection displacement may actually introduce tissue distortion by compression or tissue displacement.31

Previous attempts to determine the anatomic relationship of the lingual nerve in the third molar region have only reported the location after surgical exposure. Miloro et al. were the first to evaluate the in situ location of the lingual nerve in the third molar region in young dentate individuals. They used high-resolution magnetic resonance imaging (MRI) to avoid problems with tissue distortion by artificial fixation and surgical manipulation.32,33 Ten healthy volunteers (20 sides), with mandibular third molars and without prior dental or facial surgery, underwent axial and coronal, high-resolution magnetic resonance imaging (HR-MRI) examination of the posterior mandible and floor of mouth, from lingual to mental foramen bilaterally, to determine the exact location of the nerve. The mean vertical distance of the nerve was 2.75 ± 0.97 mm inferior to the lingual crest with 10% of the cases above the lingual crest. The mean horizontal distance of the nerve was 2.53 ± 0.67 mm from the lingual plate with 25% of the cases in direct contact with the lingual plate. There was no correlation between right and left lingual nerve measurements33 which agrees with the results of Pogrel et al.28,29 The results of this study are similar to Behnia et al.30 but contrast sharply with those of previous studies. Most likely this incongruity is due to the probable fixation artifact and iatrogenic displacement of the lingual nerve in the previous cadaveric and clinical reports. Although the sample size is small in this study, the ability of HR-MRI to locate the precise location of the lingual nerve in situ, eliminating the possibility of iatrogenic displacement, reconfirms the vulnerable position of this structure during third molar surgery.

The variable position of the lingual nerve, especially when it may be found directly on the lingual plate or in the soft tissues above the lingual crest and in the retromolar pad area, is clearly an important factor in the etiology of lingual nerve damage and emphasizes the importance of protecting and or avoiding the nerve during surgical procedures. They indeed exemplify why some of the factors that were described by Schwartz (1973) as being involved in the development of lingual nerve somatosensory disturbances can occur. Such factors included incision placement, burs passing through the lingual plate, overzealous currettement of the follicle on the lingual, deep suture bites on the lingual, scar tissue formation, overzealous retraction of the tongue and lingual flap if used.3

WHICH TECHNIQUE?

The Lingual Split-Bone vs. the Conventional Buccal Approach

The incidence of lingual nerve damage with the lingual split-bone and conventional buccal approach has been studied extensively (Table 1). In 1970, Rud4 was the first to prospectively compare the lingual split-bone technique with the buccal approach. The split-bone technique, used in 718 impacted third molars under local anesthesia, was found to be faster than the buccal approach for deep horizontal or distoverted impactions. There was no reported lingual nerve damage in 162 mandibular third molars extracted using the buccal approach. However, temporary impairment of lingual sensation, with the return of normal sensation after a few months, was reported in 1% of cases using the split-bone method. There was also one case of permanent lingual paraesthesia (0.1%) lasting more than two and a half years when the lingual split-bone method was used (Table 1, #1).

Nearly two decades after Rud's study, Mason14 (1988) performed a prospective investigation into the occurrence of lingual sensory disturbance after the removal of 1040 impacted lower third molars under general anesthesia. The effects of surgical, operator, and anatomical variables on the incidence and duration of lingual nerve dysesthesia were examined. The incidence of temporary lingual dysesthesia (11.5%), including all degrees of sensory deficit, and permanent lingual damage (0.6%) was higher than that reported in previous studies (Table 1, #1-10). There were no significant effects related to retention, or removal of the plate after the lingual split, nor operator skill level on lingual nerve impairment. There were, however, highly significant effects related to lingual flap elevation, overhanging distal bone removal, and lingual plate-splitting (Table 1, #11). Thus, the work of both Rud4 and Mason14 appear to support the buccal approach without lingual flap elevation for mandibular third molar removal.

Unlike the previous comparative studies of lingual sensory morbidity using different surgical techniques, Middlehurst and his colleagues studied a single operator at a single site using a model of symmetric impactions to serve as internal controls. Middlehurst et al.15 compared the postoperative morbidity arising from the lingual split and buccal approaches under general anesthesia when used simultaneously on 30 patients with radiographically symmetrical impactions. The strengths of this study were its prospective nature and the fact that both techniques were used on each patient with the side allocation randomized. As a result, bias and differing complication rates associated with multiple operators were eliminated. Mandibular third molars removal by lingual split produced less pain, swelling and lingual nerve disturbance than with the buccal approach (Table 1, #12). A possible explanation for the higher incidence of sensory disturbance with the buccal approach may be the greater duration of lingual traction or increased tissue tension with the approach.15 Based on the merits of this study, there was renewed support for the lingual split method. Furthermore, with the results of Middlehurst et al.15 published the same year as that of Mason's,14 provided more fuel to the fiery debate as to which surgical method was ideal in decreasing the incidence of lingual nerve sensory disturbance. However, the two studies cannot be compared directly as Middlehurst et al.15 used lingual flap retraction and possibly distal bone removal with their buccal approach, which Mason14 had shown increases the risk of lingual nerve damage. Also, although the model of symmetrical impactions and side randomization was useful in comparing most postoperative complications using the two surgical methods, it may be argued that it is limited in use for comparing lingual dysesthesia differences since as previously stated, the position of the nerve on one side bears no statistical relationship to the position of the nerve on the opposite side.28,29,33

In 1989, Blackburn and Bramley16 studied 1,117 consecutive surgeries for the removal of lower third molars by a variety of operators. Reinforcing Mason's results,14 the factor most strongly implicated in lingual sensory dysesthesias was the raising and retraction of the lingual flap with a Howarth's periosteal elevator (Table 1, #13). Howarth's, being a narrow instrument, designed as a nasal rasp rather than a lingual nerve retractor can only offer protection over a small distance even if correctly positioned.16 Also, because it is a long instrument, it can act as a lever exerting considerable force on the lingual nerve if the nerve becomes trapped between the elevator and bone.16 All cases of permanent damage occurred where a bur was used to remove distal bone which further supports Mason's14 work. Consequently, the removal of distal bone should be avoided since it is usually removed blindly with its view being obscured by the crown of the third molar and false faith placed on the retractor to protect the nerve. Surprisingly however, the performance of a lingual split was not associated with lingual nerve damage except where the bone fragment removed was large enough to include the mylohyoid groove.

A few years later, in 1992, Rood18 performed a prospective study comparing the surgical removal of 790 impacted third molars using the lingual split technique with chisels and the buccal approach with a drill to remove buccal and distal bone. Lingual retraction with the Howarth's periosteal elevator was used with both surgical methods. There were more temporary lingual injuries using the lingual split and significantly more permanent with the bur (Table 1, #15). This finding agrees with the work by Blackburn and Bramley.16 Since the lingual retractor was used in all cases, there must be another factor of surgical technique to explain the higher incidence of permanent damage with the bur. The most likely explanation is the removal of distal bone with the bur and perforation through it, and inadequate lingual nerve protection by the Howarth.18

On the other hand, Carmichael and McGowan's19 survey of 1,339 third molars removed by all grades of staff at West of Scotland Oral Surgery Unit found no significant difference between chisel and bur use in lingual nerve sensory disturbance. It was not, however, noted whether distal bone was removed with the bur during mandibular third molar removal with the buccal approach. Additionally19 these authors also noted a significant increase in lingual dysesthesia with lingual flap retraction using a Howarth's elevator.

In 1993, Absi and Shepherd20 conducted a prospective study similar in design to the work of Middlehurst et al.15 with an even larger sample size. This design greatly enhanced the statistical power and validity of the study in comparison to previous studies. A total of 52 consecutive healthy patients with bilateral similarly impacted third molars were removed by the same operator during the same operation. Thus eliminating differing complication rates associated with multiple operators. The study was controlled internally using lingual split on one side and buccal approach on the other, the sides were randomized to eliminate bias, and a Howarth's was used in both cases. There was a 21% incidence of temporary dysesthesia by lingual split and 23% by buccal approach and no permanent disturbance. However, the differences were not statistically significant. There was also no evidence of difference in either efficiency or outcome between the two methods of mandibular third molar removal. The superior design of this study has resulted in reliable results that agree with Carmichael and McGowan's19 survey of there being no difference between the lingual split and buccal approach with respect to lingual sensory impairment. The high rate of lingual dysesthesia associated with both techniques is most likely due to lingual flap retraction with a Howarth's. Fortunate, also was that the dysfunction's found in both groups were transient.

In 1995, Walters23 conducted a retrospective, randomly chosen personal audit of 100 cases he performed, in which a split-bone technique was employed using a Howarth's periosteal to retract the lingual tissues. His 10% incidence of transient lingual nerve damage prompted modifications in surgical technique. Walters noted that it was difficult to place a Howarth's in stable position and that it may breach the periosteum low down on the lingual plate.23 He believed that the Rowe's and Hovell's lingual retractors were too large and bulky so and therefore developed a new, smaller but broader retractor. Walters' personal audit of 1,001 consecutive third molar surgeries using a broader lingual retractor combined with a newly designed periosteal elevator reported a 20-fold reduction in the incidence of lingual nerve damage (Table 1, #20). Although the low incidence is promising, it needs to be evaluated in a prospective randomized trial with a single, as well as multiple operators of all skill levels, if its use is to be justified.

In order to confirm whether lingual flap retraction is responsible for the high incidence of lingual nerve damage, Robinson and Smith24 compared the incidence of lingual dysesthesia, with and without lingual flap retraction, in a prospective randomized study with multiple operators of all skill levels. A total of 771 operations were randomly allocated to be performed, with and without lingual flap retraction, and insertion of a Howarth's periosteal elevator. Mandibular third molar removal with lingual flap retraction resulted in higher risk of both temporary and permanent lingual sensory disturbance than surgery without lingual flap retraction. (Table 1, no. 21) They concluded that the use of a Howarth's for lingual flap retraction should be avoided since it is ineffective in protecting the lingual nerve for two possible reasons. Firstly, the lingual nerve may be trapped against the lingual plate due to incorrect positioning of the elevator during placement between the lingual periosteum and bone. Secondly, the elevator may not always be positioned correctly between the lingual nerve and rotating bur as suggested by Rood.18 Also, since the lingual nerve has been found above the lingual crest, Robinson and Smith may have lowered the incidence of lingual nerve damage in the group without flap retraction if the operators were allowed to elevate tissues over the third molar crown as far as the lingual plate during surgery. The results of this study clearly indicated however that lingual tissue retraction can be considered as a substantial factor in lingual nerve trauma.

More recent papers by Bataineb (2001), Gullicher et al (2001) and Renton et al (2001) have shed further light on this controversy.24,25,26 These studies were all prospective and attempted to define variables that had been previously suggested and scrutinize their importance in an appropriate statistical fashion. Bataineb after the analysis of 741 third molar extractions performed under local anesthesia by a buccal approach, with or without lingual flap retraction found a 2.6 % incidence of lingual paresthesias. After a period of three months all the somatosensory disturbances had resolved. He determined, based on his statistics that the only valid factor related to its occurrence was the elevation of the lingual tissues. The type of impaction, experience of the operator, removal of bone and or sectioning of the teeth were claimed to be unrelated. Scrutiny of his data and the fact of only using a chi-square test in the pattern that he did, leaves his conclusion somewhat questionable.

Renton and McGurk assessed patient, dental and surgical factors collected on 2,134 lower wisdom tooth extractions (1,384 patients) performed by the different approaches and surgeons.36 They determined and overall incidence of temporary and permanent nerve injury of 1% and 0.3% respectively. Using a Student's t test, one way ANOVA and other multivariate analysis they found in their cohort that the important variables for permanent nerve injury, in order of their importance to be: 1: Perforation of the lingual cortical plate 2: The expertise or skill of the surgeon. 3: The difficulty of the extraction. 4: Defined visualization of the nerve. 5: The age of the patient (Table 2).

Gulicher and Gerlach analyzed the variables in lingual nerve dysfunction in 1,106 impacted mandibular third molar removals using a buccal approach with periosteal protection on the lingual employing the X2 test.38 They incurred an overall incidence of nerve dysfunction of 2.1%, of which 0.37% were deemed permanent. The statistically important parameter predictive of nerve damage were if the procedure was performed under general anesthesia, and the experience of the operator.

CONCLUSION

It is difficult to compare the two techniques, the lingual split-bone and the conventional buccal approach, with different studies since they vary dramatically in criteria for inclusion, techniques used, time span and sample size. Many studies are also less than statistically ideal due to inherent biases, retrospective nature, and comparisons between complication rates in different centers in non-randomized surgeries performed by many different surgeons. Furthermore, studies which use surveys are known to report unreliable responses, since some responders may have estimated their total number of extractions and those of associates in their practice. It is scientifically unacceptable to compare results reported by different clinicians using different methods at different sample sizes with different assessments and analyses. As a result, the only way to determine the most appropriate surgical method is with prospective randomized clinical trials comparing the lingual split-bone with the conventional buccal approach.

Previous prospective randomized studies have shown there is merit in performing either technique, the lingual split-bone or the conventional buccal approach, since there is no difference in lingual nerve morbidity using either surgical approach. The real culprit in the high rates of lingual sensory disturbance is the elevation and retraction of the lingual flap itself, particularly with a Howarth's, during either the lingual split or buccal approach with distal bone removal. Although changing from a Howarth's to a specifically designed retractor for lingual nerve protection, or not extending the position of the periosteal past the alveolar crest may reduce the incidence of lingual nerve morbidity, the variable position of the lingual nerve, especially when it may be found directly on the lingual plate or in the soft tissues above the lingual crest, precludes the complete elimination of lingual nerve disturbances. In this respect it also seems clear that the skill of the operator is of great importance. Skill, coupled with anatomical, dental and patient factors will ultimately determine the potential for nerve injury (Fig. 9).

Dr. Lam is Resident, Oral and Maxillofacial Surgery; PhD. Harron Scholar, Collaborative Program in Neuroscience, Faculty of Dentistry, University of Toronto.

Dr. Holmes is Assistant Head, Director of Undergraduate Education, Surgical Director, Surgical Orthodontic Treatment Program, Department of Oral & Maxillofacial Surgery, Faculty of Dentistry, Uiversity of Toronto

Oral Health welcomes this original article.

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40. Mozsary PG, Middleton RA. Microsurgical reconstruction of the Lingual nerve: J. Oral Maxfac Surg. 1984; 42: 415 - 420.

Table 1

The reported incidence of lingual nerve sensory disturbance following the use of different methods of removal of mandibular third molars with (w) or without (w/o) lingual flap retraction.

AuthorYearTemporaryPermanentMethod
IncidenceIncidenceUsed
1.Rud419701%0.14%lingual-split w/
0%0%drill w/o
2.Van Gool et al.519770.2%0%--
3.Bruce et al.619801.1%--drill w/o
4.Rood719836.6%0%lingual-split w/
5.Hochwald et al.819834.3%0%lingual-split w/
6.Rud919843%0%lingual-split w/
7.Goldberg et al.1019850.6%0.2%drill
8.Alling III1119860.06%0.007%drill w/o
9.Sisk et al.1219860.25%0.25%drill
10.Wofford & Miller1319870.7%0.2%drill
11.Mason14198811.5%0.6%drill/lingual-split w , w/o
19.8%--lingual split w/
8.3%--drill w/ and w/o
12.Middlehurst et al.15198823%0%drill w/ (Howarth's)
0%0%lingual-split (Howarth's)
13.Blackburn & Bramley16198910.5%0.5%drill/lingual-split w/ ,w/o
18.0%--drill/lingual-split w/ (Howarth's)
4.2%--drill w/o
14.Von Arx & Simpson17198922%0%lingual-split w/
15.Rood18199212.8%0%lingual-split w/ (Howarth's)
3.2%2.0%drill w/ (Howarth's)
16.Carmichael & McGowan19199219.6%0.6%lingual-split w/ (Howarth's)
13.5%0.6%drill w/ (Howarth's)
17.Absi & Shepherd20199321%0%lingual-split w/ (Howarth's)
23%0%drill w/ (Howarth's)
18.Chiapasco et al.2119930%0%drill w/o
19.Schultze-Mosgau and Reich2219931.9%0%drill w/ (periosteal elevator)
20.Walters23199510%0%lingual-split w/ (Howarth's)
0.5%0%lingual-split w/ (new retractor)
21.Robinson & Smith2419966.9%0.8%drill w/ (Howarth's)
0.8%0.3%drill w/o
22.Moss & Wake2519990.8 %0%lingual-split w/ (Hovell's)
23.Hill & Mostafa352001<5.0%0%drill w/
24.Renton & McGeriach3620011.0%0.3%variable
25.Gullicher & Geriach3820012.1 %0.37%drill w/ elevator
26.Bataineb3720015.6%0drill w/ elevator
1.30drill w/o

Table 2: Recommendations

For the specialist and non specialist the following recommendations can be made:

1. That with the conventional buccal approach nerve injury can occur in a range of 0.3%9 to 4.2%.14 Injuries can increase to up to 23%14 if the lingual tissues are elevated.

2. There is risk that there will be a permanent nerve dysfunction at a level of 0.2- 0.3 % and this can increase to the order of 2%18 with lingual flap manipulation.

3. Remember that your surgical skill is an important determining factor in nerve injuries.

4. Other definable and statistically important predictors of injury include: Perforation of the lingual cortical plate by the drill, the difficulty of the extraction, defined visualization of the nerve at the time of surgery and age of the patient.

5. All patients should be informed of the risk of nerve injury as it can result in a permanent impairment of function and can be a source of litigation.

6. The person who elects to take out wisdom teeth should be aware of the tremendous anatomical variations of the lingual nerves position in the lower third molar area as this allows appreciation of what surgically the operator might be cautious in doing.

7. Surgically avoid: elevating the lingual tissues, overzealous currettement of the socket lingually ,overzealous retraction of the lingual tissues if found necessary, overzealous retraction of the tongue and floor of mouth in the floor of the mouth in the third molar area, taking deep bites of tissue on the lingual side when placing sutures, placing the distal releasing component of the incision too far medially of the external oblique ridge in the retromolar pad area and if you are contemplating performing an opercutectomy remember that the nerve can sit in this area. (Table 3)

8. Always keep site of your bur tip when removing bone from the distal aspect of the tooth. This will help you prevent plate perforations.

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TABLE 2
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FIGURE 2A
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FIGURE 2B
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FIGURE 3
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TABLE 3
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FIGURES 4-6
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FIGURES 7 & 8
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FIGURE 9
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