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Does 3-dimensional imaging of the third molar reduce the risk of experiencing inferior alveolar nerve injury owing to extraction?
ORIGINAL CONTRIBUTIONS
Does 3-dimensional imaging of the third molar reduce the risk of experiencing inferior alveolar nerve injury owing to extraction? A meta-analysis Adrià Clé-Ovejero, DDS; Alba Sánchez-Torres, DDS, MS; Octavi Camps-Font, DDS, MS; Cosme Gay-Escoda, MD, DDS, MS, PhD, EBOS, OMFS; Rui Figueiredo, DDS, MS, PhD; Eduard Valmaseda-Castellón, DDS, MS, PhD, EBOS
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nferior alveolar nerve (IAN) injuries are 1 of the most critical complications that can occur as a result of mandibular third-molar (M3M) extraction1-5; IAN injuries can cause neurosensory impairment of the lower lip and chin area, which clearly affects the patient’s quality of life.1 This complication, which affects from 0.4% to 5.5%6 of patients, is usually temporary, but on occasion, it also can lead to permanent symptoms. The risk of experiencing nerve injury is higher in cases in which the neurovascular bundle is exposed during surgery.3,7 Some factors related to the surgical technique and the surgeon’s experience could have an impact on the patient’s risk of experiencing IAN injuries.3,7 In addition, some investigators have described radiographic warning signs.2 The most important predictor seems to be the proximity of the M3M roots to the mandibular canal (MC).1,6 Traditionally, clinicians have used panoramic radiographic (PR) images to assess the relationship between a patient’s M3M roots and the MC. In patients who have a high risk of experiencing IAN injuries, owing to the M3M being in close proximity with the MC, clinicians usually recommend obtaining computed tomographic (CT) images so that the surgeon can have a preoperative, 3-dimensional (3D)
ABSTRACT Background. Clinicians generally use panoramic radiographic (PR) images to assess the proximity of the mandibular third molar to the inferior alveolar nerve (IAN). However, in cases in which a patient needs to undergo a third-molar extraction, many clinicians also assess computed tomographic (CT) images to prevent nerve damage. Types of Studies Reviewed. Two of the authors independently searched MEDLINE (through PubMed), Cochrane Library, Scopus, and Ovid. The authors included randomized or nonrandomized longitudinal studies whose investigators had compared the number of IAN injuries after third-molar extraction in patients who had undergone preoperative CT with patients who had undergone only PR. Results. The authors analyzed the full text of 26 of the 745 articles they initially selected. They included 6 studies in the meta-analysis. Four of the studies had a high risk of bias, and the investigators of only 1 study had used blinding with the patients. The authors observed no statistically significant differences between groups related to the total number of nerve injuries (risk ratio, 0.96; 95% confidence interval, 0.50 to 1.85; P ¼ .91). The prognosis of the injuries was similar for both groups. Conclusions and Practical Implications. Although having preoperative CT images might be useful for clinicians in terms of diagnosing and extracting mandibular third molars, having these CT images does not reduce patients’ risk of experiencing IAN injuries nor does it affect their prognosis. Key Words. Third molar; computed tomography; panoramic radiography; mandibular nerve; alveolar nerve. JADA 2017:-(-):--http://dx.doi.org/10.1016/j.adaj.2017.04.001
Copyright ª 2017 American Dental Association. All rights reserved.
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view of the area.1 Nevertheless, the investigators of some studies have concluded that the use of 3D imaging does not seem to reduce the number of nerve injuries.14,6 In addition, 3D imaging is associated with higher costs1,6 and higher levels of radiation exposure compared with PR.1,4 In spite of these facts, some clinicians systematically indicate obtaining preoperative CTs before performing M3M extraction to avoid legal issues. Therefore, a meta-analysis of the published data would be of great interest to clinicians. Consequently, the aim of this study was to determine whether obtaining preoperative CT images reduces either the risk of experiencing or the severity of IAN injuries after M3M extraction in comparison with obtaining PR images. METHODS
We ensured that the methodology of our study adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement.8 Study selection criteria. We included randomized and nonrandomized controlled trials and prospective and retrospective cohort studies whose investigators had compared the number of IAN injuries that patients had experienced after undergoing M3M extraction with whether the patients had undergone preoperative CT or whether they had undergone only preoperative PR. We applied no restrictions regarding language or publication date. We excluded all of the articles that did not meet these criteria. The main outcome variable was the number of IAN injuries for each group; we defined an IAN injury as a loss of sensation in the lower lip or chin areas, either subjectively reported by the patient or assessed by means of clinical testing. The secondary variables were: - type of lesion: We considered the lesion to be persistent if the symptoms lasted longer than 6 months; - risk of experiencing nerve injury, estimated by using a previously obtained radiographic assessment: We classified the level of risk of experiencing IAN injury as being moderate if there was a superimposition of the M3M root and the MC, if there was at least 1 radiographic warning sign (according to Rood and Shehab’s criteria9), or both. If we noted that there was more than 1 radiographic warning sign, we considered that the patient had a high risk of experiencing IAN injury as a result of undergoing M3M extraction. Search strategy. We conducted an electronic search of articles published up to March 12, 2017, in MEDLINE (PubMed), Cochrane Library, Scopus, and Ovid databases. We used the following search strategies for each database: (((“Tomography, X-Ray Computed”[Mesh]) OR “Cone-Beam Computed Tomography”[Mesh]) AND (“Molar, Third”[Mesh]) OR “Mandibular Nerve/
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injuries”[Mesh]) for MEDLINE (PubMed), (“X Ray Computed Tomography Scanner” OR “Cone Beam Computed Tomography”) AND (“Third Molar” OR “Mandibular Nerve”) for the Cochrane Library, (“Computed Tomography, X Ray” OR “Cone Beam Computed Tomography”) AND (“Third Molar” OR “Mandibular Nerve”) for Scopus, and (X Ray computed tomography or Cone Beam computed tomography) and (Third Molar or Mandibular nerve injury) for Ovid. We completed the search by manually screening the references cited in the selected articles and reviews. Selection of studies. Two reviewers (A.C.-O., A.S.-T.) independently screened the title and abstract of each article to decide its eligibility. They then assessed the full text of the selected articles. Figure 18 lists the studies we removed at this stage and the reasons for exclusion. A third reviewer (O.C.-F.) resolved any disagreements. We calculated the k statistic to measure the reviewers’ level of agreement. In situations in which the reviewers identified multiple reports with the same sets of patients, they included only the study with the longest follow-up time. Data extraction and method of analysis. Two reviewers (A.C.-O., A.S.-T.) independently extracted the data using data extraction tables. Whenever possible, they retrieved the following information from the selected articles: names of authors, year of publication, country in which the study was conducted, study design, and details associated with the participants, interventions, and outcomes. We considered the number of IAN injuries to be the primary outcome variable. The secondary outcomes comprised the type of lesion and the preoperative estimation of the risk of experiencing nerve injury. Risk of bias assessment. We assessed the risk of bias according to the guidelines provided in the Cochrane Handbook for Systematic Reviews of Interventions, Version 5.1.0,10 and we performed the data extraction and meta-analysis with Review Manager software, Version 5.3 (Cochrane Collaboration). We used the Newcastle-Ottawa Scale11 to assess the cohort studies. Statistical analysis. We carried out the statistical analysis using Review Manager software. For dichotomous outcomes, we used risk ratios (RR) with 95% confidence intervals (CI) to estimate the effect of the operation. We used parametric and nonparametric tests (Pearson c2 test and Fisher exact test) to compare the groups. We set the level of significance at a P value of less than .05. ABBREVIATION KEY. 3D: 3-dimensional. CT: Computed tomographic. IAN: Inferior alveolar nerve. M3M: Mandibular third molar. MC: Mandibular canal. NR: Not reported. PR: Panoramic radiographic. RCT: Randomized controlled trial.
Identification
ORIGINAL CONTRIBUTIONS
Records identified through MEDLINE (PubMed) (n = 298)
Records identified through Cochrane Library (n = 10)
Records identified through Ovid (n = 140)
Records identified through Scopus (n = 297)
Eligibility
Screening
Records after duplicates removed (n = 533)
Records screened (n = 533)
Records excluded (n = 507)
Full-text articles assessed for eligibility (n = 26)
Full-text articles excluded, with reasons (n = 20) • Number of injuries not specified (n = 4)5,14-16 • CT image obtained for all patients (n = 13)17-29 • Case series study (n = 1)30 • Ecological study (n = 1)31 • No comparisons made between CT and panoramic radiographic groups (n = 1)7
Included
Studies included in qualitative synthesis (n = 6)
Studies included in quantitative synthesis (meta-analysis) (n = 6)
Figure 1. Flow chart of the article selection process for the systematic review and meta-analysis, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement.8 CT: Computed tomographic.
We performed a meta-analysis only for the studies whose investigators had compared similar techniques and reported the same outcome measures. We conducted a subgroup analysis taking into consideration the preoperative risk of experiencing IAN damage. We estimated statistical heterogeneity by means of using the c2 test (Cochran Q test value) and I2 analyses. We interpreted a c2 test P value of less than .10 and an I2 value of greater than 50% as having a significant level of heterogeneity.12 We selected a fixed-effects model or a random-effects model according to these values.
If we had found a sufficient number of meta-analyzed trials (more than 10), we would have performed an analysis of publication bias, an assessment of clinical heterogeneity, and an analysis of sensitivity, in accordance with guidelines for analysis by Higgins and Thompson.12 RESULTS
Study selection and description. As shown in Figure 1,1-8,13-31 the initial electronic search yielded 745 references. After we removed duplicates, we screened the abstracts of 533 articles. We selected 26 articles1-7,13-31
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of some studies included patients that, on the basis of the results of preoperative testing, had a 3 + + – + + + Guerrero and colleagues, 2014 ? high risk of experiencing IAN injury.1,6,13 SanmartíGhaeminia and colleagues,1 2015 + + – + – + + García and colleagues6 4 selected patients whose Petersen and colleagues, 2016 + + + + + + + PR images showed suKorkmaz and colleagues,13 2017 + – + + + + ? perimposition of the MC and the M3M roots, fully formed roots, and the presence of at least 1 of 7 radiographic signs described by Rood and Shehab9 regarding the proximity between these structures. In addition, Petersen and colleagues4 included patients whose PR images showed contact or overlap between the tooth or root complex and the MC. We considered the patientss included in the study by Petersen and colleagues4 Figure 2. Risk of bias assessment, according to the Cochrane Handbook for Systematic Reviews of Interventions, to have a moderate risk of Version 5.1.0.10 þ: Low risk of bias. : High risk of bias. ?: Unclear risk of bias. experiencing IAN injury, although these authors for full-text analysis, and we included only 6 articles1-4,6,13 did not classify the patients’ risk of experiencing injury. in the meta-analysis. The level of agreement between the In both of their studies, Guerrero and colleagues2,3 reviewers was good, with a k statistic index of 0.909. We selected patients who had a moderate risk of experiselected 5 randomized controlled trials (RCT)1-4,13 and 1 encing IAN injury. They excluded patients who they retrospective cohort study.6 considered to have a “high risk” (with a high probability After examining the full text of the 26 articles, we of experiencing harm to the neurovascular bundle) and excluded 20 of the articles for the following reasons: the “low risk” (no clear radiographic relationship between investigators did not specify the number of IAN injuries the M3M and the MC) of experiencing IAN injury. in each group,5,14-16 the investigators performed CT for Quantitative synthesis. The prevalence of IAN all patients,17-29 the investigators’ study design did not neurosensory disturbance was 9.3% (52 of 560) for the comply with the inclusion criteria (case series30 and CT group and 8.3% (44 of 532) for the PR group. We ecological design31), and the investigators did not detected persistent neurosensory disturbances in 1.5% of compare the CT and the PR groups.7 patients (7 of 477) for the CT group and 0.9% (4 of 445) Risk of bias assessment. We classified 41-3,13 of the 5 for the PR group. Table 2 shows the prevalence of IAN RCTs1-4,13 as having a high risk of bias, owing to the disturbances according to different preoperative classiinvestigators’ lack of blinding regarding participants and fications of risk. personnel1-3,13 and lack of providing incomplete outcome We did not find statistically significant differences in data,1 as shown in Figure 2.1-4,13 the prevalence of IAN injury between the CT and PR We awarded the retrospective cohort study6 4 points groups (RR, 0.96; 95% CI, 0.50 to 1.85; P ¼ .91) or for the selection category, 1 point for the comparability between the studies whose investigators found that pacategory, and 3 points for the outcome category, totaling tients had a moderate risk (RR, 1.02; 95% CI, 0.27 to 3.86; 8 points; therefore, we classified the results of the cohort P ¼ .97) or a high risk (RR, 0.85; 95% CI, 0.33 to 2.23; study6 as being of high quality. P ¼ .75) of experiencing potential damage (Figure 31,3,4,6,13). Data extraction. Qualitative synthesis. The inThe investigators of 3 studies found persistent investigators of the selected studies included different types juries. Ghaeminia and colleagues1 observed 5 lesions in of patients (Table 11-4,6,13). For example, the investigators the CT group and 2 in the PR group that persisted el
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Guerrero and colleagues,2 2012
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TABLE 1
Characteristics of the studies included in the meta-analysis regarding participants, interventions, and outcomes. STUDY
Guerrero and Colleagues,2 2012
PATIENTS
OUTCOMES
Assessment Criteria
Radiographic Technique
Sample Size (N)
Nerve Lesions, No. (%)
Persistent Lesions (n)
Moderate risk
Cases that were not considered to be high risk (with a high probability of experiencing harm to the neurovascular bundle) or low risk (no clear radiographic relationship between the mandibular third molar and the MC*) of experiencing IAN† injury
CT‡
43
1 (2.3)
0
PR§
43
1 (2.3)
0
SanmartíGarcia and Colleagues,6 2012
High risk
Guerrero and Colleagues,3 2014
Moderate risk
Ghaeminia and Colleagues,1 2015
High risk
Petersen and Colleagues,4 2016
Moderate risk
Korkmaz and Colleagues,13 2017
High risk
* † ‡ § ¶ # **
INTERVENTIONS
Preoperative Risk
Superimposition of roots and MC and any 1 of the 7 radiographic warning signs, cited by Rood and Shehab** Cases that were not considered to be high risk (with a high probability of experiencing harm to the neurovascular bundle) or low risk (no clear radiographic relationship between the mandibular third molar and the MC) of experiencing IAN injury Superimposition of roots and MC covering more than one-half the height of the MC Superimposition of roots and MC Close relationship between the MC and the third molar, defined as the presence of at least 1 of the following 6 radiographic markers: interruption of the white line of the MC, darkening of the root, narrowing of the MC or roots, dark and bifid roots, deflected roots, diversion of the MC
NR¶
CT
95
15 (15.8)
1
PR
55
6 (10.9)
1
CT
126
2 (1.5)
NR
PR
130
5 (3.8)
NR
CT
156
11 (7.1)
5
PR
164
9 (5.5)
2
CT
111
21 (18.9)
1
PR
116
13 (11.2)
1
CT
72
3 (4.2)
0
PR
67
11 (16.4)
0
STUDY DESIGN
Persistent Lesion Follow-up (mo)
RCT# (parallel)
12
Cohort (retrospective)
NR
RCT (parallel, multicenter)
8
RCT (parallel)
6
RCT (parallel)
6
RCT (parallel)
MC: Mandibular canal. IAN: Inferior alveolar nerve. CT: Computed tomographic. PR: Panoramic radiographic. NR: Not reported. RCT: Randomized controlled trial. Source: Rood and Shehab.9
after an 8-month follow-up period, whereas SanmartíGarcía and colleagues6 and Petersen and colleagues4 each classified only 1 lesion in each group as being persistent (at least 12 and 6 months of evolution, respectively). We did not detect statistically significant differences in persistent lesions (RR, 1.64; 95% CI, 0.50 to 5.41; P ¼ .42). In the subgroup analysis of these persistent injuries, no differences were found in patients who had a high risk of experiencing injury (RR, 1.82; 95% CI, 0.48 to 6.90;
P ¼ .38) and a moderate risk of experiencing injury (RR, 1.05; 95% CI, 0.07 to 16.50; P ¼ .98) (Figure 41,2,4,6,13). DISCUSSION
In our study, we failed to find significant differences in the rate of nerve injuries after M3M extraction between patients who had undergone preoperative CT and those who had not undergone preoperative CT. Unfortunately, there is no consensus on the criteria for the preoperative
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TABLE 2
support the hypothesis that obtaining preoperative CT images does not appear to lead to a significant decrease in the rate of IAN injury after M3M IAN INJURIES RISK IAN* INJURIES extraction. † ‡ PR GROUP CT GROUP Investigators have identified several risk factors Overall Persistent Overall Persistent that can predict a patient’s likelihood of experiModerate 9.7% (23/237) 0.6% (1/154) 7.3% (18/246) 0.6% (1/159) encing IAN injury after M3M extraction. Absence of High 9.0% (29/323) 1.9% (6/323) 9.1% (26/286) 1.0% (3/286) cortication,20,28 a dumb-bell–shaped MC,23,28 and a Overall 9.3% (52/560) 1.5% (7/477) 8.3% (44/532) 0.9% (4/445) lingual1,22,29 or interradicular29 position of the MC * IAN: Inferior alveolar nerve. are among these risk factors. Some investigators † CT: Computed tomographic. have stated that injuries occur more easily in MCs ‡ PR: Panoramic radiographic. that have a narrow configuration.1 In addition, when the MC is positioned lingually, the IAN may receive unfavorable forces if the surgeon starts his approach assessment of the risk of experiencing IAN injury after by luxating on the buccal side.29 For this reason, it is undergoing third-molar extraction. Indeed, all of the thought that most IAN injuries are the result of investigators had established their own criteria to classify compression and traction movements during M3M patients’ risk, which made it difficult for us to make surgery.17 In cases such as these, preoperative CT images comparisons. In addition, the time needed to consider a might provide useful information to the surgeon concerning where to apply the elevator. lesion to be permanent also varied. Many investigators A significant proportion (45.5%) of M3Ms have some used the term “permanent” to define a nerve injury that had not recovered by the time of the patient’s final degree of superimposition over the MC in PR.7 follow-up visit. For this reason, we determined that using According to Nakamori and colleagues,7 this superimposition, darkening of the root, and narrowing of the term “persistent” would be more appropriate, the MC on PR images correlate with an absence of because investigators could not assess the evolution of cortication7 and suggest close contact between the the patient’s injury after the period of data recording tooth and the nerve. This direct contact, which can be concluded. In our meta-analysis, we considered lesions observed in a CT image, seems to be associated with an that lasted more than 6 months to be persistent. We selected this time frame because Cheung and colleagues32 increased risk of experiencing IAN injury.19,23 However, reported that lesions that lasted more than 6 months had owing to this exposure, only those patients who have a low probability for recovery. Also, Valmaseda-Castellón a true anatomic relationship between the tooth and and colleagues,33 in the report of their prospective the nerve have a higher risk of experiencing an IAN cohort study of 1,117 M3M extractions, observed that le- impairment.26 Identifying risk factors for IAN injuries is a key issue sions that had not recovered 6 months after surgery were very likely to be permanent. involved in a clinician’s decision-making process Drawbacks related to the results of our report include regarding M3M extraction, because identifying these risk factors allows the clinician to identify patients who the fact that both the number of studies and the size of the samples were limited and that the results of 4 of have a high risk of experiencing IAN injuries. Investigators have considered the patient’s age and, espethe RCTs were associated with a high risk of bias. The cially, the anatomic proximity of the roots to the MC, to small number of participants included in these RCTs might have led to a type 2 error (a false-negative result). be the most relevant variables for predicting this These drawbacks clearly are related to the low incidence complication.17 Clinicians still consider PR to be the of IAN complications. Indeed, if we define an IAN injury criterion standard examination for M3M extraction. Clinicians do not consider the simple superimposition of after M3M as being the primary outcome and if we consider a 0.5 difference between groups to be clinically the third-molar roots over the MC to be a sign of a close relationship. In fact, the positive predictive value of IAN significant, favoring the CT group (as proposed by injury in cases of superimposition without additional Petersen and colleagues4), we find that none of the studies had a statistical power of greater than 70%. features is low. Even when the clinician finds more Therefore, the results of our meta-analysis strongly specific images, the positive predictive value still remains indicate the need for researchers to perform RCTs for small, probably owing to the low incidence of this which they have established a correct calculation of the complication.29,31 Indeed, only approximately 15% of the patients who undergo M3M extraction and who have statistical power of the study. Clinicians must take had preoperative PR images that suggested that the these limitations into account when considering the patient has a high risk of experiencing IAN injuries will results of our study. Even with these limitations, the outcomes of our meta-analysis and the results of most experience a neurosensory impairment.6 Although CT images are more specific for clinicians to detect the true of the studies included in our meta-analysis seem to
Percentages of nerve disturbances.
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ORIGINAL CONTRIBUTIONS
Study or Subgroup
CT Events Total
PR Events Total
Risk Ratio Weight M–H, Random, 95% CI
Risk Ratio M–H, Random, 95% CI
1.1.1 Moderate risk of experiencing potential damage to the IAN Guerrero and colleagues,3 2014
2
126
5
130
11.3%
0.41 (0.08 to 2.09)
Petersen and colleagues,4 2016
21
111
13
116
27.5%
1.69 (0.89 to 3.20)
246
38.9%
1.02 (0.27 to 3.86)
55 164 67 286
22.2% 22.9% 16.1% 61.1%
1.45 (0.60 to 3.51) 1.28 (0.55 to 3.02) 0.25 (0.07 to 0.87) 0.85 (0.33 to 2.23)
532
100.0%
0.96 (0.50 to 1.85)
237
Subtotal (95% CI)
18
23 Total events 2 2 2 Heterogeneity: τ = 0.61; χ1 = 2.53, P = .11; I = 60% Test for overall effect: z = 0.03 (P = .97) 1.1.2 High risk of experiencing potential damage to the IAN Sanmarti-Garcia and colleagues,6 2012 Ghaeminia and colleagues,1 2015 Korkmaz and colleagues,13 2017 Subtotal (95% CI)
15 11 3
95 156 72 323
29 Total events 2 2 2 Heterogeneity: τ = 0.47; χ2 = 5.81, P = .05; I = 66% Test for overall effect: z = 0.32 (P = .75)
6 9 11 26
560
Total (95% CI)
52 Total events 2 2 2 Heterogeneity: τ = 0.30; χ4 = 9.12, P = .06; I = 56% Test for overall effect: z = 0.11 (P = .91) 2 2 Test for subgroup differences: χ1 = 0.05, P = .83; I = 0%
44 0.01
0.1
1
Favors CT
10
100
Favors PR
Figure 3. Meta-analysis: inferior alveolar nerve injury after mandibular third-molar extraction. CI: Confidence interval. CT: Computed tomographic. IAN: Inferior alveolar nerve. M-H: Mantel–Haenszel. PR: Panoramic radiographic.
Study or Subgroup
CT Events Total
PR Events Total
2.1.1 Moderate risk of experiencing potential damage to the IAN Guerrero and colleagues,2 2014 0 0 43 Petersen and colleagues,4 2016
1
Subtotal (95% CI) Total events Heterogeneity: Not applicable Test for overall effect: z = 0.03 (P = .98)
111 154
1
43 116 159
Weight
Risk Ratio M–H, Fixed, 95% CI
23.3% 23.3%
Not estimable 1.05 (0.07 to 16.50) 1.05 (0.07 to 16.50)
Risk Ratio M–H, Fixed, 95% CI
1
1
2.1.2 High risk of experiencing potential damage to the IAN Sanmarti-Garcia and colleagues,6 2012 Ghaeminia and colleagues,1 2015 Korkmaz and colleagues,13 2017 Subtotal (95% CI) Total events 2 2 Heterogeneity: χ1 = 0.86, P = .35; I = 0% Test for overall effect: z = 0.88 (P = .38) Total (95% CI)
1 5 0
95 156 72 323
1 2 0
55 164 67 286
30.2% 46.5%
0.58 (0.04 to 9.07) 2.63 (0.52 to 13.35)
76.7%
Not estimable 1.82 (0.48 to 6.90)
445
100.0%
1.64 (0.50 to 5.41)
3
6
477
Total events 7 Heterogeneity: χ22 = 0.98, P = .061; I2 = 0% Test for overall effect: z = 0.81 (P = .42) 2 2 Test for subgroup differences: χ1 = 0.13, P = .72; I = 0%
4 0.01
0.1 Favors CT
1
10
100
Favors PR
Figure 4. Meta-analysis: persistent inferior alveolar nerve injury after mandibular third-molar extraction. CI: Confidence interval. CT: Computed tomographic. IAN: Inferior alveolar nerve. M-H: Mantel–Haenszel. PR: Panoramic radiographic.
anatomic relationship between M3Ms and MCs, the positive predictive value of CT images is still low and, to our knowledge, there are no data suggesting that there would be any reduction in the prevalence of IAN
impairment when 3D techniques are used, compared with conventional PR. According to the results of this meta-analysis, clinicians should not perform CT routinely before M3M
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surgery. However, in specific cases in which the clinician suspects a close relationship between the MC and the M3M after observing PR images, we recommend obtaining CT images.18 CONCLUSIONS
According to the results of our meta-analysis, clinicians should not perform CT routinely before M3M surgery because using CT images does not seem to reduce the incidence or affect the patient’s prognosis of IAN injuries in comparison with using PR images. n Dr. Clé-Ovejero is a fellow, Master of Oral Surgery and Orofacial Implantology, Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona, Spain. Dr. Sánchez-Torres is a graduate of the Master of Oral Surgery and Orofacial Implantology, and an associate professor of oral surgery, Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona; and a researcher, Bellvitge Biomedical Research Institute, Barcelona, Spain. Dr. Camps-Font is a graduate of the Master of Oral Surgery and Orofacial Implantology, and an associate professor of oral surgery, Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona; and a researcher, Bellvitge Biomedical Research Institute, Barcelona, Spain. Dr. Gay-Escoda is the chair and a professor, Oral and Maxillofacial Surgery, Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona; the director of the Master Degree Program in Oral Surgery and Implantology, EFHRE (European Foundation for Health Research and Education) International University/FUCSO (Catalonian Foundation for Oral Health); a coordinator and researcher, Bellvitge Biomedical Research Institute, Barcelona; and the head, Department of Maxillofacial Surgery and Implantology, Teknon Medical Center, Barcelona, Spain. Dr. Figueiredo is an associate professor, Oral Surgery, Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona; and a researcher, Bellvitge Biomedical Research Institute (IDIBELL), Barcelona, Spain. Address correspondence to Dr. Figueiredo at Faculty of Medicine and Health Sciences, Campus de Bellvitge, C/Feixa Llarga, s/n; Pavelló Govern, 2a planta, Despatx 2.9, 08907 L’Hospitalet de Llobregat, University of Barcelona, Barcelona, Spain, e-mail [email protected]. Dr. Valmaseda-Castellón is a professor, Oral Surgery, and a professor, Master of Oral Surgery and Orofacial Implantology, Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona; and a researcher, Bellvitge Biomedical Research Institute, Barcelona, Spain. Disclosure. None of the authors reported any disclosures. ORCID Number. Rui Figueiredo: http://orcid.org/0000-0002-2122-6530 The authors conducted this study in association with the Odontological and Maxillofacial Pathology and Therapeutics Research Group of the Bellvitge Biomedical Research Institute. The authors thank Mary Georgina Hardinge for her assistance in correcting the English in the manuscript. 1. Ghaeminia H, Gerlach NL, Hoppenreijs TJ, et al. Clinical relevance of cone beam computed tomography in mandibular third molar removal: a multicentre, randomised, controlled trial. J Craniomaxillofac Surg. 2015; 43(10):2158-2167. 2. Guerrero ME, Nackaerts O, Beinsberger J, Horner K, Schoenaers J, Jacobs R; SEDENTEXCT Project Consortium. Inferior alveolar nerve sensory disturbance after impacted mandibular third molar evaluation using cone beam computed tomography and panoramic radiography: a pilot study. J Oral Maxillofac Surg. 2012;70(10):2264-2270. 3. Guerrero ME, Botetano R, Beltran J, Horner K, Jacobs R. Can preoperative imaging help to predict postoperative outcome after wisdom tooth removal? A randomized controlled trial using panoramic radiography versus cone-beam CT. Clin Oral Investig. 2014;18(1):335-342. 4. Petersen LB, Vaeth M, Wenzel A. Neurosensoric disturbances after surgical removal of the mandibular third molar based on either panoramic
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imaging or cone beam CT scanning: a randomized controlled trial (RCT). Dentomaxillofac Radiol. 2016;45(2):20150224. 5. Gallesio C, Berrone M, Ruga E, Boffano P. Surgical extraction of impacted inferior third molars at risk for inferior alveolar nerve injury. J Craniofac Surg. 2010;21(6):2003-2007. 6. Sanmartí-Garcia G, Valmaseda-Castellón E, Gay-Escoda C. Does computed tomography prevent inferior alveolar nerve injuries caused by lower third molar removal? J Oral Maxillofac Surg. 2012;70(1):5-11. 7. Nakamori K, Fujiwara K, Miyazaki A, et al. Clinical assessment of the relationship between the third molar and the inferior alveolar canal using panoramic images and computed tomography. J Oral Maxillofac Surg. 2008;66(11):2308-2313. 8. Moher D, Liberati A, Tetzlaff J, Altman DG; PRISMA Group. Preferred reporting items for systematic reviews and meta-analyses: the PRISMA Statement. PLoS Med. 2009;6(7):e1000097. 9. Rood JP, Shehab BA. The radiological prediction of inferior alveolar nerve injury during third molar surgery. Br J Oral Maxillofac Surg. 1990; 28(1):20-25. 10. Higgins JP, Green S, eds. Cochrane Handbook for Systematic Reviews of Interventions, Version 5.1.0 (updated March 2011). The Cochrane Collaboration; 2011. Available at: www.handbook.cochrane.org. Accessed April 14, 2017. 11. Wells GA, Shea B, O’Connell D, et al. The Newcastle-Ottawa Scale (NOS) for assessing the quality of nonrandomised studies in metaanalyses. The Ottawa Hospital Research Institute; 2014. Available at: www. ohri.ca/programs/clinical_epidemiology/oxford.asp. Accessed April 14, 2017. 12. Higgins JP, Thompson SG. Quantifying heterogeneity in a metaanalysis. Stat Med. 2002;21(11):1539-1558. 13. Korkmaz YT, Kayıpmaz S, Senel FC, Atasoy KT, Gumrukcu Z. Does additional cone beam computed tomography decrease the risk of inferior alveolar nerve injury in high-risk cases undergoing third molar surgery? Does CBCT decrease the risk of IAN injury? Int J Oral Maxillofac Surg. 2017;46(5):628-635. 14. Sigron GR, Pourmand PP, Mache B, Stadlinger B, Locher MC. The most common complications after wisdom-tooth removal, part 1: a retrospective study of 1,199 cases in the mandible. Swiss Dent J. 2014;124(10): 1042-1046, 1052-1056. 15. Roeder F, Wachtlin D, Schulze R. Necessity of 3D visualization for the removal of lower wisdom teeth: required sample size to prove noninferiority of panoramic radiography compared to CBCT. Clin Oral Investig. 2012;16(3):699-706. 16. Ghaeminia H, Meijer GJ, Soehardi A, et al. The use of cone beam CT for the removal of wisdom teeth changes the surgical approach compared with panoramic radiography: a pilot study. Int J Oral Maxillofac Surg. 2011; 40(8):834-839. 17. Selvi F, Dodson TB, Nattestad A, Robertson K, Tolstunov L. Factors that are associated with injury to the inferior alveolar nerve in high-risk patients after removal of third molars. Br J Oral Maxillofac Surg. 2013;51(8): 868-873. 18. Hasegawa T, Ri S, Shigeta T, et al. Risk factors associated with inferior alveolar nerve injury after extraction of the mandibular third molar: a comparative study of preoperative images by panoramic radiography and computed tomography. Int J Oral Maxillofac Surg. 2013;42(7):843-851. 19. Xu GZ, Yang C, Fan XD, et al. Anatomic relationship between impacted third mandibular molar and the mandibular canal as the risk factor of inferior alveolar nerve injury. Br J Oral Maxillofac Surg. 2013;51(8): e215-e219. 20. Jun SH, Kim CH, Ahn JS, Padwa BL, Kwon JJ. Anatomical differences in lower third molars visualized by 2D and 3D X-ray imaging: clinical outcomes after extraction. Int J Oral Maxillofac Surg. 2013;42(4):489-496. 21. Umar G, Obisesan O, Bryant C, Rood JP. Elimination of permanent injuries to the inferior alveolar nerve following surgical intervention of the “high risk” third molar. Br J Oral Maxillofac Surg. 2013;51(4):353-357. 22. Neves FS, de Almeida SM, Bóscolo FN, et al. Risk assessment of inferior alveolar neurovascular bundle by multidetector computed tomography in extractions of third molars. Surg Radiol Anat. 2012;34(7): 619-624. 23. Ueda M, Nakamori K, Shiratori K, et al. Clinical significance of computed tomographic assessment and anatomic features of the inferior alveolar canal as risk factors for injury of the inferior alveolar nerve at third molar surgery. J Oral Maxillofac Surg. 2012;70(3):514-520.
ORIGINAL CONTRIBUTIONS
24. Nakayama K, Nonoyama M, Takaki Y, et al. Assessment of the relationship between impacted mandibular third molars and inferior alveolar nerve with dental 3-dimensional computed tomography. J Oral Maxillofac Surg. 2009;67(12):2587-2591. 25. Jhamb A, Dolas RS, Pandilwar PK, Mohanty S. Comparative efficacy of spiral computed tomography and orthopantomography in preoperative detection of relation of inferior alveolar neurovascular bundle to the impacted mandibular third molar. J Oral Maxillofac Surg. 2009;67(1): 58-66. 26. Tantanapornkul W, Okouchi K, Fujiwara Y, et al. A comparative study of cone-beam computed tomography and conventional panoramic radiography in assessing the topographic relationship between the mandibular canal and impacted third molars. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2007;103(2):253-259. 27. Maegawa H, Sano K, Kitagawa Y, et al. Preoperative assessment of the relationship between the mandibular third molar and the mandibular canal by axial computed tomography with coronal and sagittal reconstruction. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2003;96(5): 639-646. 28. Shiratori K, Nakamori K, Ueda M, Sonoda T, Dehari H. Assessment of the shape of the inferior alveolar canal as a marker for increased risk of
injury to the inferior alveolar nerve at third molar surgery: a prospective study. J Oral Maxillofac Surg. 2013;71(12):2012-2019. 29. Ghaeminia H, Meijer GJ, Soehardi A, Borstlap WA, Mulder J, Berge SJ. Position of the impacted third molar in relation to the mandibular canal: diagnostic accuracy of cone beam computed tomography compared with panoramic radiography. Int J Oral Maxillofac Surg. 2009;38(9):964-971. 30. Suomalainen A, Apajalahti S, Vehmas T, Venta I. Availability of CBCT and iatrogenic alveolar nerve injuries. Acta Odontol Scand. 2013; 71(1):151-156. 31. Susarla SM, Dodson TB. Preoperative computed tomography imaging in the management of impacted mandibular third molars. J Oral Maxillofac Surg. 2007;65(1):83-88. 32. Cheung LK, Leung YY, Chow LK, Wong MC, Chan EK, Fok YH. Incidence of neurosensory deficits and recovery after lower third molar surgery: a prospective clinical study of 4338 cases. Int J Oral Maxillofac Surg. 2010;39(4):320-326. 33. 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(4):377-383.
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Does 3-dimensional imaging of the third molar reduce the risk of experiencing inferior alveolar nerve injury owing to extraction? A meta-analysis Adrià Clé-Ovejero, DDS; Alba Sánchez-Torres, DDS, MS; Octavi Camps-Font, DDS, MS; Cosme Gay-Escoda, MD, DDS, MS, PhD, EBOS, OMFS; Rui Figueiredo, DDS, MS, PhD; Eduard Valmaseda-Castellón, DDS, MS, PhD, EBOS
I
nferior alveolar nerve (IAN) injuries are 1 of the most critical complications that can occur as a result of mandibular third-molar (M3M) extraction1-5; IAN injuries can cause neurosensory impairment of the lower lip and chin area, which clearly affects the patient’s quality of life.1 This complication, which affects from 0.4% to 5.5%6 of patients, is usually temporary, but on occasion, it also can lead to permanent symptoms. The risk of experiencing nerve injury is higher in cases in which the neurovascular bundle is exposed during surgery.3,7 Some factors related to the surgical technique and the surgeon’s experience could have an impact on the patient’s risk of experiencing IAN injuries.3,7 In addition, some investigators have described radiographic warning signs.2 The most important predictor seems to be the proximity of the M3M roots to the mandibular canal (MC).1,6 Traditionally, clinicians have used panoramic radiographic (PR) images to assess the relationship between a patient’s M3M roots and the MC. In patients who have a high risk of experiencing IAN injuries, owing to the M3M being in close proximity with the MC, clinicians usually recommend obtaining computed tomographic (CT) images so that the surgeon can have a preoperative, 3-dimensional (3D)
ABSTRACT Background. Clinicians generally use panoramic radiographic (PR) images to assess the proximity of the mandibular third molar to the inferior alveolar nerve (IAN). However, in cases in which a patient needs to undergo a third-molar extraction, many clinicians also assess computed tomographic (CT) images to prevent nerve damage. Types of Studies Reviewed. Two of the authors independently searched MEDLINE (through PubMed), Cochrane Library, Scopus, and Ovid. The authors included randomized or nonrandomized longitudinal studies whose investigators had compared the number of IAN injuries after third-molar extraction in patients who had undergone preoperative CT with patients who had undergone only PR. Results. The authors analyzed the full text of 26 of the 745 articles they initially selected. They included 6 studies in the meta-analysis. Four of the studies had a high risk of bias, and the investigators of only 1 study had used blinding with the patients. The authors observed no statistically significant differences between groups related to the total number of nerve injuries (risk ratio, 0.96; 95% confidence interval, 0.50 to 1.85; P ¼ .91). The prognosis of the injuries was similar for both groups. Conclusions and Practical Implications. Although having preoperative CT images might be useful for clinicians in terms of diagnosing and extracting mandibular third molars, having these CT images does not reduce patients’ risk of experiencing IAN injuries nor does it affect their prognosis. Key Words. Third molar; computed tomography; panoramic radiography; mandibular nerve; alveolar nerve. JADA 2017:-(-):--http://dx.doi.org/10.1016/j.adaj.2017.04.001
Copyright ª 2017 American Dental Association. All rights reserved.
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view of the area.1 Nevertheless, the investigators of some studies have concluded that the use of 3D imaging does not seem to reduce the number of nerve injuries.14,6 In addition, 3D imaging is associated with higher costs1,6 and higher levels of radiation exposure compared with PR.1,4 In spite of these facts, some clinicians systematically indicate obtaining preoperative CTs before performing M3M extraction to avoid legal issues. Therefore, a meta-analysis of the published data would be of great interest to clinicians. Consequently, the aim of this study was to determine whether obtaining preoperative CT images reduces either the risk of experiencing or the severity of IAN injuries after M3M extraction in comparison with obtaining PR images. METHODS
We ensured that the methodology of our study adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement.8 Study selection criteria. We included randomized and nonrandomized controlled trials and prospective and retrospective cohort studies whose investigators had compared the number of IAN injuries that patients had experienced after undergoing M3M extraction with whether the patients had undergone preoperative CT or whether they had undergone only preoperative PR. We applied no restrictions regarding language or publication date. We excluded all of the articles that did not meet these criteria. The main outcome variable was the number of IAN injuries for each group; we defined an IAN injury as a loss of sensation in the lower lip or chin areas, either subjectively reported by the patient or assessed by means of clinical testing. The secondary variables were: - type of lesion: We considered the lesion to be persistent if the symptoms lasted longer than 6 months; - risk of experiencing nerve injury, estimated by using a previously obtained radiographic assessment: We classified the level of risk of experiencing IAN injury as being moderate if there was a superimposition of the M3M root and the MC, if there was at least 1 radiographic warning sign (according to Rood and Shehab’s criteria9), or both. If we noted that there was more than 1 radiographic warning sign, we considered that the patient had a high risk of experiencing IAN injury as a result of undergoing M3M extraction. Search strategy. We conducted an electronic search of articles published up to March 12, 2017, in MEDLINE (PubMed), Cochrane Library, Scopus, and Ovid databases. We used the following search strategies for each database: (((“Tomography, X-Ray Computed”[Mesh]) OR “Cone-Beam Computed Tomography”[Mesh]) AND (“Molar, Third”[Mesh]) OR “Mandibular Nerve/
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injuries”[Mesh]) for MEDLINE (PubMed), (“X Ray Computed Tomography Scanner” OR “Cone Beam Computed Tomography”) AND (“Third Molar” OR “Mandibular Nerve”) for the Cochrane Library, (“Computed Tomography, X Ray” OR “Cone Beam Computed Tomography”) AND (“Third Molar” OR “Mandibular Nerve”) for Scopus, and (X Ray computed tomography or Cone Beam computed tomography) and (Third Molar or Mandibular nerve injury) for Ovid. We completed the search by manually screening the references cited in the selected articles and reviews. Selection of studies. Two reviewers (A.C.-O., A.S.-T.) independently screened the title and abstract of each article to decide its eligibility. They then assessed the full text of the selected articles. Figure 18 lists the studies we removed at this stage and the reasons for exclusion. A third reviewer (O.C.-F.) resolved any disagreements. We calculated the k statistic to measure the reviewers’ level of agreement. In situations in which the reviewers identified multiple reports with the same sets of patients, they included only the study with the longest follow-up time. Data extraction and method of analysis. Two reviewers (A.C.-O., A.S.-T.) independently extracted the data using data extraction tables. Whenever possible, they retrieved the following information from the selected articles: names of authors, year of publication, country in which the study was conducted, study design, and details associated with the participants, interventions, and outcomes. We considered the number of IAN injuries to be the primary outcome variable. The secondary outcomes comprised the type of lesion and the preoperative estimation of the risk of experiencing nerve injury. Risk of bias assessment. We assessed the risk of bias according to the guidelines provided in the Cochrane Handbook for Systematic Reviews of Interventions, Version 5.1.0,10 and we performed the data extraction and meta-analysis with Review Manager software, Version 5.3 (Cochrane Collaboration). We used the Newcastle-Ottawa Scale11 to assess the cohort studies. Statistical analysis. We carried out the statistical analysis using Review Manager software. For dichotomous outcomes, we used risk ratios (RR) with 95% confidence intervals (CI) to estimate the effect of the operation. We used parametric and nonparametric tests (Pearson c2 test and Fisher exact test) to compare the groups. We set the level of significance at a P value of less than .05. ABBREVIATION KEY. 3D: 3-dimensional. CT: Computed tomographic. IAN: Inferior alveolar nerve. M3M: Mandibular third molar. MC: Mandibular canal. NR: Not reported. PR: Panoramic radiographic. RCT: Randomized controlled trial.
Identification
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Records identified through MEDLINE (PubMed) (n = 298)
Records identified through Cochrane Library (n = 10)
Records identified through Ovid (n = 140)
Records identified through Scopus (n = 297)
Eligibility
Screening
Records after duplicates removed (n = 533)
Records screened (n = 533)
Records excluded (n = 507)
Full-text articles assessed for eligibility (n = 26)
Full-text articles excluded, with reasons (n = 20) • Number of injuries not specified (n = 4)5,14-16 • CT image obtained for all patients (n = 13)17-29 • Case series study (n = 1)30 • Ecological study (n = 1)31 • No comparisons made between CT and panoramic radiographic groups (n = 1)7
Included
Studies included in qualitative synthesis (n = 6)
Studies included in quantitative synthesis (meta-analysis) (n = 6)
Figure 1. Flow chart of the article selection process for the systematic review and meta-analysis, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement.8 CT: Computed tomographic.
We performed a meta-analysis only for the studies whose investigators had compared similar techniques and reported the same outcome measures. We conducted a subgroup analysis taking into consideration the preoperative risk of experiencing IAN damage. We estimated statistical heterogeneity by means of using the c2 test (Cochran Q test value) and I2 analyses. We interpreted a c2 test P value of less than .10 and an I2 value of greater than 50% as having a significant level of heterogeneity.12 We selected a fixed-effects model or a random-effects model according to these values.
If we had found a sufficient number of meta-analyzed trials (more than 10), we would have performed an analysis of publication bias, an assessment of clinical heterogeneity, and an analysis of sensitivity, in accordance with guidelines for analysis by Higgins and Thompson.12 RESULTS
Study selection and description. As shown in Figure 1,1-8,13-31 the initial electronic search yielded 745 references. After we removed duplicates, we screened the abstracts of 533 articles. We selected 26 articles1-7,13-31
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of some studies included patients that, on the basis of the results of preoperative testing, had a 3 + + – + + + Guerrero and colleagues, 2014 ? high risk of experiencing IAN injury.1,6,13 SanmartíGhaeminia and colleagues,1 2015 + + – + – + + García and colleagues6 4 selected patients whose Petersen and colleagues, 2016 + + + + + + + PR images showed suKorkmaz and colleagues,13 2017 + – + + + + ? perimposition of the MC and the M3M roots, fully formed roots, and the presence of at least 1 of 7 radiographic signs described by Rood and Shehab9 regarding the proximity between these structures. In addition, Petersen and colleagues4 included patients whose PR images showed contact or overlap between the tooth or root complex and the MC. We considered the patientss included in the study by Petersen and colleagues4 Figure 2. Risk of bias assessment, according to the Cochrane Handbook for Systematic Reviews of Interventions, to have a moderate risk of Version 5.1.0.10 þ: Low risk of bias. : High risk of bias. ?: Unclear risk of bias. experiencing IAN injury, although these authors for full-text analysis, and we included only 6 articles1-4,6,13 did not classify the patients’ risk of experiencing injury. in the meta-analysis. The level of agreement between the In both of their studies, Guerrero and colleagues2,3 reviewers was good, with a k statistic index of 0.909. We selected patients who had a moderate risk of experiselected 5 randomized controlled trials (RCT)1-4,13 and 1 encing IAN injury. They excluded patients who they retrospective cohort study.6 considered to have a “high risk” (with a high probability After examining the full text of the 26 articles, we of experiencing harm to the neurovascular bundle) and excluded 20 of the articles for the following reasons: the “low risk” (no clear radiographic relationship between investigators did not specify the number of IAN injuries the M3M and the MC) of experiencing IAN injury. in each group,5,14-16 the investigators performed CT for Quantitative synthesis. The prevalence of IAN all patients,17-29 the investigators’ study design did not neurosensory disturbance was 9.3% (52 of 560) for the comply with the inclusion criteria (case series30 and CT group and 8.3% (44 of 532) for the PR group. We ecological design31), and the investigators did not detected persistent neurosensory disturbances in 1.5% of compare the CT and the PR groups.7 patients (7 of 477) for the CT group and 0.9% (4 of 445) Risk of bias assessment. We classified 41-3,13 of the 5 for the PR group. Table 2 shows the prevalence of IAN RCTs1-4,13 as having a high risk of bias, owing to the disturbances according to different preoperative classiinvestigators’ lack of blinding regarding participants and fications of risk. personnel1-3,13 and lack of providing incomplete outcome We did not find statistically significant differences in data,1 as shown in Figure 2.1-4,13 the prevalence of IAN injury between the CT and PR We awarded the retrospective cohort study6 4 points groups (RR, 0.96; 95% CI, 0.50 to 1.85; P ¼ .91) or for the selection category, 1 point for the comparability between the studies whose investigators found that pacategory, and 3 points for the outcome category, totaling tients had a moderate risk (RR, 1.02; 95% CI, 0.27 to 3.86; 8 points; therefore, we classified the results of the cohort P ¼ .97) or a high risk (RR, 0.85; 95% CI, 0.33 to 2.23; study6 as being of high quality. P ¼ .75) of experiencing potential damage (Figure 31,3,4,6,13). Data extraction. Qualitative synthesis. The inThe investigators of 3 studies found persistent investigators of the selected studies included different types juries. Ghaeminia and colleagues1 observed 5 lesions in of patients (Table 11-4,6,13). For example, the investigators the CT group and 2 in the PR group that persisted el
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TABLE 1
Characteristics of the studies included in the meta-analysis regarding participants, interventions, and outcomes. STUDY
Guerrero and Colleagues,2 2012
PATIENTS
OUTCOMES
Assessment Criteria
Radiographic Technique
Sample Size (N)
Nerve Lesions, No. (%)
Persistent Lesions (n)
Moderate risk
Cases that were not considered to be high risk (with a high probability of experiencing harm to the neurovascular bundle) or low risk (no clear radiographic relationship between the mandibular third molar and the MC*) of experiencing IAN† injury
CT‡
43
1 (2.3)
0
PR§
43
1 (2.3)
0
SanmartíGarcia and Colleagues,6 2012
High risk
Guerrero and Colleagues,3 2014
Moderate risk
Ghaeminia and Colleagues,1 2015
High risk
Petersen and Colleagues,4 2016
Moderate risk
Korkmaz and Colleagues,13 2017
High risk
* † ‡ § ¶ # **
INTERVENTIONS
Preoperative Risk
Superimposition of roots and MC and any 1 of the 7 radiographic warning signs, cited by Rood and Shehab** Cases that were not considered to be high risk (with a high probability of experiencing harm to the neurovascular bundle) or low risk (no clear radiographic relationship between the mandibular third molar and the MC) of experiencing IAN injury Superimposition of roots and MC covering more than one-half the height of the MC Superimposition of roots and MC Close relationship between the MC and the third molar, defined as the presence of at least 1 of the following 6 radiographic markers: interruption of the white line of the MC, darkening of the root, narrowing of the MC or roots, dark and bifid roots, deflected roots, diversion of the MC
NR¶
CT
95
15 (15.8)
1
PR
55
6 (10.9)
1
CT
126
2 (1.5)
NR
PR
130
5 (3.8)
NR
CT
156
11 (7.1)
5
PR
164
9 (5.5)
2
CT
111
21 (18.9)
1
PR
116
13 (11.2)
1
CT
72
3 (4.2)
0
PR
67
11 (16.4)
0
STUDY DESIGN
Persistent Lesion Follow-up (mo)
RCT# (parallel)
12
Cohort (retrospective)
NR
RCT (parallel, multicenter)
8
RCT (parallel)
6
RCT (parallel)
6
RCT (parallel)
MC: Mandibular canal. IAN: Inferior alveolar nerve. CT: Computed tomographic. PR: Panoramic radiographic. NR: Not reported. RCT: Randomized controlled trial. Source: Rood and Shehab.9
after an 8-month follow-up period, whereas SanmartíGarcía and colleagues6 and Petersen and colleagues4 each classified only 1 lesion in each group as being persistent (at least 12 and 6 months of evolution, respectively). We did not detect statistically significant differences in persistent lesions (RR, 1.64; 95% CI, 0.50 to 5.41; P ¼ .42). In the subgroup analysis of these persistent injuries, no differences were found in patients who had a high risk of experiencing injury (RR, 1.82; 95% CI, 0.48 to 6.90;
P ¼ .38) and a moderate risk of experiencing injury (RR, 1.05; 95% CI, 0.07 to 16.50; P ¼ .98) (Figure 41,2,4,6,13). DISCUSSION
In our study, we failed to find significant differences in the rate of nerve injuries after M3M extraction between patients who had undergone preoperative CT and those who had not undergone preoperative CT. Unfortunately, there is no consensus on the criteria for the preoperative
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TABLE 2
support the hypothesis that obtaining preoperative CT images does not appear to lead to a significant decrease in the rate of IAN injury after M3M IAN INJURIES RISK IAN* INJURIES extraction. † ‡ PR GROUP CT GROUP Investigators have identified several risk factors Overall Persistent Overall Persistent that can predict a patient’s likelihood of experiModerate 9.7% (23/237) 0.6% (1/154) 7.3% (18/246) 0.6% (1/159) encing IAN injury after M3M extraction. Absence of High 9.0% (29/323) 1.9% (6/323) 9.1% (26/286) 1.0% (3/286) cortication,20,28 a dumb-bell–shaped MC,23,28 and a Overall 9.3% (52/560) 1.5% (7/477) 8.3% (44/532) 0.9% (4/445) lingual1,22,29 or interradicular29 position of the MC * IAN: Inferior alveolar nerve. are among these risk factors. Some investigators † CT: Computed tomographic. have stated that injuries occur more easily in MCs ‡ PR: Panoramic radiographic. that have a narrow configuration.1 In addition, when the MC is positioned lingually, the IAN may receive unfavorable forces if the surgeon starts his approach assessment of the risk of experiencing IAN injury after by luxating on the buccal side.29 For this reason, it is undergoing third-molar extraction. Indeed, all of the thought that most IAN injuries are the result of investigators had established their own criteria to classify compression and traction movements during M3M patients’ risk, which made it difficult for us to make surgery.17 In cases such as these, preoperative CT images comparisons. In addition, the time needed to consider a might provide useful information to the surgeon concerning where to apply the elevator. lesion to be permanent also varied. Many investigators A significant proportion (45.5%) of M3Ms have some used the term “permanent” to define a nerve injury that had not recovered by the time of the patient’s final degree of superimposition over the MC in PR.7 follow-up visit. For this reason, we determined that using According to Nakamori and colleagues,7 this superimposition, darkening of the root, and narrowing of the term “persistent” would be more appropriate, the MC on PR images correlate with an absence of because investigators could not assess the evolution of cortication7 and suggest close contact between the the patient’s injury after the period of data recording tooth and the nerve. This direct contact, which can be concluded. In our meta-analysis, we considered lesions observed in a CT image, seems to be associated with an that lasted more than 6 months to be persistent. We selected this time frame because Cheung and colleagues32 increased risk of experiencing IAN injury.19,23 However, reported that lesions that lasted more than 6 months had owing to this exposure, only those patients who have a low probability for recovery. Also, Valmaseda-Castellón a true anatomic relationship between the tooth and and colleagues,33 in the report of their prospective the nerve have a higher risk of experiencing an IAN cohort study of 1,117 M3M extractions, observed that le- impairment.26 Identifying risk factors for IAN injuries is a key issue sions that had not recovered 6 months after surgery were very likely to be permanent. involved in a clinician’s decision-making process Drawbacks related to the results of our report include regarding M3M extraction, because identifying these risk factors allows the clinician to identify patients who the fact that both the number of studies and the size of the samples were limited and that the results of 4 of have a high risk of experiencing IAN injuries. Investigators have considered the patient’s age and, espethe RCTs were associated with a high risk of bias. The cially, the anatomic proximity of the roots to the MC, to small number of participants included in these RCTs might have led to a type 2 error (a false-negative result). be the most relevant variables for predicting this These drawbacks clearly are related to the low incidence complication.17 Clinicians still consider PR to be the of IAN complications. Indeed, if we define an IAN injury criterion standard examination for M3M extraction. Clinicians do not consider the simple superimposition of after M3M as being the primary outcome and if we consider a 0.5 difference between groups to be clinically the third-molar roots over the MC to be a sign of a close relationship. In fact, the positive predictive value of IAN significant, favoring the CT group (as proposed by injury in cases of superimposition without additional Petersen and colleagues4), we find that none of the studies had a statistical power of greater than 70%. features is low. Even when the clinician finds more Therefore, the results of our meta-analysis strongly specific images, the positive predictive value still remains indicate the need for researchers to perform RCTs for small, probably owing to the low incidence of this which they have established a correct calculation of the complication.29,31 Indeed, only approximately 15% of the patients who undergo M3M extraction and who have statistical power of the study. Clinicians must take had preoperative PR images that suggested that the these limitations into account when considering the patient has a high risk of experiencing IAN injuries will results of our study. Even with these limitations, the outcomes of our meta-analysis and the results of most experience a neurosensory impairment.6 Although CT images are more specific for clinicians to detect the true of the studies included in our meta-analysis seem to
Percentages of nerve disturbances.
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Study or Subgroup
CT Events Total
PR Events Total
Risk Ratio Weight M–H, Random, 95% CI
Risk Ratio M–H, Random, 95% CI
1.1.1 Moderate risk of experiencing potential damage to the IAN Guerrero and colleagues,3 2014
2
126
5
130
11.3%
0.41 (0.08 to 2.09)
Petersen and colleagues,4 2016
21
111
13
116
27.5%
1.69 (0.89 to 3.20)
246
38.9%
1.02 (0.27 to 3.86)
55 164 67 286
22.2% 22.9% 16.1% 61.1%
1.45 (0.60 to 3.51) 1.28 (0.55 to 3.02) 0.25 (0.07 to 0.87) 0.85 (0.33 to 2.23)
532
100.0%
0.96 (0.50 to 1.85)
237
Subtotal (95% CI)
18
23 Total events 2 2 2 Heterogeneity: τ = 0.61; χ1 = 2.53, P = .11; I = 60% Test for overall effect: z = 0.03 (P = .97) 1.1.2 High risk of experiencing potential damage to the IAN Sanmarti-Garcia and colleagues,6 2012 Ghaeminia and colleagues,1 2015 Korkmaz and colleagues,13 2017 Subtotal (95% CI)
15 11 3
95 156 72 323
29 Total events 2 2 2 Heterogeneity: τ = 0.47; χ2 = 5.81, P = .05; I = 66% Test for overall effect: z = 0.32 (P = .75)
6 9 11 26
560
Total (95% CI)
52 Total events 2 2 2 Heterogeneity: τ = 0.30; χ4 = 9.12, P = .06; I = 56% Test for overall effect: z = 0.11 (P = .91) 2 2 Test for subgroup differences: χ1 = 0.05, P = .83; I = 0%
44 0.01
0.1
1
Favors CT
10
100
Favors PR
Figure 3. Meta-analysis: inferior alveolar nerve injury after mandibular third-molar extraction. CI: Confidence interval. CT: Computed tomographic. IAN: Inferior alveolar nerve. M-H: Mantel–Haenszel. PR: Panoramic radiographic.
Study or Subgroup
CT Events Total
PR Events Total
2.1.1 Moderate risk of experiencing potential damage to the IAN Guerrero and colleagues,2 2014 0 0 43 Petersen and colleagues,4 2016
1
Subtotal (95% CI) Total events Heterogeneity: Not applicable Test for overall effect: z = 0.03 (P = .98)
111 154
1
43 116 159
Weight
Risk Ratio M–H, Fixed, 95% CI
23.3% 23.3%
Not estimable 1.05 (0.07 to 16.50) 1.05 (0.07 to 16.50)
Risk Ratio M–H, Fixed, 95% CI
1
1
2.1.2 High risk of experiencing potential damage to the IAN Sanmarti-Garcia and colleagues,6 2012 Ghaeminia and colleagues,1 2015 Korkmaz and colleagues,13 2017 Subtotal (95% CI) Total events 2 2 Heterogeneity: χ1 = 0.86, P = .35; I = 0% Test for overall effect: z = 0.88 (P = .38) Total (95% CI)
1 5 0
95 156 72 323
1 2 0
55 164 67 286
30.2% 46.5%
0.58 (0.04 to 9.07) 2.63 (0.52 to 13.35)
76.7%
Not estimable 1.82 (0.48 to 6.90)
445
100.0%
1.64 (0.50 to 5.41)
3
6
477
Total events 7 Heterogeneity: χ22 = 0.98, P = .061; I2 = 0% Test for overall effect: z = 0.81 (P = .42) 2 2 Test for subgroup differences: χ1 = 0.13, P = .72; I = 0%
4 0.01
0.1 Favors CT
1
10
100
Favors PR
Figure 4. Meta-analysis: persistent inferior alveolar nerve injury after mandibular third-molar extraction. CI: Confidence interval. CT: Computed tomographic. IAN: Inferior alveolar nerve. M-H: Mantel–Haenszel. PR: Panoramic radiographic.
anatomic relationship between M3Ms and MCs, the positive predictive value of CT images is still low and, to our knowledge, there are no data suggesting that there would be any reduction in the prevalence of IAN
impairment when 3D techniques are used, compared with conventional PR. According to the results of this meta-analysis, clinicians should not perform CT routinely before M3M
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ORIGINAL CONTRIBUTIONS
surgery. However, in specific cases in which the clinician suspects a close relationship between the MC and the M3M after observing PR images, we recommend obtaining CT images.18 CONCLUSIONS
According to the results of our meta-analysis, clinicians should not perform CT routinely before M3M surgery because using CT images does not seem to reduce the incidence or affect the patient’s prognosis of IAN injuries in comparison with using PR images. n Dr. Clé-Ovejero is a fellow, Master of Oral Surgery and Orofacial Implantology, Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona, Spain. Dr. Sánchez-Torres is a graduate of the Master of Oral Surgery and Orofacial Implantology, and an associate professor of oral surgery, Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona; and a researcher, Bellvitge Biomedical Research Institute, Barcelona, Spain. Dr. Camps-Font is a graduate of the Master of Oral Surgery and Orofacial Implantology, and an associate professor of oral surgery, Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona; and a researcher, Bellvitge Biomedical Research Institute, Barcelona, Spain. Dr. Gay-Escoda is the chair and a professor, Oral and Maxillofacial Surgery, Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona; the director of the Master Degree Program in Oral Surgery and Implantology, EFHRE (European Foundation for Health Research and Education) International University/FUCSO (Catalonian Foundation for Oral Health); a coordinator and researcher, Bellvitge Biomedical Research Institute, Barcelona; and the head, Department of Maxillofacial Surgery and Implantology, Teknon Medical Center, Barcelona, Spain. Dr. Figueiredo is an associate professor, Oral Surgery, Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona; and a researcher, Bellvitge Biomedical Research Institute (IDIBELL), Barcelona, Spain. Address correspondence to Dr. Figueiredo at Faculty of Medicine and Health Sciences, Campus de Bellvitge, C/Feixa Llarga, s/n; Pavelló Govern, 2a planta, Despatx 2.9, 08907 L’Hospitalet de Llobregat, University of Barcelona, Barcelona, Spain, e-mail [email protected]. Dr. Valmaseda-Castellón is a professor, Oral Surgery, and a professor, Master of Oral Surgery and Orofacial Implantology, Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona; and a researcher, Bellvitge Biomedical Research Institute, Barcelona, Spain. Disclosure. None of the authors reported any disclosures. ORCID Number. Rui Figueiredo: http://orcid.org/0000-0002-2122-6530 The authors conducted this study in association with the Odontological and Maxillofacial Pathology and Therapeutics Research Group of the Bellvitge Biomedical Research Institute. The authors thank Mary Georgina Hardinge for her assistance in correcting the English in the manuscript. 1. Ghaeminia H, Gerlach NL, Hoppenreijs TJ, et al. Clinical relevance of cone beam computed tomography in mandibular third molar removal: a multicentre, randomised, controlled trial. J Craniomaxillofac Surg. 2015; 43(10):2158-2167. 2. Guerrero ME, Nackaerts O, Beinsberger J, Horner K, Schoenaers J, Jacobs R; SEDENTEXCT Project Consortium. Inferior alveolar nerve sensory disturbance after impacted mandibular third molar evaluation using cone beam computed tomography and panoramic radiography: a pilot study. J Oral Maxillofac Surg. 2012;70(10):2264-2270. 3. Guerrero ME, Botetano R, Beltran J, Horner K, Jacobs R. Can preoperative imaging help to predict postoperative outcome after wisdom tooth removal? A randomized controlled trial using panoramic radiography versus cone-beam CT. Clin Oral Investig. 2014;18(1):335-342. 4. Petersen LB, Vaeth M, Wenzel A. Neurosensoric disturbances after surgical removal of the mandibular third molar based on either panoramic
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injury to the inferior alveolar nerve at third molar surgery: a prospective study. J Oral Maxillofac Surg. 2013;71(12):2012-2019. 29. Ghaeminia H, Meijer GJ, Soehardi A, Borstlap WA, Mulder J, Berge SJ. Position of the impacted third molar in relation to the mandibular canal: diagnostic accuracy of cone beam computed tomography compared with panoramic radiography. Int J Oral Maxillofac Surg. 2009;38(9):964-971. 30. Suomalainen A, Apajalahti S, Vehmas T, Venta I. Availability of CBCT and iatrogenic alveolar nerve injuries. Acta Odontol Scand. 2013; 71(1):151-156. 31. Susarla SM, Dodson TB. Preoperative computed tomography imaging in the management of impacted mandibular third molars. J Oral Maxillofac Surg. 2007;65(1):83-88. 32. Cheung LK, Leung YY, Chow LK, Wong MC, Chan EK, Fok YH. Incidence of neurosensory deficits and recovery after lower third molar surgery: a prospective clinical study of 4338 cases. Int J Oral Maxillofac Surg. 2010;39(4):320-326. 33. 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(4):377-383.
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