Journal of Cranio-Maxillo-Facial Surgery xxx (2015) 1e6
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The effect of two enhancement tools on the assessment of the relationship between third molars and the inferior alveolar canal Larissa Rangel Peixoto a, Amanda Katarinny Goes Gonzaga b, Saulo Leonardo Sousa Melo c, Maria Luiza dos Anjos Pontual d, Andrea dos Anjos Pontual d, Daniela Pita de Melo e, * ~o Pessoa, PB, Brazil Department of Oral Diagnosis, Federal University of Paraíba, Joa Department of Oral Pathology, Federal University of Rio Grande do Norte, Natal, RN, Brazil c Department of Oral Pathology, Radiology & Medicine, The University of Iowa College of Dentistry, Iowa City, IA, USA d Department of Clinical and Preventive Dentistry, Federal University of Pernambuco, Recife, PE, Brazil e Department of Oral Diagnosis, State University of Paraíba, Campina Grande, PB, Brazil a
b
a r t i c l e i n f o
a b s t r a c t
Article history: Paper received 16 December 2014 Accepted 9 March 2015 Available online xxx
Objective: This study aims to assess the relationship between the inferior alveolar canal (IAC) and inferior third molars using digital panoramic images (DPI) with and without enhancement and compare the panoramic signs with cone beam computed tomography (CBCT) findings. Methods: The DPIs and CBCT of 50 patients were analyzed. The DPIs were copied and enhanced using edge enhancement and an invert tool and then analyzed by two observers using the scores: darkening of the root; deflection of the root; narrowing of the root; superimposition of the root; bifurcation of the root over the IAC; diversion of the IAC; interruption of the cortex of the IAC, and no radiographic findings noted. Kappa and exact binominal tests were used to analyze the correlation between DPIs and CBCT images. The intimate relationship scores were evaluated using a t-test and ManneWhitney test. Results: The original DPIs, and the edge enhanced and invert tool images produced kappa coefficients of 0.528, 0.528 and 0.551, respectively. There was no difference among the methods evaluated in this study (p ¼ 0.981). Conclusion: Similar agreement was observed between DPIs with and without enhancement. However, panoramic radiography is not the ideal method to analyze the relationship between lower third molars and the IAC. © 2015 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Keywords: Mandibular nerve Panoramic radiography Third molar X-ray computed tomography
1. Introduction The surgical removal of impacted mandibular third molars is a common procedure in oral maxillofacial surgery. Studies on impacted mandibular third molar positioning and its relationship with the inferior alveolar nerve (IAN) are of high importance due to their contribution to detailed surgical planning (Flores et al., 2009). Although the risk of permanent nerve injury is low, and the overall risk of IAN injury associated with third molar extraction ranges
* Corresponding author. State Universty of Paraíba, Rua Baraúnas, 351, Bairro rio, Campina Grande, PB, 58429-500, Brazil. Universita E-mail addresses: [email protected] (L.R. Peixoto), amandaggonzaga@gmail. com (A.K.G. Gonzaga), [email protected] (S.L.S. Melo), [email protected] (M.L.A. Pontual), [email protected] (A.A. Pontual), [email protected] (D.P. Melo).
from 0.5 to 5%, for affected patients there is considerable dissatisfaction and morbidity (Blaeser et al., 2003). The anatomical proximity of the roots of the mandibular third molar and the IAN increases the risk of nerve lesion during surgical procedures. Assessment of the proximity of these structures is extremely necessary and should be done using imaging techniques with a high level of accuracy, to avoid possible damage to nerve tissues (Flygare and Ohman, 2008; Jhamb et al., 2009). However, none of the imaging techniques give this information 100% of the time (Khan et al., 2011). Panoramic radiographs have been often used for preoperative imaging before removal of impacted mandibular third molars. When there is overlap between the third molar and the inferior alveolar canal (IAC) signs of darkening of the root, or diversion of the alveolar inferior canal have been found to be significantly related to nerve injury (Suomalainen et al., 2010). The advantages of
http://dx.doi.org/10.1016/j.jcms.2015.03.008 1010-5182/© 2015 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Peixoto LR, et al., The effect of two enhancement tools on the assessment of the relationship between third molars and the inferior alveolar canal, Journal of Cranio-Maxillo-Facial Surgery (2015), http://dx.doi.org/10.1016/j.jcms.2015.03.008
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L.R. Peixoto et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2015) 1e6
panoramic radiographs include low cost and wide availability, it does not fulfill the precise observation of the anatomical relationship between structures due to its two-dimensional nature and unequal magnification (Kamrun et al., 2013). Some cases require a tridimensional view of the topographic relationship between the roots of the third inferior molar and the IAC (Gomes et al., 2008). Previous studies have shown that computed tomography (CT) and cone beam computed tomography (CBCT) used preoperatively permit a precise determination of the relationship between the inferior third molar and the IAC (Jhamb et al., 2009; Suomalainen et al., 2010; Kamrun et al., 2013). However, patients are often exposed to unnecessary radiation and the use of methods with lower doses should be encouraged. Digital panoramic images (DPI) permit the enhancement of the original image with different enhancement tools. Studies have compared the overall quality of enhanced and non-enhanced DPI (Gijbels et al., 2000); for caries diagnosis (Akarslan et al., 2008); for visibility of anatomical structures (Yalcinkaya et al., 2006; Baksi et al., 2010) and for the diagnosis of mandibular radiolucent lesions (Raitz et al., 2012). Although image enhancement processing may increase the interpretation time, if this increases the accuracy of determination of the anatomical proximity of third inferior molar roots to the IAC, this could enhance the use of DPI in preoperative planning. Based on what was stated above, this study aims to assess the relationship between the alveolar canal and inferior third molars using digital panoramic images with and without enhancement and compare the panoramic signs with CBCT findings. 2. Material and methods This study was approved by the last author Institutional Review Board (protocol number 10764313.4.0000.5187) and is in compliance with the Helsinki Declaration. DPIs and their corresponding CBCT images of 73 inferior third molars were selected from a private practice archive. Images were acquired between January 2012 and March 2013. The selected files were from 50 patients, 24 women and 26 men, with ages ranging from 18 to 77 years (mean age 45.62; SD 15.61). The majority of subjects selected for this study were referred for preoperative evaluation of impacted or partially erupted inferior third molars. Others were selected by the fact that the same subject had DPI and CBCT images taken with a maximum interval of 6 months from each other for different diagnostic reasons. The selected images should show at least one inferior third molar, with at least 2/3 of the roots completely grown (Nolla's stage 8). Images that presented lesions interfering with the inferior third molar position were also excluded. DPIs were obtained using Kodak 9000C (Eastman Kodak, Rochester, NY, EUA) panoramic X-ray unit at 70 kV and 15 mA and stored in a tagged image file format (TIFF). Each selected DPI was copied twice, enhanced using edge enhancement and invert tools, applied with Kodak Dental Image Software 6.5 (Eastman Kodak, Rochester, NY, EUA) software and codified. The CBCT images were previously obtained using i-CAT Cone Beam 3D Imaging System (Imaging Science International, Hatfield, PA, USA) with a 20 cm 25 cm amorphous silicon flat-panel image detector. Images were obtained at 120 kVp, 5.5 mA and a voxel size of 0.2 mm, with an exposure time of 40 s. The volumetric acquisitions were exported as digital imaging and communications in medicine (DICOM) files and saved to a portable hard disk for later reconstruction.
After the enhancement of the DPIs, the total number of DPIs e original and two group enhanced e and CBCT images to be evaluated by the observers was 292 (219 DPIs e 73 originals and 146 enhanced, and 73 CBCT volumes). 2.1. Viewing sessions Prior to all examination sessions, verbal and practical instructions and calibration tests were performed. The DPIs, with and without enhancement, were visualized using Kodak Dental Imaging Software (Kodak Dental Systems, Carestream Health, Rochester, NY, EUA), displayed in a Sony VAIO (SVS151C1SX Intelcore i7, Windows 8) laptop with a 17.3-inch color monitor placed in a quiet room with dimmed light. The observers were only allowed to use the zoom tool. Two experienced oral radiologists assessed all DPIs. The panoramic images (original, edge enhanced and inverted) (Fig. 1) were evaluated in random order, with a minimum interval of two days between each evaluation. The number of images evaluated per day was established by the observer's choice; however they were counseled to evaluate a maximum of 25 images, since visual fatigue can impair image evaluation. A minimum interval of fifteen days between the evaluations of the same DPI was established. To evaluate the relationship between inferior third molars and the mandibular canal, the following signs of close relationship between third inferior molar and IAC classification was used: darkening of the root; deflection of the root; narrowing of the root; superimposition of the root; bifurcation of the root over the inferior alveolar canal; diversion of the inferior alveolar canal; interruption of the cortex of inferior alveolar canal; and no radiographic findings noted (Monaco et al., 2004; Sedaghatfar et al., 2005; Flores et al., 2009). CBCT images were assessed by the same observers using i-CAT Workstation (Imaging Sciences International, Pennsylvania, USA), displayed in a Sony VAIO (SVS151C1SX Intelcore i7, Windows 8) laptop with a 17.3-inch color monitor placed in a quiet room with dimmed light. The CBCT images were evaluated 15 days after the panoramic images. CBCT images were three-dimensionally evaluated using two-dimensional, multiplanar, reformatted slices (axial, sagittal, coronal, panoramic, and cross-sectional images) (Fig. 2). For the CBCT images, the anatomical relationship between the third molar and the mandibular canal was classified into two types: (1) Separation e no interruption of the canal cortical bone between the third molar root and the canal wall was recognized, so the canal does not come in contact with the tooth; and (2) Contact e interruption of the of the canal cortical bone was recognized and the canal is in contact with the tooth. To avoid differences between the observer's ratings, when disagreement existed between them, another trained observer with 15 years' experience as an oral radiologist performed a joint assessment to reach agreement. 2.2. Data analysis Kappa coefficient (kw) test was used to analyze the agreement for each close relationship classification viewed in DPIs with CBCT images. An exact binominal test was used to assess kw significance levels. Categorical data (signs of close relationship) was analyzed using Student's t-test and ManneWhitney tests, when parametric tests could not be applied. Descriptive data was also used.
Please cite this article in press as: Peixoto LR, et al., The effect of two enhancement tools on the assessment of the relationship between third molars and the inferior alveolar canal, Journal of Cranio-Maxillo-Facial Surgery (2015), http://dx.doi.org/10.1016/j.jcms.2015.03.008
L.R. Peixoto et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2015) 1e6
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Fig. 1. Partial panoramic images with and without enhancement (original, invert tool and edge enhancement). Darkening of the roots, A) original; A1) invert tool; A2) edge enhancement. Interruption of the cortical of the alveolar canal, B) original; B1) invert tool; B2) edge enhancement. Superimposition of the roots, C) original; C1) invert tool; C2) edge enhancement.
3. Results Original DPIs showed a close relationship of the IAC and the roots of the inferior third molar in 27 cases (37%) and 26 (96.3%) of those were in agreement with the results found for CBCT images. 46 (63%) CBCT images did not show signs of close relationship, but only 29 (63%) of the corresponding DPIs agreed with these results (Table 1). The original DPIs that presented a positive response were compared with the CBCT responses to evaluate which signs of a close relationship between the IAC and third molar roots corresponded to the three-dimensional results (Table 2). The invert enhanced DPIs showed 46 images without signs of a close relationship between the IAC and the roots of the inferior third molar and 30 images (65.2%) agreed with CBCT results (Table 3). The invert enhanced DPIs that presented a positive response were compared with the CBCT responses (Table 4). Statistical values for edge enhanced DPIs agreed with the results found for original panoramic images (Table 5). The edge enhanced DPIs
that presented a positive response were compared with the CBCT responses (Table 6). Kappa values for the three modalities of DPIs evaluated, original, invert and edge enhanced, were 0.528, 0.551 and 0.528 respectively (p ¼ 0.981). 4. Discussion Removal of mandibular third molars is one of the most common dental operations. For this reason, the study of the relationship between an impacted third molar and the inferior alveolar canal is fundamental for prevention of inferior alveolar nerve lesions (Koong et al., 2006; Ohman et al., 2006; Neugebauer et al., 2008; Ferretti et al., 2009). Once the surgeon is aware of those close relationships, a better treatment plan may be designed. Wang et al. (2012), for example, suggested an effective way to avoid IAN injury during tooth extraction by applying orthodontic brackets or mini bone screws on the antagonist maxillary molars to extrude the impacted lower third molar prior to surgery.
Please cite this article in press as: Peixoto LR, et al., The effect of two enhancement tools on the assessment of the relationship between third molars and the inferior alveolar canal, Journal of Cranio-Maxillo-Facial Surgery (2015), http://dx.doi.org/10.1016/j.jcms.2015.03.008
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Fig. 2. A1) Partial panoramic images with and without enhancement (original, invert tool and edge enhancement); A2) Partial CBCT panoramic reconstruction; A3) Cross-section slices of the inferior third molar; A4) Sagittal slices of the third molar, all showing no sign of close proximity of the third molar roots and the IAC. B1) Partial panoramic images with and without enhancement (original, invert tool and edge enhancement); B2) Partial CBCT panoramic reconstruction; B3) Cross-section slices of the inferior third molar; B4) Sagittal slices of the third molar, all showing signs of the close proximity of the third molar roots and the IAC.
The existence of one or more radiographic signs of a close relationship between third molar roots and the IAC is considered to be a risk factor for nerve lesions (Ferretti et al., 2009). The indicative signs of a close relationship between third molar roots and the IAC are: darkening of the root; deflection of the root; narrowing of the root; superimposition of the root; bifurcation of the root over the inferior alveolar canal; diversion of the inferior alveolar canal; interruption of the cortex of the IAC (Monaco et al., 2004; Koong et al., 2006; Ohman et al., 2006; Ferretti et al., 2009). In the present study, 27 (37%) third molars showed indicative signs of a close relationship with the IAC; this may be due to the sample selection from a private dental radiology service database Table 1 Equivalence relationship between original panoramic images and CBCT (goldstandard). Original
Yes No Total
CBCT
Total
Yes
No
26 1 27
17 29 46
43 30 73
which included patients with and without indications for removal of the inferior third molar and the inclusion/exclusion criteria which included factors such as acquisition of DPI and CBCT images with a maximum interval of 6 months from each other and a third molar with at least 2/3 of the roots completely grown. A smaller number of third molars with signs of a close relationship with the IAC were found by Bell (2004), where 12% of the sample showed
Table 2 Comparison of the signs of close relationship found in the original panoramic image modality and CBCT images results (gold-standard). Close relationship sign
True-positive
False-positive
Total
Darkening of the roots Deflection of the root Narrowing of the root Superimposition of the root Bifurcation of the root over the inferior alveolar canal Diversion of the inferior alveolar canal Interruption of the cortex of the inferior alveolar canal
9 0 1 5 0
8 1 1 1 2
17 1 2 6 2
2
0
2
9
4
13
Please cite this article in press as: Peixoto LR, et al., The effect of two enhancement tools on the assessment of the relationship between third molars and the inferior alveolar canal, Journal of Cranio-Maxillo-Facial Surgery (2015), http://dx.doi.org/10.1016/j.jcms.2015.03.008
L.R. Peixoto et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2015) 1e6 Table 3 Equivalence relationship between invert enhanced panoramic image modality and CBCT (gold-standard). Invert tool
Yes No Total
CBCT
Total
Yes
No
26 1 27
16 30 46
42 31 73
5
Table 5 Equivalence relationship between edge enhanced panoramic image modality and CBCT (gold-standard). Edge enhancement tool
CBCT
Yes No Total
Total
Yes
No
26 1 27
17 29 46
43 30 73
signs of close relationship with the IAC. In agreement with our results, studies reported that one of the most frequent signs of a close relationship of the third molar roots and the IAC is the interruption of the cortex of the IAC, which leads to a higher risk of IAN lesion during surgical procedures (Koong et al., 2006; Gomes et al., 2008; Nakamori et al., 2008; Ferretti et al., 2009; Tantanapornkul et al., 2009). Other panoramic features reported to be suggestive of close contact between the root and IAC were darkening of the root, diversion of the mandibular canal and narrowing of the root (Sedaghatfar et al., 2005; Tantanapornkul et al., 2009). Albert et al. (2006) compared panoramic radiographs and CBCT images of 19 patients on the assessment of the radiographic signs of a close relationship of the IAC and third molar roots. Topographic proximity was found in 77.4% of the evaluated panoramic images, and darkening of the roots was the most frequent radiographic sign (45.2%). CBCT images confirmed the presence of a close relationship in 92.1% of the cases. Their percentage of topographic proximity to the IAC was 2.1 times higher than ours; however the small sample of the referred study should be taken in account when considering this difference. In the present study, darkening of the roots and interruption of the cortex of the alveolar canal were the most common signs of close relationship found in the evaluated DPIs, followed by superimposition of the roots. According to Blaeser et al. (2003) radiographic signs such as diversion of the inferior alveolar canal and darkening of a mandibular third molar root are statistically related to IAN injury during third molar removal. The absence of radiographic signs of a close relationship of the roots and IAC is associated with a minimal risk of injury of the IAN. When assessing the effect of enhancement tools on DPI detection of the third molar close relationship with the IAC, there was no statistically significant difference between the modalities with and without enhancement. However, when comparing the results found for each modality with CBCT, panoramic images e both original and enhanced e presented a high number of false-positive results. Nevertheless, the low cost and higher accessibility of panoramic radiography are the main reason for its wide use by professionals when evaluating signs of the close relationship between inferior third molar roots and the IAC (Koong et al., 2006;
Ohman et al., 2006; Nakagawa et al., 2007; Neugebauer et al., 2008; Jhamb et al., 2009). The use of invert tools and edge enhancement on DPIs improved the capacity of image assessment, when compared with original images, when assessing fine endodontic files and periapical lesions (Friedlander et al., 2002; Guneri and Akdeniz, 2004). However, in the present study, the use of those tools did not demonstrate any significant difference when compared with original images. The panoramic image does not enable a precise observation of the anatomical relationship of different structures due to its twodimensional nature and the presence of image magnification and distortions. The presence of signs of an anatomically close relationship between the inferior third molar's roots and the IAC indicates a high risk of an IAN lesion during surgery. If those signs are observed in the panoramic image, CBCT is necessary to correctly evaluate this close relationship three-dimensionally (Bell, 2004; Albert et al., 2006; Nakamori et al., 2008). According to Suomalainen et al. (2010), CBCT showed a perfect match when compared with the gold-standard to locate the IAC and could detect and locate the IAC in relation to the inferior third molar without difficulty in all CBCT scans, but it did not show a perfect match when assessing root anatomy, as the number of roots varies. A number of studies have combined different bi-dimensional image modalities as panoramic or intraoral images with a supplementary open mouth posteroanterior radiograph; panoramic radiograph and symmetric PA cephalometric radiograph (Neugebauer et al., 2008), MNBR stereography or panoramic and a series of three intraoral radiographs (Wenzel et al., 1998) determining the localization of IAC. When combining two or more bidimensional images for diagnosis, radiation dose should be taken in account. Another fact to be concerned about is the exposure dose of the CBCT system chosen for inferior third molar image evaluation. CBCT systems can acquire several single X-ray projections using a pulsatile or continuous beam, rotating at 180 e720 around the area of interest, using different exposure parameters (Kv, mA), all of which can affect the exposure dose. According to SEDENTEXCT project guidelines, the effective dose of panoramic radiography ranges from 2.7 to 24.3 mSv, while the CBCT system effective dose ranges from 11 to 674 mSv for the dento-alveolar region (small
Table 4 Comparison of the signs of close relationship found in the invert enhanced panoramic image modality and CBCT images results (gold-standard).
Table 6 Comparison of the signs of close relationship found in the edge enhanced panoramic image modality and CBCT images results (gold-standard).
Close relationship sign Darkening of the roots Deflection of the root Narrowing of the root Superimposition of the root Bifurcation of the root over the inferior alveolar canal Diversion of the inferior alveolar canal Interruption of the cortex of the inferior alveolar canal
True-positive
False-positive
Total
Close relationship sign
True-positive
False-positive
Total
8 0 1 5 0
8 1 0 2 2
16 1 1 7 2
7 0 1 8 0
10 0 0 2 0
17 0 1 10 0
2
0
2
1
3
4
10
3
13
Darkening of the roots Deflection of the root Narrowing of the root Superimposition of the root Bifurcation of the root over the inferior alveolar canal Diversion of the inferior alveolar canal Interruption of the cortex of the inferior alveolar canal
9
2
11
Please cite this article in press as: Peixoto LR, et al., The effect of two enhancement tools on the assessment of the relationship between third molars and the inferior alveolar canal, Journal of Cranio-Maxillo-Facial Surgery (2015), http://dx.doi.org/10.1016/j.jcms.2015.03.008
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and median FOV), and from 30 to 1073 mSv for the craniofacial region (large FOV) (Sedentexct Project, 2012). The wide range of effective dose variation among CBCT systems highlights the need for professional advice on the choice of image system to be used for inferior third molar and IAC relationship evaluation. CBCT is an important high resolution image modality for the assessment of low contrast bony anatomical structures, and is considered by some authors as the image modality of choice for obtaining the true anatomical relationship between the inferior third molar roots and the IAC (Ohman et al., 2006; Neugebauer et al., 2008; Ferretti et al., 2009; Jhamb et al., 2009). Although DPIs give a low-dose alternative image for topographic evaluation of the close relationship between the inferior third molar roots and the IAC, when their results are compared with CBCT, a high number of false-positive values are found for both the original and enhanced images. This shows that panoramic images, enhanced or not, are not a substitute for CBCT images in high risk IAN injury situations. In agreement with this study, comparing radiographic and tomography images, authors observed that the most trustworthy radiographic image for planning procedures involving areas close to the IAC is the CT image (Friedlander et al., 2002; Blaeser et al., 2003; Guneri and Akdeniz, 2004; Albert et al., 2006; Nakagawa et al., 2007; Nakamori et al., 2008; Ferretti et al., 2009). 5. Conclusion There was no difference between original, invert enhanced and edge enhanced DPIs, resulting in similar agreement between original and enhanced modalities when assessing the proximity of mandibular molar roots to the IAC. Darkening of the root and narrowing of the root were the most frequent signs of a close relationship found in this study. Preoperatively, DPIs, enhanced or not, should not be used without the aid of CBCT images in cases when high risk IAN injury signs are noted. Conflict of interest The authors denied any conflict of interest. Acknowledgments We are grateful to CAPES Foundation for the scholarship e Undergraduate Research Scholar support and to State University of Paraíba and Federal University of Pernambuco for the technical support. References €r K, Erten H: A comparison of the diagnostic Akarslan ZZ, Akdevelioglu M, Güngo accuracy of bitewing, periapical, unfiltered and filtered digital panoramic images for approximal caries detection in posterior teeth. Dentomaxillofac Radiol 37: 458e463, 2008 Albert DGM, Gomes AC, do Egito Vasconcelos BC, de Oliveira e Silva ED, Holanda GZ: Comparison of orthopantomographs and conventional tomography images for assessing the relationship between impacted lower third molars and the mandibular canal. J Oral Maxillofac Surg 64: 1030e1037, 2006 €z E, Sogur E, Mert A: Perception of anatomical structures in digitally Baksi BG, Alpo filtered and conventional panoramic radiographs: a clinical evaluation. Dentomaxillofac Radiol 39: 424e430, 2010 Bell GW: Use of dental panoramic tomographs to predict the relation between mandibular third molar teeth and the inferior alveolar nerve. Radiological and surgical findings, and clinical outcome. Br J Oral Maxillofac Surg 42: 21e27, 2004 Blaeser BF, August MA, Donoff RB, Kaban LB, Dodson TB: Panoramic radiographic risk factors for inferior alveolar nerve injury after third molar extraction. J Oral Maxillofac Surg 61: 417e421, 2003
Ferretti F, Malventi M, Malasoma R: Dental magnetic resonance imaging: study of impacted mandibular third molars. Dentomaxillofac Radiol 38: 387e392, 2009 Flores JA, Flores FW, Unfer MK, Ferrari R: Relation between the third inferior molar with the inferior alveolar nerve. Int J Dent 8: 211e214, 2009 Flygare L, Ohman A: Preoperative imaging procedures for lower wisdom teeth removal. Clin Oral Investig 12: 291e302, 2008 Friedlander LT, Love RM, Chandler NP: A comparison of phosphor-plate digital images with conventional radiographs for the perceived clarity of fine endodontic files and periapical lesions. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 93: 321e327, 2002 Gijbels F, De Meyer AM, Bou Serhal C, Van den Bossche C, Declerck J, Persoons M, et al: The subjective image quality of direct digital and conventional panoramic radiography. Clin Oral Investig 4: 162e167, 2000 Gomes AC, Vasconcelos BCE, Silva EDO, Caldas Jr AJ, Pita Neto IC: Sensitivity and specificity of pantomography to predict inferior alveolar nerve damage during extraction of impacted lower third molars. J Oral Maxillofac Surg 66: 256e259, 2008 Guneri P, Akdeniz BG: Fraudulent management of digital endodontic images. Int Endod J 37: 214e220, 2004 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 67: 58e66, 2009 Kamrun N, Tetsumura A, Nomura Y, Yamaguchi S, Baba O, Nakamura S, et al: Visualization of the superior and inferior borders of the mandibular canal a comparative study using digital panoramic radiographs and cross-sectional computed tomography images. Oral Surg Oral Med Oral Pathol Oral Radiol 115: 550e557, 2013 Khan I, Halli R, Gadre P, Gadre K: Correlation of panoramic radiographs and spiral CT scan in the preoperative assessment of close relationship of the inferior alveolar canal to impacted mandibular third molars. J Craniofac Surg 22: 566e570, 2011 Koong B, Pharoah MJ, Bulsara M, Tennant M: Methods of determining the relationship of the mandibular canal and third molars: a survey of Australian oral and maxillofacial surgeons. Aust Dent J 51: 64e68, 2006 Monaco G, Montevecchi M, Bonetti GA, Gatto MR, Checchi L: Reliability of panoramic radiography in evaluating the topographic relationship between the mandibular canal and impacted third molars. J Am Dent Assoc 135: 312e318, 2004 Nakagawa Y, Ishii H, Nomura Y, Watanabe NY, Hoshiba D, Kobayashi K, et al: Third molar position: reliability of panoramic radiography. J Oral Maxillofac Surg 65: 1303e1308, 2007 Nakamori K, Fujiwara K, Miyazaki A, Tomihara K, Tsuji M, Nakai M, 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 66: 2308e2313, 2008 Neugebauer J, Shirani R, Mischkowski RA, Ritter L, Scheer M, Keeve E, et al: Comparison of cone-beam volumetric imaging and combined plain radiographs for localization of the mandibular canal before removal of impacted lower third molars. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 105: 633e642, 2008 Ohman A, Kivij€ arvi K, Blomb€ ack U, Flygare L: Pre-operative radiographic evaluation of lower third molars with computed tomography. Dentomaxillofac Radiol 35: 30e35, 2006 Raitz R, Assunç~ ao Junior JN, Fenyo-Pereira M, Correa L, de Lima LP: Assessment of using digital manipulation tools for diagnosing mandibular radiolucent lesions. Dentomaxillofac Radiol 41: 203e210, 2012 Sedaghatfar M, Augus MA, Dodson TB: Panoramic radiographic findings as predictors of inferior alveolar nerve exposure following third molar extraction. J Oral Maxillofac Surg 63: 3e7, 2005 SEDENTEXCT Project: Radiation protection: cone beam CT for dental and maxillofacial radiology: evidence-based guidelines. Available from: http://www. sedentexct.eu/content/guidelines-cbct-dental-and-maxillofacial-radiology, 2012 [accessed 10.11.14]; 2012 ~ I, Mattila M, Turtola L, Vehmas T, Peltola JS: Reliability of Suomalainen A, Venta CBCT and other radiographic methods in preoperative evaluation of lower third molars. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 109: 276e284, 2010 Tantanapornkul W, Okochi K, Bhakdinaronk A, Ohbayashi N, Kurabayashi T: Correlation of darkening of impacted mandibular third molar root on digital panoramic images with cone beam computed tomography findings. Dentomaxillofac Radiol 38: 11e16, 2009 Wang Y, He D, Yang C, Wang B, Qian W: An easy way to apply orthodontic extraction for impacted lower third molar compressing to the inferior alveolar nerve. J Craniomaxillofac Surg 40: 234e237, 2012 Wenzel A, Aagaard E, Sindet-Pedersen S: Evaluation of a new radiographic technique: diagnostic accuracy for mandibular third molars. Dentomaxillofac Radiol 27: 255e263, 1998 Yalcinkaya S, Künzel A, Willers R, Thoms M, Becker J: Subjective image quality of digitally filtered radiographs acquired by Dürr Vistascan system compared with conventional radiographs. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 101: 643e651, 2006
Please cite this article in press as: Peixoto LR, et al., The effect of two enhancement tools on the assessment of the relationship between third molars and the inferior alveolar canal, Journal of Cranio-Maxillo-Facial Surgery (2015), http://dx.doi.org/10.1016/j.jcms.2015.03.008
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The effect of two enhancement tools on the assessment of the relationship between third molars and the inferior alveolar canal Larissa Rangel Peixoto a, Amanda Katarinny Goes Gonzaga b, Saulo Leonardo Sousa Melo c, Maria Luiza dos Anjos Pontual d, Andrea dos Anjos Pontual d, Daniela Pita de Melo e, * ~o Pessoa, PB, Brazil Department of Oral Diagnosis, Federal University of Paraíba, Joa Department of Oral Pathology, Federal University of Rio Grande do Norte, Natal, RN, Brazil c Department of Oral Pathology, Radiology & Medicine, The University of Iowa College of Dentistry, Iowa City, IA, USA d Department of Clinical and Preventive Dentistry, Federal University of Pernambuco, Recife, PE, Brazil e Department of Oral Diagnosis, State University of Paraíba, Campina Grande, PB, Brazil a
b
a r t i c l e i n f o
a b s t r a c t
Article history: Paper received 16 December 2014 Accepted 9 March 2015 Available online xxx
Objective: This study aims to assess the relationship between the inferior alveolar canal (IAC) and inferior third molars using digital panoramic images (DPI) with and without enhancement and compare the panoramic signs with cone beam computed tomography (CBCT) findings. Methods: The DPIs and CBCT of 50 patients were analyzed. The DPIs were copied and enhanced using edge enhancement and an invert tool and then analyzed by two observers using the scores: darkening of the root; deflection of the root; narrowing of the root; superimposition of the root; bifurcation of the root over the IAC; diversion of the IAC; interruption of the cortex of the IAC, and no radiographic findings noted. Kappa and exact binominal tests were used to analyze the correlation between DPIs and CBCT images. The intimate relationship scores were evaluated using a t-test and ManneWhitney test. Results: The original DPIs, and the edge enhanced and invert tool images produced kappa coefficients of 0.528, 0.528 and 0.551, respectively. There was no difference among the methods evaluated in this study (p ¼ 0.981). Conclusion: Similar agreement was observed between DPIs with and without enhancement. However, panoramic radiography is not the ideal method to analyze the relationship between lower third molars and the IAC. © 2015 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Keywords: Mandibular nerve Panoramic radiography Third molar X-ray computed tomography
1. Introduction The surgical removal of impacted mandibular third molars is a common procedure in oral maxillofacial surgery. Studies on impacted mandibular third molar positioning and its relationship with the inferior alveolar nerve (IAN) are of high importance due to their contribution to detailed surgical planning (Flores et al., 2009). Although the risk of permanent nerve injury is low, and the overall risk of IAN injury associated with third molar extraction ranges
* Corresponding author. State Universty of Paraíba, Rua Baraúnas, 351, Bairro rio, Campina Grande, PB, 58429-500, Brazil. Universita E-mail addresses: [email protected] (L.R. Peixoto), amandaggonzaga@gmail. com (A.K.G. Gonzaga), [email protected] (S.L.S. Melo), [email protected] (M.L.A. Pontual), [email protected] (A.A. Pontual), [email protected] (D.P. Melo).
from 0.5 to 5%, for affected patients there is considerable dissatisfaction and morbidity (Blaeser et al., 2003). The anatomical proximity of the roots of the mandibular third molar and the IAN increases the risk of nerve lesion during surgical procedures. Assessment of the proximity of these structures is extremely necessary and should be done using imaging techniques with a high level of accuracy, to avoid possible damage to nerve tissues (Flygare and Ohman, 2008; Jhamb et al., 2009). However, none of the imaging techniques give this information 100% of the time (Khan et al., 2011). Panoramic radiographs have been often used for preoperative imaging before removal of impacted mandibular third molars. When there is overlap between the third molar and the inferior alveolar canal (IAC) signs of darkening of the root, or diversion of the alveolar inferior canal have been found to be significantly related to nerve injury (Suomalainen et al., 2010). The advantages of
http://dx.doi.org/10.1016/j.jcms.2015.03.008 1010-5182/© 2015 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Peixoto LR, et al., The effect of two enhancement tools on the assessment of the relationship between third molars and the inferior alveolar canal, Journal of Cranio-Maxillo-Facial Surgery (2015), http://dx.doi.org/10.1016/j.jcms.2015.03.008
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panoramic radiographs include low cost and wide availability, it does not fulfill the precise observation of the anatomical relationship between structures due to its two-dimensional nature and unequal magnification (Kamrun et al., 2013). Some cases require a tridimensional view of the topographic relationship between the roots of the third inferior molar and the IAC (Gomes et al., 2008). Previous studies have shown that computed tomography (CT) and cone beam computed tomography (CBCT) used preoperatively permit a precise determination of the relationship between the inferior third molar and the IAC (Jhamb et al., 2009; Suomalainen et al., 2010; Kamrun et al., 2013). However, patients are often exposed to unnecessary radiation and the use of methods with lower doses should be encouraged. Digital panoramic images (DPI) permit the enhancement of the original image with different enhancement tools. Studies have compared the overall quality of enhanced and non-enhanced DPI (Gijbels et al., 2000); for caries diagnosis (Akarslan et al., 2008); for visibility of anatomical structures (Yalcinkaya et al., 2006; Baksi et al., 2010) and for the diagnosis of mandibular radiolucent lesions (Raitz et al., 2012). Although image enhancement processing may increase the interpretation time, if this increases the accuracy of determination of the anatomical proximity of third inferior molar roots to the IAC, this could enhance the use of DPI in preoperative planning. Based on what was stated above, this study aims to assess the relationship between the alveolar canal and inferior third molars using digital panoramic images with and without enhancement and compare the panoramic signs with CBCT findings. 2. Material and methods This study was approved by the last author Institutional Review Board (protocol number 10764313.4.0000.5187) and is in compliance with the Helsinki Declaration. DPIs and their corresponding CBCT images of 73 inferior third molars were selected from a private practice archive. Images were acquired between January 2012 and March 2013. The selected files were from 50 patients, 24 women and 26 men, with ages ranging from 18 to 77 years (mean age 45.62; SD 15.61). The majority of subjects selected for this study were referred for preoperative evaluation of impacted or partially erupted inferior third molars. Others were selected by the fact that the same subject had DPI and CBCT images taken with a maximum interval of 6 months from each other for different diagnostic reasons. The selected images should show at least one inferior third molar, with at least 2/3 of the roots completely grown (Nolla's stage 8). Images that presented lesions interfering with the inferior third molar position were also excluded. DPIs were obtained using Kodak 9000C (Eastman Kodak, Rochester, NY, EUA) panoramic X-ray unit at 70 kV and 15 mA and stored in a tagged image file format (TIFF). Each selected DPI was copied twice, enhanced using edge enhancement and invert tools, applied with Kodak Dental Image Software 6.5 (Eastman Kodak, Rochester, NY, EUA) software and codified. The CBCT images were previously obtained using i-CAT Cone Beam 3D Imaging System (Imaging Science International, Hatfield, PA, USA) with a 20 cm 25 cm amorphous silicon flat-panel image detector. Images were obtained at 120 kVp, 5.5 mA and a voxel size of 0.2 mm, with an exposure time of 40 s. The volumetric acquisitions were exported as digital imaging and communications in medicine (DICOM) files and saved to a portable hard disk for later reconstruction.
After the enhancement of the DPIs, the total number of DPIs e original and two group enhanced e and CBCT images to be evaluated by the observers was 292 (219 DPIs e 73 originals and 146 enhanced, and 73 CBCT volumes). 2.1. Viewing sessions Prior to all examination sessions, verbal and practical instructions and calibration tests were performed. The DPIs, with and without enhancement, were visualized using Kodak Dental Imaging Software (Kodak Dental Systems, Carestream Health, Rochester, NY, EUA), displayed in a Sony VAIO (SVS151C1SX Intelcore i7, Windows 8) laptop with a 17.3-inch color monitor placed in a quiet room with dimmed light. The observers were only allowed to use the zoom tool. Two experienced oral radiologists assessed all DPIs. The panoramic images (original, edge enhanced and inverted) (Fig. 1) were evaluated in random order, with a minimum interval of two days between each evaluation. The number of images evaluated per day was established by the observer's choice; however they were counseled to evaluate a maximum of 25 images, since visual fatigue can impair image evaluation. A minimum interval of fifteen days between the evaluations of the same DPI was established. To evaluate the relationship between inferior third molars and the mandibular canal, the following signs of close relationship between third inferior molar and IAC classification was used: darkening of the root; deflection of the root; narrowing of the root; superimposition of the root; bifurcation of the root over the inferior alveolar canal; diversion of the inferior alveolar canal; interruption of the cortex of inferior alveolar canal; and no radiographic findings noted (Monaco et al., 2004; Sedaghatfar et al., 2005; Flores et al., 2009). CBCT images were assessed by the same observers using i-CAT Workstation (Imaging Sciences International, Pennsylvania, USA), displayed in a Sony VAIO (SVS151C1SX Intelcore i7, Windows 8) laptop with a 17.3-inch color monitor placed in a quiet room with dimmed light. The CBCT images were evaluated 15 days after the panoramic images. CBCT images were three-dimensionally evaluated using two-dimensional, multiplanar, reformatted slices (axial, sagittal, coronal, panoramic, and cross-sectional images) (Fig. 2). For the CBCT images, the anatomical relationship between the third molar and the mandibular canal was classified into two types: (1) Separation e no interruption of the canal cortical bone between the third molar root and the canal wall was recognized, so the canal does not come in contact with the tooth; and (2) Contact e interruption of the of the canal cortical bone was recognized and the canal is in contact with the tooth. To avoid differences between the observer's ratings, when disagreement existed between them, another trained observer with 15 years' experience as an oral radiologist performed a joint assessment to reach agreement. 2.2. Data analysis Kappa coefficient (kw) test was used to analyze the agreement for each close relationship classification viewed in DPIs with CBCT images. An exact binominal test was used to assess kw significance levels. Categorical data (signs of close relationship) was analyzed using Student's t-test and ManneWhitney tests, when parametric tests could not be applied. Descriptive data was also used.
Please cite this article in press as: Peixoto LR, et al., The effect of two enhancement tools on the assessment of the relationship between third molars and the inferior alveolar canal, Journal of Cranio-Maxillo-Facial Surgery (2015), http://dx.doi.org/10.1016/j.jcms.2015.03.008
L.R. Peixoto et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2015) 1e6
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Fig. 1. Partial panoramic images with and without enhancement (original, invert tool and edge enhancement). Darkening of the roots, A) original; A1) invert tool; A2) edge enhancement. Interruption of the cortical of the alveolar canal, B) original; B1) invert tool; B2) edge enhancement. Superimposition of the roots, C) original; C1) invert tool; C2) edge enhancement.
3. Results Original DPIs showed a close relationship of the IAC and the roots of the inferior third molar in 27 cases (37%) and 26 (96.3%) of those were in agreement with the results found for CBCT images. 46 (63%) CBCT images did not show signs of close relationship, but only 29 (63%) of the corresponding DPIs agreed with these results (Table 1). The original DPIs that presented a positive response were compared with the CBCT responses to evaluate which signs of a close relationship between the IAC and third molar roots corresponded to the three-dimensional results (Table 2). The invert enhanced DPIs showed 46 images without signs of a close relationship between the IAC and the roots of the inferior third molar and 30 images (65.2%) agreed with CBCT results (Table 3). The invert enhanced DPIs that presented a positive response were compared with the CBCT responses (Table 4). Statistical values for edge enhanced DPIs agreed with the results found for original panoramic images (Table 5). The edge enhanced DPIs
that presented a positive response were compared with the CBCT responses (Table 6). Kappa values for the three modalities of DPIs evaluated, original, invert and edge enhanced, were 0.528, 0.551 and 0.528 respectively (p ¼ 0.981). 4. Discussion Removal of mandibular third molars is one of the most common dental operations. For this reason, the study of the relationship between an impacted third molar and the inferior alveolar canal is fundamental for prevention of inferior alveolar nerve lesions (Koong et al., 2006; Ohman et al., 2006; Neugebauer et al., 2008; Ferretti et al., 2009). Once the surgeon is aware of those close relationships, a better treatment plan may be designed. Wang et al. (2012), for example, suggested an effective way to avoid IAN injury during tooth extraction by applying orthodontic brackets or mini bone screws on the antagonist maxillary molars to extrude the impacted lower third molar prior to surgery.
Please cite this article in press as: Peixoto LR, et al., The effect of two enhancement tools on the assessment of the relationship between third molars and the inferior alveolar canal, Journal of Cranio-Maxillo-Facial Surgery (2015), http://dx.doi.org/10.1016/j.jcms.2015.03.008
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Fig. 2. A1) Partial panoramic images with and without enhancement (original, invert tool and edge enhancement); A2) Partial CBCT panoramic reconstruction; A3) Cross-section slices of the inferior third molar; A4) Sagittal slices of the third molar, all showing no sign of close proximity of the third molar roots and the IAC. B1) Partial panoramic images with and without enhancement (original, invert tool and edge enhancement); B2) Partial CBCT panoramic reconstruction; B3) Cross-section slices of the inferior third molar; B4) Sagittal slices of the third molar, all showing signs of the close proximity of the third molar roots and the IAC.
The existence of one or more radiographic signs of a close relationship between third molar roots and the IAC is considered to be a risk factor for nerve lesions (Ferretti et al., 2009). The indicative signs of a close relationship between third molar roots and the IAC are: darkening of the root; deflection of the root; narrowing of the root; superimposition of the root; bifurcation of the root over the inferior alveolar canal; diversion of the inferior alveolar canal; interruption of the cortex of the IAC (Monaco et al., 2004; Koong et al., 2006; Ohman et al., 2006; Ferretti et al., 2009). In the present study, 27 (37%) third molars showed indicative signs of a close relationship with the IAC; this may be due to the sample selection from a private dental radiology service database Table 1 Equivalence relationship between original panoramic images and CBCT (goldstandard). Original
Yes No Total
CBCT
Total
Yes
No
26 1 27
17 29 46
43 30 73
which included patients with and without indications for removal of the inferior third molar and the inclusion/exclusion criteria which included factors such as acquisition of DPI and CBCT images with a maximum interval of 6 months from each other and a third molar with at least 2/3 of the roots completely grown. A smaller number of third molars with signs of a close relationship with the IAC were found by Bell (2004), where 12% of the sample showed
Table 2 Comparison of the signs of close relationship found in the original panoramic image modality and CBCT images results (gold-standard). Close relationship sign
True-positive
False-positive
Total
Darkening of the roots Deflection of the root Narrowing of the root Superimposition of the root Bifurcation of the root over the inferior alveolar canal Diversion of the inferior alveolar canal Interruption of the cortex of the inferior alveolar canal
9 0 1 5 0
8 1 1 1 2
17 1 2 6 2
2
0
2
9
4
13
Please cite this article in press as: Peixoto LR, et al., The effect of two enhancement tools on the assessment of the relationship between third molars and the inferior alveolar canal, Journal of Cranio-Maxillo-Facial Surgery (2015), http://dx.doi.org/10.1016/j.jcms.2015.03.008
L.R. Peixoto et al. / Journal of Cranio-Maxillo-Facial Surgery xxx (2015) 1e6 Table 3 Equivalence relationship between invert enhanced panoramic image modality and CBCT (gold-standard). Invert tool
Yes No Total
CBCT
Total
Yes
No
26 1 27
16 30 46
42 31 73
5
Table 5 Equivalence relationship between edge enhanced panoramic image modality and CBCT (gold-standard). Edge enhancement tool
CBCT
Yes No Total
Total
Yes
No
26 1 27
17 29 46
43 30 73
signs of close relationship with the IAC. In agreement with our results, studies reported that one of the most frequent signs of a close relationship of the third molar roots and the IAC is the interruption of the cortex of the IAC, which leads to a higher risk of IAN lesion during surgical procedures (Koong et al., 2006; Gomes et al., 2008; Nakamori et al., 2008; Ferretti et al., 2009; Tantanapornkul et al., 2009). Other panoramic features reported to be suggestive of close contact between the root and IAC were darkening of the root, diversion of the mandibular canal and narrowing of the root (Sedaghatfar et al., 2005; Tantanapornkul et al., 2009). Albert et al. (2006) compared panoramic radiographs and CBCT images of 19 patients on the assessment of the radiographic signs of a close relationship of the IAC and third molar roots. Topographic proximity was found in 77.4% of the evaluated panoramic images, and darkening of the roots was the most frequent radiographic sign (45.2%). CBCT images confirmed the presence of a close relationship in 92.1% of the cases. Their percentage of topographic proximity to the IAC was 2.1 times higher than ours; however the small sample of the referred study should be taken in account when considering this difference. In the present study, darkening of the roots and interruption of the cortex of the alveolar canal were the most common signs of close relationship found in the evaluated DPIs, followed by superimposition of the roots. According to Blaeser et al. (2003) radiographic signs such as diversion of the inferior alveolar canal and darkening of a mandibular third molar root are statistically related to IAN injury during third molar removal. The absence of radiographic signs of a close relationship of the roots and IAC is associated with a minimal risk of injury of the IAN. When assessing the effect of enhancement tools on DPI detection of the third molar close relationship with the IAC, there was no statistically significant difference between the modalities with and without enhancement. However, when comparing the results found for each modality with CBCT, panoramic images e both original and enhanced e presented a high number of false-positive results. Nevertheless, the low cost and higher accessibility of panoramic radiography are the main reason for its wide use by professionals when evaluating signs of the close relationship between inferior third molar roots and the IAC (Koong et al., 2006;
Ohman et al., 2006; Nakagawa et al., 2007; Neugebauer et al., 2008; Jhamb et al., 2009). The use of invert tools and edge enhancement on DPIs improved the capacity of image assessment, when compared with original images, when assessing fine endodontic files and periapical lesions (Friedlander et al., 2002; Guneri and Akdeniz, 2004). However, in the present study, the use of those tools did not demonstrate any significant difference when compared with original images. The panoramic image does not enable a precise observation of the anatomical relationship of different structures due to its twodimensional nature and the presence of image magnification and distortions. The presence of signs of an anatomically close relationship between the inferior third molar's roots and the IAC indicates a high risk of an IAN lesion during surgery. If those signs are observed in the panoramic image, CBCT is necessary to correctly evaluate this close relationship three-dimensionally (Bell, 2004; Albert et al., 2006; Nakamori et al., 2008). According to Suomalainen et al. (2010), CBCT showed a perfect match when compared with the gold-standard to locate the IAC and could detect and locate the IAC in relation to the inferior third molar without difficulty in all CBCT scans, but it did not show a perfect match when assessing root anatomy, as the number of roots varies. A number of studies have combined different bi-dimensional image modalities as panoramic or intraoral images with a supplementary open mouth posteroanterior radiograph; panoramic radiograph and symmetric PA cephalometric radiograph (Neugebauer et al., 2008), MNBR stereography or panoramic and a series of three intraoral radiographs (Wenzel et al., 1998) determining the localization of IAC. When combining two or more bidimensional images for diagnosis, radiation dose should be taken in account. Another fact to be concerned about is the exposure dose of the CBCT system chosen for inferior third molar image evaluation. CBCT systems can acquire several single X-ray projections using a pulsatile or continuous beam, rotating at 180 e720 around the area of interest, using different exposure parameters (Kv, mA), all of which can affect the exposure dose. According to SEDENTEXCT project guidelines, the effective dose of panoramic radiography ranges from 2.7 to 24.3 mSv, while the CBCT system effective dose ranges from 11 to 674 mSv for the dento-alveolar region (small
Table 4 Comparison of the signs of close relationship found in the invert enhanced panoramic image modality and CBCT images results (gold-standard).
Table 6 Comparison of the signs of close relationship found in the edge enhanced panoramic image modality and CBCT images results (gold-standard).
Close relationship sign Darkening of the roots Deflection of the root Narrowing of the root Superimposition of the root Bifurcation of the root over the inferior alveolar canal Diversion of the inferior alveolar canal Interruption of the cortex of the inferior alveolar canal
True-positive
False-positive
Total
Close relationship sign
True-positive
False-positive
Total
8 0 1 5 0
8 1 0 2 2
16 1 1 7 2
7 0 1 8 0
10 0 0 2 0
17 0 1 10 0
2
0
2
1
3
4
10
3
13
Darkening of the roots Deflection of the root Narrowing of the root Superimposition of the root Bifurcation of the root over the inferior alveolar canal Diversion of the inferior alveolar canal Interruption of the cortex of the inferior alveolar canal
9
2
11
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and median FOV), and from 30 to 1073 mSv for the craniofacial region (large FOV) (Sedentexct Project, 2012). The wide range of effective dose variation among CBCT systems highlights the need for professional advice on the choice of image system to be used for inferior third molar and IAC relationship evaluation. CBCT is an important high resolution image modality for the assessment of low contrast bony anatomical structures, and is considered by some authors as the image modality of choice for obtaining the true anatomical relationship between the inferior third molar roots and the IAC (Ohman et al., 2006; Neugebauer et al., 2008; Ferretti et al., 2009; Jhamb et al., 2009). Although DPIs give a low-dose alternative image for topographic evaluation of the close relationship between the inferior third molar roots and the IAC, when their results are compared with CBCT, a high number of false-positive values are found for both the original and enhanced images. This shows that panoramic images, enhanced or not, are not a substitute for CBCT images in high risk IAN injury situations. In agreement with this study, comparing radiographic and tomography images, authors observed that the most trustworthy radiographic image for planning procedures involving areas close to the IAC is the CT image (Friedlander et al., 2002; Blaeser et al., 2003; Guneri and Akdeniz, 2004; Albert et al., 2006; Nakagawa et al., 2007; Nakamori et al., 2008; Ferretti et al., 2009). 5. Conclusion There was no difference between original, invert enhanced and edge enhanced DPIs, resulting in similar agreement between original and enhanced modalities when assessing the proximity of mandibular molar roots to the IAC. Darkening of the root and narrowing of the root were the most frequent signs of a close relationship found in this study. Preoperatively, DPIs, enhanced or not, should not be used without the aid of CBCT images in cases when high risk IAN injury signs are noted. Conflict of interest The authors denied any conflict of interest. Acknowledgments We are grateful to CAPES Foundation for the scholarship e Undergraduate Research Scholar support and to State University of Paraíba and Federal University of Pernambuco for the technical support. References €r K, Erten H: A comparison of the diagnostic Akarslan ZZ, Akdevelioglu M, Güngo accuracy of bitewing, periapical, unfiltered and filtered digital panoramic images for approximal caries detection in posterior teeth. Dentomaxillofac Radiol 37: 458e463, 2008 Albert DGM, Gomes AC, do Egito Vasconcelos BC, de Oliveira e Silva ED, Holanda GZ: Comparison of orthopantomographs and conventional tomography images for assessing the relationship between impacted lower third molars and the mandibular canal. J Oral Maxillofac Surg 64: 1030e1037, 2006 €z E, Sogur E, Mert A: Perception of anatomical structures in digitally Baksi BG, Alpo filtered and conventional panoramic radiographs: a clinical evaluation. Dentomaxillofac Radiol 39: 424e430, 2010 Bell GW: Use of dental panoramic tomographs to predict the relation between mandibular third molar teeth and the inferior alveolar nerve. Radiological and surgical findings, and clinical outcome. Br J Oral Maxillofac Surg 42: 21e27, 2004 Blaeser BF, August MA, Donoff RB, Kaban LB, Dodson TB: Panoramic radiographic risk factors for inferior alveolar nerve injury after third molar extraction. J Oral Maxillofac Surg 61: 417e421, 2003
Ferretti F, Malventi M, Malasoma R: Dental magnetic resonance imaging: study of impacted mandibular third molars. Dentomaxillofac Radiol 38: 387e392, 2009 Flores JA, Flores FW, Unfer MK, Ferrari R: Relation between the third inferior molar with the inferior alveolar nerve. Int J Dent 8: 211e214, 2009 Flygare L, Ohman A: Preoperative imaging procedures for lower wisdom teeth removal. Clin Oral Investig 12: 291e302, 2008 Friedlander LT, Love RM, Chandler NP: A comparison of phosphor-plate digital images with conventional radiographs for the perceived clarity of fine endodontic files and periapical lesions. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 93: 321e327, 2002 Gijbels F, De Meyer AM, Bou Serhal C, Van den Bossche C, Declerck J, Persoons M, et al: The subjective image quality of direct digital and conventional panoramic radiography. Clin Oral Investig 4: 162e167, 2000 Gomes AC, Vasconcelos BCE, Silva EDO, Caldas Jr AJ, Pita Neto IC: Sensitivity and specificity of pantomography to predict inferior alveolar nerve damage during extraction of impacted lower third molars. J Oral Maxillofac Surg 66: 256e259, 2008 Guneri P, Akdeniz BG: Fraudulent management of digital endodontic images. Int Endod J 37: 214e220, 2004 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 67: 58e66, 2009 Kamrun N, Tetsumura A, Nomura Y, Yamaguchi S, Baba O, Nakamura S, et al: Visualization of the superior and inferior borders of the mandibular canal a comparative study using digital panoramic radiographs and cross-sectional computed tomography images. Oral Surg Oral Med Oral Pathol Oral Radiol 115: 550e557, 2013 Khan I, Halli R, Gadre P, Gadre K: Correlation of panoramic radiographs and spiral CT scan in the preoperative assessment of close relationship of the inferior alveolar canal to impacted mandibular third molars. J Craniofac Surg 22: 566e570, 2011 Koong B, Pharoah MJ, Bulsara M, Tennant M: Methods of determining the relationship of the mandibular canal and third molars: a survey of Australian oral and maxillofacial surgeons. Aust Dent J 51: 64e68, 2006 Monaco G, Montevecchi M, Bonetti GA, Gatto MR, Checchi L: Reliability of panoramic radiography in evaluating the topographic relationship between the mandibular canal and impacted third molars. J Am Dent Assoc 135: 312e318, 2004 Nakagawa Y, Ishii H, Nomura Y, Watanabe NY, Hoshiba D, Kobayashi K, et al: Third molar position: reliability of panoramic radiography. J Oral Maxillofac Surg 65: 1303e1308, 2007 Nakamori K, Fujiwara K, Miyazaki A, Tomihara K, Tsuji M, Nakai M, 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 66: 2308e2313, 2008 Neugebauer J, Shirani R, Mischkowski RA, Ritter L, Scheer M, Keeve E, et al: Comparison of cone-beam volumetric imaging and combined plain radiographs for localization of the mandibular canal before removal of impacted lower third molars. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 105: 633e642, 2008 Ohman A, Kivij€ arvi K, Blomb€ ack U, Flygare L: Pre-operative radiographic evaluation of lower third molars with computed tomography. Dentomaxillofac Radiol 35: 30e35, 2006 Raitz R, Assunç~ ao Junior JN, Fenyo-Pereira M, Correa L, de Lima LP: Assessment of using digital manipulation tools for diagnosing mandibular radiolucent lesions. Dentomaxillofac Radiol 41: 203e210, 2012 Sedaghatfar M, Augus MA, Dodson TB: Panoramic radiographic findings as predictors of inferior alveolar nerve exposure following third molar extraction. J Oral Maxillofac Surg 63: 3e7, 2005 SEDENTEXCT Project: Radiation protection: cone beam CT for dental and maxillofacial radiology: evidence-based guidelines. Available from: http://www. sedentexct.eu/content/guidelines-cbct-dental-and-maxillofacial-radiology, 2012 [accessed 10.11.14]; 2012 ~ I, Mattila M, Turtola L, Vehmas T, Peltola JS: Reliability of Suomalainen A, Venta CBCT and other radiographic methods in preoperative evaluation of lower third molars. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 109: 276e284, 2010 Tantanapornkul W, Okochi K, Bhakdinaronk A, Ohbayashi N, Kurabayashi T: Correlation of darkening of impacted mandibular third molar root on digital panoramic images with cone beam computed tomography findings. Dentomaxillofac Radiol 38: 11e16, 2009 Wang Y, He D, Yang C, Wang B, Qian W: An easy way to apply orthodontic extraction for impacted lower third molar compressing to the inferior alveolar nerve. J Craniomaxillofac Surg 40: 234e237, 2012 Wenzel A, Aagaard E, Sindet-Pedersen S: Evaluation of a new radiographic technique: diagnostic accuracy for mandibular third molars. Dentomaxillofac Radiol 27: 255e263, 1998 Yalcinkaya S, Künzel A, Willers R, Thoms M, Becker J: Subjective image quality of digitally filtered radiographs acquired by Dürr Vistascan system compared with conventional radiographs. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 101: 643e651, 2006
Please cite this article in press as: Peixoto LR, et al., The effect of two enhancement tools on the assessment of the relationship between third molars and the inferior alveolar canal, Journal of Cranio-Maxillo-Facial Surgery (2015), http://dx.doi.org/10.1016/j.jcms.2015.03.008
