The Saudi Dental Journal (2014) xxx, xxx–xxx
King Saud University
The Saudi Dental Journal www.ksu.edu.sa www.sciencedirect.com
ORIGINAL ARTICLE
Pre-operative assessment of relationship between inferior dental nerve canal and mandibular impacted third molar in Saudi population S. Shujaat a,*, H.M. Abouelkheir b, K.S. Al-Khalifa c, B. Al-Jandan a, H.F. Marei a a Department of Oral and Maxillofacial Surgery, College of Dentistry, University of Dammam, P.O. Box 1982, Dammam 31411, Saudi Arabia b Department of Oral and Maxillofacial Radiology, College of Dentistry, University of Dammam, P.O. Box 1982, Dammam 31411, Saudi Arabia c Department of Dental Public Health, College of Dentistry, University of Dammam, P.O. Box 1982, Dammam 31411, Saudi Arabia
Received 29 May 2013; revised 5 January 2014; accepted 31 March 2014
KEYWORDS Inferior alveolar nerve; Mandibular third molar; Impaction; Relationship
Abstract Objective: To study the correlation between the position of the inferior dental (ID) nerve canal and the angulation of impacted mandibular third molars using dental cone beam computed tomography (CBCT). Materials and methods: The study considered 100 impactions in 85 patients (60 males, 25 females), for whom an initial panoramic radiographic assessment had revealed that the ID canal and the lower 3rd molar were in close proximity. A CBCT scan of each patient was carried out to assess how the ID nerve canal position influenced the class and position of impaction, angulation of impaction, and bone contact. Results: Class I position B impactions were found in the majority of cases, where the position of the ID canal was approximate to the lingual plate and inferior to the 3rd molar (85.7%). The results were statistically significant (p = 0.001). 96% of the ID canals showed bone contact. Of these, 77.1% of ID canals exhibited lingual bone contact, inferior to impaction. The results were statistically significant (p = 0.001). Horizontally angulated impactions were most common in the mandible, and significantly associated with lingual and inferior positioning of the ID canal (76.2%).
* Corresponding author. Tel.: +966 596025943. E-mail address: [email protected] (S. Shujaat). Peer review under responsibility of King Saud University.
Production and hosting by Elsevier 1013-9052 ª 2014 King Saud University. Production and hosting by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.sdentj.2014.03.005 Please cite this article in press as: Shujaat, S. et al., Pre-operative assessment of relationship between inferior dental nerve canal and mandibular impacted third molar in Saudi population. The Saudi Dental Journal (2014), http://dx.doi.org/10.1016/j.sdentj.2014.03.005
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S. Shujaat et al. Conclusions: Our sample population most commonly exhibited horizontally angulated class I position B impactions of the mandible. The position of the ID canal significantly influenced the type of impaction and bone contact. ª 2014 King Saud University. Production and hosting by Elsevier B.V. All rights reserved.
1. Introduction The extraction of an impacted or erupted third molar is regarded to be the most common dentoalveolar procedure performed in oral and maxillofacial surgery (Grossi et al., 2007; Leung and Cheung, 2009). The principal teeth that present as impactions are either third molars or canines. The prevalence of impacted teeth varies among different populations depending on the age group, assessment method, and diversity within the sample population (Chu et al., 2003). Mandibular third molars are considered to be the most commonly impacted teeth. Before planning extraction of an impacted mandibular third molar, the proximity between the mandibular canal and the impacted molar should be assessed to minimize the risk of inferior alveolar nerve damage (Sedaghatfar et al., 2005). Trauma to the inferior alveolar nerve during surgical extraction of a deeply impacted third molar is a well-known complication (Rood and Shehab, 1990) and continues to be frequently reported (Hillerup, 2007). Conventional two dimensional (2-D) radiographic images, such as panoramic radiographs, are most commonly used to assess the relationship between the inferior dental (ID) nerve canal and mandibular third molar (Dalili et al., 2011). However, three dimensional (3-D) radiographic modalities such as computed tomography and CBCT provide more accurate information with less distortion compared to the 2-D images. In addition, 3-D imaging modalities provide cross-sectional (buccolingual), axial, sagittal, coronal and panoramic views that can be used to assess in detail the relationship between the ID nerve canal and the mandibular third molar. To avoid nerve injury, CBCT is recommended in cases where there is radiographic evidence of close proximity between the ID canal and mandibular third molar (Flygare and Ohman, 2008; SEDENTEXCT, 2009). Detailed guidelines for the clinical application of CBCT were elaborated by the SEDENTEXCT project (SEDENTEXCT, 2009). According to these guidelines, a CBCT scan should be performed following a decision to extract an impacted mandibular third molar when a radiographic investigation shows that the molar is in close proximity to the inferior alveolar nerve canal (SEDENTEXCT, 2009). Ongoing review of these guidelines is necessary to take into account new evidence. The present study is the first, to our knowledge, that uses dental CBCT to investigate the correlation between the position of the ID canal and the angulation of the impacted mandibular third molar among the population of the Eastern region of Saudi Arabia. 2. Materials and methods The study was retrospective in design; therefore, no ethical approval was required. The sample consisted of 85 patients (60 males, 25 females; Age range: 20–39 years), exhibiting a
total of 100 impactions where an initial panoramic radiographic assessment demonstrated overlap and/or close proximity between the mandibular 3rd molar and ID canal. A CBCT scan (120 kV, 5 mA, I-CATTM, 3-D imaging system, Imaging Sciences International Inc., Hatfield, PA, USA) was carried out in all cases, at a clinically standard resolution (0.3 mm voxel, 8.9 s). ICAT vision software (Q version 1.8.1.10, Imaging Science International, Hatfield, PA, USA) was used to identify the relationship of the ID nerve canal to the mandibular 3rd molar. Using a cross sectional view, and adjusting the position in panoramic view, provided an outline of the ID nerve canal and allowed its buccolingual position to be determined (Fig. 1a and b). All the scans were assessed by one radiologist and one specialist in oral and maxillofacial surgery. The impactions were categorized based on Winter’s classification of 3rd molar impaction (Winter, 1926) as well as the Pell–Gregory classification in relation to ramus of the mandible (class I, II and III) and position of 3rd molar in relation to occlusal surface of 2nd molar (A, B and C) (Alling and Alling, 1993). 3. Statistical analyses Data was analyzed by utilizing the Statistical Package for the Social Sciences (SPSS-19.0) software package (IBM, Chicago, USA). Values of the ID canal position, impaction class, bone contact and angulation of impaction were sorted according to their frequency and percentage. Pearson’s chi-square test was applied to evaluate the correlation between impaction, nerve positioning, bone contact and impaction angulation. Results with p < 0.05 were considered statistically significant. 4. Results The position of the ID nerve canal in relation to the impacted mandibular third molar typically fell into one of the following 3 categories: buccal and inferior, lingual and inferior, or middle (apex of roots) and inferior (Maegawa et al., 2003). In all the cases, the ID nerve canal was found to be inferior to the impacted mandibular third molar. Table 1 illustrates that lingual and inferior positioning of the ID nerve canal is significantly associated with IIIB (100%), IIIC (100%) and IB (85.7%) impactions. Middle and inferior positioning of the nerve was significantly associated with IA impactions (42.9%), whereas buccal and inferior positioning of the nerve showed significant association with IC impactions (25%). The association between the ID canal position and the impaction class and position was statistically significant (p = 0.049). According to Table 2, lingual and inferior positioning of the ID nerve canal was significantly associated with bone contact (77.1%), whereas middle and inferior positioning of the canal was significantly associated with the absence of bone contact (100%). In both cases the value of p was 0.001. Table 3 illustrates the position of the ID canal and its correlation with the angulation of mandibular third molar impaction, according to Winter’s classification. Horizontal, mesioangular, and vertical
Please cite this article in press as: Shujaat, S. et al., Pre-operative assessment of relationship between inferior dental nerve canal and mandibular impacted third molar in Saudi population. The Saudi Dental Journal (2014), http://dx.doi.org/10.1016/j.sdentj.2014.03.005
Relationship between inferior dental nerve canal and mandibular impacted third molar
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Figure 1 CBCT scan (a) inferior dental (ID) canal position on panoramic view of CBCT, (b) cross-sectional view of ID canal, lingual and inferior to the impaction. Table 1 Relationship of class & position of mandibular 3rd molar impaction* and position of ID canal. The bold numbers are the significantly high frequency at p < 0.05, by applying chi square test. Class & position of impaction
IA IB IC IIA IIB IIIB IIIC Total number of cases *
Position of ID canal
Total
Buccal + inferior
Lingual + inferior
Middle + inferior
0 .0% 0 .0% 4* 25.0% 2 20.0% 2 7.7% 0 .0% 0 .0% 8 8.0%
8 57.1% 24* 85.7% 10 62.5% 6 60.0% 20* 76.9% 2* 100.0% 4* 100.0% 74 74.0%
6* 42.9% 4 14.3% 2 12.5% 2 20.0% 4 15.4% 0 .0% 0 .0% 18 18.0%
14 100.0% 28 100.0% 16 100.0% 10 100.0% 26 100.0% 2 100.0% 4 100.0% 100 100.0%
Shows statistical significance (p = 0.049).
impactions showed significant association with lingual and inferior positioning of the nerve (horizontal = 76.2%; mesioangular = 78.6%; vertical = 71.4%), whereas distoangular impactions showed significant association with the middle and inferior position of the ID nerve canal (100%). Overall, the angulation of impaction was significantly correlated with the ID nerve canal position (p = 0.039).
5. Discussion When the inferior dental nerve is in close proximity to an impaction, the nerve is at a greater risk of injury during removal of the impaction. Surgical removal of such impactions
Please cite this article in press as: Shujaat, S. et al., Pre-operative assessment of relationship between inferior dental nerve canal and mandibular impacted third molar in Saudi population. The Saudi Dental Journal (2014), http://dx.doi.org/10.1016/j.sdentj.2014.03.005
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S. Shujaat et al. Table 2 Bone contact* and position of ID canal. The bold numbers are the significantly high frequency at p < 0.05, by applying chi square test. Bone contact
Contact No contact Total number of cases *
Position of ID canal
Total
Buccal + inferior
Lingual + inferior
Middle + inferior
8 8.3% 0 .0% 8 8.0%
74* 77.1% 0 .0% 74 74.0%
14 14.6% 4* 100.0% 18 18.0%
96 100.0% 4 100.0% 100 100.0%
Shows statistical significance (p = 0.001).
Table 3 Angulation of impaction* and position of ID canal. The bold numbers are the significantly high frequency at p < 0.05, by applying chi square test. Angulation of impaction
Position of ID canal Buccal + inferior
Lingual + inferior
Middle + inferior
Distoangular
0 .0% 2 4.8% 4 14.3% 2 7.1% 8 8.0%
0 .0% 32* 76.2% 22* 78.6% 20* 71.4% 74 74.0%
2* 100.0% 8 19.0% 2 7.1% 6 21.4% 18 18.0%
Horizontal Mesioangular Vertical Total number of cases *
Total
2 100.0% 42 100.0% 28 100.0% 28 100.0% 100 100.0%
Shows statistical significance (p = 0.039).
is much safer when preceded by radiographic imaging to determine the location of the ID canal. Compared with 2-D radiography, 3-D radiography provides more information about the position of the nerve; this knowledge can be used to determine a treatment plan. This study used CBCT scanning, a 3-D radiographic method, to determine the correlation between the ID nerve position and the impaction. We found that the ID canal was most frequently positioned lingually, rather than buccally, to the impacted mandibular third molar. This finding is in accordance with that of other studies that had used volumetric imaging to assess the relationship between the mandibular third molar and the ID canal (De Melo Albert et al., 2006; Ohman et al., 2006; Tantanapornkul et al., 2007). Superior positioning of the ID nerve canal in relation to the impaction was not observed in our sample population. In the majority of cases (74%), the ID nerve canal passed in contact with the lingual plate of the mandible, and no perforation of the lingual plate was observed in any of the cases. Furthermore, only 8% of the impaction cases showed buccal positioning of the ID canal, which is in agreement with other reports that the ID canal has a low prevalence of buccal positioning in relation to the impacted mandibular third molar (Miller et al., 1990; Maegawa et al., 2003). Hassan (2010) studied the pattern of third molar impaction in the western region of Saudi Arabia. The author concluded that majority of the impactions in the mandible were mesioangular (33.4%). In addition, Syed et al. (2012) also found mesioangular impactions of the mandible to be more common (50.75%) in the Saudi population. Our study, however, found
horizontally angulated impactions to be the most common. This may be attributed to the difference in ethnicity of our sample population versus that of the previous studies. The sample population studied by Hassan (2010) involved people living in the western region of Saudi Arabia that is also known as Hijaz, and who represented a global range of ethnic groups. Our sample population belonged to Saudi Arabia’s eastern region, which has a less diverse range of ethnic groups. Our results are in agreement with those of Tantanapornkul et al. (2007), who had also observed a greater prevalence of horizontal impactions (52%) when studying a sample of 85 female patients and 50 male patients between the age of 18 and 74, although our study included more male patients and a narrower age range as well as a different ethnic population. In our study, position B impaction was found to be most common (56%) which is in agreement with Hassan (2010) and Quek et al. (2003). Sex predilection was not considered because of the limited number of female cases (25 of 100). A larger sample size is required to confirm our findings. Further investigation is required to study the sex predilection of these findings among the specific ethnic population of Saudi Arabia’s eastern region. 6. Conclusions Among the population of Saudi Arabia’s eastern region, the ID canal was most frequently approximate to the lingual plate and inferior to the 3rd molar. The most common mandibular impactions were class I, position B, and horizontally angled.
Please cite this article in press as: Shujaat, S. et al., Pre-operative assessment of relationship between inferior dental nerve canal and mandibular impacted third molar in Saudi population. The Saudi Dental Journal (2014), http://dx.doi.org/10.1016/j.sdentj.2014.03.005
Relationship between inferior dental nerve canal and mandibular impacted third molar Funding Funding body: Ministry of higher education, University of Dammam, Deanship of scientific research. Grant No.: 2012124. Ethical approval Ethical approval not required. Conflict of interest No conflict of interest. References Alling, R.D., Alling III, C.C., 1993. Mandibular third molars. Part I. Buccal-occlusal approaches. In: Alling, C.C., IIIIII, Helfrick, J.F., Alling, R.D. (Eds.), . In: Impacted Teeth. WB Saunders, Philadelphia, pp. 149–202. Chu, F.C., Li, T.K., Lui, V.K., Newsome, P.R., Chow, R.L., Cheung, L.K., 2003. Prevalence of impacted teeth and associated pathologies–a radiographic study of the Hong Kong Chinese population. Hong Kong Med. J. 9, 158–163. Dalili, Z., Mahjoub, P., Sigaroudi, A.K., 2011. Comparison between cone beam computed tomography and panoramic radiography in the assessment of the relationship between the mandibular canal and impacted class C mandibular third molars. Dent. Res. J. (Isfahan) 8, 203–210. De Melo Albert, D.G., Gomes, A.C., Do Egito Vasconcelos, B.C., De Oliveira e Silva, E.D., Holanda, G.Z., 2006. Comparison of orthopantomographs and conventional tomography image for assessing the relationship between impacted lower third molars and mandibular canal. J. Oral Maxillofac. Surg. 64, 1030–1037. Flygare, L., Ohman, A., 2008. Preoperative imaging procedures for lower wisdom teeth removal. Clin. Oral Investig. 12, 291–302. Grossi, G.B., Maiorana, C., Garramone, R.A., Borgonovo, A., Creminelli, L., Santoro, F., 2007. Assessing postoperative discomfort after third molar surgery: a prospective study. J. Oral Maxillofac. Surg. 65, 901–917. Hassan, A.H., 2010. Pattern of third molar impaction in Saudi population. Clin. Cosmet. Investig. Dent. 2, 109–113.
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Hillerup, S., 2007. Iatrogenic injury to oral branches of the trigeminal nerve: records of 449 cases. Clin. Oral Investig. 11, 133–142. Leung, Y.Y., Cheung, L.K., 2009. Safety of coronectomy versus excision of wisdom teeth: a randomized controlled trial.. Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endod. 108, 821–827. Maegawa, H., Sano, K., Kitgawa, Y., Ogasawara, T., Miyauchi, K., Sekine, J., Inokuchi, T., 2003. Preoperative assessment of the relationship between the mandibular third molar and mandibular canal by axial computed tomography. Oral Surg. Oral Med. Oral Pathol. 96, 639–646. Miller, C.S., Nummikoski, P.V., Barnett, D.A., Langlais, R.P., 1990. Cross sectional tomography. A diagnostic technique for determining the buccolingual relationship of the impacted mandibular third molars and the inferior alveolar neurovascular bundle. Oral Surg. Oral Med. Oral Pathol. 70, 791–797. Ohman, A., Kivijari, K., Blomback, U., Flygare, L., 2006. Preoperative radiographic evaluation of lower third molars with computed tomography. Dentomaxillofac. Radiol. 35, 30–35. Quek, S.L., Tay, C.K., Tay, K.H., Toh, S.L., Lim, K.C., 2003. Pattern of third molar impaction in a Singapore Chinese population: a retrospective radiographic survey. Int. J. Oral Maxillofac. Surg. 32, 548–552. Rood, J.P., Shehab, B.A., 1990. The radiological prediction of inferior alveolar nerve injury during third molar surgery. Br. J. Oral Maxillofac. Surg. 28, 20–25. Sedaghatfar, M., August, M.A., Dodson, T.B., 2005. Panoramic radiographic findings as predictors of inferior alveolar nerve exposure following third molar extraction. J. Oral Maxillofac. Surg. 63, 3–7. SEDENTEXCT, 2009. Radiation protection: cone beam CT for dental and maxillofacial radiology. Provisional guidelines, (v1.1 May 2009). Available from: (accessed 16 December). Syed, K.B., Kota, Z., Ibrahim, M., Bagi, M.A., Assiri, M.A., 2012. Prevalence of impacted molar teeth among Saudi population in Asir region, Saudi Arabia – a retrospective study of 3 years. J. Int. Oral Health 5, 43–47. Tantanapornkul, W., Okouchi, K., Fujiwara, Y., Yamashiro, M., Maruoka, Y., Ohbayashi, N., Kurabayashi, T., 2007. A comparative study of cone-beam computed tomography in assessing the topographic relationship between the mandibular canal and impacted third molars. Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endod. 103, 253–259. Winter, G.B., 1926. The Principles of Exodontia as Applied to the Impacted Third Molar. American Medical Book Co., St. Louis, MO.
Please cite this article in press as: Shujaat, S. et al., Pre-operative assessment of relationship between inferior dental nerve canal and mandibular impacted third molar in Saudi population. The Saudi Dental Journal (2014), http://dx.doi.org/10.1016/j.sdentj.2014.03.005
King Saud University
The Saudi Dental Journal www.ksu.edu.sa www.sciencedirect.com
ORIGINAL ARTICLE
Pre-operative assessment of relationship between inferior dental nerve canal and mandibular impacted third molar in Saudi population S. Shujaat a,*, H.M. Abouelkheir b, K.S. Al-Khalifa c, B. Al-Jandan a, H.F. Marei a a Department of Oral and Maxillofacial Surgery, College of Dentistry, University of Dammam, P.O. Box 1982, Dammam 31411, Saudi Arabia b Department of Oral and Maxillofacial Radiology, College of Dentistry, University of Dammam, P.O. Box 1982, Dammam 31411, Saudi Arabia c Department of Dental Public Health, College of Dentistry, University of Dammam, P.O. Box 1982, Dammam 31411, Saudi Arabia
Received 29 May 2013; revised 5 January 2014; accepted 31 March 2014
KEYWORDS Inferior alveolar nerve; Mandibular third molar; Impaction; Relationship
Abstract Objective: To study the correlation between the position of the inferior dental (ID) nerve canal and the angulation of impacted mandibular third molars using dental cone beam computed tomography (CBCT). Materials and methods: The study considered 100 impactions in 85 patients (60 males, 25 females), for whom an initial panoramic radiographic assessment had revealed that the ID canal and the lower 3rd molar were in close proximity. A CBCT scan of each patient was carried out to assess how the ID nerve canal position influenced the class and position of impaction, angulation of impaction, and bone contact. Results: Class I position B impactions were found in the majority of cases, where the position of the ID canal was approximate to the lingual plate and inferior to the 3rd molar (85.7%). The results were statistically significant (p = 0.001). 96% of the ID canals showed bone contact. Of these, 77.1% of ID canals exhibited lingual bone contact, inferior to impaction. The results were statistically significant (p = 0.001). Horizontally angulated impactions were most common in the mandible, and significantly associated with lingual and inferior positioning of the ID canal (76.2%).
* Corresponding author. Tel.: +966 596025943. E-mail address: [email protected] (S. Shujaat). Peer review under responsibility of King Saud University.
Production and hosting by Elsevier 1013-9052 ª 2014 King Saud University. Production and hosting by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.sdentj.2014.03.005 Please cite this article in press as: Shujaat, S. et al., Pre-operative assessment of relationship between inferior dental nerve canal and mandibular impacted third molar in Saudi population. The Saudi Dental Journal (2014), http://dx.doi.org/10.1016/j.sdentj.2014.03.005
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S. Shujaat et al. Conclusions: Our sample population most commonly exhibited horizontally angulated class I position B impactions of the mandible. The position of the ID canal significantly influenced the type of impaction and bone contact. ª 2014 King Saud University. Production and hosting by Elsevier B.V. All rights reserved.
1. Introduction The extraction of an impacted or erupted third molar is regarded to be the most common dentoalveolar procedure performed in oral and maxillofacial surgery (Grossi et al., 2007; Leung and Cheung, 2009). The principal teeth that present as impactions are either third molars or canines. The prevalence of impacted teeth varies among different populations depending on the age group, assessment method, and diversity within the sample population (Chu et al., 2003). Mandibular third molars are considered to be the most commonly impacted teeth. Before planning extraction of an impacted mandibular third molar, the proximity between the mandibular canal and the impacted molar should be assessed to minimize the risk of inferior alveolar nerve damage (Sedaghatfar et al., 2005). Trauma to the inferior alveolar nerve during surgical extraction of a deeply impacted third molar is a well-known complication (Rood and Shehab, 1990) and continues to be frequently reported (Hillerup, 2007). Conventional two dimensional (2-D) radiographic images, such as panoramic radiographs, are most commonly used to assess the relationship between the inferior dental (ID) nerve canal and mandibular third molar (Dalili et al., 2011). However, three dimensional (3-D) radiographic modalities such as computed tomography and CBCT provide more accurate information with less distortion compared to the 2-D images. In addition, 3-D imaging modalities provide cross-sectional (buccolingual), axial, sagittal, coronal and panoramic views that can be used to assess in detail the relationship between the ID nerve canal and the mandibular third molar. To avoid nerve injury, CBCT is recommended in cases where there is radiographic evidence of close proximity between the ID canal and mandibular third molar (Flygare and Ohman, 2008; SEDENTEXCT, 2009). Detailed guidelines for the clinical application of CBCT were elaborated by the SEDENTEXCT project (SEDENTEXCT, 2009). According to these guidelines, a CBCT scan should be performed following a decision to extract an impacted mandibular third molar when a radiographic investigation shows that the molar is in close proximity to the inferior alveolar nerve canal (SEDENTEXCT, 2009). Ongoing review of these guidelines is necessary to take into account new evidence. The present study is the first, to our knowledge, that uses dental CBCT to investigate the correlation between the position of the ID canal and the angulation of the impacted mandibular third molar among the population of the Eastern region of Saudi Arabia. 2. Materials and methods The study was retrospective in design; therefore, no ethical approval was required. The sample consisted of 85 patients (60 males, 25 females; Age range: 20–39 years), exhibiting a
total of 100 impactions where an initial panoramic radiographic assessment demonstrated overlap and/or close proximity between the mandibular 3rd molar and ID canal. A CBCT scan (120 kV, 5 mA, I-CATTM, 3-D imaging system, Imaging Sciences International Inc., Hatfield, PA, USA) was carried out in all cases, at a clinically standard resolution (0.3 mm voxel, 8.9 s). ICAT vision software (Q version 1.8.1.10, Imaging Science International, Hatfield, PA, USA) was used to identify the relationship of the ID nerve canal to the mandibular 3rd molar. Using a cross sectional view, and adjusting the position in panoramic view, provided an outline of the ID nerve canal and allowed its buccolingual position to be determined (Fig. 1a and b). All the scans were assessed by one radiologist and one specialist in oral and maxillofacial surgery. The impactions were categorized based on Winter’s classification of 3rd molar impaction (Winter, 1926) as well as the Pell–Gregory classification in relation to ramus of the mandible (class I, II and III) and position of 3rd molar in relation to occlusal surface of 2nd molar (A, B and C) (Alling and Alling, 1993). 3. Statistical analyses Data was analyzed by utilizing the Statistical Package for the Social Sciences (SPSS-19.0) software package (IBM, Chicago, USA). Values of the ID canal position, impaction class, bone contact and angulation of impaction were sorted according to their frequency and percentage. Pearson’s chi-square test was applied to evaluate the correlation between impaction, nerve positioning, bone contact and impaction angulation. Results with p < 0.05 were considered statistically significant. 4. Results The position of the ID nerve canal in relation to the impacted mandibular third molar typically fell into one of the following 3 categories: buccal and inferior, lingual and inferior, or middle (apex of roots) and inferior (Maegawa et al., 2003). In all the cases, the ID nerve canal was found to be inferior to the impacted mandibular third molar. Table 1 illustrates that lingual and inferior positioning of the ID nerve canal is significantly associated with IIIB (100%), IIIC (100%) and IB (85.7%) impactions. Middle and inferior positioning of the nerve was significantly associated with IA impactions (42.9%), whereas buccal and inferior positioning of the nerve showed significant association with IC impactions (25%). The association between the ID canal position and the impaction class and position was statistically significant (p = 0.049). According to Table 2, lingual and inferior positioning of the ID nerve canal was significantly associated with bone contact (77.1%), whereas middle and inferior positioning of the canal was significantly associated with the absence of bone contact (100%). In both cases the value of p was 0.001. Table 3 illustrates the position of the ID canal and its correlation with the angulation of mandibular third molar impaction, according to Winter’s classification. Horizontal, mesioangular, and vertical
Please cite this article in press as: Shujaat, S. et al., Pre-operative assessment of relationship between inferior dental nerve canal and mandibular impacted third molar in Saudi population. The Saudi Dental Journal (2014), http://dx.doi.org/10.1016/j.sdentj.2014.03.005
Relationship between inferior dental nerve canal and mandibular impacted third molar
3
Figure 1 CBCT scan (a) inferior dental (ID) canal position on panoramic view of CBCT, (b) cross-sectional view of ID canal, lingual and inferior to the impaction. Table 1 Relationship of class & position of mandibular 3rd molar impaction* and position of ID canal. The bold numbers are the significantly high frequency at p < 0.05, by applying chi square test. Class & position of impaction
IA IB IC IIA IIB IIIB IIIC Total number of cases *
Position of ID canal
Total
Buccal + inferior
Lingual + inferior
Middle + inferior
0 .0% 0 .0% 4* 25.0% 2 20.0% 2 7.7% 0 .0% 0 .0% 8 8.0%
8 57.1% 24* 85.7% 10 62.5% 6 60.0% 20* 76.9% 2* 100.0% 4* 100.0% 74 74.0%
6* 42.9% 4 14.3% 2 12.5% 2 20.0% 4 15.4% 0 .0% 0 .0% 18 18.0%
14 100.0% 28 100.0% 16 100.0% 10 100.0% 26 100.0% 2 100.0% 4 100.0% 100 100.0%
Shows statistical significance (p = 0.049).
impactions showed significant association with lingual and inferior positioning of the nerve (horizontal = 76.2%; mesioangular = 78.6%; vertical = 71.4%), whereas distoangular impactions showed significant association with the middle and inferior position of the ID nerve canal (100%). Overall, the angulation of impaction was significantly correlated with the ID nerve canal position (p = 0.039).
5. Discussion When the inferior dental nerve is in close proximity to an impaction, the nerve is at a greater risk of injury during removal of the impaction. Surgical removal of such impactions
Please cite this article in press as: Shujaat, S. et al., Pre-operative assessment of relationship between inferior dental nerve canal and mandibular impacted third molar in Saudi population. The Saudi Dental Journal (2014), http://dx.doi.org/10.1016/j.sdentj.2014.03.005
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S. Shujaat et al. Table 2 Bone contact* and position of ID canal. The bold numbers are the significantly high frequency at p < 0.05, by applying chi square test. Bone contact
Contact No contact Total number of cases *
Position of ID canal
Total
Buccal + inferior
Lingual + inferior
Middle + inferior
8 8.3% 0 .0% 8 8.0%
74* 77.1% 0 .0% 74 74.0%
14 14.6% 4* 100.0% 18 18.0%
96 100.0% 4 100.0% 100 100.0%
Shows statistical significance (p = 0.001).
Table 3 Angulation of impaction* and position of ID canal. The bold numbers are the significantly high frequency at p < 0.05, by applying chi square test. Angulation of impaction
Position of ID canal Buccal + inferior
Lingual + inferior
Middle + inferior
Distoangular
0 .0% 2 4.8% 4 14.3% 2 7.1% 8 8.0%
0 .0% 32* 76.2% 22* 78.6% 20* 71.4% 74 74.0%
2* 100.0% 8 19.0% 2 7.1% 6 21.4% 18 18.0%
Horizontal Mesioangular Vertical Total number of cases *
Total
2 100.0% 42 100.0% 28 100.0% 28 100.0% 100 100.0%
Shows statistical significance (p = 0.039).
is much safer when preceded by radiographic imaging to determine the location of the ID canal. Compared with 2-D radiography, 3-D radiography provides more information about the position of the nerve; this knowledge can be used to determine a treatment plan. This study used CBCT scanning, a 3-D radiographic method, to determine the correlation between the ID nerve position and the impaction. We found that the ID canal was most frequently positioned lingually, rather than buccally, to the impacted mandibular third molar. This finding is in accordance with that of other studies that had used volumetric imaging to assess the relationship between the mandibular third molar and the ID canal (De Melo Albert et al., 2006; Ohman et al., 2006; Tantanapornkul et al., 2007). Superior positioning of the ID nerve canal in relation to the impaction was not observed in our sample population. In the majority of cases (74%), the ID nerve canal passed in contact with the lingual plate of the mandible, and no perforation of the lingual plate was observed in any of the cases. Furthermore, only 8% of the impaction cases showed buccal positioning of the ID canal, which is in agreement with other reports that the ID canal has a low prevalence of buccal positioning in relation to the impacted mandibular third molar (Miller et al., 1990; Maegawa et al., 2003). Hassan (2010) studied the pattern of third molar impaction in the western region of Saudi Arabia. The author concluded that majority of the impactions in the mandible were mesioangular (33.4%). In addition, Syed et al. (2012) also found mesioangular impactions of the mandible to be more common (50.75%) in the Saudi population. Our study, however, found
horizontally angulated impactions to be the most common. This may be attributed to the difference in ethnicity of our sample population versus that of the previous studies. The sample population studied by Hassan (2010) involved people living in the western region of Saudi Arabia that is also known as Hijaz, and who represented a global range of ethnic groups. Our sample population belonged to Saudi Arabia’s eastern region, which has a less diverse range of ethnic groups. Our results are in agreement with those of Tantanapornkul et al. (2007), who had also observed a greater prevalence of horizontal impactions (52%) when studying a sample of 85 female patients and 50 male patients between the age of 18 and 74, although our study included more male patients and a narrower age range as well as a different ethnic population. In our study, position B impaction was found to be most common (56%) which is in agreement with Hassan (2010) and Quek et al. (2003). Sex predilection was not considered because of the limited number of female cases (25 of 100). A larger sample size is required to confirm our findings. Further investigation is required to study the sex predilection of these findings among the specific ethnic population of Saudi Arabia’s eastern region. 6. Conclusions Among the population of Saudi Arabia’s eastern region, the ID canal was most frequently approximate to the lingual plate and inferior to the 3rd molar. The most common mandibular impactions were class I, position B, and horizontally angled.
Please cite this article in press as: Shujaat, S. et al., Pre-operative assessment of relationship between inferior dental nerve canal and mandibular impacted third molar in Saudi population. The Saudi Dental Journal (2014), http://dx.doi.org/10.1016/j.sdentj.2014.03.005
Relationship between inferior dental nerve canal and mandibular impacted third molar Funding Funding body: Ministry of higher education, University of Dammam, Deanship of scientific research. Grant No.: 2012124. Ethical approval Ethical approval not required. Conflict of interest No conflict of interest. References Alling, R.D., Alling III, C.C., 1993. Mandibular third molars. Part I. Buccal-occlusal approaches. In: Alling, C.C., IIIIII, Helfrick, J.F., Alling, R.D. (Eds.), . In: Impacted Teeth. WB Saunders, Philadelphia, pp. 149–202. Chu, F.C., Li, T.K., Lui, V.K., Newsome, P.R., Chow, R.L., Cheung, L.K., 2003. Prevalence of impacted teeth and associated pathologies–a radiographic study of the Hong Kong Chinese population. Hong Kong Med. J. 9, 158–163. Dalili, Z., Mahjoub, P., Sigaroudi, A.K., 2011. Comparison between cone beam computed tomography and panoramic radiography in the assessment of the relationship between the mandibular canal and impacted class C mandibular third molars. Dent. Res. J. (Isfahan) 8, 203–210. De Melo Albert, D.G., Gomes, A.C., Do Egito Vasconcelos, B.C., De Oliveira e Silva, E.D., Holanda, G.Z., 2006. Comparison of orthopantomographs and conventional tomography image for assessing the relationship between impacted lower third molars and mandibular canal. J. Oral Maxillofac. Surg. 64, 1030–1037. Flygare, L., Ohman, A., 2008. Preoperative imaging procedures for lower wisdom teeth removal. Clin. Oral Investig. 12, 291–302. Grossi, G.B., Maiorana, C., Garramone, R.A., Borgonovo, A., Creminelli, L., Santoro, F., 2007. Assessing postoperative discomfort after third molar surgery: a prospective study. J. Oral Maxillofac. Surg. 65, 901–917. Hassan, A.H., 2010. Pattern of third molar impaction in Saudi population. Clin. Cosmet. Investig. Dent. 2, 109–113.
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Hillerup, S., 2007. Iatrogenic injury to oral branches of the trigeminal nerve: records of 449 cases. Clin. Oral Investig. 11, 133–142. Leung, Y.Y., Cheung, L.K., 2009. Safety of coronectomy versus excision of wisdom teeth: a randomized controlled trial.. Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endod. 108, 821–827. Maegawa, H., Sano, K., Kitgawa, Y., Ogasawara, T., Miyauchi, K., Sekine, J., Inokuchi, T., 2003. Preoperative assessment of the relationship between the mandibular third molar and mandibular canal by axial computed tomography. Oral Surg. Oral Med. Oral Pathol. 96, 639–646. Miller, C.S., Nummikoski, P.V., Barnett, D.A., Langlais, R.P., 1990. Cross sectional tomography. A diagnostic technique for determining the buccolingual relationship of the impacted mandibular third molars and the inferior alveolar neurovascular bundle. Oral Surg. Oral Med. Oral Pathol. 70, 791–797. Ohman, A., Kivijari, K., Blomback, U., Flygare, L., 2006. Preoperative radiographic evaluation of lower third molars with computed tomography. Dentomaxillofac. Radiol. 35, 30–35. Quek, S.L., Tay, C.K., Tay, K.H., Toh, S.L., Lim, K.C., 2003. Pattern of third molar impaction in a Singapore Chinese population: a retrospective radiographic survey. Int. J. Oral Maxillofac. Surg. 32, 548–552. Rood, J.P., Shehab, B.A., 1990. The radiological prediction of inferior alveolar nerve injury during third molar surgery. Br. J. Oral Maxillofac. Surg. 28, 20–25. Sedaghatfar, M., August, M.A., Dodson, T.B., 2005. Panoramic radiographic findings as predictors of inferior alveolar nerve exposure following third molar extraction. J. Oral Maxillofac. Surg. 63, 3–7. SEDENTEXCT, 2009. Radiation protection: cone beam CT for dental and maxillofacial radiology. Provisional guidelines, (v1.1 May 2009). Available from: (accessed 16 December). Syed, K.B., Kota, Z., Ibrahim, M., Bagi, M.A., Assiri, M.A., 2012. Prevalence of impacted molar teeth among Saudi population in Asir region, Saudi Arabia – a retrospective study of 3 years. J. Int. Oral Health 5, 43–47. Tantanapornkul, W., Okouchi, K., Fujiwara, Y., Yamashiro, M., Maruoka, Y., Ohbayashi, N., Kurabayashi, T., 2007. A comparative study of cone-beam computed tomography in assessing the topographic relationship between the mandibular canal and impacted third molars. Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endod. 103, 253–259. Winter, G.B., 1926. The Principles of Exodontia as Applied to the Impacted Third Molar. American Medical Book Co., St. Louis, MO.
Please cite this article in press as: Shujaat, S. et al., Pre-operative assessment of relationship between inferior dental nerve canal and mandibular impacted third molar in Saudi population. The Saudi Dental Journal (2014), http://dx.doi.org/10.1016/j.sdentj.2014.03.005
