Imaging Sci Dent.  2019 Sep;49(3):213-218. 10.5624/isd.2019.49.3.213.

Diversion of the mandibular canal: Is it the best predictor of inferior alveolar nerve damage during mandibular third molar surgery on panoramic radiographs?

• Tassoker M

• KMID: 2458370
• DOI: http://doi.org/10.5624/isd.2019.49.3.213

Abstract

PURPOSE
The aim of this study was to evaluate the relationship between the mandibular canal and impacted mandibular third molars using cone-beam computed tomography (CBCT) and to compare the CBCT findings with signs on panoramic radiographs (PRs).
MATERIALS AND METHODS
This retrospective study consisted of 200 mandibular third molars from 200 patients who showed a close relationship between the mandibular canal and impacted third molars on PRs and were referred for a CBCT examination of the position of the mandibular canal. The sample consisted of 124 females and 76 males, with ages ranging from 18 to 47 years (mean, 25.75±6.15 years). PRs were evaluated for interruption of the mandibular canal wall, darkening of the roots, diversion of the mandibular canal, and narrowing of the mandibular canal. Correlations between the PR and CBCT findings were statistically analyzed.
RESULTS
In total, 146 cases (73%) showed an absence of canal cortication between the mandibular canal and impacted third molar on CBCT images. A statistically significant relationship was found between CBCT and PR findings (P<0.05). The absence of canal cortication on CBCT images was most frequently accompanied by the PR sign of diversion of the mandibular canal (96%) and least frequently by interruption of the mandibular canal wall (65%).
CONCLUSION
CBCT examinations are highly recommended when diversion of the mandibular canal is observed on PR images to reduce the risk of mandibular nerve injury, and this sign appears to be more relevant than other PR signs.

Keyword

Mandibular Nerve; Tooth, Impacted; Cone-Beam Computed Tomography; Radiography, Panoramic

MeSH Terms

Cone-Beam Computed Tomography
Female
Humans
Male
Mandibular Nerve*
Molar, Third*
Radiography, Panoramic
Retrospective Studies
Tooth, Impacted

Figure

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  Fig. 1 Cropped panoramic images show darkening of the roots (A), diversion of mandibular canal (B), interruption of the mandibular canal wall (C), and narrowing of the mandibular canal (D).

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  Fig. 2 Lingually positioned inferior alveolar canal without cortication.

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  Fig. 3 Inferiorly located inferior alveolar canal with cortication.

Reference

1. Hasegawa T, Ri S, Shigeta T, Akashi M, Imai Y, Kakei Y, et al. Risk factors associated with inferior alveolar nerve injury after extraction of the mandibular third molar - a comparative study of preoperative images by panoramic radiography and computed tomography. Int J Oral Maxillofac Surg. 2013; 42:843–851.

2. Hasani A, Ahmadi Moshtaghin F, Roohi P, Rakhshan V. Diagnostic value of cone beam computed tomography and panoramic radiography in predicting mandibular nerve exposure during third molar surgery. Int J Oral Maxillofac Surg. 2017; 46:230–235.

3. Szalma J, Lempel E, Jeges S, Szabó G, Olasz L. The prognostic value of panoramic radiography of inferior alveolar nerve damage after mandibular third molar removal: retrospective study of 400 cases. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2010; 109:294–302.

4. Ghai S, Choudhury S. Role of panoramic imaging and cone beam CT for assessment of inferior alveolar nerve exposure and subsequent paresthesia following removal of impacted mandibular third molar. J Maxillofac Oral Surg. 2018; 17:242–247.

5. Korkmaz YT, Kayıpmaz S, Senel FC, Atasoy KT, Gumrukcu Z. Does additional cone beam computed tomography decrease the risk of inferior alveolar nerve injury in high-risk cases undergoing third molar surgery? Does CBCT decrease the risk of IAN injury. Int J Oral Maxillofac Surg. 2017; 46:628–635.

6. Clé-Ovejero A, Sánchez-Torres A, Camps-Font O, Gay-Escoda C, Figueiredo R, Valmaseda-Castellón E. Does 3-dimensional imaging of the third molar reduce the risk of experiencing inferior alveolar nerve injury owing to extraction?: A meta-analysis. J Am Dent Assoc. 2017; 148:575–583.

7. Tachinami H, Tomihara K, Fujiwara K, Nakamori K, Noguchi M. Combined preoperative measurement of three inferior alveolar canal factors using computed tomography predicts the risk of inferior alveolar nerve injury during lower third molar extraction. Int J Oral Maxillofac Surg. 2017; 46:1479–1483.

8. Elkhateeb SM, Awad SS. Accuracy of panoramic radiographic predictor signs in the assessment of proximity of impacted third molars with the mandibular canal. J Taibah Univ Med Sci. 2018; 13:254–261.

9. Neves FS, Souza TC, Almeida SM, Haiter-Neto F, Freitas DQ, Bóscolo FN. Correlation of panoramic radiography and cone beam CT findings in the assessment of the relationship between impacted mandibular third molars and the mandibular canal. Dentomaxillofac Radiol. 2012; 41:553–557.

10. Tantanapornkul W, Okouchi K, Fujiwara Y, Yamashiro M, Maruoka Y, Ohbayashi N, et al. A comparative study of cone-beam computed tomography and conventional panoramic radiography in assessing the topographic relationship between the mandibular canal and impacted third molars. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2007; 103:253–259.

11. Şekerci AE, Şişman Y. Comparison between panoramic radiography and cone-beam computed tomography findings for assessment of the relationship between impacted mandibular third molars and the mandibular canal. Oral Radiol. 2014; 30:170–178.

12. Shiratori K, Nakamori K, Ueda M, Sonoda T, Dehari H. Assessment of the shape of the inferior alveolar canal as a marker for increased risk of injury to the inferior alveolar nerve at third molar surgery: a prospective study. J Oral Maxillofac Surg. 2013; 71:2012–2019.

13. Jung YH, Nah KS, Cho BH. Correlation of panoramic radiographs and cone beam computed tomography in the assessment of a superimposed relationship between the mandibular canal and impacted third molars. Imaging Sci Dent. 2012; 42:121–127.

14. Sedaghatfar M, August MA, Dodson TB. Panoramic radiographic findings as predictors of inferior alveolar nerve exposure following third molar extraction. J Oral Maxillofac Surg. 2005; 63:3–7.

15. Ghaeminia H, Meijer GJ, Soehardi A, Borstlap WA, Mulder J, Bergé SJ. Position of the impacted third molar in relation to the mandibular canal. Diagnostic accuracy of cone beam computed tomography compared with panoramic radiography. Int J Oral Maxillofac Surg. 2009; 38:964–971.

16. Xu GZ, Yang C, Fan XD, Yu CQ, Cai XY, Wang Y, et al. Anatomic relationship between impacted third mandibular molar and the mandibular canal as the risk factor of inferior alveolar nerve injury. Br J Oral Maxillofac Surg. 2013; 51:e215–e219.