Observation of retromolar canals on cone beam computed tomography
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ORIGINAL ARTICLE
Observation of retromolar canals on cone beam computed tomography Yunwen Hou1 · Guanying Feng1 · Wen Lin1 · Ruixia Wang1 · Hua Yuan1,2 Received: 17 August 2019 / Accepted: 4 November 2019 © Japanese Society for Oral and Maxillofacial Radiology and Springer Nature Singapore Pte Ltd. 2019
Abstract Objective To evaluate the incidence and location of retromolar canal (RMC) in an eastern Chinese population using cone beam computed tomography (CBCT) images. Methods Six hundred and fifty-seven patients (276 males and 381 females, 19–49 years old) from east China were enrolled. Both right and left sides of the mandible were examined (n = 1314). Two-dimensional (2D) images of various planes in the mandibular ramus region and reconstructed three-dimensional (3D) images were reviewed. The course of the RMC and the location of the retromolar foramina (RMF) were observed. Results Retromolar canal (RMC) was observed in 25.9% (170/657) of patients and 15.7% of sides (206/1314). 20.4% patients had unilateral RMC (134/657) and 5.5% had bilaterally RMC (36/657). Most RMC are horizontally curved course (Type B, 45.6%), followed by vertically curved course (Type A, 44.2%). Type C RMC, which run independently from separate foramina in the mandibular ramus, were relatively rare (10.2%). The distance from the middle of the RMF to the distal end of the second molar ranged from 4.56 to 24.01 mm and the mean distance was 11.97 mm. Conclusion RMC is not a rare anatomical structure in the eastern Chinese population. CBCT should be applied as a diagnostic tool to provide detailed information involving the retromolar area. Keywords Cone beam CT(CBCT) · Retromolar canal (RMC) · Retromolar foramina (RMF) · Incidence · Oral surgery
Introduction Abundant research achievements of morphology of the mandible and its anatomical variations have been described to affect the development of clinical oral surgery plan. Retromolar foramina (RMF), the aperture of the retromolar canal (RMC), may be discovered on the bone surface in the retromolar triangle region. Anatomical dissection found Yunwen Hou and Guanying Feng contributed equally to this work. * Ruixia Wang [email protected] * Hua Yuan [email protected] 1
Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, 140 Hanzhong Rd., Nanjing 210029, People’s Republic of China
Department of Oral and Maxillofacial Surgery, Affiliated Hospital of Stomatology, Nanjing Medical University, Nanjing, China
2
that inferior alveolar neurovascular bundles go through the RMC [1]. It makes the surgical procedures involving the retromolar regions more complicated, such as dental implant surgery, impacted third molar extraction and sagittal split ramus osteotomy. RMC has been described as a subtype of the bifid mandibular canal called the ‘retromolar type’ [2]. Chavez-Lomeli et al. suggested that bifid and trifid mandibular canals occurred as a result of the incomplete fusion of three distinct inferior dental nerve (incisors, primary and permanent molars) during embryonic
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