Submit Manuscript | http://medcraveonline.com Abbreviations: IAC, inferior alveolar canal; CT, computed tomography; CBCT. cone beam computed tomography; CEJ, cement enamel junction Introduction Dentigerous cyst is the most common developmental odontogenic cyst, which is believed to arise from the enlargement of the follicular space around the crown of impacted or unerupted tooth. In 1853, the term dentigerous cyst was coined by Paget. The literal meaning of dentigerous is “tooth bearing”. 5 One of the theories that explain the pathogeneses of this cyst is the accumulation of fuid between the unerupted tooth and the reduced enamel epithelium. The incidence of DC is two times more in males than females, where 70% occurs in the mandible and 30% in the maxilla. 5 Although a DC may be associated with any unerupted tooth but the mandibular third molar and maxillary canine are the most involved followed by mandibular premolar and maxillary third molar. 5 Dentigerous cyst is discovered by routine radiographs or when radiographs are taken to investigate the failure of a tooth eruption, a missing tooth or misalignment. No pain or discomfort is present with the cyst unless its secondary infected. Radiographically, the cyst appear well defned (unless infected), unilocular radiolucency associated with the crown of unerupted tooth. The involved tooth can be displaced away from its path of eruption. While a normal follicular space is 3-4mm, a DC is suspected when the space is more than 5mm. 1 The classical treatment of DC is enucleation and extraction of the involved tooth. 6 The present paper reports an additional case of DC with an unusual behavior of the IAC. Case report A 55-years-old male presented to our department, with a chief complain of severe pain in the mandibular left molar region. Past medical and dental history revealed that approximately one year ago the patient complained of pain at the same region, where defective endodontic treatment was performed on tooth #36 in a private dental clinic but no permanent relief was obtained. No trauma history was reported. On extra oral inspection, there was a swelling on the lower left side. Intraoral examination showed obliteration of the left labial vestibule compared to the right premolar molar area. Teeth #36-37 showed no pain on percussion. Absence of the wisdom tooth #38 was noticed. The panoramic examination revealed a well-defned, corticated unilocular radiolucent area associated with an inverted tooth #38, located near the angle of the mandible, occupying the whole height of the ramus from the upper border of the mandible till the lower border, with a marked thinning of the borders. The inferior alveolar canal (IAC) is remarkably non visible at the region of the lesion (Figure 1). A CBCT was performed to identify the extension of the lesion and its relation with the IAC. Panoramic reconstruction (Figure 2A & 2B) shows a well-defned low density unilocular lesion circumscribing the crown of tooth #38 located vertically from the mid ramus extending below the level of the IAC, horizontally it extend from the apical third of the mesial root of #37 till the mid portion of the ascending ramus. Axial cuts (Figure 3) show expansion of the alveolar process and thinning and interruption of both lingual and buccal cortical plates. The roots of #37 show no resorption. The lesion is attached to tooth #38 at the level of the CEJ (Figure 4). The ectopic position of the IAC is also seen very clearly in the maximum intensity projection panoramic reconstruction (Figure 2B) and in the cross sectional images which shows the canal within the lesion (Figure 5A & 5B). After clinical and radiographic examination, a provisional diagnosis of dentigerous cyst was made; however, kerato cyst odontogenic tumor, amleloblastoma, ameloblastic fbroma were also considered in the differential diagnosis. Keratocyst don’t expand the bone to the same degree as presented here and attachment to the teeth will be more apically. Ameloblastic fbroma usually occurs in young patients which is not the case. Ameloblastoma would have presented internal septa if big in size as in this case. The most probable diagnosis is dentigerous cyst. The operation was performed under local anesthesia. Incision was made followed by raising a full thickness buccal mucoperiosteal fap. The lesion was then identifed and the canal was viewed and confrmed, as seen on CBCT, to be passing in the center of the lesion. J Dent Health Oral Disord Ther. 2015;2(2):53‒55. 53 ©2015 Moussa et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and build upon your work non-commercially. Unusual behavior of the mandibular canal associated to a dentigerous cyst Volume 2 Issue 2 - 2015 Sara Moussa, Sayde Sokhn, Ibrahim Nasseh Department of Oral and Maxillo facial Imaging-School of Dentistry, Lebanese University, Lebanon Correspondence: Ibrahim Nasseh, Department of Oral and Maxillofacial Imaging-School of Dentistry, Lebanese University, Beirut, Lebanon, Tel 9613302232, Email Received: November 22, 2014 | Published: April 14, 2015 Abstract A dentigerous cyst is an epithelial-lined developmental odontogenic cavity that encloses the crown of an unerupted tooth at the cemento-enamel junction (CEJ). Dentigerous cysts are the second most common odontogenic cysts after radicular cysts, accounting for approximately 24% of all true cysts in the jaws. 1–3 They are usually solitary in occurrence. The condition is frequently seen with the permanent dentition, usually associated with impacted mandibular third molars and maxillary canines. Pain, swelling, and facial asymmetry are occasionally seen; however, they are usually asymptomatic and observed during radiographic examination. 4 This report describes a rare case of a dentigerous cyst associated with an impacted mandibular left 3rd molar with an ectopic position of the inferior alveolar canal (IAC). Keywords: dentigerous cyst, ectopic tooth, third molar Journal of Dental Health Oral Disorders & Terapy Case Report Open Access