Background and objectives: The retromolar canal is an anatomical variant that needs consideration in local anesthesia and surgical procedures involving the retromolar area. Complications such as local anesthetic insufficiency, a sensory deficit, hemorrhage and traumatic neuroma may arise in the absence of recognition of these variants. The aim of this study is to determine the prevalence and course of retromolar canal in the Iranian population. Methods: This study is a descriptive cross sectional study. The cross sectional sagittal and three dimensional images from volumetric CBCT. data of 270 patients were reconstructed using on demand imaging analysis software. Retromolar canals were classified into two types according to the courses. The width and location (distance from the third molar) of retromolar canals were evaluated. Results were analyzed with SPSS 20 software and were assessed using the t_test and chi_square test. Results: Retromolar canal was observed in 9/25 % of patients. The mean width of the retromolar foramen was 1/43 mm, and the mean distance from anterior border of retromolar foramen to the distal CEJ of the second molar was 13/33 mm. Conclusion: The prevalence of retromolar canals in the Iranian population was lower than that was reported in previous studies. It can be observed in 9/25 % of Iranian patients. Damage to the retromolar canal may be unavoidable during surgical procedures may result in paresthesia, excessive bleeding, postoperative hematoma, or traumatic neuroma. Therefore, the clinician must pay particular attention to the identification of a retromolar canal by preoperative radiographic examination and additional CBCT scanning is recommended.

Background and objectives: An effective factor in choosing the correct place for the dental implant and performing surgical procedures in the posterior regions of mandible is the position of the mandibular canal. Failure to consider this important landmark will damage the inferior alveolar nerve. Considering the widespread use of implants and the precision of the images obtained from CBCT. The aim of this study was to evaluate the rate of visibility of mandibular canal by CBCT in order to prevent damage to the inferior alveolar nerves and arteries. Methods: In this study, 90 archived CBCT images of patients from a private center of oral and maxillofacial radiology in Yazd that was taken by technician was evaluated during 2012-2019. The visibility of the mandibular canal in reconstructed panoramic images of CBCT was assessed by a dentistry student trained by the maxillofacial radiologist in five areas in different thicknesses on each side. Data were analyzed using SPSS 17 software. Chi-square, and correlation coefficient were done. Results: In total, in 53.38% of CBCT images both borders of mandibular canal were visible, in 17.95%, only one border was visible (difficult observation) and in 28.7% of cases, lack of visibility of mandibular canal was reported. There was no significant difference between sex, age, side and thickness in mandibular canal visibility (P >0.05). Conclusion: In more than half of CBCT images, both borders were clearly visible in both right and left sides; therefore we can conclude that CBCT is a useful tool for the observation of mandibular canal before surgeries.