a 34-year - old male patient with no systemic conditions or any metabolic disorders presented with a previously taken routine panoramic radiograph showing signs of a close relationship between the left ltm and the mandibular canal , such as darkening and deflection of the roots , and narrowing and diversion of the mandibular canal . this initial radiographic analysis led us to suggest that the patient undergo a cbct scan , which he did . a cbct machine ( i - cat classic , image sciences international , hatfield , pa , usa ) was used and configured with the following diagnostic protocol : 0.25 mm voxel , 120 kvp , 8 ma , and field of view ( fov ) 16 cm in diameter and 6 cm in height . from the scan , three - dimensional ( 3d ) reconstructed images were rendered using dentalslice ( bioparts , so paulo , brazil ) software . on these preoperative cbct images , the vertical impaction of the left ltm was confirmed and classified as level b(ltm partially buried in the bone ) , according to pell and gregory 's classification.7 additionally , a cyst - like lesion was found associated with its crown . cross - sectional cbct images showed that the mandibular canal came into contact with a root curvature and the lingual plate ( fig . because of its intimate contact with the mandibular canal , it could be foreseen that ltm surgical extraction would increase the risk of ian injury . therefore , we decided to use an orthodontic miniscrew to extrude the ltm prior to its surgical removal . the risks and benefits of the available treatment options were explained to the patient , and he decided in favor of using the miniscrew to extrude the ltm and provided informed consent . the first step of the treatment was to perform an initial surgical procedure to remove the bone around the occlusal and buccal surfaces of the ltm crown by using a piezoelectric surgical unit ( piezosonic , driller , so paulo , sp , brazil ) and to remove the cyst lesion associated with this crown . after an 8 week healing period , there was gingival recession , and part of the ltm occlusal surface was seen in the clinical examination . accordingly , an orthodontic separator was installed to avoid ltm impaction caused by contact with the adjacent second molar . thus , an orthodontic miniscrew ( 8 mm in length and 1.5 mm in diameter ; morelli , so paulo , brazil ) was inserted into the buccal cortex between the first and second antagonist maxillary molars . elastic traction was applied between the miniscrew and the orthodontic hook installed on the ltm occlusal surface with two orthodontic elastics . during the first week the patient reported a light " pins and needles " sensation in part of the tongue , lasting 3 days . at 3 weeks after miniscrew installation , the roots did not fracture , and the ltm was easily removed from the alveolar socket . during surgery the root curvature , found to be in contact with the mandibular canal , was observed by examining the ltm after it was extracted and cleaned ( fig . the patient stated no significant discomfort during the ltm extrusion period , or during the extraction surgery . additionally , no adjacent mandibular second molar loosening or displacement was observed during the entire treatment time . in some studies on ltm extraction , panoramic radiography has been used as an initial examination to check the proximity between ltm roots and the ian.4,5,6 however , it does not offer cross - sectional images of the surgery site . computed tomographic ( ct ) images have been described as essential tools to diagnose the contact between ltm and the mandibular canal three - dimensionally.8 these findings are in accordance with what was observed in the present case report , insofar as cbct imaging detected the intimate contact between root curvatures and the ian , confirmed by the ltm shape observed after its extraction . in the present case , pre- and postoperative cbct scans were necessary to confirm the detachment of the left ltm roots from the mandibular canal . compared with other ct methods , cbct offers advantages such as reduced effective radiation doses , shorter acquisition scan time , easier imaging , and lower costs.9 in addition , an fov of 6 cm in height was used to restrain the scan to the mandible area . for this type of scan in standard resolution , the effective doses emitted by the cbct device used in this study were 23.9 sv and 96.2 sv ( using both the 1990 and the recently approved 2007 international commission on radiological protection recommended tissue weighting factors , respectively).10 in order to avoid ian injury risks during ltm extraction , different orthodontic approaches have been developed . 4,5 bonetti et al4 demonstrated a technique of complex orthodontic appliances used in the inferior arch and required to achieve the anchorage needed to extrude ltm , which was the main disadvantage of their technique.4 on the other hand , two other studies on an orthodontic aid to extrude ltm described a simpler technique to make ltm surgical removal easier , and observed that this technique could also be important to improve the periodontal status of the neighboring sites.11 additionally , these studies reported that a minimum period of 3 months was required to achieve satisfactory orthodontic extrusion of the ltm.4,11 another article on orthodontic - aided extraction of a vertically impacted ltm showed a technique of bracketing the antagonist maxillary molars to achieve the anchorage required to extrude the ltm using elastic traction.5 according to their study , a mean period of 35 days was required to complete the orthodontic ltm traction . this finding supported the present case , which also used elastic traction , resulting in an orthodontic treatment time of 5 weeks ( 2 weeks with the orthodontic separator , and 3 weeks with the mini implant with elastic traction ) to obtain ltm extrusion . however , in their study , an orthodontic bracket with a hook was placed on the ltm buccal surface to establish the orthodontic elastic,5 whereas in the present case , the hook was installed on the ltm occlusal surface , leading to less contact with the patient 's cheek mucosa . furthermore , in the present case , two elastics were used , thus reducing traction time . on the other hand , an initial surgical procedure was required to remove the bone around the occlusal and buccal surfaces of the ltm crown by using a piezoelectric surgical unit , which has recently been described as an effective method of significantly reducing surgical time and avoiding postoperative complications , such as facial swelling and trismus , in cases of third molar surgery.12 as a first - time application , park et al6 used an orthodontic miniscrew placed in the mandible , near the lower first molar , to offer the anchorage needed to extrude the ltm . in their study , cbct cross - sectional images were used to confirm the contact between the ltm roots and the mandibular canal , thus supporting the role of cbct imaging , as described in the present case . on the other hand , passive bracketing was also used in their study , leading to variable degrees of patient discomfort during the traction periods , contrasting with the findings of the present case report , in which no significant discomfort during orthodontic traction was reported by the patient who was analyzed . in conclusion , the present report demonstrated the role of the miniscrew in avoiding ian injury in cases of vertically impacted ltm extraction . our report further supported the usefulness of cbct imaging to diagnose the initial contact between the mandibular canal and the ltm , and their later detachment during the course of the treatment . therefore , enhanced visualization of the mandibular canal location and its relationship with the ltm roots could improve pre - treatment and surgical planning .
one of the most common oral surgical procedures is the extraction of the lower third molar ( ltm ) . 
 postoperative complications such as paresthesia due to inferior alveolar nerve ( ian ) injury are commonly observed in cases of horizontal and vertical impaction . 
 the present report discusses a case of a vertically impacted ltm associated with a dentigerous cyst . 
 an intimate contact between the ltm roots and the mandibular canal was observed on a panoramic radiograph and confirmed with cone - beam computed tomographic ( cbct ) cross - sectional cuts . 
 an orthodontic miniscrew was then used to extrude the ltm prior to its surgical removal in order to avoid the risk of inferior alveolar nerve injury . 
 cbct imaging follow - up confirmed the success of the ltm orthodontic extrusion .