Use of an intraoperative navigation system for retrieving a broken dental instrument in the mandible: a case report

Endodontic files, burs, and occasionally, other dental instruments tend to break off during surgical procedures because of defective manufacturing, stress, fatigue, rust, or poor handling [11]. The diameter, length, and position of the fragment within the root canal can all influence its nonsurgical or surgical removal. Periapical surgery in the mandibular premolar and molar areas presents certain technical difficulties regarding the proximity of the apices to the mandibular canal [12]. Further, it is essential to minimize the surgical invasion to protect the surrounding healthy tissue during foreign body removal from the jaw [8]. Therefore, as in the present case, it was necessary to carefully remove the instrument that migrated into the jawbone. Multiple methods of localizing and removing broken dental instruments have been described, including plain film radiography, fluoroscopy, image intensifiers, reference markers, and even magnets [13–15].

In this case, an intraoperative navigation system was used to locate the broken dental fragment and aid in its removal. Navigation was initially developed for stereotactic interventions in neurosurgery but has been recently introduced to other specialties. The use of navigation systems to retrieve foreign bodies during craniomaxillofacial surgery has been previously reported [16, 17].

Image-guided systems can improve preoperative planning and provide high-degree intraoperative accuracy and precision. However, the navigational accuracy is limited by the system used, the method of obtaining the imaging data, and syncing the imaging data with the patient’s actual position during the procedure. Some limitations of the currently available image-guided systems should be considered because most were originally developed for neurosurgical purposes [18]. Therefore, care must be ensured when performing oral-maxillofacial surgery, particularly in the mandible region, as it is not approved for use in this region because of the constant movement of this area. However, if the mandible were to be held in an identical position during image acquisition and the surgical procedure, then it can be assumed that all structures within the image would be fixed in an identical position, thereby enabling the use of the navigation system in its intended fashion. It was difficult to use navigation surgery in the mandible as the mobile nature of the mandible complicates its synchronization with the preoperative imaging data during surgery.

Furthermore, there are currently three possible solutions for the application of navigation in the mandible. The first approach is to mount a dynamic reference frame to the mandible that enables continuous tracking of the mandibular movement and its position during the surgery [19]. This method enables the direct tracking of the mandible via a tooth-mounted sensor frame and tooth-supported fiducial markers useful for mandibular navigation. Using this approach, the mandible is allowed to freely move during the surgery. However, the fixation of the reference requires a special procedure and is more time-consuming and complicated. In addition, the reference frame may influence the operation, possibly losing its position. The second method is an intermaxillary fixation. By maintaining an immobile intercuspal position, mandibular synchronization can be intraoperatively ensured [20]. However, this approach considerably limits access to the surgical site and is not feasible for transoral surgery. The third strategy is to position the mandible in a reproducible posture or a defined position against the maxilla, using an occlusion splint. Although artificial fixation of the mandible via a template appears to introduce no additional error, this strategy is sensitive to the relative movement of the mandible, which in turn reduces the accuracy of the navigation system [21].

In the present case, a navigation system for the mandibular lesion was further beneficial in determining the accurate location of the object and provided us, the oral-maxillofacial surgeons, with intraoperative guidance for the safe and reliable use of an individual occlusion splint. This splint, which could be easily made from a simple impression, used each tooth of the maxilla and mandible as a fixed source. Therefore, it is possible to reproduce the mandibular position for various mandibular movements. This method also has the advantages of improving surgical and oromandibular anatomical accuracy, manifesting precise individual dental root positions, minimizing surgical invasiveness, and reducing operation time using an easily constructed splint.