# Augmented Reality-Assisted Surgical Exposure of an Impacted Tooth: A Pilot Study
## 4 Discussion  
In this pilot study, there was an impacted canine and, due to orthodontic needs, surgical exposure was necessary to align it to the upper arch. From the three-dimensional analysis of the CBCT, the impacted canine was in contact with the vestibular part of the root of the lateral incisor and the palatine part of the root of the central incisor [12; 13; 14]. Considering the apical position of the crown and contact with the adjacent roots, accurate surgical exposure was essential to avoid iatrogenic damage  
Figure 13: Interruption of object tracking and consequent displacement of the 3D model caused by the patient’s movement. to the adjacent teeth [14; 15; 16]. Augmented Reality was, therefore, used to minimise the possibility of surgical error. Through software that uses algorithms for object recognition and object tracking, real-time superimposition of the 3D file image onto the video frame acquired by the camera positioned in front of the patient's mouth was possible. The final 3D model was created by combining the six anterior teeth taken from the intraoral scan with the same teeth plus the included canine taken from the CBCT segmentation. The 3D file was uploaded into the software and manually positioned onto the image of the patient's teeth. Model tracking was straightforward to set up without prior registration of targets or surroundings. Software model tracking was enabled to use 3D files and their anatomical markers, as they are references for the patients. When a 3D file that contains other digital information is inserted (in this case, the impacted canine and the roots of the adjacent teeth), the software is better able to superimpose the object onto video reality. Any failure to align the 3D file with the video frame was marked by the red margin. For this reason, the image of the impacted canine was reduced to just the vestibular portion of the crown to optimise recognition of the file by the software. Using dental-supported extraoral templates could aid current software in the recognition and tracking phases. A preclinical study on the phantom, with the support of an extra-oral template used as a recognition marker, reports successful and encouraging preliminary results performed to evaluate the visualisation of a plan for performing maxillofacial surgery [17]. The patient's teeth were tracked directly and standard digital RGB cameras were adopted, with visible light as a source of information. The presence of an assistant who takes care of repositioning the file and restarting the registration every time the software loses tracking, either after fast displacement of the patient's head or if an instrument is placed between the teeth and the camera lens, is required, which makes it challenging to use Augmented Reality during surgery. Reproducing images on the PC screen as an AR display type could make the image of reality less ergonomic for the clinician. The surgeon must turn his gaze from the patient's mouth to the PC to view the AR image. Smart glasses with Video-See-Through (VST) mode and Optical See-Through (OST) mode could be an advantage for using this technology so that the operator can avoid turning to the screen to see the software image [18; 19; 20]. However, direct projection within the field of view with smart glasses could be uncomfortable; the weight and bulk of the glasses currently on the market could alter the surgeon's comfort. In a recent review documenting AR's use in dentistry, the authors collected some adverse information on the time it takes. Three out of six dentits reported an increase of at least 1 h to perform AR [21]. The preparation time of digital files clearly varies depending on numerous variables, the software used, and the references chosen to perform object recognition. However, preparing the files for this case report was quick and easy; the time needed to create the uploaded file in the Augmented Reality software was around 15 min.