# Augmented Reality-Assisted Surgical Exposure of an Impacted Tooth: A Pilot Study
## 2 Materials and Methods  
A 27-year-old male patient visited our clinic for a resolution of his malocclusion. Following objective examination and collection of radiographs, photographs, and CBCT, the patient was diagnosed with class II malocclusion, a deep bite with dental inclusions of the upper right canine. The possibility, not without risks, of removing and supporting the right upper impacted canine in the arch was assessed. The operational difficulty was due to the deep retention of the tooth in question (vestibular side) and its contiguous relationship with the roots of the adjacent tooth. The patient was informed of all the risks of close proximity (including tooth ankylosis and resorption of the roots of the incisors), and an agreement was reached with the patient to proceed with this treatment. The designated operating procedure involves aligning the canine in the upper arch to re-establish adequate occlusion and aesthetics. This was possible through traction of the canine after surgical exposure, which was performed by supporting a bone conduction screw trans-palatal bar. Skeletal anchorage by palatal mini-screws was chosen for dissipation of the reaction counterforces on bone bases, minimising possible unwanted dental effects. Computer-Aided Design and Computer-Aided Manufacturing (CAD-CAM) technology was used to plan the site and size of the mini-screws to be inserted into the palate and to build a surgical template for insertion (Figure 1). After insertion of the two mini-screws and the trans-palatal bar using a printed tooth-supported drill guide (Figure 2), we proceeded with surgical exposure of the canine to perform the tooth traction. In the vestibular-apical zone of the lateral incisor, the impacted canine was not clinically detectable via palpation. To have clinical certainty about the canine position, it was decided to use AR by superimposing the surgical site and the operator's visual field with CBCT information. This technology aims both to provide the design of the flap for surgical access directly on the patient and to minimise the error of the osteotomy point to avoid iatrogenic damage to the adjacent teeth roots. The first step towards visualising the patient's impacted tooth in AR was to create a 3D file that the software could easily detect. It was decided to use the patient's teeth as software identification markers. The maxillary arch was scanned using an optical intraoral scanner (TRIOS 4; 3 Shape A/S, Copenhagen, Denmark). The file was exported in Polygon File Format (PLY). Using open-source CAD software (Meshmixer, Autodesk, Inc., San Francisco, CA, USA), the part of the upper arch from the first premolar to the other premolars was selected. The anterior sector's teeth, incisal edges, and cusps were the anatomical markers required to match the patient's mouth and perform object recognition (Figure 3). Figure 1: Digital project of the trans-palatal bar and mini-screws. Figure 2: Intraoral view after insertion of computer-guided mini-screws. To this file, which corresponded faithfully to reality, we added the digital information required: the position of the impacted crown of the canine. From the maxillary CBCT, Digital Imaging and Communications in Medicine (DICOM) files were imported into open-source medical software (InVesalius, CTI, Campinas, Brazil) to segment and export an STL file of the area of interest (Figure 4). Only the six anterior teeth and the crown of the impacted tooth were selected from the 3D file (Figure 5). Figure 4: Three-dimensional imaging reconstructions based on a sequence of two-dimensional DICOM files acquired with cone beam computer tomography (Carica Dati: Upload Data; Seleziona l’area interessata: Select the interested area; Configura la superficie 3D: Configure 3D surface; Strato assiale: Axial plane; Strato aggittale: Sagittal plane; Strato coronale: Coronal plane; Sx: Left; Dx: Right). Figure 5: Edited 3D model exported from the 3D reconstruction software. Figure 3: Edited optical intraoral scan.