# Augmented Reality-Assisted Surgical Exposure of an Impacted Tooth: A Pilot Study
## 2 Materials and Methods
Two 3D files were imported into CAD-CAM design software (Ceramill Mind; Amann Girrbach AG, Koblach, Austria) for superimposition. Matching was easily achieved by marking six common points (Figure 6) and combining files. For this alignment, the \"Best fit matching\" function of the software was used, which utilizes algorithms to perform the alignment of the two meshes. Six areas of the teeth were selected where edges were present, as recommended by the software manufacturer. A 3D file of the anterior sector of the intraoral scan plus the endosseous position of the crown of the impacted canine was exported (Figure 7). A full HD video camera was positioned in front of the patient's mouth, connected via an HDMI cable to a laptop. The AR software was started (VisionLib; Visometry, Darmstadt, Germany) and the video camera was designated as an input source. The camera calibration was then performed using a chessboard pattern (Figure 8). The camera calibration was essential for the impact on tracking quality and stability. A correct calibration improves the superimposition quality of 3D content. Calibration was performed using the pattern of a special graphic chessboard printed on A4 format paper. The chessboard was placed 40 cm away from the camera. After starting the calibration  
Figure 6: Application of landmarks for the superimposition process in CAD-CAM software. Points 1, 2, 3, 4, 5, 6 represent the points marked to perform the matching (Numero punti: Number of points; Traccia punto su ogg. in mov: Track point on moving object). Figure 7: A three-dimensional final model containing the intraoral scan end of the endosseous position of the crown of the impacted teeth. on the software, 300 images were collected. All corners of the chessboard were visible in the camera image during calibration. For performing the correct calibration, the pattern should not be distorted. To avoid distortion and consequent calibration alteration, the chessboard printed on A4 format paper was glued onto a rigid plastic panel that allowed its use without bending the pattern. The 3D file was uploaded to the software. The patient's lips were spread apart with a mouth opener, and the assistant, who was trained in using the software, aligned the file image onto the projection of the patient's teeth (Figure 9). The software recognises the edges of files in images transmitted from the camera and the border colour changes. From the red border, the outline turns green, signalling the correct overlapping of the object to the video images. Figure 8: The graphical user interface of AR software: preoperative calibration. Figure 9: Setup of the Augmented Reality in the operating room. By observing real-time alignments on the PC screen, it was possible to evaluate the exact position of the canine crown and make markers on the gum to determine the incision lines and the osteotomy to perform the surgical exposure (Figure 10). Margins of 3 mm from the canine crown were generally maintained for flap design or for the benefit of optimal direct vision to perform the osteotomy. The tooth was exposed by removing the buccal bone cortex and, after obtaining hemostasis with gauze soaked in tranexamic acid, the eyelet was bonded with composite (Figure 11). After successful wound healing, the eyelet was connected with a wire anchored to the trans-palatal bar tied on the first upper molars and solidarised on the palate with mini-screws to perform the orthodontic traction and bring the impacted canine into the dental arch. Figure 11: Surgical exposure and bonding of the impacted canine. Figure 2:0 Pre-operatory evaluation in Augmented Reality view after alignment of the digital model in the operatory field.