# Digital Evaluation of the Accuracy of Computer-Guided Dental Implant Placement: An In Vitro Study
## 2 Materials and Methods  
Amongst the patients who visited Kyungpook National University Dental Hospital, one patient who was scheduled to undergo surgery of the left mandibular second premolar with an identifiable inferior alveolar nerve was randomly selected. Before placing the implant, we took a preliminary impression and created a diagnostic cast using hard plaster. A 3D model scanner (Freedom HD, Degree of Freedom, Seoul, Korea) was used to scan the diagnostic model and save the patient's intraoral soft tissue surface information in a Surface Tesselation Language (STL) file. The patient's hard-tissue information was obtained using CBCT (Alphard-3030, ASAHI Rogentgen, Kyoto, Japan) and stored as a Digital Imaging and Communication in Medicine (DICOM) file. Twenty partially edentulous resin study models were produced using a 3D printer (ZENITH, Dentis, Daegu, Korea). To replicate the cancellous bone on the mandibular second premolar alveolar bone, the resin on the opposite side of the study models was removed from the surface of the alveolar bone, and the removed portion was hardened by filling it with orthodontic resin (Dentsply Sirona, York, PA, USA) and sawdust. Twenty partially edentulous resin study models were scanned (CS3600, Carestream Dental LLC, Atlanta, GA, USA) and the results were saved as standard tessellation language (STL) files. Pilot experiments were conducted 2 times to determine the sample size, and 8 samples per software were calculated using a power analysis software (G*Power v3.1.9.2, Heinrich Heine University, Dusseldorf, Germany) (actual power = 95.05%; power = 95%; \(\alpha\) = 0.05). To increase power, the number of samples presented in this study was determined to be 10 per software. Using the Deltanine (Daesung, Seoul, Republic of Korea) and R2 gate (Megagen, Daegu, Republic of Korea) implant planning CAD software; the CBCT DICOM file taken before placement, and the intraoral scanning STL file were retrieved and overlapped (Figure 1A), the implant position was planned (Figure 1B), and a computer-assisted implant surgical guide was produced (Figure 1C). Ten implant surgical guides per software were designed and fabricated using a personal 3D printer (\(n\) = 10) (Figure 1D). The implants (TSIII SA (\(\mathcal{O}\) 4.0, L = 10 mm), Osstem, Busan, Korea) were placed by one skilled investigator using the computer-assisted implant surgical guides and one guide surgical kit (Osstem, Busan, Korea). All implant fixture placement procedures were conducted by one skilled investigator. The accuracy of the implant fixture placement angle was evaluated by measuring the angle of the straight line connecting the top and bottom of each implant fixture (Figure 2A). Accuracy of the implant fixture placement depth was confirmed by measuring the length of the straight line connecting the planned implant fixture apex and the placed implant fixture apex (Figure 2B). Figure 1: Process of surgical guide production. (**A**) Overlap between data. (**B**) Implant position plan. (**C**) Virtual surgical guide production. (**D**) Surgical guide production through a 3D printer. To evaluate the apical deviation and angular deviation, 3D inspection software (Geomagic control X, 3D system, Morrisville, NY, USA) was used, and the scan, design, and sleeve indicator STL files were extracted from the implant planning CAD software and overlapped to show the position of the planned implant fixture (Figure 3A). To confirm the position of the actual implant fixture, the study models with implant fixtures were scanned with a connected scan body (Oostem, Busan, Korea) to extract STL files, and were overlapped with the scanned file by connecting the scan body-implant fixture complex (Figure 3B). Precise scan data was obtained by calibration of the 3D scanner, and the operator performed the evaluation by confirming the exact overlapping in the 3D inspection software.