# Accuracy of Different Head Movements of Intraoral Scanner in Full Arch of Both Maxilla and Mandible
## 4 Discussion  
The results rejected the null hypothesis. This one-way scan path in the present study showed the significant occlusal deviations of the maxilla at left central incisor, left first premolar, left second molar, and right second molar among most head movements except the 8-figure movement. The mandibular occlusal deviation was higher at the bilateral posterior segment among most head movements, except for the 8-figure movement and A-P. B-L deviations of the maxilla showed both low deviation (Linear, Circle, and A-P) and high deviation (8-figure, S-figure, and Wave). The mandibular B-L deviation was similar with slight ups at the right first premolar and second molar. The scan strategies in this study included one scan path and six head movements via TRIOS 3 IOS. [PERSON] et al. [18] showed an ex vivo study to evaluate trueness via TRIOS 3 and CBCT; the mean and standard deviation of 120 \(\pm\) 34 \(\upmu\)m were similar to this present study. [PERSON] et al. [19] showed the trueness of the full dental arch vis IOS TRIOS was 55.3 \(\pm\) 8.7 \(\upmu\)m. Although the trueness values were lower than our maxilla results, the authors in this present study did demonstrate consistent scanning conditions and specifications. Moreover, the ICC was 0.819 with 95% confident interval = 0.702-0.904, indicating the reliability in this study was moderate to good [20]. These deviations could be attributed to the inevitable shaking and movement when holding the IOS. The 3D model reconstruction would cause larger deviations in the curved areas of the dental arch, like premolars, canines, and the distal surface of the molars, which require more angles to be flipped during shooting. [PERSON] et al. [21] demonstrated for a left-handed dental student's response that the maxilla is more difficult than the mandible, and the quarter I was the most complicated quarter to work. In this present study, the right-handed dentist could easily operate patient quadrants II and III, while the lower jaw was visible directly and more easily located and scanned than the upper jaw. On the other hand, the parallel confocal design of the TRIOS series helped to reconstruct the digital dental model via focused and defocused images from the different angles around the object. The sharpness area is directly related to the dexterity of the operator who can generate static images and motion blur [22]. Figure 9: The box plot shows the repetitive deviation of the six head movements in 10 scans. All movements showed similar precision in the mandible. The Linear, Circle, S-figure, A-P, and 8-figure movements could all be classified as moving in a linear movement, while the Wave movement was flipping. Firstly, the A-P and 8-figure movements moved on a partially repeated path, and these movements might increase the image sheets and deviations from superimpositions. The occlusal deviations of the maxilla and mandible demonstrated the findings (Figures 4 and 5); however, the trueness of B-L was influenced more by the S- and 8-figure movements. These findings might be attributed to the conflict of path and movement and demonstrated that the deviation will be more minor when the path and movement are in the same direction. However, when the path and movement conflict, the deviation will be more significant. [PERSON] et al. (2018) showed similar findings, where the deviations of a continued scan with horizontal direction (87.60 \(\pm\) 5.76 \(\upmu\)m) were lower than that for a vertical direction (102.38 \(\pm\) 7.48 \(\upmu\)m). Secondly, the results of the wave movement showed similar occlusal deviations as linear and circular; still, a slightly higher deviation in the B-L side could indicate that the flip was not violent and did not affect the focus in this confocal design scanner.