# Accuracy of Different Head Movements of Intraoral Scanner in Full Arch of Both Maxilla and Mandible
## 2 Materials and Methods
### Scan Strategies  
The scan strategies that included one scan path with six different scan movements were performed in this study. The maxilla line scanning path was as follows: initially, for the occlusal surface, starting with the left second molar and continuing until the right second molar, returning via palatal surface, and finally sweeping once over the buccal surfaces. The mandibular line path started from the second molar occlusal side of III quarter, proceeding longitudinally along the arch and ending at the right second molar, and then continuing on the lingual side and, finally, the buccal surface. The path all but followed the manufacturer's protocol. However, for the consistency and rigor of the experiment, the maxilla path was slightly modified, and a pilot study was done to prove that there was no statistical difference between the two paths. Then, six scan head movements were used in this study, following the same scan path. The G power analysis was used to estimate the required sample size, assuming six test groups, an effect size of 0.6, the probability of Type I (\(\alpha\)) error of 0.05, type II error (\(\beta\)) of 0.08, and the power of 0.92. The sample size was 60 and, thus, determined to be 10 per group. The dentist performed each movement 10 times, and a total of 120 scans were recorded. Although the sample size of scans was only 120, the study's estimation of statistical power was 92% (\(>\) optimal values of 80%); therefore, our results had a 92% valid probability of being significant. This highly statistical power shows that the tests were most likely valid and strengthens the evidence coming from the study. According to the research of [PERSON] et al. [17], except for the common U-shaped movement, they also mixed zigzag motion during the scanning process, which means that the scanning movement was no longer limited to linear and wave. Therefore, six scanning movements were designed accordingly in this study (see supplement Video S1), which followed the same scanning path and are as follow (Figure 1). Linear movement refers to moving along the outline of the dental arch. Circle movement refers to making a counterclockwise circle movement for each tooth along the dental arch. Figure 1: One scan path with six scan head movements. Wave movement means that when each tooth is scanned, the wrist swings left and right on the occlusal side, and then the wrist swings up and down on the buccal or lingual side. The 8-figure movement refers to movement like writing the numeral \"8\". Initially, the scan head would move from the upper left second molar counterclockwise, then move through the upper left first molar to finish the numeral \"8\". Each movement would cover two teeth. The S-figure movement refers to a \"letter s-shaped\" movement. The process would move from upper left second molar counterclockwise, then move through the upper left first molar to finish the S-figure movement. Each movement would cover two teeth. The A-P movement refers to a forward and backward movement. Each movement would cover two teeth. Trueness is defined as comparing a reference data set and a test data set and determining the absolute accuracy of a scanner. Generally speaking, trueness only finds the maximum value of deviation in the tooth. However, we separately discussed the maximum deviation of the occlusal and buccal-lingual (B-L) surface in this study. The occlusal deviation would help to determine the occlusion of each tooth, and the B-L deviation would help to find the deformation of the full arch. Using the \"best fit matching \"and \"cut view\" tool in the CAD software program (Exocad DentalCAD; Exocad GmbH, Align Technology Inc., Santa Clara, CA, USA), we could calculate differences between each measuring point of a model and the farthest corresponding point of the superimposed model in occlusal and B-L direction deviation (Figures 2 and 3). One model including 14 teeth with occlusal deviation and B-L deviation was recorded, and a total of 1680 data points in one jaw were recorded.