# Accuracy of Different Head Movements of Intraoral Scanner in Full Arch of Both Maxilla and Mandible
## 1 Introduction  
The three elements of computer-aided design and computer-aided manufacturing (CAD/CAM) are data acquisition, software, and manufacture; this concept was first introduced by Dr. [PERSON] in 1973 [1]. Digital data acquisition could be obtained via an intraoral scanner (IOS) or desktop scanner, while the pioneering IOS device used in clinical dentistry was the CEREC system in 1987 [1]. Many IOS devices have been launched in dentistry and have become increasingly popular in dental clinics in the past decade [2]. Three imaging principles [3] commonly used in IOS development are triangulation, confocal, and active wavefront sampling. Among them, TRIOS 3 uses the ultrafast optical sectioning technique based on the confocal laser principle; so, it is one of the most popularoral scanners clinically. Clinicians should go through a proper learning curve [4] and focus on one or two IOS devices in dental practice. Studies on the accuracy of most IOS were compared and proven to reach clinical needs. In contrast, the accuracy of some IOS was even better than that of traditional silicone impression materials [5; 6]. On the other hand, the accuracy of IOS has been demonstrated to have significant differences in the deviations, which depend on the scanner used, the scan field, the scan strategy, environmental interference, etc. [PERSON] et al. [7; 8] tested many IOS scanners and showed that different significant deviations ranged from 17.80 um to 200.24 um among the scanners. At the same time, [PERSON] [9] stated the risk of scan deviation in a single crown was low, but full-arch scanning still had its limitations and discrepancies. Recording full-arch digital data appears complicated but is useful for full-mouth rehabilitation. [PERSON] et al. [3] reviewed articles and stated that different scan strategies would affect the accuracy of the full-arch scan. Saliva, blood, cheek and tongue movements, rebound after gingivae, patient's mouth-opening durability, etc., will affect the performance of oral scan quality. [PERSON] et al. [10] demonstrated that 3900 K and 500 lux of ambient light would be the most appropriate lighting conditions for optical impression, while [PERSON] et al. [11] revealed that room light would result in better accuracy for TRIOS 3. According to the International Organization for Standard (ISO-5725-1) [12], accuracy comprises trueness and precision. Trueness refers to the degree of deviation of the measured value from the actual dimension, while precision refers to the closeness of the repeated measurement value. The scan strategies that include scan path, gesture, sequential range, or combination might influence accurate modeling. [PERSON] et al. [13] demonstrated the trueness of three scan paths via the TRIOS 3 Pod scanner, and the results revealed the scan path from occlusal-palatal, returning via buccal surface, showed the highest trueness in full-arch scans. [PERSON] et al. [14] showed the accuracy of 13 strategies that included scan path and sequential range via the CEREC series system, and the results revealed the lowest deviation in one design, while [PERSON] et al. [15] showed the accuracy of four scan strategies that included scan path, sequential range, and gestures via four IOS, revealing TRIOS 3 was not affected by different strategies. Additionally, [PERSON] et al. [9] demonstrated the accuracy of four strategies that included scan path and sequential range via four IOS, revealing that accuracy was not affected by different scanning strategies. Accordingly, the accuracy of varying scan strategies remains controversial, the factors deserve further clarification, and the deviation of occlusal and buccal-lingual of TRIOS3 is still unknown. This in vitro study aimed to compare maxilla and mandible full-arch IOS scan trueness and precision via one scan path with six different head movements. The IOS scanner was a TRIOS 3 Pod wired using a standard speed technique based on the confocal laser principle.