{'fraction_non_alphanumeric': 0.07715244129705554, 'fraction_numerical': 0.07156168468132687, 'mean_word_length': 4.834782608695652, 'pattern_counts': {'":': 0, '<': 2, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
[Trueness of 4 three-dimensional facial scanners: an in vitro study].

Objective: To investigate the trueness of 4 three-dimensional (3D) facial scanners and to evaluate the applicability of their clinical use. Methods: An art head model was used as the scanning object, and it was scanned by Handyscan 3D scanner in an enclosed environment with a fixed light source to obtain the reference digital model. Three fixed 3D facial scanners (A: 3dMDface; B: Facego Pro; C: RDS Facescan) and a portable hand-held 3D facial scanner (D: Revopoint POP 2) were used to scan the art head model 10 times, and 10 models of each scan group were obtained. The face of the reference model was divided into 16 regions according to anatomy and muscle distributions in the Geomagic Wrap software with saved boundary curves of whole face and each region. The test models were also divided into 16 regions through the curves above after registered with the reference model through "Best fit" function. The root-mean-square error (RMS) of the complete test models and their segmented regions compared with the reference model and its corresponding regions were calculated by 3D comparison function. The smaller the RMS, the higher the accuracy. One-way ANOVA and SNK post-test were used for statistical analysis. Results: RMS of complete test models scanned by A, B, C, D scanners were (0.295±0.005), (0.216±0.053), (0.059±0.012) and (0.103±0.026) mm (F=123.81, P<0.001), respectively. There was significant difference between any two groups (P<0.05). For each facial region, the group D had the best trueness in nasal region, lip region, left orbital region and right orbital region [RMS were (0.079±0.032), (0.061±0.019), (0.058±0.021), (0.081±0.032) mm, respectively], while the group C had the best trueness in frontal region, left buccal region, right buccal region, left zygomatic region, right zygomatic region, left parotideomasseteric region, right parotideomasseteric region, left temporofacial region, right temporofacial region, mental region, left infraorbital region and right infraorbital region [RMS were (0.039±0.011), (0.034±0.007), (0.033±0.007), (0.066±0.023), (0.038±0.022), (0.070±0.030), (0.067±0.024), (0.063±0.029), (0.045±0.023), (0.063±0.006), (0.039±0.010), (0.046±0.008) mm, respectively]. Conclusions: On the basis of art head model scanning, although the overall average deviation between the scanning model and the reference models obtained by the four kinds of 3D facial scanners were small, the portable handheld 3D facial scanner (D) has better accuracy than the fixed 3D facial scanners (A, B, C) in the orbital area, nasal area, lip area and areas with rich features.