Table 1.

Characteristics of the included studies.

Author, Year [Reference]	Type of Study	Study Objective	Study Material	Number of Subjects	Test Group	Control Group	Intraoral Scanner Model	Results
Jacob et al. 2015 [15]	Case—control study	Comparison of the accuracy of two intraoral scanners and one extraoral scanner	3D intraoral and extraoral scans	15 subjects	Intraoral scans, extraoral scans of dental cats	Intraoral scans, extraoral scans of dental cats	iTero element, Lythos Ortho Insight 3D,	While all three scanners produced reliable measurements, Ortho Insight 3D systematically underestimated arch length and canine height. Measurements taken from all three scanners were highly reliable, with intraclass correlations ranging from 0.926 to 0.999. Method errors were all less than 0.25 mm
Park et al. 2015 [16]	RCCT	Evaluation of the influence of proper training in intraoral scanning among dental hygienists.	Questionnaires before and after the training	34 hygienists, 17 per group. The hygienists from the other group served as patients in the group using a different scanner, thus assessing the patient’s comfort during the scanning.	iTero element group	3Shape group	iTero element, 3Shape Trios	The first preliminary questionnaire was given initially before the training sessions and the second questionnaire was completed upon the completion of all the training sessions. Both evaluated parameters as difficulties of using intraoral scanners with digital impression method compared to conventional impression-taking method, patient comfort, and degree of awareness about intraoral scanners. The parameter of awareness included anticipated accuracy, patient convenience, efficiency, clinical application, and interest in further use. Results of this study indicated that participants generally preferred Trios intraoral scanner over iTero as an operator after the training. However, participants consider iTero as easier to handle during the scan and indicated, that it provides much higher patients comfort. The usefulness of intraoral scanner could be a successful alternative to conventional impression-taking with proper training.
Nalaci et al. 2015 [17]	RCCT	Evaluation of reliability of measurements by superimposition of 3D digital models	Digital models, classic dental casts and cephalometric radiographs of adolescent patients	10 female and 10 male II Class subjects; (mean age: 16)	The posterior movements of the maxillary first molars evaluated on superimposed 3D models before and after treatment	(a) The distal movements of the maxillary first molars evaluated on cephalometric radiographs (b) The distal movements of the maxillary first molars evaluated on photocopies of plaster models	3 Shape R700 model	There was no significant difference observed in values of distalization of the upper molars, premolars, or incisors among all three groups. The measurement differences among the 3D digital models, cephalometric radiography, and plaster model photocopy methods were insignificant. Cronbach’s alpha value was closest to ideal 1 for the measurement on 3D models. The use of superimposed 3D models on Orthocad Software as the evaluation of treatment results seems as valid alternative for conventional evaluation method.
Taneva et al. 2015 [18]	Case—control study	Creation of control points on rugae palatine patterns using 3D digital models in order to identify victims	3D intraoral scans, 2D photos	15 subjects from the university clinic and 15 subjects from private orthodontic practices	Intraoral scans, extraoral scans of dental cats	Scans after follow-up, 2D photos	iTero element, Ortho Insight 3D	No statistically significant mean differences exist between different digital model conversion techniques, between OrthoCAD™ and Ortho Insight 3D™, and between Ortho Insight 3D™. Twelve palatal 3D landmarks could be used for human identification over time, certain landmarks showed more significant impact on the matching process
Kim and Lagravére 2016 [19]	RCCT	Comparison of accuracy of 3D models of conventional dental casts vs. CBCT scans	Digital models, classic dental casts and CBCT scans of adolescent patients	50 models and corresponding casts and digital models	Measurements on the 3D models using Ortho Insight 3D software	(a) Measurements of CBCT scans converted to DICOM files using Avizo Software (b) Manual measurements taken on classic dental cast	Ortho Insight 3D laser scanner	Intra-examiner measurement errors were determined by randomly selecting 10 patient records, and the mesiodistal width measurements were repeated three times 1 week apart by the same examiner. CBCT exhibited the lowest error reliability, while scanned digital models had the highest intra-examiner error reliability. The mutual compatibility of measurements deviates in the case of calculating anterior Bolton ratio at the level of agreement of 0.886. However, Bolton analysis can be accurately and reliably performed on scanned digital models using the proposed Ortho Insight system.
Solaberrieta et al. 2016 [20]	Case—control	To locate the 3D spatial position of the mandibular cast and determine its occlusal contacts in a novel way by using an intraoral scanner as part of the virtual occlusal record procedure	3D intraoral scans, dental casts	4 participants	3D intraoral scans	3D scans from industrial scanner	Lava Cos, 3Shape Trios, Zfx Intrascan, ATOS Compact Scan 5M	Intraoral virtual occlusal recording is a valid procedure to locate a mandibular cast on a virtual articulator. The contacts observed with this procedure were accurate enough. Moreover, virtual contacts provided more objective and meaningful information. Lava Cos and Trios 3-Shape intraoral scanners showed similar characteristics, both of them being good enough to carry out this procedure. The LavaCos requires coating and has a comfortable small tip, whereas the Trios 3-Shape scanner has a larger tip and is much faster. The best results regarding the virtual occlusal record sections were obtained when the distance between the sections was maximum. Two or three sections can be required to establish perfect occlusal record.
Wesemann et al. 2017 [21]	Case—control compa-rative study	Comparison of the accuracy and time efficiency of an indirect and direct digitalization workflow with that of a 3D printer to identify the most suitable method for orthodontic use.	3D intraoral scans, CBCT scans, conventional dental casts	None—comparison of the scanning quality on hypothetical dental cast	Intraoral scans of master model with separately: 3Shape R700, 3Shpae R900, 3Shape Colorpod	Dental casts, CBCT scans	3 Shape Tripod R700 3Shape Tripod R900 3Sape Trios Colorpod	The most accurate results were obtained by the R900. The R700 and the TRIOS intraoral scanner showed worse, but still comparable results. CBCT-3D-rendering revealed significantly higher accuracy with regard to dental casts than dental impressions. The chairside time required for digital impressions was 27% longer than for conventional impressions. For orthodontic demands, intraoral scanners are a useful alternative. For prosthodontic use, no more than one quadrant and three additional teeth should be provided as the scanning area on one seat.
Lee 2018 [22]	Case—control study	Comparison of two intraoral scanners based on 3D surface analysis	3D intraoral scans and dental casts scans	32 adult participants	3D intraoral scans	3D dental casts scans	3Shape Trios 3 iTero Element 2	The mean deviations between two intraoral scans were 0.057 mm in the maxilla and 0.069 mm in the mandible. The histogram showed local variations between the two scanners in the posterior area. In three-dimensional deviations, intraoral scans showed a slight shift towards the models. There were no statistically significant differences between the two scanners.
Deferm et al. 2017 [23]	Case—control study	Assessment of the feasibility of 3D intraoral scanning for documentation of palatal soft tissue by evaluating the accuracy of shape, color, and curvature.	3D intraoral scans, dental casts	Scans of 10 participants by 2 different observers	Intraoral scans	Dental casts	3Shape Trios	Mean average distance error between the conventional models and the intraoral scans models was 0.02 ± 0.07 mm. Mean interobserver color difference was −0.08 ± 1.49°, 0.28 ± 0.78% and 0.30 ± 1.14% for respectively hue, saturation, and value, whilethe interobserver differences for overall and maximum surface irregularity were 0.01 ± 0.03 and 0.00 ± 0.05 mm. what showed that intraoral scanner is tool, which provide reliable, reproducible and accurate results, and therefore allows to freely document the palate.
Zhonpeng et al. 2019 [24]	Case—control study	Comparison of the differences in palatal region between indirect and direct digital models and the scanning sequences	3D intraoral scans and dental casts scans	35 adult participants (9 men and 26 women (24–27 years old)	(a) 3D intraoral scans with the start point behind the central incisors (b) 3D intraoral scans with the start point behind the central incisors	Scans of dental casts	3Shape Trios 3 Pod	When evaluating accuracy of intraoral scanning in the palatal region, the superimposition method should be appropriately adjusted. It means that to obtain a certain comparison of scanning accuracy, soft tissues (palate), dentition (dental arch) and the entire scan (angulation of one to the other) must be assessed in separated evaluation. Palatal trueness is affected by scanning sequences. To get the best impression one needs to begin the scanning procedure from the palatal side of posterior teeth.
Favero et al. 2019 [25]	Case—control study	Comparison of the accuracy of 3D digital impressions obtained using two intraoral scanners and three scanning methodologies.	3D intraoral scans	None—comparison of the scanning quality on hypothetical dental cast	Technique A (from tooth #27 up to tooth #17); Technique B (from tooth #11 up to tooth #17 and then from tooth #21 up to tooth #27) Technique C (from tooth #12 up to tooth #17, and then from tooth #12 up to tooth #27) - scanned with Carestream 3600	Technique A (from tooth #27 up to tooth #17); Technique B (from tooth #11 up to tooth #17 and then from tooth #21 up to tooth #27) Technique C (from tooth #22 up to tooth #17, and then from tooth #12 up to tooth #27) - scanned with Zfx Evolution	Zfx Evolution, Carestream 3600	The scanning technique had a statistically significant effect on the quality of the scan (p < 0.0001).When scanning begins from tooth #12 up to tooth #17, and then from tooth #12 up to tooth #27 it is less volumetric whereas the scanner did not present any significant influence (p = 0.91).
Yilmaz et al. 2019 [26]	RCCT	Comparison of Accuracy of 3D models vs. conventional dental casts	Digital and classic dental casts of adolescent patients	20 female, 10 male subjects; (mean age: 14.36 ± 6.30)	Measurements on 3D models with 3Shape Ortho Analyzer 2013 software	Manual measurements on classic dental cast	3 Shape TriosColor-P1	The study checked the accuracy of measurements of the spaces between the teeth in both dental arches and also Bolton’s analysis was carried out. To increase the reliability of the measurements, they were repeated five times, and the arithmetic average value was used for the evaluation. Conventional analysis required 33% more time then the digital one. (mean 894.33 s vs. 597.73 s) There were no significant differences between the accuracy achieved p < 0.001. The digital analysis is as reliable as conventional model analysis and it seems to be more time effective.
Winkler & Gkantidis 2020 [27]	Case—control study	Comparison of the precision of intraoral scanners and the industrial scanner	3D scan with industrial scanner Artec Space Spider, with CS 3600, with TRIOS 3	12 adult volunteers (8 men, 4 women, age: 27–52 years)	3D scans with the use of: (a) CS 3600, (b) TRIOS 3.	3D scan with industrial scanner Artec Space Spider	Carestream 3600 3Shape Trios 3	The precision of the intraoral scanners (TRIOS 3 and CS 3600) was tested after superimposing the dental arch surface models obtained from repeated scans. In overall, TRIOS 3 showed better precision than the CS 3600(approximately 10μm). However, looking into the detail, both devices showed a clear imprecision, especially on buccal side of anterior teeth. Both devices do not show the accuracy of an industrial scanner, however, their accuracy is completely sufficient for clinical applications.
Jihu Song & Minji Kim 2020 [28]	Case—control study	Evaluation of scanned images of 4 clinically used intraoral scanners with different types of brackets	3D intraoral scans	4 different study models	(a) Study model with metal brackets (b) Study model with ceramic brackets (c) Study model with resin brackets	Study model without any brackets	Carestream CS3600, i500, 3Shape Trios3, Sirona Omnicam	Image data were analyzed with the 3D analysis software—Geomagic. Not only both scanners (p < 0.05) and brackets (p < 0.05) had a significant impact, but also interaction between scanner and brackets was statistically significant (p < 0.05). Brackets which were translucent or reflective to light such as resin and metal brackets tended to show higher discrepancy values. From the point of view of the clinician, all scanners showed acceptable deviation results, however CS3600 and Trios3 were most accurate comparing to control model.
Schlenz et al. 2020 [29]	Case—control study	Analysis of the ability of analog and digital impression techniques to display the interdental areas in periodontal patients	3D scans and dental casts	30 patients, age: 48–87	Intraoral scans	Conventional dental casts	True Definition, Carestream 3600, 3Shape Trios 3, Primescan	True definition scanner gave the most adequate results, displaying the highest percentage of interdental areas, followed by Primescan, Carestream and 3Shape. However, regardless the technique of scanning or type of scanner, intraoral scans always demonstrated the number and condition of recessions better than conventional casts.
Stafeev et al. 2020 [30]	Case—control study	Comparison of classic method of finding centric relation to new digital method using 3D Scans	3D scans and classic models and frontal deprogrammer	5 patients, 20 registrations of the centric jaw relation for each patient	Intraoral scans	Conventional deprogrammation method	3Shape Trios 3	The reproducibility of the digital mandible position in the centric relation reached 0.119 ± 0.012 mm for frontal deprogrammer, 0.225 ± 0.028, p ≤ 0.05 for bilateral manipulation by p.E. Dawson, 0.207 ± 0.02, p ≤ 0.05 for leaf gauge, and 0.120 ± 0.013, p ≤ 0.05 for intraoral device for recording the Gothic arch angle. All methods of searching for centric relation do not coincide completely. However, the most precise were the methods using the frontal deprogrammer and the intraoral recording of gothic angle. In terms of reproducibility, the Avantis 3D program most accurately identified the mandible position, when searching for the position of centric relation. By choice of the many, many factors that should be considered such as the condition of the stomatognathic system, the manual skills of the doctor, the psychoemotional status of the patient, and the material provision.