Smartphone applications for facial scanning: A technical and scoping review
Abstract
Introduction
Facial scanning through smartphone scanning applications (SSA) is increasingly being used for medical applications as cost-effective, chairside method. However, clinical validation is lacking. This review aims to address: (1) Which SSA could perform facial scanning? (2) Which SSA can be clinically used? (3) Which SSA have been reported and scientifically validated for medical applications?
Methods
Technical search for SSA designed for face or object scanning was conducted on Google, Apple App Store, and Google Play Store from August 2022 to December 2023. Literature search was performed on PubMed, Cochrane, EMBASE, MEDLINE, Scopus, IEEE Xplore, ACM Digital Library, Clinicaltrials.gov, ICTRP (WHO) and preprints up to 2023. Eligibility criteria included English-written scientific articles incorporating at least one SSA for clinical purposes. SSA selection and data extraction were executed by one reviewer, validated by second, with third reviewer being consulted for discordances.
Results
Sixty-three applications designed for three-dimensional object scanning were retrieved, with 52 currently offering facial scanning capabilities. Fifty-six scientific articles, comprising two case reports, 16 proof-of-concepts and 38 experimental studies were analysed. Thirteen applications (123D Catch, 3D Creator, Bellus 3D Dental Pro, Bellus 3D Face app, Bellus 3D Face Maker, Capture, Heges, Metascan, Polycam, Scandy Pro, Scaniverse, Tap tap tap and Trnio) were reported in literature for digital workflow integration, comparison or proof-of-concept studies.
Conclusion
Fifty-two SSA can perform facial scanning currently and can be used clinically, offering cost-effectiveness, portability and user-friendliness. Although clinical validation is crucial, only 13 SSA were scientifically validated, underlying awareness of potential pitfalls and limitations.
1 INTRODUCTION
Facial morphology is integral to a wide range of fields, including dentistry, medicine, social science and art, as it expresses uniqueness and can serve as an identifier of individuals.1 In a clinical perspective, the analysis of facial morphology has classically been performed with two-dimensional (2D) photography. However, this approach does not permit the quantification of facial volume or asymmetry, which constitutes the primary advantage of three-dimensional (3D) photography and facial scanning.2-4 Facial scanning simplifies the gathering and examination of clinical data, which can be employed in diagnosis, treatment planning and communication.5
The technology behind facial scanners has been continuously developed over the decades. The pioneering integration into clinical practice began with the use of 3D laser scanning, which involves timing a laser's reflection to calculate object distance using triangulation.6 Although this method yields high image resolution,6, 7 it is also time-consuming and prone to motion artefacts.8-10 The modern generation of scanners addresses this challenge by reducing scan time, relying on principles such as photogrammetry, stereophotogrammetry and structured light.11-13 Photogrammetry uses stitched photographs, while stereophotogrammetry, the current clinical standard, captures object images from multiple positions and calculates 3D coordinates through mathematical registration in post-processing software.14-16 It offers faster scanning time with reproducible results and serves as a cost-effective alternative to laser scanning, though it may require longer post-processing and could lead to surface artefacts and uneven coverage.6, 17 Structured light technology reduces costs while providing speed and cost-effectiveness. It operates by projecting light onto surfaces and capturing shapes from various angles using trigonometric triangulation with an active sensor.18-21 However, it is sensitive to lighting conditions and can lead to motion artefacts and variable repeatability.12 The main advantage of all mentioned scanning technologies is the fact that they do not involve radiation and they are non-invasive.22 Nevertheless, cost and limited accessibility hinder their clinical use.
Smartphone could serve as a low-cost alternative for obtaining scans with the excellent precision, ranging from 0.96 to 0.99.23-25 The new smartphone generations, equipped with internal cameras and structured infrared light, can produce quality 3D scans.26, 27 The technologies behind their success are the TrueDepth camera and the Light Detection and Ranging technology (LiDAR). The built-in TrueDepth camera uses a light-emitting diode to project a grid of over 30 000 infrared dots, recording depth within milliseconds. This allows for real-time data collection, even in low-light conditions with the use of an infrared illuminator.28-30 LiDAR functions by emitting light pulses and measuring their reflections to calculate object distances, creating 2D or 3D maps from the data points.31, 32 The availability and capability of current smartphones, together with the development of supporting applications, have facilitated their widespread use in 3D facial identification, reconstruction and medical planning, having various clinical applications.33, 34
Despite this, there are limited studies on the availability of smartphone scanning applications (SSA) for clinical purposes and how they can be used. Therefore, this study aims to answer the following questions: (1) Which SSA can perform face scanning for clinical purposes? (2) Are there applications suitable for clinical settings and how are they used? (3) Which applications reported in the literature have been validated for medical applications?
2 MATERIALS AND METHODS
To comprehensively address all the questions, the review was structured into two distinct parts. Part 1 was a technical review focused on evaluating SSA, requiring a separate search to obtain the most up-to-date data directly from search engines, as scientific research often trails behind technological advancements and commercialization. Part 2 constituted a scoping review of the existing literature on the related subject.
2.1 Part 1: Technical review of smartphone scanning applications
2.1.1 Eligibility criteria
The inclusion criteria for this search encompassed smartphone applications capable of scanning human faces, as explicitly described in the application's description or demonstrated through illustrations. Additionally, applications with the capability to scan objects were also considered, given their utilization in clinical literature. The time frame for inclusion spanned applications available in stores from July 2022 to December 2023. On the other hand, exclusion criteria involved applications not specifically designed for photography purposes, particularly those not intended for face scanning or object scanning.
2.1.2 Information sources
To identify potential SSA, electronic searches were performed on the following search engines from August 2022 to December 2023: Google, Apple App Store, and Google Play Store. The search terms used included: ‘face scan application’, ‘face scanning application’, ‘facial scan application’, ‘facial scanning application’ and ‘scanning application’. Identical terms without the word ‘application’ were applied in both the Apple App Store and Google Play Store. Upon displaying the search results, applications developed by the same developers and suggested related applications were further reviewed.
2.1.3 SSA selection, data collection and synthesis of the results
One reviewer (TJ) independently selected the SSA, and this selection was double checked by a second reviewer (XL). For data collection, a chart was designed by one reviewer (TJ) and thoroughly discussed with a second one (XL). The collected information from various sources included the developer's details, application name, operating system (e.g. Android/iPhone Operating System [iOS]), version information, whether there was a version update in 2023 and the reasons for it, availability (i.e. free or in app purchase), the country where the developer is based, language support, application's purpose (e.g. clinical, entertainment, photography or tool), privacy data collected by the applications, and any other relevant remarks. The privacy data collected by the applications encompassed contact information, identifiers, diagnostics, location, usage data and user content. These data were categorized as either ‘No data collection’, ‘No data available’ or ‘Data collection’. In the case of data collection, the specific types of data collected were specified. To synthesize the data, an Excel file was initially piloted by the first reviewer (TJ). The final version of this file was then converted into a Word table after discussion with a second reviewer (XL). In instances of disagreement, a third reviewer was consulted, and consensus was achieved.
2.2 Part 2: Scoping review of the literature
2.2.1 Protocol and registration
The protocol for this scoping review was written before commencement and follows the PRISMA Extension for Scoping Reviews (PRISMA-ScR), accessible through http://prisma-statement.org. PRISMA-ScR was developed in accordance with the guidelines published by the EQUATOR (Enhancing the Quality and Transparency of Health Research) Network for the development of reporting guidelines. The protocol was pre-registered in Open Science Framework (https://doi.org/10.17605/OSF.IO/KN6RS).
2.2.2 Eligibility criteria
For this scoping review, studies incorporating at least one SSA into their methods, specifically for scanning the facial region, conducted in vitro or in vivo and for clinical purposes were included. Exclusion criteria encompass studies that do not incorporate SSA in their methods, conference abstracts and systematic reviews.
2.2.3 Information sources
To identify potentially relevant articles, the following electronic databases were explored, covering the publication up to December 2023: PubMed, Cochrane, EMBASE, MEDLINE, Scopus, IEEE Xplore, ACM Digital Library, Clinicaltrials.gov, ICTRP (WHO) and preprints. The search strings were initially drafted with the assistance of biomedical reference librarians and refined through discussions by two reviewers (TJ and XL). The final search strings and the modified versions used in each respective database are available in Table S1. The resulting search results were exported to the reference manager EndNote (version 20, Clarivate Analytics, Pennsylvania, USA), where duplicates were eliminated. Subsequently, a manual examination of the reference lists of key articles was conducted to identify additionally relevant articles.
2.2.4 Study selection
Two reviewers (TJ and XL) initially screened the same list of articles based on their titles and subsequently reviewed potentially relevant abstracts to enhance consistency among the reviewers. Following this, a full-text screening was conducted to determine whether the articles met the inclusion criteria. Any controversies were dealt through discussion or further involvement of a senior advisor (RJ).
2.2.5 Data items and data charting process
One reviewer (TJ) developed a data-charting, which was subsequently validated by the second reviewer (XL). Any discrepancies were resolved through discussion. The following information was collected from the included articles: application(s) used, article characteristics (e.g. authors and year of publication), study characteristics (e.g. design, field of study, application integration and objectives), study population and clinical applicability.
2.2.6 Synthesis of results and critical appraisal
The Excel file was initially drafted by the first reviewer (TJ). Following a discussion with the second reviewer (XL), the finalized version of this file was then transformed into a Word table. Articles were grouped into three main categories based on the integration of applications: (i) those incorporating smartphone applications as part of a specific digital workflow, (ii) those comparing smartphone applications with other hardware/software or techniques (i.e. comparative studies) and (iii) those using smartphone applications as a research tool. They were respectively labelled as ‘Workflow’, Comparison’ and ‘Validation’.
An additional data extraction table was created for studies comparing different SSA. This table included information such as the device used (hardware), principle used (e.g. static stereophotogrammetry, portable structured light, magnetic resonance imaging, laser or not applicable). This information was separately compiled for the control and test groups involved in the study, followed by the study's conclusion.
3 RESULTS
3.1 Part 1: Technical review of smartphone scanning applications
A total of 82 applications were identified through the search engines and manual searching; After thorough consideration, 63 applications, including 11 applications with sales termination, were deemed eligible.
Table 1 shows the list of smartphone applications with potential use for face scanning. The majority of these applications operated on the iOS system (n = 37, 59%), followed by 16 on the Android system (25%) and 10 were compatible with both systems (16%). The initial iOS version supported was 9.3, with the most common iOS-based application version being 15.0 (n = 11). For android, the initial and most common version supported was 4.0 (n = 6). These applications were developed by 53 developers from 19 different countries, with 28 developers based in the United States (53%), followed by Canada, Germany and Japan (6% each).
| Developer | Application name | Operating system | Availability | Country of the developer | Language support | Purpose of the application | Literature/ clinical use | Privacy data collected | Remarks | ||
|---|---|---|---|---|---|---|---|---|---|---|---|
| System | Version | Version update in 2023, why | |||||||||
| 3D ProBox tech. | 3D ProBox | Android | Android 4.0 or later | Yes, bug fixed | Free | Turkey | English | Photography (human, object, place) | No | Contact info, diagnostics, identifiers, location, user content | Optional subscription |
| Abound Labs Inc. | Metascan 3D scanner | iOS | iOS 14.0 or later | Yes, bug fixed, performance | In app purchase | USA | English | Photography (object, place, interior) | No | Diagnostics, location, usage data, user content | LiDAR mode for capable devices |
| Aimfire | Camarada | Android | Android 4.4 or later | No | In app purchase | USA | English | Photography (Object, exterior) | No | No data available | Last update in December 2018 |
| AR Generation | MagiScan | iOS, Android | iOS 15.0 or later Android 4.0 or later | Yes, user interface | In app purchase | Poland | English +20 more | Photography (object, graphic design) | No |
Diagnostics, identifiers, location, usage data, user content |
|
| Autodesk | 123D Catch | iOS, Android | No data | No | In app purchase | USA | English | Photography (human, object, place) | Yes | No data collection | Sale termination |
| Bellus 3D Inc | Bellus 3D Dental Pro | iOS | iOS 12.2 or later | No | In app purchase | USA | English | Photography (facial scan) | Yes | No data available | Sale termination |
| Bellus 3D Face Maker | iOS | iOS 13 or later | No | In app purchase | USA | English | Photography (facial scan) | Yes | No data available | Sale termination | |
| Bellus 3D Face app | iOS | IOS 11.1 or later | No | In app purchase | USA | English | Photography (facial scan) | Yes | No data available | Sale termination | |
| Brawny Lads Software, LCC | EM3D | iOS | iOS 13.0 or later | No | In app purchase | USA | English | Photography (human) | No | No data collection | |
| Capacity | 3DShot: 3D Product Photography | Android | Android 7.0 or later | Yes, performance | Free | USA | English | Photography (human, object, place) | No | Contact info, diagnostics, identifiers, location, user content | |
| Dmitriy Evdokimenko | Modelified | iOS | iOS 14.1 or later | No | In app purchase | Turkey | English | Photography (human, object) | No | No data available | Last update in July 2021 |
| EORA 3D | Eora Studio | Android | Android 6.0 or later | No | Free | Australia | English | Photography (object) | No | No data available | Last update in August 2018 |
| Evgeny Zhukov | 3D LiDAR Scanner | iOS | Android 14.0 or later | No | Free | USA | English | Photography (environment, object) | No | No data collection | |
| EyeCue Vision Technologies LTD | Qlone 3D Scanner | iOS, Android | iOS 12.0 or later Android 7.0 or later | Yes, optimization | In app purchase | USA | English +16 more | Photography (facial scan, human, object) | No | Location, usage data | |
| HAN WEI WANG | 3D Lidar Viewer | iOS | Android 13.0 or later | No | Free | China | English | Photography (object) | No | No data collection | |
| Heytopia LLC | 3D Photos: Photogrammetry USDZ | iOS | Android 14.1 or later | No | In app purchase | USA | English | Photography (object) | No | No data collection | |
| 3D Photos Pro–Object Capture | iOS | Android 14.1 or later | No | In app purchase | USA | English | Photography (object) | No | No data collection | ||
| Itseez3D Inc. | ItSeez3D | iOS | iOS 11.0 or later | No | In app purchase | USA | English | Photography (human, object) | No | Contact info, diagnostics, user content | Only for iPad |
| Kiri Innovations Science and Tech. | 3DScanLink | iOS | iOS 13.0 or later | No | In app purchase | Canada | English | Photography (object) | No | No data collection | |
| 3D Scanner & NeRF: KIRI Engine | iOS, Android | iOS 13.0 or later Android 4.0 or later | Yes, performance | In app purchase | Canada | English | Photography (human, object) | No | App Store: No data collection Play Store: Contact info, usage data, user content | Optional setting for privacy | |
| Laan Consulting Corp | 3D Scanner App | iOS | iOS 14.0 or later | No | Free | Canada | English | Photography (object) | No | Diagnostics, usage data, | LiDAR capable devices is required |
| Lagarrigue Aquitaine | Captevia | iOS | iOS 10.0 or later | Yes, bug fixed, security | Free | France | English +4 more | Photography (human) | No | No data available | Structure sensor is required Sale termination |
| Lubos Vonasek | 3D Live Scanner | Android | Android 9.0 or later | No | Free | Germany | English | Photography (face scan, interior, exterior) | No | No data available | Last update in July 2022 |
| Marek Simonik | Heges 3D scanner | iOS | iOS 14.0 or later | No | In app purchase | Czech Republic | English | Photography (face scan) | Yes | No data collection | |
| Memera | Overlay Scan–3D Models+LiDAR | iOS | iOS 15.0 or later | Yes, performance | Free | English | Photography (exterior, object) | No | No data collection | For industrial workflow | |
| Mod Tech Labs | MOD 3D Scanner | Android | Android 4.0 or later | No | Free | USA | English | Photography (object) | No | No data available | Last update in March 2022 |
| Nettelo Inc. | Nettelo–3D body scanning and analysis | Android | Android 4.0 or later | Yes, bug fixed | Free | USA | English +1 more | Photography (human) | No | Contact info, identifiers user content | |
| Niels Jansson | Patchy Scan 3D–AR | iOS | iOS 15.0 or later | Yes, performance | In app purchase | Netherlands | English | Photography (object) | No | No data collection | |
| Face Scan–Blendshapes | iOS | iOS 15.0 or later | No | In app purchase | Netherlands | English | Photography (face scan) | No | No data collection | ||
| Nova Research Co., Ltd. | GoodScan 3D | iOS | iOS 15.0 or later | No | In app purchase | Thailand | English +1 more | Photography (exterior, object) | No | No data collection | |
| Pix4D S.A. | PIX4Dcatch: 3D scanner | iOS, Android | iOS 15.0 or later | Yes, bug fixed, performance | Free | Switzerland | English +6 more | Photography (exterior, forensics) | No | Contact info, diagnostics, identifiers, location, usage data, user content | |
| Polycam Inc. | Polycam | iOS | iOS 14.2 or later | Yes, performance | In app purchase | USA | English +14 more | Photography (object, interior) | No | Diagnostics usage data | |
| Proteor | Orten 3D Cam | iOS | iOS 12.0 or later | Yes, performance, system compatibility | Free | USA | English | Photography (human, object) | No | Contact info, identifiers | Structure sensor is required |
| Reality Apps LLC | Real Scan | iOS | iOS 16.0 or later | Yes, performance | In app purchase | USA | English +1 more | Photography (object) | No | No data collection | |
| Recon-3D Inc. | Recon-3D | iOS | iOS 15.0 or later | Yes, bug fixed, performance | In app purchase | Canada | English | Photography (object, forensics) | No | Contact info, diagnostics, identifiers, location, user content | |
| Revopoint 3D Tech. Inc | Revo Scan–3D Scanner App | iOS, Android | iOS 13, Android 4.0 or later | Yes, bug fixed | Free | USA | English | Photography (object) | No | No data collection | External Revopoint 3D MINI scanner is required |
| Scandy Inc. | Scandy Pro | iOS | iOS 15.0 or later | Yes, performance | In app purchase | USA | English | Photography (object) | Yes | Diagnostics, usage data | |
| STL Maker | iOS | iOS 12.0 or later | No | In app purchase | USA | English | Photography (face scan, object) | No | Diagnostics, location, usage data | ||
| Shijiang Zhou | 3DD Capture | iOS | iOS 14.0 or later | No | Free | China | English +4 more | Photography (object) | No | No data collection | |
| SmartMobileVision | Scann3D | Android | Android 5.1 or later | No | In app purchase | USA | English | Photography (object) | No | No data collection | |
| Smart Soft, K.K. | 3D Object Capture | iOS | iOS 15.0 or later | Yes, performance | In app purchase | Japan | English +3 more | Photography (object) | No | No data collection | Further processing in MacOS is required |
| Sony | Sony 3D Creator | Android | Android 8.0 or later | No | Free | Japan | English +37 more | Photography (face scan, object) | Yes | No data available | Last update in January 2022 |
| Spectre3D | Spectre3D | iOS, Android | iOS 14.0 or later | No | In app purchase | USA | English | Photography (human, object, environment) | No | No data collection | |
| State Of The Art | Handy 3D Scanner | Android | Android 5.0 or later | No | Free | USA | English | Photography (object) | No | No data available | Last update in May 2021 |
| Supportec Lean Services B.V. | Capture 3D | iOS, Android | iOS 12.2 or later | No | Free | USA | English | Photography (object) | No | No data collection | Structure sensor is required |
| Svetlana Nasonova | 3D TrueDepth Camera Scan | iOS | iOS 13.0 or later | No | In app purchase | Russia | English | Photography (object) | No | Diagnostics, identifiers | TrueDepth camera capable device is required |
| Unreal Engine | RealityScan–3D Scanning App | iOS, Android | iOS 16 or later | Yes, bug fixed | Free | USA | English | Photography (object) | No | Contact info, diagnostics, identifiers, location, usage data, user content | |
| SuTV | 3DScanner–Photos to 3D Model | Android | Android 5.0 or later | Yes, performance | Free | Vietnam | English | Photography (object) | No | Contact info, identifiers | Optional setting for privacy |
| Tahir Akbar | Photogrammetry for 3D scan | iOS | iOS 14.3 or later | No | In app purchase | Pakistan | English | Photography (object) | No | No data available | Sale termination |
| Lidar 3d Scanner | iOS | iOS 15.0 or later | No | In app purchase | Pakistan | English | Photography (object) | No | No data available | Sale termination | |
| 3D TrueDepth Camera Scan | iOS | iOS 13.0 or later | No | In app purchase | Pakistan | English | Photography (human, object) | No | No data available | Sale termination | |
| Threedium | Unlimited 3D scanner | Android | Android 8.0 or later | No | Free | UK | English | Photography (object) | No | No data available | Last update in August 2022 |
| Toolbox Al, Inc | Scaniverse | iOS | iOS 14.0 or later | Yes, bug fixed | Free | USA | English | Photography (object) | Yes | Contact info, diagnostics, identifiers, location, usage data, user content | LiDAR capable devices is required |
| Trendideen Lueers | Projook–3D Scan | Android | Android 4.4 or later | No | Free | Germany | English | Photography (object) | No | Contact info, identifiers, usage data, user content | Optional setting for privacy |
| Trnio Inc. | Trnio 3D scanner | iOS | iOS 13.0 or later | No | In app purchase | USA | English | Photography (object) | Yes | No data available | Sale termination |
| Trnio Plus 3D scanner | iOS | iOS 15.0 or later | In app purchase | USA | English +5 more | Photography (object) | No | No data available | Sale termination, LiDAR capable devices is required | ||
| Tycho Technolgoies Pvt Ltd | Scanamaze | Android | Android 7.0 or later | Yes, bug fixed, performance | Free | India | English | Photography (object) | No | User content | No optional setting for privacy |
| Vastly Underrated GmbH | xplicator 3D scan | iOS | iOS 9.3 or later | No | In app purchase | Germany | English | Photography (object) | No | No data available | Last update in March 2018 |
| WOGO inc. | WIDAR – 3D scan and edit | iOS, Android | iOS 14.5 or later | No | In app purchase | Japan | English +1 more | Photography (object) | No | Contact info, identifier, location, usage data, user content | |
| Xplorazzi Tech | 3D Scanner Pro | Android | Android 5.1 or later | No | In app purchase | USA | English | Photography (object) | No | No data available | Sale termination |
| xOne 3D Scanner | Android | Android 8.0 or later | Yes, bug fixed, performance | In app purchase | USA | English | Photography (object) | No | No data collection | ||
| XRPro, LLC |
Scanner–Structure SDK |
iOS | iOS 13.0 or later | Yes, performance | Free | USA | English | Photography (object) | No | Identifier, usage data | Structure sensor is required |
| Xyken | SureScan 3D Scanner, 3D App | iOS | iOS 15.0 or later | Yes, performance | In app purchase | USA | English | Photography (object) | No | No data collection | |
- Abbreviations: App, Application; iOS, iPhone operating system; LiDAR, light detection and ranging technology; MacOS, Macintosh operating system.
In 2023, 25 different companies actively released new versions of various applications, addressing technical issues or bug fixes, improving user interface, optimizing the SSA, managing security, and enhancing the system compatibility and performance. Performance improvements included expanding file format options, sharing capabilities, transformation and data capturing. While 40% of applications could be downloaded for free, the remaining SSA required payment for file export through in-app purchases. All SSA were in English, with 14% (n = 9) supporting a second language (French) and 14% (n = 9) supporting more than three languages.
Among the applications in the list, 13 were used in scientific literature (123D Catch, 3D Creator, Bellus 3D Dental Pro, Bellus 3D Face app, Bellus 3D Face Maker, Capture, Heges, Metascan, Polycam, Scandy Pro, Scaniverse, Tap tap tap and Trnio), and of these, six had terminated sales (123D Catch, Bellus 3D Dental Pro, Bellus 3D Face app, Bellus 3D Face Maker, Heges and Trnio), while two (Capture and Tap tap tap) lacked further information. In terms of privacy data collected by applications, 23 applications collected various types of user data. On other hand, 19 applications, including those with terminated sales (30%), did not provide data collection details, and 20 applications (32%) explicitly stated that they did not collect any data. Figure 1 illustrates examples of scans from commercial scanners alongside some available SSA.
3.2 Part 2: Scoping review of the literature
After removing duplicates, a total of 11 293 citations were identified through electronic databases and manual searching, from which 56 studies2, 22-25, 28, 33-82 were considered eligible for review. Figure 2 presents the search flowchart.
The characteristics of the included studies are described in Table 2. The 56 studies comprised two case reports (4%),51, 66 16 proof-of-concept (28%)28, 35-37, 40, 48, 52, 53, 56-58, 73, 79-82 and 38 experimental studies (68%).2, 22-25, 33, 34, 38, 39, 41-47, 49, 50, 54, 55, 59-65, 67-72, 74-78 There is a notable increase in publications, ranging from one publication in 201635 to 18 in 2022.28, 40, 42-44, 47, 49, 51, 57, 58, 61, 64, 66, 67, 69, 71, 72, 82 These studies were primarily conducted in the fields of dentistry (n = 44)2, 22-25, 28, 33, 34, 36-55, 58-66, 68, 70-72, 74, 77, 81 and medicine (n = 12),35, 56, 57, 67, 69, 73, 75, 76, 78-80, 82 encompassing forensics, general medicine, neurology, ophthalmology and plastic surgery. Half of the facial scanning application implementations were in comparative studies that contrasted smartphone applications with dedicated clinical scanners (50%).2, 23-25, 28, 33, 34, 38, 41, 45, 47, 49, 50, 54, 59-63, 67-70, 72, 74-77 The majority of studies included adult participants (n = 38, 68%),22, 24, 33-44, 46-49, 51-55, 57, 59-61, 63-65, 68, 70, 71, 74, 75, 77, 78, 81 followed by children (n = 7, 12%),28, 56, 58, 66, 67, 69, 79 model or mannequin heads (n = 8, 14%),2, 23, 25, 45, 50, 62, 72, 76 human cadavers (n = 2, 4%)80, 82 or did not disclose this information (n = 1, 2%).73
| Application(s) | Author, year | Study design | Field of study | Application integration | Objectives | Study population | Clinical applicability | |
|---|---|---|---|---|---|---|---|---|
| 1 | 123D Catch | Elbashti et al., 201923 | Experimental |
|
Comparison | To evaluate the accuracy of a smartphone application for digitizing a facial defect for 3D modelling | A stone model with defect | Data acquisition with a smartphone SSA for 3D modelling is not as accurate as that achieved with commercial laser scanner |
| 2 | 123D Catch | Salazar-Gamarra et al., 201635 | Proof of concept |
|
Workflow | To present technique to obtain 3D models using mobile device and free software for 3D printing facial prosthesis | An adult who needed prosthetic rehabilitation | SSA could be a feasible solution for obtaining 3D model for maxillofacial prosthesis, especially with a user-friendly tutorial that serves clinical needs |
| 3 | 3D Creator | Daher et al., 201836 | Proof of concept |
|
Workflow | To explain a simple and accessible workflow that use 3D facial scanning benefits to general practitioners | An adult patient | SSA can be a cost-effective and fast tool for processes that do not require high precision, such as patient education and 3D digital smile design |
| 4 | Bellus 3D Dental Pro | Li et al., 202137 | Proof of concept |
|
Workflow | To describe the application of a virtual dental patient with dynamic occlusion during aesthetic restoration in a digital workflow | An adult Patient who needed aesthetic restoration of maxillary incisor | Face scan obtained from SSA can be used to create virtual dental patient with dynamic occlusion, improving aesthetic outcomes |
| 5 | Bellus 3D Dental Pro | Lin et al., 202338 | Experimental |
|
Comparison, Research tool | To compare the performance of various virtual articulator mounting procedures | 14 Healthy adults | The use of SSA provides a suitable and radiation-free option for clinicians |
| 6 | Bellus 3D Dental Pro | Oancea et al., 202039 | Experimental |
|
Research tool | To test the reliability of the correlation between the occlusal vertical dimension and anthropometric/cephalometric methods | 10 healthy adults | SSA can help with predictable occlusal vertical dimension registration, with strong agreement between measurements, but additional measurement methods are still necessary for determination |
| 7 | Bellus 3D Dental Pro | Pan et al., 202240 | Proof of concept |
|
Workflow | To introduce a customized mask retainer for improved surgical mask fit | 10 healthy adults | SSA can provide 3D facial scan data at a low price and can be incorporated for 3D printing techniques |
| 8 | Bellus 3D Dental Pro | Pelliterri et al., 202141 | Experimental |
|
Comparison | To compare the degree of accuracy of facial scanners as routine diagnostic tests | 25 healthy adults who had finished growing | SSA had slightly less consistent distance measurements than the commercial scanner, but both methods produced comparable, consistent, and reproducible scans |
| 9 | Bellus 3D Dental Pro | Raffone et al., 202242 | Experimental |
|
Research tool | To investigate the trueness and precision of a low-cost portable face scanner, with two different scan techniques |
10 healthy adults |
SSA can be suitable for clinical use with the suggestion of using guided technique for reliable clinical use with motion artefact reduction |
| 10 | Bellus 3D Dental Pro | Raffone et al., 202243 | Experimental |
|
Research tool |
To evaluate matching reliability of multiple face scans using frontal adhesives references |
9 healthy adults | SSA with adhesive references seems to be suitable for clinical superimposition, even with different facial expressions |
| 11 | Bellus 3D Dental Pro | Thurzo et al., 202244 | Experimental |
|
Comparison | To assess accuracy of facial scan created with TrueDepth sensors compared to facial surface from the CBCT | 60 healthy adults | TrueDepth sensor with SSA has limited clinical applicability and cannot yet match CBCT accuracy due to differences in distance, with variations over 3 mm in some facial regions |
| 12 | Bellus 3D Dental Pro | Thurzo et al., 202228 | Proof of concept |
|
Workflow | To introduce a non-invasive 3D scanning and printing method for addressing problems from upper airway obstruction | An infant with Pierre Robin sequence | TrueDepth sensor with SSA is an accessible 3D facial scanner that can be used to create orthodontic appliances with personalized extraoral parts |
| 13 | Bellus 3D Dental Pro, Capture, Heges, Scandy Pro | Kühlman et al., 202345 | Experimental |
|
Comparison | To investigate overall and regional accuracy (trueness and precision) of facial scans from four SSA | A mannequin head | Mean absolute differences and standard deviations for trueness and precision of all SSA are less than 1 mm, which can be considered highly acceptable for clinical use |
| 14 | Bellus 3D Dental Pro | Caputo et al., 202346 | Experimental |
|
Workflow | To evaluate swelling after impacted third molar removal with two osteotomy methods | 22 healthy adults | SSA can provide 3D facial scans as reliable data for objective and reproducible comparisons, reducing variables of error |
| 15 | Bellus 3D Face app | Mai et al., 202247 | Experimental |
|
Comparison | To evaluate effects of extraoral markers on facial integration accuracy in smartphone and stereophotogrammetry face scanning | 10 healthy adults with full anterior teeth | Stereophotogrammetry is generally more accurate than smartphones, especially with markers, as smartphones are susceptible to motion artefacts |
| 16 | Bellus 3D Face app | Swennen et al., 202048 | Proof of concept |
|
Workflow | To present a proof of concept and prototype of a reusable custom-made 3D printed face mask | A healthy adult | Smartphones with SSA s make 3D facial scanning available worldwide with the proof of their value in the workflow |
| 17 | Bellus 3D Face app | Wang et al., 202249 | Experimental |
|
Comparison | To evaluate the trueness of one stationary and two mobile systems for 3D facial scanning | Healthy adults | SSA provides reliable 3D reconstruction, but smartphone capacity and data acquisition sequence may affect trueness |
| 18 | Bellus 3D Face app | Gallardo et al., 202350 | Experimental |
|
Comparison | To evaluate the trueness of 3D facial scanning by using Bellus3D and + ID ReCap Photo | A mannequin head | SSA demonstrated clinically acceptable trueness, but lower repeatability compared to a portable structured-light scanner |
| 19 | Bellus 3D Face app | Atusay et al., 202251 | Case report |
|
Workflow | To describe workflow for patient smile transformation using intraoral scanner, SSA and design software | An adult patient with current smile dissatisfaction | SSA can effectively deliver desired outcomes to patients and facilitate treatment planning and fabrication processes |
| 20 | Bellus 3D Face app | Granata et al., 202052 | Proof of concept |
|
Workflow | To describe workflow for integrating 3D files from intraoral, CBCT and facial scans as well as their clinical use with the digital bite device | An adult with planned for implant-supported maxillary prosthesis | SSA can provide 3D facial scans to be integrated into the workflow along with intraoral scans and CBCT using digital bite |
| 21 | Bellus 3D Face app | Lo Russo et al., 201953 | Proof of concept |
|
Workflow | To describe the procedure for merging intraoral, perioral, nose scans obtained with intraoral scanner with face scan obtained with mobile phone | An adult with complete edentulism | Combining 3D facial scans from SSA with intraoral scans effectively integrates into a digital patient for optimizing individual tooth arrangement in digital denture design |
| 22 | Bellus 3D Face app | Mai et al., 202054 | Experimental |
|
Comparison | To evaluate the impact of reference images on dentofacial integration accuracy in smartphone and stereophotogrammetry face-scanning systems | A healthy adult with full anterior teeth | SSA ‘s scan quality may be inferior to stereophotogrammetry due to depth sensitivity, especially in regions with low depth contrast, such as central incisors, resulting in reconstruction difficulties |
| 23 | Bellus 3D Face app | Popov et al., 202378 | Experimental |
|
Research tool | To access accuracy, precision, inter-operator reliability of method using SSA as exophthalmometer | Adults with exophthalmos and healthy adults | SSA provide high accuracy and precision, inter-operator reliability for smartphone exophthalmometry |
| 24 | Bellus 3D Face app | Singh et al., 202377 | Experimental |
|
Research tool | To compare accuracy of 3D images obtained from SSA, direct anthropometry and static stereophotogrammetry | 22 healthy adults who underwent orthognathic surgery | SSA demonstrated no difference in linear and angular measurements compared to the clinical standard, with fair trueness and clinically acceptable variation in differences |
| 25 | Bellus 3D Face app | Abbate et al., 202355 | Experimental |
|
Workflow | To quantitatively measure the degree of facial ptosis in diverse population, according to gender, age and BMI | 60 healthy adults | Facial scans obtained by SSA provided very accurate, low cost, easily reproducible facial scans suitable for morphological study |
| 26 | Bellus 3D Face app | Akan et al., 202133 | Experimental |
|
Comparison | To investigate the clinical effectiveness and practicality of 3D facial soft tissue captured with a smartphone | 26 healthy adults without moustache or beard | Smartphones equipped with depth sensors are suitable options for 3D imaging in clinical practice. The scans partially resemble scans from static stereophotogrammetry devices |
| 27 | Bellus 3D Face app | Alazzam et al., 202156 | Proof of concept |
|
Workflow | To demonstrate the use of affordable technology, combining a smartphone, open-source CAD software and a 3D printer for planning ear location in unilateral microtia reconstruction | A child with unilateral microtia reconstruction | SSA was chosen for its user-friendly interface and child safety. It integrates with CAD system for cost-effective and time-saving pre-operative treatment planning |
| 28 | Bellus 3D Face app | Alhazmi et al., 202257 | Proof of concept |
|
Workflow | To present workflow for producing custom facial orthosis for burn scar management using a smartphone scanner and desktop 3D printing | An adult patient with facial burn scar | Using smartphone-based scanner is a key advantage in this digital framework with CAD and 3D printing. Smartphone camera and software advancements provide comparable precision to commercial scanners |
| 29 | Bellus 3D Face app | Alisha et al., 202258 | Proof of concept |
|
Workflow | To describe an innovative metal frame for aiding in hassle-free, reproducible 3D scanning of infants born with craniofacial deformity | A child with unilateral cleft lip and palate | A smartphone-based scanner, combined with a frame, provides distortion-free scans in seconds, proving its usefulness in real-time clinical scenarios |
| 30 | Bellus 3D Face app | Amornvit and Sanohkan, 20192 | Experimental |
|
Comparison | To analyse the facial scans and compare them with those obtained from various scanners with the direct measurement | Printed polylactic acid model | SSA showed low accuracy in measuring length and depth, requiring further development. However, it spent the least time scanning |
| 31 | Bellus 3D Face app | Andrews et al., 202324 | Experimental |
|
Comparison | To evaluate the trueness and precision of SSA and assess post-processing analysis reliability | 29 healthy adults | TrueDepth camera with the SSA captures facial images acceptably, with excellent precision and high repeatability. It is a cost-effective, portable and clinically suitable alternative for facial scans |
| 32 | Bellus 3D Face app | Dallazen et al., 202359 | Experimental |
|
Comparison | To compare 2D and 3D methods used in post-operative oedema assessment following surgical removal of the third molar | 20 healthy adults | Facial scans from smartphones and photogrammetry showed no difference with moderate correlation. Scans accurately outline and demonstrate pre- and post-oedema differences objectively |
| 33 | Bellus 3D Face app, Heges, Capture, Scandy Pro, Trnio | Dzelzkaleja et al., 202160 | Experimental |
|
Comparison | To find and test SSA that are suitable for 3D face scanning purposes | 2 healthy adults | SSA have room for improvement in both software and hardware, as they currently vary in their approaches and all have some limitations |
| 34 | Bellus 3D Face app, Capture | D‘Ettorre et al., 202261 | Experimental |
|
Comparison | To compare 3D facial scans obtained using two TrueDepth system-supported SSA and stereophotogrammetry-based device | 40 healthy adults | SSA with TrueDepth sensors show promising accuracy with longer acquisition times than stereophotogrammetry but are portable and cost-effective |
| 35 | Bellus 3D Face app, Scandy Pro, Heges | Loy et al., 202362 | Experimental |
|
Comparison | To investigate the accuracy 3D facial scanning SSA compared to professional scanner | A mannequin head | SSA had comparable trueness, precision and reproducibility to professional scanners, with no clinically significant differences for craniomaxillofacial purposes, with mostly errors less than 1 mm |
| 36 | Bellus 3D Face app, Bellus 3D Face Camera Pro | Amezua et al., 202163 | Experimental |
|
Workflow, Comparison | To assess the impact of the facial scanning method on the precision and repeatability of a virtual facebow record technique | An adult with full dentate, class I occlusion and mesoprosopic facial form | SSA offer advantages such as affordability, ease of use, minimal patient disturbing and shorter scanning times. But structured-light devices give better accuracy, significantly improving virtual facebow record repeatability |
| 37 | Bellus 3D Face Camera Pro | Liu et al., 202125 | Experimental |
|
Comparison | To compare the trueness and precision of Bellus 3D and 3dMD with each other and with direct anthropometry | A mannequin head | SSA could be clinically accepted as a substitute, as the mean difference between the commercial scanner is submillimeter, with clinically acceptable trueness for diagnosis and treatment planning, and good repeatability |
| 38 | Bellus 3D Face Camera Pro | Piedra-Cascón et al., 202022 | Experimental |
|
Research tool | To evaluate the accuracy of a dual-structured light facial scanner and to measure the interexaminer variability | 10 healthy adults with complete dentate | Integrated SSA dual-structured light scanner is non-invasive, accurate, reproducible, with relatively high precision, and clinically acceptable for treatment planning purposes |
| 39 | Bellus 3D Face Camera Pro | Friscia et al., 202264 | Experimental |
|
Research tool | To evaluate the efficacy of Hilotherapy face mask in reducing facial oedema after orthognathic surgery | 74 healthy adults with Class III undergoing orthognathic surgery | SSA is an accurate, low-cost, smart, fast, repeatable and a self-made tool for face scanning |
| 40 | Bellus 3D Face Camera Pro | Revilla-León et al., 202065 | Experimental |
|
Research tool |
To analyse the perceptions regarding disparities of the maxillary dental midline and the occlusal plane when analysing on 2D and 3D simulations |
A healthy adult | SSA can be used to create 3D model which obtained overall higher ratings than 2D images |
| 41 | Bellus 3D ProFace, Heges | Beretta et al., 202266 | Case report |
|
Workflow | To demonstrate how technology and diagnostic imaging enable 3D integration of face scan and intraoral scan | Children | TrueDepth technology is an effective substitute, as smartphone are portable, cheaper, more accessible user-friendly for all clinicians |
| 42 | Bellus 3D ProFace, Heges | Kamath et al., 202267 | Experimental |
|
Comparison | To reduce skin mask pressure, mask strap tension and evaluate several facial scanning technologies | 14 infants with level II and III NICU | SSA was mobile, non-invasive, low cost, rapid and accurate tool to develop accurate 3D models |
| 43 | Bellus FaceMaker, Heges, Scandy Pro, Scaniverse, Trnio | Van Lint et al., 202368 | Experimental |
|
Comparison | To compare smartphone SSA portable photogrammetry-based device | 50 healthy adults | Applications on smartphones or tablets can be valuable in the field of facial imaging. Some SSA offer clinical scanning possibilities |
| 44 | Capture | Campomanes et al., 202269 | Experimental |
|
Comparison | To describe a method for using a smartphone scanning application to capture facial anatomy for custom glasses design | 3 Children with craniosynostosis, hydrocephalus and microtia (for comparison) | A method using SSA can provide a non-invasive, portable, low-cost solution for 3D surface scanning for patients with craniofacial anomalies |
| 45 | Heges | Bartella et al., 202370 | Experimental |
|
Comparison | To evaluate two face scanning SSA can produce sufficiently accurate data for clinical analysis | 50 healthy adults | smartphone-based device was more user friendly and appear to be adequate for patient education despite errors of up to 3 mm |
| 46 | Heges | Li et al., 202271 | Experimental |
|
Workflow | To investigate the trueness and precision of virtual facebow records using a smartphone as a 3D face scanner | 2 healthy adults with full dentition | The use of SSA in dental practice shows promise as it accurately captures maxilla position with deviations around 1 mm in linear distance and 1° in angulation |
| 47 | Heges | Unkovskiy et al., 202272 | Experimental |
|
Comparison | To compare a stationary scanner, portable extraoral structured light scanner, intraoral scanners and smartphone-based scanner | 4 models with detailed replicas of nasal, orbital, auricular defects, and intact auricle | SSA showed clinically acceptable trueness but lower precision. The use of SSA in maxillofacial rehabilitation should be approached with caution due to inconsistent accuracy |
| 48 | Heges | Xia et al., 202379 | Proof of concept |
|
Workflow | To propose smartphone-based registration system for infant full-head scan | An infant | SSA are low-cost system which can achieve the full-head 3D scan within 2 s |
| 49 | Heges | You et al., 202173 | Proof of concept |
|
Workflow | To describe workflow for individualized 3D printed ear model fabrication | A patient with microtia | SSA has the distinct advantages of low cost, wide availability and portability, raising the possibility for clinicians to incorporate 3D printing in various clinical applications |
| 50 | MeiXuan | Chong et al., 202174 | Experimental |
|
Comparison | To evaluate the validity and reproducibility of self-developing imaging system | 20 healthy adults | Self-developed application was proven to be accurate and reliable for clinical use |
| 51 | Metascan | Krogager et al., 202380 | Proof of concept |
|
Workflow | To adapt and test the technique for visualization of facial nerve's anatomy and analyse feasibility and limitation | A cadaver | Empirical testing and optimization of light condition, type of equipment, and post-processing software are required to optimal use SSA |
| 52 | Polycam | Inal et al., 202381 | Proof of concept |
|
Workflow | To describe technique for the use of SSA for scanning an ear to fabricate a 3D-printed cast of auricular prosthesis | An adult patient | SSA are a cost-effective way to obtain 3D data. Although they provide less accurate data than face scanner images, they can facilitate workflow |
| 53 | Scandy Pro | Rudy et al., 202075 | Experimental |
|
Comparison | To compare SSA with portable 3D camera used in plastic surgery | 16 healthy adults | The precision of smartphone-based scanners was superior to that of other portable 3D scanners, offering repeatable reliability at a relatively negligible cost |
| 54 | Scandy Pro | To et al., 202376 | Experimental |
|
Comparison | To compare self-developing imaging system with commercial scanners | A mannequin head | There is clinically similarly significant accurate performance between SSA, self-developed systems and commercial scanner |
| 55 | Tap tap tap | Nightingale et al., 202034 | Experimental |
|
Comparison | To quantitatively compare scans captured by inexperienced operators | 20 healthy adults without scar | SSA offer a potential alternative for use in clinical practice with ease of use for new operators |
| 56 | Trnio 3D scanner | Maiese et al., 202282 | Proof of concept |
|
Workflow | To introduce a new diagnostic tool for 3D autopsy report | 10 cadavers | SSA can provide trustworthy 3D models in terms of quality and measurement accuracy. It preserves 3D information, which is useful, especially in cases with traumatic lesions |
-
Note:
: Dentistry, 
: Forensics, 
: Medicine, 
: Neurology, 
: Ophthalmology, 
: Plastic surgery.
- Abbreviations: 2D, two-dimensional; 3D, three-dimensional; BMI, body mass index; CAD, computer-aided design; CBCT, cone beam computed tomography; SSA, smartphone scanning applications.
Regarding the 28 studies comparing SSA in Table 3,2, 23-25, 33, 34, 38, 41, 44, 45, 47, 49, 50, 54, 59-63, 67-70, 72, 74-77 a majority of them compared smartphone applications with commercial scanners based on the principle of stereophotogrammetry (static n = 92, 24, 25, 33, 47, 54, 61, 62, 77 and portable n = 541, 68, 70, 74, 75). Smartphones and tablets based on the iOS operating system were predominantly used, with the iPhone X (Apple Inc., CA, USA) being the most commonly employed device. Applications from Bellus 3D Inc. were the frequently utilized in 21 studies.2, 24, 25, 33, 34, 38, 41, 44, 45, 47, 49, 50, 54, 59-63, 67, 68, 77 The results indicated that smartphone applications offer cost-effective alternatives, with properties ranging from limited to acceptable when compared to commercial scanners.
| Author, year | Control | Test | Conclusion | ||
|---|---|---|---|---|---|
| Device used (hardware) | Principle | Device used (hardware) | Application (software) | ||
| Akan et al., 202133 | 3dMD Face System | Static sterophotogrammetry | iPhone X (Apple Inc. CA, USA) | Bellus 3D Face app (Bellus 3D, Inc, CA, USA) | Images acquiring with SSA show a partial similarity with the images acquired with 3dMD |
| Amezua et al., 202163 | Artec Space Spider | Portable structured light | iPhone X (Apple Inc. CA, USA), MediaPad M3 (Huawei Technologies Co, Ltd, Shenzhen, China | Bellus 3D Face app, Bellus 3D Face Camera Pro (Bellus 3D, Inc, CA, USA) | Accurate facial scanning significantly improved the repeatability of the virtual facebow record technique |
| Amornvit and Sanohkan, 20192 | EinScan Pro, EinScan Pro 2X Plus, Planmeca ProMax 3D Mid | Portable structured light, Static sterophotogrammetry | iPhone X (Apple Inc. CA, USA) | Bellus 3D Face app (Bellus 3D, Inc, CA, USA) | 3D scanner accuracy depends on scan length, pattern and technology |
| Andrews et al., 202324 | 3dMD Face System | Static sterophotogrammetry | iPhone 11 Pro (Apple Inc. CA, USA) | Bellus 3D Face app (Bellus 3D, Inc, CA, USA) | SSA can provide 3D model with acceptable accuracy and excellent precision |
| Bartella et al., 202370 | Nikon D5500 | Portable stereophotogrammetry | iPad Pro 3 (Apple Inc. CA, USA) | Heges 3D scanner (Marek Simonik, Saint Helena) | Photogrammetry demonstrated greater accuracy while SSA are more user friendly |
| Campomanes et al., 202269 | Not mentioned | Magnetic resonance imaging | iPhone X (Apple Inc. CA, USA) | Capture (Standard Cyborg Inc, CA, USA) | Measurements from SSA and MRI did not consistently differ |
| Chong et al., 202174 | Vectra H1 | Portable stereophotogrammetry | iPad/iPhone (Apple Inc. CA, USA) | MeiXuan (Beijing, China) | The developing 3D facial scanning system is validated to enable patients to take 3D images on their own |
| D‘Ettorre et al., 202261 | 3dMDtrio | Static sterophotogrammetry | iPhone Xs (Apple Inc. CA, USA) | Bellus 3D Face app (Bellus 3D, Inc, CA, USA), Capture (Standard Cyborg Inc, CA, USA) | SSA need precision and compliance, with cost and portability advantages |
| Dallazen et al., 202359 | Not applicable | Not applicable | iPhone 11 (Apple Inc. CA, USA) | Bellus 3D Face app (Bellus 3D, Inc, CA, USA) | Digital methods demonstrated greater homogeneity than manual method |
| Dzelzkaleja et al., 202160 | Not applicable | Not applicable | iPhone Xr (Apple Inc. CA, USA), Honour 20 (Huawei Technologies Co, Ltd, Shenzhen, China) | Bellus 3D Face app (Bellus 3D, Inc, CA, USA), Heges 3D scanner (Marek Simonik, Saint Helena), Capture (Standard Cyborg Inc, CA, USA), Scandy Pro (Scandy Inc, LA, USA), Trnio (Trnio Inc, USA), 3D Scanner Pro (Laan Labs, NY, USA) | Each SSA offered varying accuracy, pricing, user-friendliness and scanning times |
| Elbashti et al., 201923 | Vivid 910 | Laser scanner | iPhone 6 s (Apple Inc. CA, USA) | 123D Catch (Autodesk, CA, USA) | Data acquisition with an SSA is not as accurate as commercially available laser scanning |
| Gallardo et al., 202350 | ATOS Core | Portable structured light | iPhone X (Apple Inc. CA, USA) | Bellus 3D Face app (Bellus 3D, Inc, CA, USA), ReCap Photo (Autodesk Inc, CA, USA) | Both systems produced clinically acceptable 3D face models for aesthetic restoration planning |
| Kamath et al., 202267 | Anaheim, Artec Space Spider | Photogrammetry, portable structured light | iPhone X (Apple Inc. CA, USA) | Bellus 3D ProFace (Bellus 3D, Inc, CA, USA), Heges (Marek Simonik, Saint Helena) | SSA are low-cost, safe, rapid and accurate for preterm infant facial topography |
| Kühlman et al., 202345 | Not applicable | Not applicable | iPad Pro 4 (Apple Inc. CA, USA) | Bellus 3D Dental Pro (Bellus 3D, Inc, CA, USA), Capture (Standard Cyborg Inc, CA, USA), Heges (Marek Simonik, Saint Helena), Scandy Pro (Scandy, LA, USA) | Trueness and precision of SSA were clinically acceptable for diagnosis and treatment planning |
| Lin et al., 202338 | Not applicable | Not applicable | iPhone 13 Pro (Apple Inc. CA, USA) |
Bellus 3D Dental Pro (Bellus 3D, Inc, CA, USA), Heges (Marek Simonik, Saint Helena) |
The performance of both SSA in virtual mounting was similar |
| Liu et al., 202125 | 3dMD Face System | Static sterophotogrammetry | Samsung Galaxy Table 3 (Samsung, Suwon, South Korea) | Bellus 3D Face Camera Pro (Bellus 3D, Inc, CA, USA) | The trueness of each scanner was clinically acceptable for diagnosis and treatment planning |
| Loy et al., 202362 | 3dMD Face System, Vectra H2, Artec EVA | Static sterophotogrammetry | iPhone 12 Pro (Apple Inc. CA, USA) | Bellus 3D Face app (Bellus 3D, Inc, CA, USA), Scandy Pro (Scandy, LA, USA), Hedges (Marek Simonik, Saint Helena) | SSA had comparable trueness, precision and reproducibility to professional systems |
| Mai et al., 202054 | Canon EOS 100D | Static sterophotogrammetry | iPhone X (Apple Inc. CA, USA) | Bellus 3D Face app (Bellus 3D, Inc, CA, USA) | Integration accuracy relied on markers and there was no difference between devices with references |
| Mai et al., 202247 | Canon EOS 100D, MetraSCAN-R | Static sterophotogrammetry, portable laser scanner | iPhone X (Apple Inc. CA, USA) | Bellus 3D Face app (Bellus 3D, Inc, CA, USA) | Integration accuracy was enhanced with the use of extraoral markers and stereophotogrammetry system |
| Nightingale et al., 202034 | Artec Space Spider | Portable structured light | iPhone 8 s (Apple Inc. CA, USA) | Tap tap tap (LLC, USA) | SSA offers fast, noninvasive, cost-effective scanning with quick operator learning |
| Pelliterri et al., 202141 | Face hunter facial scanners | Portable stereophotogrammetry | Not mentioned | Bellus 3D Dental Pro (Bellus 3D, Inc, CA, USA) | Facial scan provides excellent analytical tool for clinical evaluation |
| Rudy et al., 202075 | Vectra H1 | Portable stereophotogrammetry | iPhone X (Apple Inc. CA, USA) | Scandy Pro (Scandy, LA, USA) | SSA is accurate and precise to within 0.5 mm compared to commercial scanner |
| Singh et al., 202377 | 3dMD Face System | Static sterophotogrammetry | iPhone 12 (Apple Inc. CA, USA) | Bellus 3D Face app (Bellus 3D, Inc, CA, USA) |
SSA have limited clinical applications specific to macro-proportional áreas such as central and flat facial regions |
| Thurzo et al., 202244 | Not mentioned | Cone beam computed tomography | Not mentioned | Bellus 3D Dental Pro (Bellus 3D, Inc, CA, USA) | Significant differences over 3 mm in facial regions limit TrueDepth sensor clinical use |
| To et al., 202376 |
EinScan Pro 2X Plus, Arc-7 |
Portable structured light | iPhone 11 (Apple Inc. CA, USA) | Scandy Pro (Scandy, LA, USA) | Self-developing system competes well with mid-cost scanners in terms of accuracy, portability and affordability |
| Unkovskiy et al., 202272 | Artec Space Spider | Portable structured light | iPhone 11 Pro (Apple Inc. CA, USA) | Heges (Marek Simonik, Saint Helena) | SSA showed clinically acceptable trueness but inferior precision |
| Van Lint et al, 202368 | Vectra H1 | Portable stereophotogrammetry | iPad Pro (Apple Inc. CA, USA) | Heges (Marek Simonik, Saint Helena), Bellus Face App (Bellus 3D, Inc, CA, USA), Scandy Pro (Scandy, LA, USA), Scaniverse (Toolbox Al, Inc, CA, USA), Trnio (Trnio Inc, USA) | Bellus, Trnio and Scaniverse s are not significantly different from the gold standard |
| Wang et al., 202249 | Arc-7, EinScan Pro 2X Plus | Portable structured light | iPad Pro 2020 (Apple Inc. CA, USA) | Bellus 3D Dental Pro (Bellus 3D, Inc, CA, USA) | All systems are reliable 3D facial scan, but structured light scanner is recommended for higher trueness |
- Abbreviations: 3D, three-dimensional; MRI, magnetic resonance imaging; SSA, smartphone scanning applications.
Regarding clinical applicability, 79% of articles focused on research in dentistry, where SSA were employed for orthodontics, restorative dentistry, prosthodontics and surgery. The most common clinical purposes were morphological analysis, SSA accuracy and performance assessment, and documenting facial changes pre- and post-operatively. SSA were also integrated into digital workflows for designing prostheses and restorations. Most studies concluded that, although SSA do not always achieve the precision of commercial scanners, they offer clinically acceptable results and can provide a high degree of trueness and repeatability, while being cost-effective and user-friendly. The remaining studies (21%) were focused on medical purposes, with SSA being employed in fields such as forensics, ophthalmology, neurology, plastic surgery and non-specific medical specialties. Most studies concluded in this category concluded that SSA applications are practical and efficient choice for creating 3D models in clinical settings, as they are considered user-friendly, cost-effective, non-invasive and could be integrated into digital workflows with reliability comparable to commercial scanners.
4 DISCUSSION
Although commercial scanners have existed for decades, their application remains largely confined to advanced medical centres due to various constraints. In this context, this hybrid review aims to explore the balance between scientific knowledge and clinical needs. Our results reveal the presence of several SSA in the market with potential for face scanning, 75% of which were designed for the iOS operating system. This system receives more frequent updates compared to those on the Android system, potentially influencing users' choices. The possibility of downloading the SSA and using a trial phase could also impact decision-making, allowing users to assess performance before committing to a purchase or subscription.
In 2022, in compliance with the European Union (EU) protection policy, particularly the General Data Protection Regulation (GDPR), all applications submitted or updated in the Apple App Store and Google Play Store were required to declare privacy data collection. This regulation significantly impacted the dynamics and potential termination of SSA sales.83, 84 According to our results, it is possible to obtain facial scans with SSA without collecting facial images by selecting SSA that clearly declare no data collection, particularly in updates after 2022. This was clearly stated in 32% of the available applications observed in this study. Nevertheless, it is crucial to emphasize that this information regarding no data collection is declared by developers, and thus, it cannot be fully verified. Furthermore, SSA may be classified as medical devices based on their intended use, falling under the Medical Device Regulation outlined in EU Regulation 2017. Developers are also required to demonstrate their legal compliance to ensure their safety and intended functionality.85, 86 This regulatory aspect could potentially explain why 11 SSA were terminated from sales and left the market, as they may have lacked proper certification and could influence the statement of purpose of the applications. None of the SSA included in this review explicitly define themselves as suitable for medical or clinical use.
The SSA reported in scientific studies were used for several clinical purposes, primarily in morphological analysis and integration into digital workflows to produce prostheses.2, 22-25, 28, 33-76, 81 The diverse study populations, including both adults and children, confirm the safety and non-invasiveness of this technology, particularly in cases where traditional methods like photogrammetry and laser scanners are unsuitable for neonatal faces.67 Although SSA still provide less accuracy and precision than commercial scanners, they do provide clinically acceptable trueness and repeatability. However, their potential limitation lies in depth sensitivity, especially in areas with low depth contrast such as central incisors, leading to challenges in reconstruction.38 Of course, the demand for accuracy varies across different clinical processes. The continuous development of both smartphones and applications advancements, as well as their integration into scanners have made comparative studies a focal point in exploring possible alternatives to traditional scanners. This suggests that, despite their promising capabilities, the application of SSA in clinical settings should be approached cautiously, considering factors such as GDPR compliance and obtaining the patient's consent, as facial scans inherently contain important data for identification.
For comparative studies,2, 23-25, 33, 34, 38, 41, 44, 45, 47, 49, 50, 54, 59-63, 67-70, 7274-77 scanners based on stereophotogrammetry, such as the 3dMD Face System (Atlanta, GA, USA), Vectra H1-2 (Canfield Scientific, NJ, USA), Face hunter facial scanners (Zirkonzahn GmbH, Gais, Italy), or professional cameras with post-processing software, considered clinical standards, were commonly used as references. However, researchers choosing SSA based on the results present in the existing literature should be mindful of their dynamic nature, as these applications are rapidly updated to enhance performance and capabilities. Conversely, non-updated or outdated SSA may become less effective and could eventually discontinue their services due to various limitations. The selection of applications may also be influenced by highly recommended SSA that appear on search engines during the research period, such as Heges, Scandy Pro, Scaniverse and Trnio. While checking online platforms provides the advantage of staying up to date, the clinical validity of these applications may not have been thoroughly validated. Overall, the conclusions from the comparative studies2, 23-25, 33, 34, 38, 41, 44, 45, 47, 49, 50, 54, 59-63, 67-70, 72, 74-77 suggest that SSA have the potential to be valuable tools in various clinical and diagnostic settings, offering advantages including cost-effectiveness, portability, and user-friendliness. Again, their accuracy and precision, exceeding 3 mm in some regions, should be carefully considered, particularly in specific clinical applications.
The limitation of this review derives from the hybrid nature of scoping reviews, combining scientifically validated information with an exploration of available SSA with potential use for oral healthcare applications. This approach, while comprehensive, may have overlooked some SSA due to the specific search terms used and their availability on search engines. Despite this, we believe the review offers valuable insights for clinicians and researchers seeking innovative, alternative approaches in patient care. Beyond the scope of this review, a notable observation is the gap between the rapid development of digital marketing in scanning technologies, smartphones, and SSA, and the gradual pace of clinical validation and publication. This gap is not a reflection of any shortcomings in research, nor is it the fault of researchers. It is rather an aspect of the pace at which scientific advancement lags behind technological development and commercialization. Nevertheless, clinical validation is crucial for further implementation in clinical settings and the review should also be re-conducted for an update every 5 years.
5 CONCLUSION
Fifty-two SSA currently available in the market can perform facial scanning and can be used clinically, addressing aims 1 and 2. Regarding aim 3, only 13 SSA applications have been clinically validated so far (123D Catch, 3D Creator, Bellus 3D Dental Pro, Bellus 3D Face app, Bellus 3D Face Maker, Capture, Heges, Metascan, Polycam, Scandy Pro, Scaniverse, Tap tap tap and Trnio), where only five applications are currently available (3D Creator, Metascan, Polycam, Scandy Pro and Scaniverse). These applications could be an alternative option for scanning purposes in a clinical setting, offering user-friendliness, cost-effectiveness and portability. Moreover, they offer clinically acceptable trueness and repeatability, while remaining non-invasive for patients across all age ranges. However, it is crucial to note that SSA cannot yet achieve the full capabilities of commercial scanners, and further clinical validation is needed to make medical professionals aware of potential pitfalls and other limitations.
AUTHOR CONTRIBUTIONS
TJ: Conceptualization, methodology, data collection, analysis and interpretation, writing – original draft, writing – review and editing, final approval. XL: Conceptualization, methodology, data collection, writing – review and editing, final approval. RCF: Conceptualization, methodology, interpretation, supervision, writing – review and editing, final approval. MC: Conceptualization, methodology, interpretation, supervision, writing – review and editing, final approval. RJ: Conceptualization, methodology, supervision, writing – review and editing, final approval.
ACKNOWLEDGEMENTS
The authors would like to acknowledge Thomas Vandendriessche, Chayenne Van Meel, Norin Hamouda, and Krizia Tuand, the biomedical reference librarians of the KU Leuven Libraries – 2Bergen – learning Centre Désiré Collen (Leuven, Belgium), for their assistance in conducting the systematic literature search. Additionally, thanks to Hendrik De Beuckeleer and Lucas De Caluwe for their assistance in initially conducting partial of the application search and trials.
FUNDING INFORMATION
Self-funding.
CONFLICT OF INTEREST STATEMENT
The authors declare no conflict of interest.
ETHICS STATEMENT
Since the current study is a technical and a scoping review, ethical approval was not required as it does not involve direct human or animal subjects.
Open Research
DATA AVAILABILITY STATEMENT
The authors confirm that the data supporting the findings of this study are included within the article and its supplementary materials.
