Facial aesthetic analysis has great significance for comprehensive diagnosis and treatment planning among different dental specialities. Orthodontists often evaluate facial soft tissue using two-dimensional (2D) records, such as cephalograms and photographs from frontal and sagittal views [1,2]. Despite the fact that this method is still widely used, it does not provide a realistic result from the patient's facial surface [3,4].

With the advance of technology, high-quality three-dimensional (3D) facial imaging has become a tangible reality and is considered a reliable tool to capture facial topography [5]. Moreover, 3D surface imaging methods combine several images of an object from different perspectives into one 3D topography. They are a good alternative for routine or repeated facial imaging because these systems use visible and non-invasive light [5]. The technologies used for generating 3D images include digital stereophotogrammetry, laser-beam scanning, and structured light pattern methods [6,7].

According to the International Organization for Standardization 5725-1, accuracy refers to trueness and precision. The former consists of the ability of a scanner to provide a 3D reconstruction as close to its true dimensions as possible, and the latter refers to the level of agreement between independent facial images obtained by repeated scanning procedures under similar conditions. Therefore, precision analyses the reproducibility of the facial scanner [8].

Among the various methods, scanners incorporating stereophotogrammetry are the most used in dentistry [9], [10], [11]. This could be explained by their well-reported geometric trueness and precision [12], [13], [14]. However, the economic investment to acquire these systems is significantly high, and they are not necessarily easy to use because of their complex scanning protocols [15], [16], [17].

Alternatively, structured light is a promising 3D surface imaging reconstruction technology, and the latest versions of mobile devices, such as smartphones and tablets, are equipped with cameras based on this technology [18], [19], [20], [21], [22]. Cameras with infrared structured light depth-sensing work with the time-of-flight principle, which is the time taken for the light to travel from the sensor array to an object back and forth, and then a 3D image is reconstructed based on the depth map of the object and its surroundings [22], [23], [24]. Additionally, tablet and smartphone devices have a simple and easy-to-use interface, and developers can create and customize applications for 3D scanning with the use of open-source scripts and software coding [18,25].

This study aimed to investigate the overall and regional accuracy (trueness and precision) of digital three-dimensional face scans obtained by four tablet-based applications on an (iPad Pro) iPad Pro® 2020 (Apple Inc., Cupertino, CA, USA). The null hypothesis was that no significant differences in accuracy (trueness and precision) would be found between the digital and manual soft-tissue interlandmark measurements performed on the 3D facial reconstructions and the mannequin head, respectively.