## 1 Introduction  
Currently, the indications and limitations of conventional impressions are well documented through decades of in vitro and in vivo trials [1; 2]. An intraoral scanner (IOS) is used to directly record the structural surface shape of teeth and related structures within a patient's mouth in order to obtain a digital impression, and laboratory scanners are powerful machines capable of digitizing gypsum models or conventional impressions with a very small deviation in trueness and precision [3]. However, digital impressions are continually evolving, and there are still several unknowns that require thorough investigation.  
The accuracy of an impression, either conventional or digital, is essential for the longevity of the final restoration. The accuracy of a digital impression is determined by assessing two variables that are independent of each other: trueness and precision. The trueness of an IOS determines the ability of rendering a 3D model as closely as possible regarding surface geometry to the real dimensions of the scanned surface. The precision of an IOS dictates the reproducibility of a scan and, therefore, the predictability of a scan [4; 5].  
Several factors have been identified to have an influence on the accuracy of a digital impression. Ambiental lighting conditions can generate artefacts on the 3D model by oversaturating the scanned surfaces [6; 7; 8], the presence of liquid alters the reflective properties of intraoral structures [9], and the scanning patterns may lead to over scans with an increased chance of mesh stitching errors [10; 11]. Additionally, the experience of the operator, the calibration of the IOS, and the extension of the scanned surface have been shown to have an impact on the final accuracy of a digital model [12; 13; 14], alongside the scanning distance [15] and the model and generation of the IOS which must be taken into account [16].  
While in vitro scanning is in general easier to perform by following the recommended scanning protocol, in an in vivo scenario there are intraoral structures such as the buccal mucosa and the tongue that may impede the positioning of the scanning tip. The latest scanners provide fast surface recognition and data acquisition but, in most cases, a single scan of an area is not sufficient, since the light emitted from the IOS cannot reach all the surfaces of a tooth, particularly the interproximal spaces [17]. These mesh holes can also be intentionally created by the operator by cutting off sections of the digital impressions to remove unwanted overlapped oral tissues or after adjustments made on the abutments after the initial scan. Some studies have analyzed the influence of digital cutting, rescanning, and overlapping of scanned surfaces on the accuracy of a digital impression [18; 19], but the results can be inconsistent.  
The purpose of this study was to identify which protocol produced the most accurate digital impression of one single tooth preparation, in which data was acquired from a single uninterrupted scan, a rescanning of the area of interest in order to obtain more data, or the deletion of the area of interest followed by a rescan. The null hypothesis was that there would be no significant difference found in the trueness and precision of the IOS scans captured with the three different scanning protocols and that there would be no significant difference in the trueness and precision of the IOS scans between the analyzed in vivo and in vitro cases.