## 1 Introduction  
Interproximal enamel reduction (IER) or stripping is considered an irreversible technique used to remove controlled amounts of interproximal enamel surfaces to achieve a reduction in the mesiodistal length of interproximal dental surfaces. The result is an increase in the available space in the dental arch [1, 2]. IER is considered a more conservative orthodontic therapy than dental extractions [3] and, therefore, it is used to increase the available space without tooth extractions, allowing for teeth alignment and correct labiovevision of the incisors [4] with a mild or moderate bone-dental discrepancy (BDD) between 4-8 mm [5, 6]. IER is also recommended to improve the unaesthetic appearance caused by the loss of the interidental papilla, which is a consequence of bone loss or occlusal interproximal tooth contact [7]. In addition, IER is also used in temporary dentition to facilitate the eruption of partially erupted teeth blocked by insufficient space [8]. However, IER procedures are not recommended in small teeth, hypoplasia, severe tooth rotations, high risk of caries, poor oral hygiene, and young patients with large pulp chambers [9]. In addition, mechanic and manual IER techniques have been reported [10,11] to affect the interdental tooth enamel surfaces, leaving grooves and scratches [12]. For this reason, final polishing of interproximal tooth enamel surfaces after IER procedures are mandatory to reduce the number of dental abrasions and to obtain an interproximal tooth surface similar to untreated interproximal tooth enamel surfaces [5], ensuring favorable long-term prognosis [13]. Many measurement procedures have been used to analyze interproximal tooth enamel surfaces after IER techniques; however, most studies have used microscopic measurement methods [14] and profilometry [15], which are useful for analyzing the micro-roughness on interproximal tooth enamel surfaces after interproximal tooth enamel surface removal. Nonetheless, it is impossible to apply this in clinical situations because it is necessary to extract the teeth. [PERSON] et al. and [PERSON] et al. reported a digital technique to analyze the total amount of stripping in order to calculate the maximum mesiodistal distance in teeth based on the position of the tooth's axis; however, the placement of this axis was not tested, and they measure neither the area nor the volume of the IER procedure [16,17]. However, the main novelty of the morphometric measurement technique is the possibility of using it in vivo in a clinical situation, wherein the acquisition of the digital information is done by intraoral scanners. The development of digital measurement procedures in dental research has increased the accuracy, simplicity, and versatility of acquiring information in research applications [18]. Intraoral scanners communicate easily with computer-aided design/computer-aided manufacturing (CAD/CAM) systems. This technology has also been introduced in orthodontics, thus allowing a completely digital workflow, from impression to final framework, with clinical reliability [19] and good patients' feedback [20]. Different image capture systems--i.e., triangulation, light stripe projection, confocal parallelism images, and stereophotogrammetric videos--have been used in dental research [21]. Regardless of the scanning method, the measurements led to a three-dimensional capture made up of a point cloud that represents the object and its reference in space [22]. The most widely used digital format is standard tessellation language (STL). This format describes a succession of triangulated surfaces, where each triangle is defined by three points on a surface, which allows for a high accuracy measurement [23]. This triangulation converts cloud points into the mesh in order to calculate the volume and area of different treatments carried out on the tooth surface.  
The aim of this study was to show a novel and accurate digital measurement protocol in order to analyze the area and volume of interproximal tooth enamel surface reduction.