###### Abstract  
Background: Reverse engineering (RE) or back engineering is a process that analyzes a physical object to obtain the primary data of the same project. RE technologies have different applications in industrial settings and productive chains; however, with the advent of digital technologies in dentistry and orthodontic fields, they are involved in the new diagnostic and clinical digital workflow. For example, 3D model scanning, 3D facial scanning, models superimposition, digital orthodontic setup, anatomical volumetric assessment, soft tissue analysis, orthodontic digital guided systems, and prototyped orthodontic appliances represent a few examples of the application of RE in orthodontics. Moreover, clinicians can manipulate the data derived from original digital file to enhance diagnosis and communication with other clinicians and dental technicians; however, RE and digital technologies systems are not exempt from shortcomings, including costs and knowledge curve. In this regard, the aim of the present manuscript was to describe the use of reverse engineering technologies in modern digital orthodontics and provide helpful information for those specialists who are at the beginning of the transition from analogic to digital orthodontic workflow. reverse engineering; digital orthodontics; CAD/CAM appliances; orthodontics +
Footnote †: journal: Medical Imaging and Biomedical  
healthcare requires specialized competencies. In modern dentistry, cone-beam computed tomography (CBCT) has been the first example of RE scanning systems applied to craniofacial complex. In this respect, 3D reconstruction of the craniomaxillofacial region from CBCT is used in the diagnosis and planning of orthodontic treatment [5], maxillofacial surgery [6], oral implantology [7], often involving the transformation in a physical object (3D printing) for preliminary analysis. The use of 3D rendering of the maxilla and mandibular jaws is extremely useful for preoperative surgical planning and postoperative follow-up evaluation in oral and orthognathic surgery and for analyzing morphological, dimensional, and positional changes before and after orthodontic therapies [8; 9; 10]. Moreover, CBCT scans are fundamental to analyzing and detecting the magnitude and location of skeletal facial asymmetry, deformities, or asymmetry of temporomandibular joints (TMJ) and to planning surgical correction [11; 12; 13]. Intraoral scanners (IOS) and facial scanners (FS) represent the \"next generation\" of devices for reverse anatomical engineering aiming to obtain radiation-free surface data that can be used for both diagnosis and treatment plans and the design of oral appliances and devices. Additionally, it is possible to integrate these IOS and FS data with those obtained from CBCT for a comprehensive \"digitally-assisted\" diagnosis and treatment plan [14; 15]. Orthodontics is a field that has evolved significantly in recent decades. The introduction of 3D technology has remodeled this field, leading to more practical and patient-friendly treatment results. Furthermore, orthodontic patients \"have evolved\" with different expectations than in the past, particularly in terms of efficiency and aesthetics of the treatment and appliances used. In this regard, the integration of RE systems, CAD-CAM and 3D printing has revolutionized the orthodontic clinical workflow concerning diagnosis, doctor-patients communication, digitally assisted treatment plans, and customized and simplified appliance fabrication. The present paper aims to describe some applications of RE processes in modern dentistry, also with a specific focus on the orthodontic field and discuss their clinical indications. Start from the Basics: Simple Example of Reverse Engineering from Intra-Oral (IOS) and Facial Scans (FS)  
The basic application of RE and CAD-CAM systems in dentistry and orthodontics has the possibility of generating physical models from surface scan of dental arches.