Influence of Printing Angulation on the Accuracy (Trueness and Precision) of the Position of Implant Analogs in 3D Models: An In Vitro Pilot Study  
[PERSON]  
1 Department of Nursing and Estomatology, Faculty of Health Sciences, Rey Juan Carlos University, 28922 Madrid, Spain; [EMAIL_ADDRESS] (N.G. ); [EMAIL_ADDRESS] (M.F. ); [EMAIL_ADDRESS] (J.L.A.-M.); [EMAIL_ADDRESS] or rocio.cascos@universidadeupe.eas (R.C.) 1  
[PERSON]  
2 Department of Conservative Density and Prosthodomics, Faculty of Destrietry, 28040 Madrid, Spain 28670 Madrid, Spain 28040 Madrid, Spain 280  
using techniques such as cone beam computed tomography (CBCT) or intraoral and facial scanners. The data are then processed in CAD software, where the treatment indicated for each patient is designed. Finally, fabrication can follow one of two routes: subtractive or additive, each with its own particularities and optimal applications. Subtractive manufacturing involves the removal of material from a solid block using computer-controlled cutting tools. Traditionally associated with the machining and milling process, this method benefits from the wide availability of materials and proven efficiency and accuracy in fabricating dental restorations such as crowns, bridges, and implant frameworks. The subtractive technique can employ materials such as ceramics, nanoceramic resin composites, and metals. Its accuracy is remarkably high, although it is associated with higher material waste generation than additive methods. Subtractive equipment also requires maintenance and significant initial investment. On the other hand, additive manufacturing (AM), commonly known as 3D printing, builds objects layer by layer from a digital file. The American Society for Testing and Materials (ASTM) has described it as \"a process of joining materials to fabricate objects from 3D models, usually layer upon layer, in contrast to subtractive manufacturing methodologies\" [2]. Three-dimensional printing technology is subdivided into several techniques, including stereolithography (SLA), material jetting (MJP), direct energy deposition (DLP), material extrusion, powder bed fusion (PBF), sheet lamination, and binder jetting [3]. Among them, the most used technologies are SLA and MJP. Each technology has its particularity in terms of the materials it can process, the achievable resolution, and the production speed. Materials commonly used in dental 3D printing include light-curing resins, thermoplastic polymers, and, to a lesser extent, metals and ceramics. 3D printing is particularly advantageous in producing dental models, surgical splints, and prostheses, where geometric complexity or customization is crucial. In addition, this technique significantly reduces material waste and can be faster for certain types of objects [4]. The choice between subtractive and additive manufacturing depends on multiple factors, including the complexity of the restoration, material requirements, and time constraints. While subtractive manufacturing remains the standard for treatments that demand materials with specific mechanical and esthetic properties, additive manufacturing is emerging as a powerful alternative for applications that benefit from its ability to handle complex geometries and advanced customization. The extensive development and integration of CAD-CAM technology in dentistry has enabled various clinical applications, improving the quality and efficiency of treatments. As technology advances, we are likely to see an expansion in the capabilities and applications of both manufacturing techniques, promoting continued innovation in different dental treatments. In terms of treatments, many restorations can be fabricated employing these technologies, such as onlays, crowns, fixed partial dentures, veneers, implant abutments, full-mouth reconstructions, or orthodontic splints, among others [5]. In addition, these types of dental restorations are more anatomical and faster to produce compared to the traditional method created by laboratory technicians [6; 7].