## 1 Introduction  
The accuracy and precision of dental prosthetics are crucial for ensuring optimal performance, longevity, and patient satisfaction [1, 2]. The most popular computer-aided design/manufacturing (CAD/CAM) systems in dentistry, which are based on subtractive manufacturing (SM) technology, offer good accuracy and precision in dental prosthetics [3, 4]. However, the limitation of milling burrs in reaching all areas restricts the precise machining of fine and complex parts of dental prostheses. Additive manufacturing (AM) technology is a recent development in the field of dentistry that can address the limitations of SM technology. Recent advancements in three-dimensional (3D)-printing technology have revolutionized the manufacturing field, particularly in the production of complex geometries and customized structures in dentistry [5, 6, 7]. Among various 3D-printing techniques, polymer-based vat photopolymerization is notable because of its ability to produce highly detailed and precise dental prostheses. This process employs light to cure polymer-based resins into solid polymers, making it particularly suitable for applications requiring high accuracy and intricate details [8; 9].  
As technology advances, a variety of vat-photopolymerization printers, each with unique capabilities and specifications, have become available in the market. These printers utilize different photopolymer resins, layer thicknesses, and exposure settings, all of which can significantly influence the accuracy and fidelity of printed models [9; 10; 11]. Despite the promise of these technologies, the variability in manufacturing accuracy persists, posing challenges to their clinical implementation. The most important factors in the fabrication of dental prostheses are the accuracy and precision of the initial design image and final manufactured prosthesis [12; 13]. Accuracy evaluation methods based on various standard models were proposed for SM-based CAD/CAM systems [14; 15; 16]. However, an academically oriented model for accuracy evaluation has not been proposed for dental prostheses produced using AM technology, and it is evaluated using clinically relevant clinical models [17; 18].  
Prior to developing a new standard model for AM-accuracy evaluation, we performed a pilot test on existing international standard models for machining evaluation to evaluate their applicability to AM-accuracy evaluation [14; 15; 16]. Among the various international standard models, the Merlon fracture model defined in ISO Three-Dimensional-Printed exhibits several advantages over other standard models [14]. The Merlon fracture model, originally designed to evaluate the accuracy of SM processes, is a standardized model of most manufactured dental crowns, consisting of a base and four separate walls (referred to as merlons), and presents a potential solution for assessing AM accuracy. Therefore, despite its small size, the complexity of the four separate walls makes it a good model for evaluating the machinability of AM-fabricated dental prostheses.  
Therefore, this research investigated the feasibility of using the Merlon fracture model to evaluate the accuracy of vat-photopolymerization-based AM techniques. Two widely used 3D-printing technologies, digital light processing (DLP) and liquid-crystal display (LCD), were selected along with two polymer-based printing slurries for temporary and permanent crowns and bridges (C&Bs) to examine their influence on dimensional precision. By employing a series of quantitative metrics and comparisons, we aimed to identify the features and limitations of each 3D printer by rendering these models.