## 1 Introduction  
Ceramic structures or restorations have become more commonly used because of their favorable aesthetics and their superior biocompatibility. Pure zirconia is known to be a polymorphic material that has three allotropes: monoclinic, tetragonal, and cubic phases. They are stable at different temperature ranges. The tetragonal phase is normally stable at high temperatures (between 1170 \({}^{\circ}\)C and 2360 \({}^{\circ}\)C) but can be retained even at room temperature by adding metal oxides such as yttria. Nowadays, yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramic is widely used for dental implants and implant abutments, fixed partial dentures, and even artificial joints [1]. The use of Y-TZP in dental prostheses has risen in popularity due to its favorable esthetic properties, excellent biocompatibility, superior mechanical properties, high strength, favorable corrosion resistance, good fracture toughness, and low thermal conductivity [2, 3, 4]. In particular, Y-TZPimplants meet dental patients' demand for metal-free esthetic restorations [5]. In addition, clinical studies show satisfactory biocompatibility and osseointegration of Y-TZP implants compared to conventional titanium implants [5]. In dentistry, computer-aided design and computer-aided manufacturing (CAD/CAM) technology has emerged in the last decade as an alternative to conventional techniques for making dental prostheses [6]. The technology consists of subtractive manufacturing (SM) and additive manufacturing (AM) methods. Most ceramic-based dental prostheses, including Y-TZP restorations, have been fabricated using CAD/CAM milling, which requires four- or five-axis machining [3]. However, the waste of material and the machining costs are definite disadvantages of this SM technique [7]. In addition, cutting may form micro-cracks, which are harmful to the mechanical properties of the final SM products [7]. To address these issues, AM techniques have been introduced and applied in producing dental restorations [7]. These techniques allow high material utilization, complex shape processing, and the elimination of cutting tools [7]. The most commonly used three-dimensional (3D)-printing process for preparing ceramics includes binder jetting, laser powder bed fusion, digital light processing (DLP), and stereolithography (SLA) [8]. Among such techniques, DLP and SLA hold the most promise in manufacturing ceramic parts with high spatial resolution, unique designs, and fine finishing [9]. The composition of the resin for DLP and SLA typically involves ultraviolet (UV)-curable monomer/oligomer, a photoinitiator, diluents, and additives for the stabilization of particles [10]. These two techniques are based on the layer-by-layer solidification of a resin filled with ceramic particles via UV exposure, followed by the debinding of organic materials and final sintering [11]. The solidification principle is the only difference between the two techniques [9]. Liquid is solidified via UV-laser scanning in the SLA method, while the whole area is UV-cured simultaneously in the DLP approach [9]. Compared with SLA, therefore, high-resolution DLP is faster and cheaper owing to the ease of choosing the optimal size of the projected pixel [12]. However, its main disadvantage is the detachment force applied to each layer, which causes deformation of the sample and sometimes increases the risk of the sample dropping out of the building plate [13]. SLA is another 3D-printing technique for manufacturing ceramic products. In this technique, an organic binder is used to shape the green body component, requiring post-processing that includes debinding and sintering to produce the final object [14]. Compared to other methods, the SLA technique provides a smoother surface finish and allows greater precision in production [9]. Using SLA, different dental restorations can be mass-produced in one fabrication cycle [3]. In addition, the slurry that is used for 3D printing can be recycled [3].