## 1 Introduction  
The variety of tooth restorative materials available has significantly expanded in recent years. The ability to produce these materials through pressing, printing, and milling (using CAD/CAM technology) or a combination of these techniques is a fascinating study area. These technologies appear to significantly influence the material's mechanical properties [1], sparking further interest and engagement in the field. Digital technologies are advancing at a remarkable pace, enabling the precise restoration of hard tooth tissues while significantly streamlining laboratory processes. These digital methods enhance clinical workflows, ultimately reducing patient stress and discomfort. To support these innovations, new and improved materials are essential for restorations such as inlays, onlays, and overlays. Notable materials include yttria-stabilised zirconia, zirconia-reinforced composites, and specialised 3D-printed composites [2, 3]. CAD/CAM technology is an adaptable system that can create a diverse array of tooth restorative materials, including lithium disilicate, zirconia, polymer-infiltrated ceramics,and various polymer-based composites [4; 5; 6]. This flexibility establishes CAD/CAM as an essential tool in the realm of tooth restoration. Lithium disilicate restorations are highly effective and have a high survival rate. Data indicate that the survival rate ranges from 92% to 97.8% after five years and from 85.5% to 96.7% after ten years [7]. This high survival rate should instil confidence in the effectiveness of these restorations. Indirect CAD/CAM resin composite materials exhibit higher edge stability than ceramics, permitting restorations with fragile margins [6]. Standardised industrial fabrication of the CAD/CAM blocks under high pressure and temperature results in more homogeneous and abrasion-resistant restorations than direct composite restorations [8; 9]. Ceramics are generally superior to CAD/CAM polymer-based materials in flexural strength, abrasion resistance, and discolouration rates, whereas CAD/CAM polymer-based materials are more friendly to opposing dentition [10; 11; 12]. Zirconium has undergone significant advancements, now incorporating multiple layers that blend 4Y and 5Y compositions to demonstrate enhanced properties. One notable example is Max ZirCAD Prime. This multilayer zirconium material is engineered with varying yttria content across its layers, resulting in different performance characteristics [3]. The variation in yttria content significantly influences each layer's phase composition and mechanical properties in the multilayer zirconia structure. In e.max ZirCAD Multi, different concentrations of yttria--5 mol% in the enamel layer and 4 mol% in the dentin layer--result in distinct microstructures and phase stability. The higher yttria content in the enamel layer (5Y-PSZ) enhances its translucency and aesthetic qualities while also improving its resistance to crack propagation, which is crucial for the incisal edge's durability. Conversely, the lower yttria content in the dentin layer (4Y-PSZ) may provide a different balance of strength and toughness, providing the necessary support and resilience for the underlying structure. These adjustments in yttria levels tailor the mechanical properties to meet the specific demands of each layer, ultimately contributing to the overall performance of the material, including its fracture toughness, flexural strength, and wear resistance [13; 14]. This strategic variation not only enhances the aesthetic outcome but also ensures that the material can withstand the functional stresses encountered in clinical applications. Ceramic materials are known for their outstanding mechanical properties, including high strength, hardness, wear resistance, and stability at elevated temperatures. These characteristics make ceramics ideal for applications requiring durability and resilience. On the other hand, polymers contribute beneficial properties such as higher ductility, lower elastic modulus, and greater flexibility.