## 1 Introduction  
Zirconia, or zirconium dioxide (ZrO\({}_{2}\)), has gained popularity in restorative dentistry due to its combination of esthetics and strength. Zirconia is a glass-free type of ceramic, and zirconia atoms are packed into a regular crystalline arrangement that has high mechanical strength [1]. Dental zirconia can be divided into four main generations, based on its chemical structure. The first generation is also known as conventional 3Y-TZP (3 mol% yttria-stabilized tetragonal zirconia polycrystal). Given its high degree of opacity, it is used as a framework material and veneered with traditional ceramics to create an esthetically pleasing effect. The second generation of zirconia features high translucency, achieved by reducing the amount of alumina additive to 0.05% by weight, while maintaining the yttrium oxide stabilizer at 3% by mol. The third generation of highly transparent zirconia is produced by increasing the amount of cubic phase structures through raising the yttrium oxide content to more than 4% by mol. In this generation, the translucency of zirconia is increased, but its strength is decreased. To balance these properties, manufacturers lowered the yttrium oxide content to 4%, yielding the fourth generation of zirconia [2]. At present, dental zirconia achieves both mechanical strength and esthetics, but the adhesion between zirconia and resin cement is weak. Several techniques, such as chemical and mechanical adhesion approaches, are available to enhance the bonding strength of zirconia. A typical method for improving surface roughness and providing mechanical retention is air abrasion [1]. Under carefully controlled in vitro conditions, a good ceramic-resin cement adhesion may be achieved, but it may not hold up as well in clinical settings, leading to a significant reduction in bond strength. When attempting a restoration in the mouth, it is difficult to avoid contaminating the restoration's inner surface with materials such as silicone indicator, blood, and saliva [3]. Saliva contamination is a common cause of reduced resin cement bond strength [3; 4; 5; 6]. Saliva consists of proteins, enzymes, blood cells, bacteria, and various phosphate forms, such as phospholipids, in a water solution [7]. It interferes with bonding of the restoration to the tooth. Saliva may remain as a thin layer on the ceramic surface, blocking micromechanical and durable chemical bonds [8]. Salivary phosphates irreversibly bind to zirconia and the tooth surface, which makes removing them difficult. Consequently, saliva contamination can lead to issues when restorations contaminated with saliva are cemented, leading to adhesive failure. Numerous investigations have shown that saliva contamination interferes with the formation of stable bonds [4; 9; 10; 11]. The contamination must be removed from the restoration's inner surface prior to cementation. It is important to make sure that the inner surfaces of the restorations are properly cleaned and decontaminated after the intraoral try-in in order to obtain a sufficiently durable adhesion between the tooth structure and the restorations. The cleaning methodologies should involve chemical or mechanical methods or a mix of both [12; 13]. The mechanical technique involves sandblasting with aluminum oxide particles. The chemical techniques include cleaning solvents and acid treatment of the surface with substances such as phosphoric acid, acetone, alcohol, and acidulated phosphate fluoride. Prior research has shown that although each cleaning technique has benefits, none achieve sufficient bonding ability [12; 13]. Several experiments have used extraoral zirconia cleaning solutions (Ivoclean and Katana Cleaner) to clean the saliva-contaminated zirconia surface prior to cementation [12; 13]. These cleaning products are liquids composed of monomer (10-MDP), other ingredients, and no initiator and thus are unable to polymerize.