Dental caries is a common oral health problem in children characterized by the destruction of tooth structures at various levels. With the advent of minimally invasive techniques, bacteria in the affected carious tissue are still left behind after removing infected tissue. Microgaps around the restorations can form at margins due to polymerization shrinkage and chewing pressures. This could promote bacterial growth, particularly S. mutans, under the restoration, causing secondary caries and reducing longevity of the restoration. Thus, to overcome this, the concept of cavity disinfectants was introduced. Disinfecting the cavity after caries removal helps prevent recurrent caries, post-procedure sensitivity, and restoration failure. Several studies have reported using chlorhexidine, sodium hypochlorite, and silver, zinc, and titanium nanoparticles as cavity disinfectants. Nanoparticles are small size particles ranging from 1 to 100 nm. They exhibit efficient antibacterial properties, protect adhesives from degradation, prevent caries, inhibit biofilm formation and maturation, and promote remineralization. Among various metals that are being modified and incorporated in combination with oxide, zinc is known for its biocompatibility antibacterial effects. According to US-FDA, zinc oxide is considered as generally recognized as safe (GRAS) substance. Zinc oxide nanoparticles (ZnONPs) are chosen for their minimal cytotoxicity in human cells and as antibacterial even at low concentrations. In vitro studies confirm that ZnO NP cavity disinfectants outperform alternatives in antibacterial efficacy without compromising restoration bonding strength. The purpose of the study is to evaluate the efficacy of the zinc oxide nanoparticles - containing cavity disinfectant as an alternative to commercially available ones, with effective antimicrobial activity and unpertubed retention of the restorations placed over the cavity.