One of the main common prevalent diseases over all the world is dental caries (Anusavice 2002; Yoo et al. 2007) which result from reaction of certain bacteria with ingredients of the diet within a biofilm designated “dental plaque” (Bowen 2002). The main etiologic agent of dental caries is bacterial plaque on dental surfaces and contain oral flora. And despite the great work in the oral health community, dental caries still remains common cause of the present dental diseases (Van Gemert et al. 2008).
Streptococcus mutans is a type of bacteria that is considered the main cause of dental caries through destruction of the outer dental structures as a result of acids production (Loesche 1986). One of the risk factors in the induction of dental disorders is colonization of bacteria on teeth (Loesche 1986). Staphylococcus (Saureus and S. epidermidis) as a major human pathogen, which is one of the main causes for a number of infections which exists mainly in the mouth and extremities which are main sources for proliferation of this pathogen (Knighton 1986; Lowy 1998; Piochi and Zelante 1974; Rodis et al. 2006). Streptococcus mutans bacteria which is severely colonized in some individuals are considered to be with high caries index. Hence, extermination of these microorganisms is important for dental treatment (Rodis et al. 2006). Reaction of bacteria occurs by various methods including accumulation (Kolenbrander et al 2000), cell–cell communication and metabolic exchange (Li et al. 2001a; Roberts et al. 2001). These mechanisms helps in persistence of bacteria and their colonization, and also destruction of enamel, dentin or cementum of teeth occurs due to bacterial activity which caused by dental caries (Sutherland 2001; Paster et al. 2001; Li et al. 2001b).
Dental caries is a dependent oral disease in which fermentable dietary carbohydrates such as sucrose are the vital environmental factors involved in its induction and propagation which also aids as a substrate for the synthesis of polysaccharides in dental plaque (Yoo et al. 2007; Newbrun 1967).
Nanotechnology is an advanced field to diagnose and cure different diseases (Rezaei et al. 2019) to enhance curing, diagnosis and treatment of oral and dental diseases (Das and Nasim 2017; Sharan et al 2017), and a lot of dental materials have been used in the nanoscale to improve their properties in different forms such as nanofibers, nanopores, nanorods, nanoparticles, nanorobotic dentifrice, nanosolutions, and nanoneedles.
Zinc oxide (ZnO), titanium dioxide (TiO2), and silver are metal NPs which are categorized by their size, composition, crystallinity and structure. Their dimensions are modified into nanoscale which can alter their chemical, mechanical, electrical, structural, morphological, and optical properties. These modified structures allow the nanosized particles with high concentration to interact with the internal atoms and consequently enable the transmission of NPs into the inner cellular structures physically as they have higher surface activity (Rasmussen et al. 2010).
Studies have shown that zinc oxide can inhibit acid production by Streptococcus mutans and Lactobacillus in dental plaque (Hirota et al. 2010). Also, it was reported that it has antibacterial effects on Gram-negative and Gram-positive bacteria and is commonly used as an antibacterial agent in dental hygiene products such as toothpastes and mouthwashes due to increased surface/volume ratio.
Nanoparticles can act as an efficient antibacterial agent and is widely accepted in biomedicine. The superior bactericidal activity of NPs with antibacterial activities is attributed to their electrostatic attraction between positively charged NPs and has the potential to reduce or eliminate the evolution of more resistant bacteria. The small size of NPs improves not only their antimicrobial action with minimal adverse effects, including hypersensitivity and allergic reactions, but also their mechanical properties. Many studies investigated the antibacterial effect of NPs combined with a wide range of dental materials (Ferrando-Magraner et al. 2022).
Zinc oxide (ZnO) was chosen on this study as it is a mineral zincite that is bio-safe, biocompatible with proven strong anti-bacterial properties, which can powerfully resist broad range of microorganisms due to their ability to generate reactive oxygen species (ROS) on the surface of oxides.
The aim of the study is to evaluate the effect of adding nanozinc oxide as an antibacterial agent to tooth paste.