## 1 Introduction  
White spot lesions (WSLs) on enamel around orthodontic brackets is a common side effect of orthodontic treatment because variogenic bacteria such as _Streptococcus mutans_ (_S. mutans_) colonize plaque deposited around the brackets and produce acids such as lactic acid, which demineralize the enamel surface [1; 2; 3]. The bacteria responsible for WSLs, _S. mutans_, is a facultatively anaerobic, Gram-positive coccus (round bacterium) that is commonly found in the human oral cavity and is a cause of caries [4]. In an oral cavity with fixed orthodontic appliances, the number of _S. mutans_ increases and thus leads to the demineralization of enamel [5].  
White spot lesions on anterior teeth are considered unaesthetic as the demineralized enamel is often whiter than the surrounding enamel [6]; hence, clinicians have made several attempts to prevent the formation of WSLs [7]. For example, researchers have attempted to incorporate antibacterial agents in orthodontic adhesives in order to reduce the causative bacteria and thus prevent WSLs caused by orthodontic devices [8; 9; 10; 11]. Gallium (III) has been used an antibacterial agent as it can mimic Fe (III) [12; 13]. Iron (III) is reduced to Fe (II) by intracellular processes whereas Ga (III) is not reduced; thus, Ga (III) interferes with biological redox processes when it binds to Fe (III) protein binding sites in bacteria, which results in an antibacterial effect [12]. According to a study by [PERSON] et al., Ga-doped PO4\({}^{3-}\)-based glasses exhibited the potential to protect enamel surfaces by inhibiting the growth of _S. mutans_[13].  
Another method for preventing WSLs caused by orthodontic devices involves remineralizing the enamel by supplying Ca\({}^{2+}\) and PO4\({}^{3-}\) to the demineralized surface as these ions are leached from enamel by acid [14]. Bioactive glass (BAG) is a basic Si-O-Si structure that consists of SiO\({}_{2}\), CaO, and P\({}_{2}\)O\({}_{5}\). When BAG is added to resin paste as a filler, the strength of the paste increases [11]. In a liquid environment containing BAG, the calcium phosphate layer on an enamel surface exposed to acid grows into apatite, which results in an antibacterial effect as pH is increased and oral bacteria is reduced [15]. Mesoporous bioactive glass nanoparticles are widely used as drug carriers because of the high surface to volume ratio created by their internal pore structure [16]. In this study, Ga-doped mesoporous bioactive glass nanoparticles (GaMBN)--with wide surface pores and Ca\({}^{2+}\) and PO4\({}^{3-}\) available for remineralization--were synthesized and added to resin to form an orthodontic bonding adhesive with the potential to prevent WSLs. The objective of this study was to determine the clinical applicability of the GaMBN resin both for preventing WSLs and as an orthodontic bonding adhesive.  
Therefore, the purpose of this study was to determine whether resin containing Gallium doped mesoporous silica nanoparticles could reduce white spot lesions. To confirm the results, 1%, 3%, and 5% of GaMBN was added to the resin (CF, CharmFill Flow, Dentkist, Seoul, South Korea). After that, chemical and physical properties were checked, and anti-demineralization ability was confirmed. ANOVA and regression were used to analyze the experimental data.