## 1 Introduction  
Tooth caries is known as one of the most common chronic oral diseases in humans [1]. The main causatives for tooth caries are bacteria, food habits, and the immune response by the host. Its etiology also includes highly complicated microecological harmony of biofilm. _Streptococcus mutans_ (_S. mutans_) is considered as the primary bacterium responsible for the onset of caries while _Lactobacillus_ are the main bacteria with respect to both caries progression and formation of secondary caries. Since acid-producing bacteria could trigger the initiation of the demineralization process, secondary caries formation might occur at the tooth-restoration interface or on the surface of the tooth [1, 2, 3, 4, 5]. With advances in dentistry, new minimal-intervention techniques and materials have been investigated in order to conserve the remaining dental hard tissues and minimize the risk of pulp damage. In recent years, comprehensive research in the field of modern dentistry has led to advancement of different new dental restorative materials with improved physical and esthetic properties and treatment modalities for tooth caries. Dental restorative materials have developed in terms of filler particles, matrix composition, and structure. Resin composites and glass ionomer cements (GICs) are the most-preferred materials as a viable alternative solution for the replacement of dental amalgam based on the concerns regarding its possible harmful effects on the environment as well as biocompatibility and esthetics. Both resin composites and GICs have distinctive features that clarify their popularity and limits [6; 7; 8]. Fluoride is known as an anticariogenic element. Anticariogenic potential of the fluoride is related to its unique properties, such as decreasing demineralization, increasing remineralization, and inhibition of pellicle and biofilm formation, bacterial metabolism, and microbial growth. It is assumed that fluoride released from restorative materials affects the formation of tooth caries through all mentioned mechanisms and therefore might decrease or inhibit demineralization and increase the remineralization of tooth hard tissues [9; 10]. Recently, due to increasing demand to use fluoride-releasing dental materials for the restoration of cavities or build-up cores, several fluoride-containing hybrid dental restoratives have evolved in the dental market, such as resin-modified GICs, goimers, compomers, and bioactive resin composites. These hybrid restoratives were launched to handle the drawbacks of conventional GICs and resin composites without sacrificing their clinical advantages. They have shown a variety of fluoride-release potentials due to the differences in their matrices and hardening mechanisms [3; 8; 9; 11]. Conventional GICs' particular characteristics that make them advantageous as a restorative or an adhesive material include chemical adhesion to the tooth hard tissues without any intermediate bonding agent, anticariogenic properties caused by fluoride release, and bio and thermal compatibility with the tooth enamel. In recent years, handling properties and chemical formulations of the GICs have been considerably changed for various clinical applications [3; 8]. The most recently launched materials, termed as glass hybrids (GHs), have been shown to come with adequate wear resistance (due to the resin-based coating agent after placement). GHs contain a multifunctional monomer and are reinforced with ultrafine, highly reactive fluoroaluminosilicate glass particles [8]. Some commercial GICs consist of strontium-containing glasses. In this formulation, strontium replaces calcium. It is stable and insoluble under neutral circumstances but is released from GICs when the pH shifts towards acidic challenges [3]. To improve the antibacterial properties of GICs, silver nanoparticles have also been incorporated into their formula [3]. Another improvement in GICs was the introduction of zirconia-reinforced GICs.