## 1 Introduction  
The most used restorative materials for dental fillings are resin composites. They have excellent aesthetic characteristics, which mimic the natural teeth appearance [1]. Composites require less invasive cavity preparations compared to other restorative materials. However, composites present a reduced lifespan and concerning failure rate in clinical studies [2; 3; 4]. The most common reasons for restorations replacement are secondary caries and restoration fracture [5]. Several investigations have been attempted to defeat this problem by imparting antibacterial additives into composite restorations [6]. However, incorporating antibacterial agents to be released from the materials has shown limited long-term performance. Once the ion release occurs from a booster in the initial weeks to a few months, the amount of discharging decreases over time [7]. The approaches to overcome the limited release and promoted sustained ion release to convey an antibacterial effect are an ongoing investigation area. Another strategy to convey dental materials with antibacterial properties involves incorporating antibacterial monomers, such as polymerizable quaternary ammonium methacrylates (QAMs), where the antibacterial agent is a component of the polymer matrix, granting the polymer surface with contact-active antibacterial activity [8; 9; 10]. Quaternary ammonium methacrylates have been investigated as promising long-lasting antibacterial compounds as they co-polymerize and covalently bond with the other monomers in the composite formulation [8; 9]. More recently, dimethylaminohexadecyl methacrylate (DMAHDM) has been synthesized, and its concentration was tuned to induce a high antibacterial effect in preclinical reports [11; 12]. The robust antibacterial performance of DMAHDM is attributed to its high surface charge density that can pull toward the negatively charged cell membrane of bacteria. Besides, DMAHDM has a long alkyl-chain that could improve the monomer's penetration capability against the attached microorganisms [11; 12]. To complement the antibacterial composites' anticaries strategy, nano-sized amorphous calcium phosphate (NACP) fillers were added to the composite formulations to impart remineralization capabilities [13]. Composites containing NACP fillers release more calcium (Ca) and phosphate (P) ions during the acidic pH challenge [14]. The Ca and P ion release behavior confers buffering capacity and forms a hydroxyapatite layer to remineralize tooth surfaces subjected to demineralization [15; 16; 17]. The dual antibacterial and remineralizing formulation with DMAHDM and NACP has been intensively investigated and had demonstrated encouraging immediate anticaries outcomes with no impact on the mechanical or physical properties [15; 17]. However, new anticaries composites intended for a clinical application will be subject to aging inside the mouth and exposed to chemical, physical, and mechanical processes [18]. Polymer degradation and aging are among the most intimidating difficulties to the long-term application of new resin-based dental materials [19]. Dental composites are constituted of an organic polymer matrix, usually methacrylate-based monomer and inorganic reinforcing filler particles, commonly glass, quartz, such as alumina, or silica. As the polymer matrix is the resin component of a cured dental resin composite, over time, deterioration is expected with the clinical service [20]. Bonds made between the coupling agent and inorganic filler particles are prone to chemical hydrolysis. This process includes physical reactions such as sorption, dissolution, elution, and physical changes such as softening and swelling [21]. Additionally, the polymer's water sorption and hydrolytic degradation increase material susceptibility to wear during chewing [22]. Previous reports on bioactive composites have focused on short-term effects (up to 180 days) and ion release [23; 24].