Dental caries is one of the most common diseases that seriously threaten human oral and overall health [1]. According to the global disease prevalence statistics reported by The Lancet in 2016, dental caries in permanent teeth is the most prevalent disease [2]. Early enamel caries, also known as non-cavitated lesions, incipient caries, or white spot lesions, are characterized by small areas of demineralization occurring only in the enamel, often covered by bacterial biofilm [3]. When early enamel caries occur in the anterior teeth, they significantly affect the aesthetics of the teeth. Moreover, early enamel caries represent the earliest clinically visible progression of dental caries. If left untreated, further development into cavities can cause substantial harm to the dental hard tissues and pulp health [4]. The treatment goals for early enamel caries are twofold: to restore the aesthetics of the teeth and, more importantly, to halt the progression of caries, inhibit enamel demineralization, and promote remineralization.

In 1975, Davila et al. [5] discovered that fluid materials could enter demineralized enamel micro-pores through capillary action, blocking bacterial invasion. In 2008, DMG Company developed Icon resin infiltrant (IRI), a low-viscosity fluid material that effectively penetrates carious lesions and delays caries progression [6]. Additionally, IRI can enhance the mechanical strength of demineralized dental hard tissues and prevent further enamel destruction and caries progression [7,8]. Moreover, after light curing, refractive index of IRI matches that of enamel, which can improve the color of the white spot to achieve good aesthetic effects [9].

However, studies reveal that resin infiltrants can seal only about 60 % of enamel pore volume, leaving much demineralized enamel untreated [10]. Moreover, many in vitro studies have reported that resin infiltrants cannot completely prevent enamel demineralization, and the hardness of the resin-infiltrated area decreases after re-exposure to an acidic environment [[11], [12], [13]]. In the cariogenic environment, triethylene glycol dimethacrylate (TEGDMA) has a strong hygroscopicity which enables hydrogen ions to penetrate the resin layer along the concentration gradient, resulting in the dissolution of residual minerals in the lesion [11]. Additionally, polymerization shrinkage and microleakage of light-cured resins are common issues that may affect the penetration and long-term efficacy of resin infiltrants [14,15].

Adding bioactive fillers to resin infiltrants can improve their chemical and physical properties. Studies have shown that incorporating CaP-containing silica fillers into PLA nanofibers can inhibit demineralization [16]. However, when similar materials are used as fillers in resin-based materials, they may lead to reduced mechanical properties due to the lack of chemical bonding [17]. The addition of amorphous calcium phosphate nanoparticles (NACP) can enhance the remineralization capacity of resin infiltrants [18]. Nevertheless, other studies have demonstrated that resin-based materials with ACP fillers exhibit poor mechanical properties, durability [19].

In 1969, Hench et al. [20] first developed bioactive glass (BG) and applied it to bone tissue-related treatments. They discovered that BG can chemically bond with hard tissues and proposed that BG can degrade in physiological solutions, releasing ions to form hydroxyapatite (HA). Several studies have proven that composite resins containing bioactive glass can exhibit certain remineralization effects [[21], [22], [23]]. Research on incorporating bioactive glass into resin infiltrants is relatively scarce. Hashemian et al. [24] found in vitro that resin infiltrants with fluoride-containing BG fillers can repair enamel to some extent and enhance enamel's resistance to demineralization.

A novel bioactive glass named as PSC (10.8 mol% P2O5–54.2 mol% SiO2–35 mol% CaO), which is prepared by the sol-gel method, with significantly increased specific surface area and phosphorus content compared to traditional melt-derived bioactive glass. In physiological environments, PSC demonstrates very rapid HA formation [25,26].

This study aims to develop a resin infiltrant containing the bioactive filler PSC to enhance remineralization capacity while maintaining resin infiltrant performance, offering new insights for early enamel caries treatment.