Dental caries is a major public health concern worldwide, with a high prevalence globally [1]. Caries is a multifactorial and dynamic disease resulting from ecological changes in dental plaque. Bacteria from the plaque continue to produce acid, which decreases the local pH of the oral microenvironment and disrupts the balance between demineralization and remineralization; this imbalance leads to continuous demineralization in hard dental tissues, which results in dental caries [2]. Caries are often characterized by carious lesions, and the first clinically detectable stage involves non-cavity white spot lesions (WSLs) [3]. Non-invasive caries control is urgently needed to promote enamel remineralization at this stage. This highly conservative method preserves the tooth structure and vitality of the pulp while avoiding invasive treatments, aligning with the minimally invasive principles of contemporary dentistry [4].

Traditional methods of non-invasive caries control include fluoride, casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and resin infiltration. Fluoride is utilized by replacing the hydroxyl groups in hydroxyapatite with fluoride ions to produce fluorapatite or fluorohydroxyapatite; these are less soluble and more resistant to acid than apatite without fluoride. Fluoride has the ability to coprecipitate calcium and phosphate ions from solution, and by assisting in the precipitation of fluorinated apatite at an elevated pH, it can reduce demineralization rates [5]. A dynamic balance is sustained between the calcium and phosphate ions in the CPP-ACP complex and the unbound calcium and phosphate ions in the oral environment. When the pH is high, substantial amounts of calcium and phosphorus ions exist in the CPP-ACP. As the pH decreases, CPP-ACP releases calcium and phosphate ions, stimulating the remineralization of enamel [6]. Resin infiltration may be employed to prevent lesions that are limited to the enamel or close to the enameldentine junction. This procedure involves the removal of only minimal hard tissue and replacing the lost minerals with resin protrusions to create a barrier within the lesion [7]. Current anticaries products can restore enamel to some extent via minimally invasive means; however, these products cannot form oriented apatite crystals, and the mechanical properties of the novel remineralized layer are poor.

Our group previously employed CMC/ACP@phase-transited lysozyme (PTL) fibrils, which are enamel matrix protein mimetic analogues, in conjunction with NaClO to establish a microenvironment for mineralization. In this remineralization system, the PTL fibrils replicated the amyloid structure of amelogenin, thereby demonstrating the templatic function of amyloid proteins in amelogenesis. CMC replicated the function of non-amelogenin in stabilizing the ACP nanoparticles; this result showed the significant non-template role in the regulation of the enamel mineralization. NaClO imitated the degradation of the enamel organic matrix caused by proteases. Based on the protein-mediated biomineralization, the entire process of the three "key events" of amelogenesis was simulated in vitro. In situ-remineralized enamel possesses favourable structural and mechanical properties and provides a promising alternative therapy for repairing enamel caries. Moreover, previous studies indicate that the fibrillar structure and amyloid conformation play crucial roles in directing the enamel crystal growth, which may be a potentially significant mechanism for enamel biomineralization [8].

Silk fibroin (SF) is a natural, nonpathological amyloid-like protein that has a similar structure and self-assembly behaviour to amelogenin [9], [10], [11]. Owing to their excellent biocompatibility and biodegradability, they have been broadly used as templates for biomineralization [12]. Natural silk fibrils have been shown to induce the mineralization of HA. SF has the ability to regulate HA mineralization through strong chemical interactions. This is achieved mainly through the binding of the anions and negatively charged functional groups on the surface of SF to the positively charged Ca2 + ion; this binding results in the formation of nucleation sites. These sites promote the mineralization of the HA nanocrystals. The carboxyl and amino groups are the functional groups utilized by SF to create the active site. In the structure of SF, the light chain (L), the heavy chain (H), and the hydrophobically linked glycoprotein P25 are linked to form a secondary structure of an antiparallel β-sheet. This fold includes a considerable amount of acidic aspartic acid extending from one side (-COOH) and has a robust affinity for Ca2+[13]. These motifs are widespread in the molecular chains of SF; thus, they may be capable of regulating biomineralization. Due to its good biocompatibility, biodegradability, mechanical strength, and structural adjustability, combined with its accessibility, SF has significant potential for bone regeneration [14]. However, further investigation is needed to determine its effectiveness in the remineralization of hard dental tissues [15].

In this study, we explore the role of SF in enamel remineralization on the basis of the synergistic strategy of self-assembly and mineralization of the organic matrix and the three "key events" of enamel biomimetic mineralization; here, SF is used as a template protein, CMC is used as a biomimetic analogue of a non-template protein, and NaClO is used as a protease analogue. The aim of this study is to develop an effective and efficient biomimetic remineralization strategy for enamel restoration and to provide a reference for the development of novel bioactive anticaries materials.