Demineralization of tooth structure takes place by the removal of mineral ions from the hydroxyapatite crystals of enamel and dentin, caused by acid attack [1], [2]. When the demineralization is prolonged, the acid content gradually destroys the integrity of hydroxyapatite crystal latticework, resulting in the loss of dental structure [1,2 When the demineralization is prolonged, the acid content gradually destroys the integrity of hydroxyapatite crystal latticework, resulting in the loss of dental structure [1], [2]. Carious lesions and erosion are the two main causes of demineralization [2], and the defects produced in dental hard tissue cannot be restored to the original structure and properties of the teeth with the current clinical treatments [1], [3]. Furthermore, the restoration of the cavities with resin composite fillings fails with time due to adhesive failures caused by degradation of demineralized collagens [4]. Therefore, a potential treatment for demineralization must promote intrafibrillar mineralization as much as apatite formation [4], [5]. Considering the advances in tissue engineering and the development of new technologies and strategies, the innovation in the treatment approaches and the use of advantageous materials could conduct and increase the remineralization process.

Chitosan is a natural cationic polymer mainly derived from deacetylated chitin with significant use in several major application areas [1], [6]. It is a biocompatible and biodegradable material with antimicrobial properties and strong attachment skills [6], which make it a suitable scaffold for mineral delivery to favor organic and inorganic tissue mineralization [3]. Chitosan-based materials have the benefit of improving biocompatibility and reducing the possibility of allergic and inflammatory responses during the treatment, as well as being able to improve the bioactivities and mechanical properties of the material when incorporated with inorganic minerals [3].

Hydroxyapatite (HA) nanoparticles are a non-toxic, chemically stable, and bioactive material with distinguishing remineralization properties [7]. Due to its exceptional biocompatible characteristics, HA is significantly used in hard tissue regeneration [8], [9], and it can promote remineralization of the collagen matrix by the precipitation of calcium and phosphate ions provided by HA crystals [10]. However, the aggregation of HA and polymer results in poor mechanical properties [9], which makes the modification of HA formulation necessary. Another interesting source of minerals is Biosilicate. It is a crystalline glass-ceramic with high bioactivity, good mechanical strength, and no cytotoxic potential with antimicrobial properties and potential ability to remineralize dental structure by releases of calcium and phosphate ions [11], [12], [13].

Instead of simply mixing chitosan and minerals particles to construct a remineralizing solution, adding micromolar quantities of acid polypeptides to form a polymer-induced liquid-precursor (PILP) system can help to induce biomineralization [5]. The addition of anionic polymer to a supersaturated mineralization solution can induce an amorphous calcium phosphate deposition [4] and assist the mineralization process of a demineralized hard tissue, assisting and perhaps improving the cross-link between the collagen fibers and the mineral content in the remineralizing treatment [5].

In this context, the development of a sustainable and biocompatible remineralizing treatment is not only welcome but essential to promote better tissue remineralization and necessary to maintain the integrity of dentin structure. The treatment in question should not only be able to reinforce collagen fiber by integrating mineral content into its 3D structure; it also should protect against collagen degradation. Matrix metalloproteinases (MMPs) are key enzymes in the remodeling of extracellular matrix components, and these metal-dependent endopeptidases have the ability to degrade collagen and play an important role in the progression of dental caries [14]. Therefore, the inactivation of these enzymes is necessary to maintain the integrity of dentin structure.

Given the present situation, the objective of this study was to test experimental chitosan-based solutions associated with n-HA or Biosilicate (P2O5-Na2O-CaO-SiO2) as mineral sources, with or without L-Aspartic acid as the PILP system, on mineral deposition and activity and expression of MMPs on demineralized coronal bovine dentin and collagen fiber reinforcement.