## 1 Introduction  
Physiologically and anatomically, dentin is a complex structure, consisting of approximately 70% hydroxyapatite crystals, 18% organic matter, and 12% water and plasma-like fluids. The dentin-pulp complex is derived from the ectomesenchyme, structurally forming a true biological and functional unit [1]. Adhesion to dentin is considered more complex than adhesion to enamel due to its organic component and the presence of a smear layer that obstructs the entrance of the dentinal tubules, decreasing their permeability to adhesive systems and liners. The smear layer should be treated or eliminated, depending on the different bonding strategies and characteristics of the materials to be used [2]. Glass ionomers can chemically bond to dentin due the ion exchange layer at the interface formed by continuous diffuse of aluminum, silicon, fluorine, and strontium when present in the parent glass ionomer, and calcium and phosphorus from dentin [3]. Since [PERSON] et al. [4] introduced polyacrylic acid, it has been used as a conditioner to improve the adhesion of glass ionomers. It contains numerous functional carboxyl ions, which form hydrogen bonds that promote substrate wettability. Its use is recommended at a concentration of 10%, 20%, or 25% [5]. Another alternative is the use of orthophosphoric acid (OPA) at concentrations around 37.5%, between 5 and 10 s [6]. Acid conditioning has been shown to improve the bond strength of glass ionomers to the dentin substrate [6; 7; 8; 9; 10]. In addition, the type of conditioner, its application time, and concentration can also influence bond strength [11]. Glass ionomer cements (GIC) are biomaterials that belong to the family of acid-base cements. They are the product of the reaction of weak polymeric acids with phase-separated amorphous sodium-fluorine-aluminum-silicate glass powder [12]. They set in the presence of water and the final structure contains concentrations of unset glass that act as reinforcement. They contain three fundamental components: a soluble polymeric acid, a basic glass, and water. The glass is a complex material consisting of fluorine, calcium or strontium, aluminum silicate, and phosphorus [13]. The polymeric acid solution is mainly polyacrylic acid, although maleic and itaconic acid may be present in lower concentrations to improve handling and increase working time. They set by means of an acid-base reaction 2-3 min after mixing, although the reaction can last up to 48 h. The bioactivity of glass ionomers is produced by an ionic exchange between the material and the substrate that can be maintained over time, with an initial rapid early release phase, followed by a sustained phase [14]. Resin-modified glass ionomer cements (RMGICs) contain the same essential components as conventional GICs, but incorporate a monomer, usually 2-hydroxyethyl methacrylate (HEMA), and a photoinitiator. Therefore, they exhibit two setting reactions: light-curing and the characteristic acid-base reaction of glass ionomers [15]. High density GICs are materials of very high viscosity, whose glasses have been improved by the addition of strontium, bioactive glasses, or even zirconium. This results in a reduction in their working and hardening times, and a notable improvement in their physical-chemical and mechanical properties, together with a minimum solubility. They can be self- or light-cured [16]. Silver diamine fluoride (SDF) is a cost-effective and easy-to-use alternative for the remineralization of carious dentin (13). SDF is presented in an alkaline colorless liquid form (pH 10), composed of 24-27% silver (Ag), 8.5-10.5% ammonia (NH3), and approximately 38% fluoride (F) [9]. Currently, a triple mechanism of action of SDF against caries lesions is described: Firstly, due to the high concentrations of fluoride, a greater diffusion is achieved in enamel and dentin, favoring their remineralization.