## 4 Discussion
Caries removal with either NaOCl-based or enzyme-based CMCR methods resulted in the partial (Carisolv) or complete (Papacarie) absence of the smear layer and irregular surface characteristics when observed under SEM at 2000\(\times\) magnification [31; 56]. These surface characteristics may affect resin infiltration into the dentin and enhance micromechanical adhesion, leading to good resin infiltration in caries-affected dentin groups [57]. Pre-treatment of dentin with NaOCl derivatives, particularly in caries-affected regions, was found to promote the adhesion of self-etch adhesives to CAD [58]. The predominance of adhesive failures when bonding to carious dentin is likely related to the difficulty of the adhesive to completely infiltrate the exposed and altered collagen mesh [39]. The demineralization and remineralization processes that occur during caries result in the occlusion of dental tubules with larger, less soluble calcium phosphate crystals, further affecting adhesion. Additionally, the organic matrix of carious dentin differs from that of the normal substrate due to denatured collagen fibrils, which can also influence the fracture mode [39]. Various techniques are available to evaluate bond strength, with the most commonly used being tension or shear modes [59; 60; 61; 62]. In this systematic review, 13 studies assessed microtensile bond strength (\(\upmu\)TBS), while one study evaluated shear bond strength. Tensile bond strength tests require special testing jigs and meticulous procedures [8; 62]. Shear bond strength tests, although easier to perform, generate non-uniform stress concentration at the edge of the bonded interface during testing [63; 64]. To overcome the limitations of conventional shear or tensile bond strength tests, the \(\upmu\)TBS test was introduced. It involves bonding adhesive resins to the entire flat occlusal surface of teeth, which is then covered with a resin composite. Subsequently, the specimen is vertically sectioned into multiple serial sections, creating an hourglass shape for maximum stress development at that region [65; 66]. The \(\upmu\)TBS test, along with morphological and spectroscopic investigations, has contributed to improving resin/dentin adhesion and has shown greater discriminative power than traditional macro-shear tests [67]. This test is considered a versatile and standard method for bond strength testing, providing better control of regional differences and making more economical use of teeth. Moreover, it allows the exclusive evaluation of adhesive bond failures when the bonded surface area is approximately 1 mm\({}^{2}\), leading to better stress distribution at the true interface [66; 68; 69]. Regarding the failure mode of restorations, they can fail within the restoration itself, at the restoration and bonding adhesive interface, at the restoration and substrate interface, or only at the substrate. Cohesive failure occurs within the resin composite or dentin, adhesive failure refers to failure between dentin and bonding resin, and mixed failure involves a combination of adhesive and cohesive failures. When bonding to caries-affected dentin, an analysis of failure modes of dental adhesives showed an increased incidence of cohesive failures, possibly due to differences in the nature of the bond. The thickness of the hybrid layer or increased dentin moisture after Carisolv treatment may contribute to a slightly higher number of microscopic defects in the bonded layer as a whole. Additionally, the slight difference in dentin hardness after using Carisolv or other differences in the dentin itself can influence the failure mode [9; 16; 37; 39]. It is essential to keep in mind that the findings of this systematic review indicated that both Carisolv and Papacarie were equally effective in dental caries removal and showed similar bond strength to adhesive systems [49; 50; 70].