## 4 Discussion  
Compared to enamel, dentin has always posed a challenge for bonding [40; 41; 42], likely due to its more heterogeneous structure. Dentin is a composite material consisting of approximately 50 vol% mineral phase, 30 vol% collagen, and 20 vol% water [43]. Therefore, the bonding strategy for dentin focuses on two phases: the mineral phase, mainly composed of carbonate-rich hydroxyapatite, and the organic phase, primarily collagen, in a moist environment. The bonding method for dentin was evaluated in the current investigation. Since it is the most typical substrate in clinical practice, the bonding to carious dentin was assessed. Changes caused by carious lesions result in poorer dentin hybridization [44; 45]. In the present study, the bond strength to caries-affected dentin was lower due to low mineral content, which affected dentin hybridization. Carious dentin is composed of two distinct layers: an outer layer of infected dentin and an inner layer of affected dentin [46]. Fourier-transform infrared imaging (FTIR) analysis of caries-affected dentin (CAD) has revealed lower mineral content and reduced crystallinity  
Figure 4: Meta-analysis comparing the dentin bond strength of Clearfil SE Bond (SE adhesive) in caries-affected dentin after Papacarie and Carisolv application [31; 33]. Figure 3: Summary of risk of bias: evaluations of each study’s included item’s risk of bias [6; 9; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39]. in the mineral phase compared to normal dentin. The loss of mineral from the dentin matrix during the carious process is replaced by water, which can account for up to 53% of the volume in CAD [47]. In addition, most clinical substrates are covered with smear layers, which hinder the penetration of adhesive molecules into tooth substances [44; 48]. The occlusion of tubules in CAD leads to decreased permeability. Following cavity preparation and removal of CAD, the cavity floor is largely made up of dentin that has been damaged by caries, making it the most common bonding substrate, as opposed to sound dentin. CAD differs from sound dentin in terms of hardness, being twice as soft, even though mineral depositions occlude dental tubules. The mineral deposits in CAD, such as plate-like \(\beta\)-octocalcium phosphate (whitlockite), are not as densely packed and are therefore softer than well-packed apatite, although they may be more acid-resistant [49]. Moreover, the ultimate tensile strength of CAD is lower than that of sound dentin, possibly due to the loss of mineral in intertubular dentin. The matrix of demineralized CAD, according to a study, was just as durable as that of healthy dentin. The partial demineralization in CAD may reduce the number of MDP-dentin bonding sites and affect the chemical bonding of adhesives to CAD [50]. The lower bond strength in caries-affected dentin can be attributed to the lower mineral content surrounding and within collagen fibrils, resulting in a softer surface with a higher degree of porosity compared to sound dentin [51]. In this systematic review, which included 12 studies, the bond strength of different adhesives (etch-and-rinse, self-etch, and resin-modified glass ionomer adhesive) on CAD after treatment with chemo-mechanical caries removal (CMCR) agents was assessed. Eleven studies used Carisolv, while four studies used Papacarie. One study used SFC-V (Biosolv), and another used SFC-VIII as CMCR agents compared to Carisolv. CMCR agent Carisolv has a proteolytic action, using a combination of enzymes to selectively degrade the collagen matrix of carious dentin. The enzymes in Carisolv, such as collagenase and papain, break down the denatured collagen fibrils present in carious dentin, facilitating its removal [52]. This enzymatic action is believed to be less aggressive towards sound dentin compared to mechanical methods, as it selectively targets the demineralized and degraded collagen structure [53; 54; 55]. The CMCR method did not have any adverse effects on the bonding of adhesives to CAD [6; 9; 16; 30; 32; 33; 34; 36; 37].