Even though for normal dentin, the mild acidity of self-etch systems is not sufficiently effective in the dissolution of smear plugs, therefore smear plugs are retained in the dentinal tubules as part of the hybridized complex with less resin tag formation. In this situation, lateral penetration of the adhesive

monomers from the dentinal tubules could not contribute to hybrid layer formation of self-etch adhesives. Therefore, for self-etch systems, the presence of mineral deposits in dentinal tubules would not be an important reason why caries-affected dentin causes less penetration of adhesive monomers, leading to Palbociclib order lower bond strength than normal dentin, but a deeper mineralized zone would be the main reason. On the other hand, in the case of self-etch systems, the dentin smear layer would affect penetration of the adhesive monomers into the underlying dentin. Several studies using normal dentin have demonstrated that dentin smear layer characteristics have been reported to compromise the bonding efficacy of self-etch systems. The smear layer on dentin is composed of disorganized collagen debris binding submicron mineral particles

[33] and [34]. The smear layer of caries-affected dentin is thick and irregular, and appears to be enriched with organic components compared with that of ALK inhibitor cancer normal dentin [36] and [37]. The disorganized collagen and/or

the mineral trapped within the gelatinized collagen cannot be easily removed even when etched with phosphoric acid [43]. The disorganized collagen and the gelatinous layer within the smear layer may hinder resin monomer infiltration and prevent a perfect seal at the resin–dentin interface [34] and [43]. Therefore, the caries-affected dentin smear layer enriched with organic components would contribute to the inferior adhesion of self-etch adhesives to caries-affected dentin (Fig. 7). Sodium hypochlorite solution (NaOCl) can effectively dissolve organic substrates from biological materials. Taniguchi et al. [36] demonstrated that NaOCl treatment of smear layer-covered caries-affected others dentin eroded and thinned the smear layer due to dissolution of superficial organic components of smear layer (Fig. 8). Furthermore, they reported that pretreatment with 6% NaOCl for 15 s could significantly improve the bond strengths of 1-step and 2-step self-etch system to caries-affected dentin, while NaOCl-30 s pretreatment did not affect them [36]. On the other hand, for normal dentin, NaOCl-15 s pretreatment did not alter the bond strengths, but NaOCl-30 s pretreatment reduced them [36].