Even when there are relatively few tags, such as in superficial dentin, they may be important for resin retention. But polymer tags could contribute to this retention if they are firmly attached to the walls of tubules.6 For this to occur, the peritubular dentinal matrix must be removed to expose the circumferentially oriented collagen fibrils. The aggressiveness of Futurabond, represented by directly its low pH, may have acted positively by demineralizing the dentin matrix and probably helping the tags to bond to the exposed collagen inside the tubules. Toledano et al19 stated that prolonging the time between adhesive application and drying should be considered in order to increase dentin bond strength, because it probably resulted in more optimal water permeation within this adhesive, contributing to a more complete dissociation of the acid functional monomers, and enhancement of the resin monomer infiltration.

This was not considered in the present study, but the acetone-based adhesive could perform differently in deep dentin, if alternative bonding strategies were used instead of the manufacturer��s instructions. Although the water-based Clearfil SE Bond adhesive does not have a low pH and is classified as being moderately aggressive (pH ~2.1), the bond strength values of this adhesive to both deep and superficial dentin were statistically similar to those of the Futurabond group. The Clearfil SE Bond has an acidic primer that is applied, followed by the application of the bond resin, without the rinsing phase. This low-sensitive technique, similar to that of Futurabond, could be a factor that really influenced bonding to dentin.

In addition to forming a micromechanical bond to dentin, this adhesive system is believed to incorporate a chemical interaction with the calcium in dentin because of the 10-MDP functional monomer, which has been rated as the most promising monomer for chemical bonding to the hydroxyapatite of enamel or dentin.20 Perdig?o et al21 stated that Clearfil SE Bond is capable of providing consistently strong bonds to enamel and dentin, and the good performance of this adhesive system may be partly attributed to the intense chemical bond to tooth tissue.11 The two-step etch and rinse Adper Single Bond 2 adhesive, which has the more sensitive technique, yielded statistically similar bond strength values to those obtained with the Clearfil SE Bond, but different from the FuturaBond values, this difference being most evident in deep dentin.

Once again, increasing the sensitivity of the bonding technique, because of the conditioning and rinsing steps, may lead to more operating errors. This occurs because the ideal situation, in which this adhesive system completely penetrates Dacomitinib demineralized dentin, is more difficult to achieve.9 The results of Adper Single Bond 2 adhesive system in deep dentin can also be attributed to its specific composition, because this adhesive contains water and ethanol as solvents.