Aggressiveness ระบบตนเองกัดSome questions however arise from this particular approach: 1-Could the presence of dissolved hydroxyapatite and residual smear layer remnants interfere in the bond? 2- Are the self-etch systems able to properly demineralize enamel or sclerotic dentin? The self-etch systems were gradually modified in the last few years and one important change was the increase in their aggressiveness35 . Depending on etching aggressiveness, self-etch adhesives can be subdivided into strong (pH<1), intermediary strong (pH≈1.5) and mild (pH≈2.0)35,36,39. Strong self-etch adhesives present higher acidity compared with mild and intermediary strong systems and the interaction patterns observed in enamel and dentin resembles a phosphoric acid treatment after etch and rinse approach22. Figure 10 depicts resin tags formation after the use of Adper Prompt L-Pop (3M/ESPE, St. Paul, MN, USA), pH-0.8. The tubules are wide open, the resin tags have a funnel shape and are elongated. On the other hand, dentin treated with a mild self-etch system (All Bond SE; Bisco Inc., Schaumburg, IL, USA), pH 2.2, exhibits cylindrical and short tags (Figure 11). Despite the similar etching pattern with the etch and rinse systems, the bond strength observed for the strong self-etch adhesives was lower, especially at dentin38,39. The presence of water in the composition of self-etch systems is necessary to trigger the demineralization process. The excess of residual water during polymerization may be one of the reasons for the poor bond strength7,9,18,39. Indeed, adhesive systems that contain high concentrations of acidic resin monomers behave like permeable membranes29 and allow water movement from dentin to the composite-adhesive interface31. This may further compromise the durability of resin-dentine bonds and affect the coupling of the simplifed adhesives to auto-cured (or dual-cured) composites7,30. These two aspects; low initial bond strength and gradual degradation, due to hydrolysis, have made researchers and manufacturers rethink about monomers, pH and association of components in the bottles. Some newer self-etch adhesives present higher pH, such as Xeno IV (Dentsply Caulk, Milford, DE, USA), pH-2.1 and All Bond SE (Bisco Inc., Schaumburg, IL, USA), pH 2.2. Others, such as Adper SE Plus (3M/ESPE, St. Paul, MN, USA) present a very low pH (<1), their components are strategically distributed in the bottles. Liquid A formed of water, HEMA and a pink dye is first applied onto the cavity (Figure 12). The water will only meet the monomers in a second step, when liquid B is transferred to the cavity (Figure 13). A continuous brushing procedure is advised to force the contact of all components and help the evaporation of excess water. The pink appearance starts fading immediately and a light yellowish look takes place (Figure 14). Conversely, the Adper Easy One Bond (3M/ESPE, St. Paul, MN, USA) has all the components associated in the same bottle, including water. However, the pH of the mixture is much higher (2.3) than the pH of Adper SE Plus (3M/ESPE, St. Paul, MN, USA). These differences imply in distinct application techniques and storage. While Easy One Bond must be kept under refrigeration, Adper Scotchbond SE (3M/ESPE, St. Paul, MN, USA) can be maintained at room temperature.
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