Martins, Ayala, D'Alpino, Calixto, Gomes, Gomes moves the smear layer by conditioning the dentin applying the self-etching adhesives tested. Con- tissue (Adper Single Bond 2). After rinsing, the ad- versely, in the present study, no significant differ- hesive system is applied to the demineralized den- ence was observed among the groups, irrespective tin. The second approach (self-etching adhesive) is of the thermo-mechanical treatment. These results based on the simultaneous etching and priming of were in accordance to recent studies that revealed the smear-covered dentin. The two-step self-etch- that the microleakage in composite restorations is ing adhesive (AdheSE) contains an acidic primer not influenced by the high degree of technique sen- that eliminates the separate acid-etching and rins- sitivity associated with the use of different catego- ing steps, simplifying the bonding technique and ries of adhesive systems,20, 21 despite the thermo- reducing its technique sensitivity.19 The all-in-one mechanical treatment. self-etching adhesive system (Adper Prompt L- The thermal mechanism that causes microle- Pop) simplifies the bonding procedure even more by akage in bonded restorations is claimed to be due dissolving the smear layer with acidic resins while to the linear thermal expansion coefficient (LTEC) simultaneously promoting monomer impregnation among enamel (16.9 x 10-6 °C-1), dentine (10.6 x throughout the exposed collagen network.11 In the 10-6 °C-1), and restoration (17 to 83.5 x 10-6 °C- present study, the research hypothesis raised as- 1).22 LTEC is defined as the change in density when a sumed that the microleakage would be lower be- material undergoes a change in temperature.23 The cause of the reduced technique sensitivity when differences in LTEC generate a negative interface Figure 1. Percentage (%) of gap-free interfaces according to the experimental Figure 2. Microtensile bond strength measured immediately and after six months. groups. ASB2: Adper Single Bond 2, ASE: AdheSE, APL-P: Adper Prompt L-Pop. Different letters: significant (P<.05). Vertical bars represent + 1 standard deviation. Table 2. Median of microleakage observed at dentin margins. ADHESIVE SYSTEM Adper Single Bond 2 AdheSE Adper Prompt L-Pop CONTROL TCM April 2012 - Vol.6 Table 3. Adhesive axial gap width (standard deviation). STRESS C TMC C TMC C TMC ASB2 1,83 (2,48) 6,94 (9,42) 0 8 5 7 5 7 4 1 2 3 0 4 1 5 QUALITATIVE MICROLEAKAGE 2 3 0 0 1 1 2 1 1 0 2 0 1 0 ASE 0,69 (1,53) 1,63 (2,15) Median 0 0.5 0 0.5 0 1 APL-P 2,16 (2,71) 5,91 (6,98) 173 European Journal of Dentistry ASB2: Adper Single Bond 2; ASE: AdheSE; APL-P: Adper Prompt L-Pop; Control: no treated specimens; TCM: thermo-mechanically cycled specimens n=10 All values were statistically equivalent (ANOVA test, P>.05).