Bond strength of self-etching adhesives ized smear layer was produced using a wet-ground untreated groups (P>.05). When the microleakage silicon carbide paper for 60 s and then finished to values were compared, no significance was found #600-grit. The specimens were then randomly di- among the experimental groups (P>.05). Table 3 vided into 3 groups (n = 6) according to the adhesive shows the results and statistical analysis for ad- applied. Then, 6 layers of 1 mm-thick resin com- hesive gap extension. No significance was found posite (Filtek Supreme XT – 3M/ESPE, St. Paul, MN, among the control groups (P>.05). When the mean USA) were added to the surface of the restorations values of the thermo-mechanically treated groups to obtain specimens with the same dentin/resin were compared, the same occurred. ASE presented composite proportion. The roots were sectioned the lowest gap extension mean value compared approximately 2 mm below the cement-enamel to the cases in which both Adper Single Bond 2 junction, perpendicular to the long axis of the tooth, and Adper Prompt L-Pop were applied. Statistical using a diamond-impregnated disk (Extec, Enfield, analysis showed that the mean value noted when CT, USA) in a specific cutting machine (Isomet 1000, AdheSE was applied was significantly lower than Buehler, Lake Bluff, IL, USA) under water-cooling that observed for Adper Single Bond 2 (P<.05). No at 300 rpm. After each storage time (24 hours and significance was observed when the treated and 6 months), the teeth were longitudinally sectioned untreated groups were compared in terms of adhe- in both “x” and “y” directions across the bonded in- sive gap width. None of the adhesives were able to terface using the same cutting device under water- provide perfect sealing of the axial walls (Figure 1). cooling. This resulted in bonded stick-shaped spec- TCM treatment led to a reduction in the percentage imens with a cross-sectional area of 0.8 (±0.2 mm²). of gap-free interfaces. The squared sticks were then cemented to the test- The results of the bond strength test are sum- ing device using cyanoacrylate cement (Zapit, DVA marized in Figure 2. The immediate results showed Inc., Corona, CA, USA). This device was attached to that when Adper Single Bond 2 was applied, the a universal testing machine (Instron Model 3342, highest bond strength values (49.1 ± 11.6 MPa) Instron Corp., Canton, MA, USA) and stressed in were observed, while the lowest bond strength val- tension at a cross-speed of 1 mm/min until failure. ues were observed for Adper Prompt L-Pop (18.4 ± The sticks of each group were randomly divided to 6.6 MPa). Statistical analysis demonstrated that the be tested immediately (24 h control groups) or af- bond strength mean value of Adper Single Bond 2 ter 6 months of storage in distilled water at room was significantly higher in comparison to the mean temperature. After testing, the fractured speci- values observed when both AdheSE and Adper mens were carefully removed from the apparatus Prompt L-Pop were applied (P<.05). After 6 months, and the cross-sectional area was measured with a a significant reduction was only found for ASB2 digital caliper at the site of failure. The results were (40.3 ± 8.7 MPa) (P<.05). Despite this decrease, the recorded and the debond stress values were con- bond strength mean value of Adper Single Bond 172 verted into MPa. Statistical methods The two-way ANOVA and Bonferroni post-hoc tests were used to analyze the µTBS and adhesive gap width at a preset alpha of .05. The Kruskal-Wal- lis and Dunn post-hoc tests were used to compare the microleakage data present between groups (α =.05). rEsuL st The results of the microleakage test in the den- tin margins are presented in Table 2. Figure 1 pres- ents the proportion between perfect sealing/pres- ence of gaps according to experimental groups. Statistical analysis demonstrated no significance between the thermo-mechanically treated and European Journal of Dentistry 2 was significantly higher than those noted at any evaluation time for both AdheSE and Adper Prompt L-Pop (P<.05). dIscuIon The first hypothesis, that the application of self- etching adhesives would provide lower microleak- age values in comparison to a conventional etch- and-rinse adhesive system, was not accepted. The microleakage values when the various adhesives were used were statistically equivalent (P>.05). Ad- hesive systems were selected to represent a variety of commonly used classifications: a conventional two-step adhesive; a two-step self-etching adhe- sive, and a one-step self-etching adhesive. The first approach (conventional adhesive) completely re-