Effects of thermocycling and use of ElectroBond on microtensile strength and nanoleakage using commercial one-step self-etch adhesives

The aim of this study was to determine the effect of thermocycling and the use of an electronically assisted application technique on the microtensile bond strength and nanoleakage of bonded interfaces created using one-step self-etch adhesives. Composite build-ups were bonded coronally to sectioned human molars using XENO III or Clearfil S(3)Bond. Adhesives were applied following the manufacturers' instructions (control) or with the aid of an electrical application device (ElectroBond). Teeth were sectioned into non-trimmed bonded beams for microtensile testing. Half of the specimens were subjected to 20,000 thermocycles, and the controls were not thermocycled. All specimens were tested to failure and peak stress was calculated. Additional specimens were prepared for nanoleakage analysis using transmission electron microscopy (TEM). The immediate bond strength of both adhesives increased as a result of using the ElectroBond device (XENO III 38.9 +/- 8.1 MPa; Clearfil S(3)Bond 46.2 +/- 9.9 MPa) compared with no use of the device (XENO III 26.7 +/- 7.8 MPa; Clearfil S(3)Bond 38.9 +/- 8.1 MPa). Thermocycling significantly decreased the bond strength of XENO III (27.1 +/- 7.9 MPa with the use of ElectroBond; 20.7 +/- 9.2 MPa without the use of ElectroBond); however, thermocycling did not affect the Clearfil S(3)Bond strength (47.2 +/- 8.6 MPa with the use of ElectroBond; 33.6 +/- 8.3 MPa without the use of ElectroBond). Reduced nanoleakage was found for both resins as a result of the use of the ElectroBond device, with or without thermocycling. Application of one-step, self-etch adhesives with the ElectroBond device significantly increased microtensile bond strength and reduced nanoleakage, but the effect of thermocycling was found to be brand-dependent.